Optimization of Orthodontics Elastics. m. Manglade

MICHEL LANGLADE D. C. D. - D. S. O. - D. U. O.

OPTIMIZATION of orthodontic ELASTICS

Edited by

GAC International

MICHEL LANGLADE D. C. D. - D. S. O. - D. U. O.

OPTIMIZATION of orthodontic ELASTICS

224 pages - 159 pictures

Edited by

GAC International Inc.

185 Oval Drive Central Islip. N. Y. 11722 - 1402 Fax: (516) 582 57 04

January 2000

From the same author: CEPHALOMETRIE ORTHODONTIQUE Préface Carl F. GUGINO 281 Pages - 202 Photos - 1978.

DIAGNOSTIC ORTHODONTIQUE Préface Ruel W. BENCH 768 Pages - 552 Photos - 1981.

THERAPEUTIQUE ORTHODONTIQUE Préface Robert M. RICKETTS 3rd Edition - 1986

OPTIMISATION DES CHOIX ORTHODONTIQUES Aide à la décision 347 Pages - 146 Photos - 1994

OPTIMISATION TRANSVERSALE DES OCCLUSIONS CROISEES UNILATERALES POSTERIEURE Préface Rudolf SLAVICEK 384 Pages - 349 Photos - 1996 French editor:

MALOINE 27, rue de l’Ecole de Médecine 75006 Paris FRANCE Tél.: (33) 01.43.25.60.45 Fax: (33) 01.46.34.05.89

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And soon on the Web...

TABLE OF CONTENTS

CHAPTER I: Definitions..............................................................

p1

• Definitions • Presentation of orthodontic elastics • Elastics force use

CHAPTER II: History of Elastics Forces......................................

p5

CHAPTER III: Classification of Orthodontic Elastic Forces........

p7

• Classification • Clinical statement • Force delivery • Classification of forces • Basis for prescribed pressures • Anchorage

CHAPTER IV: Elastics Wearing Motivation................................

p 20

• Patient compliance with elastics • Motivation of elastics wearers • Motivation card • Appointment interval of elastics wearers • Headgear instruction card • Motivation scoring card

CHAPTER V: Class I Elastic Forces......................................….. • Definition • Disposition • Biomechanics of Class I elastic • Class I elastics effects with continuous archwires • Class I elastics indications • Clinical application of Class I elastics • Elastomeric chains • Clinical problems with Class I elastics • The O shape occlusal elastic

p 32

CHAPTER VI: Class II Elastics Forces........................................

p 53

• Definition • Disposition • Biomechanics of Class II elastics • Class II elastics effects with continuous archwires • Class II elastics indications • Clinical applications of Class II elastics • Clinical problems with Class II elastics • TMD and Class II elastics • Pain and Class II elastics • Orthognatics and Class II elastics • Influence of the archwire and hooked point • Bioprogressive torque Class II elastics • The Class II molar extrusion elastic • How to diminish the extrusion component force • The split positioner

CHAPTER VII: Class III Elastics Forces......................................

p 83

• Definition • Disposition • Biomechanics of Class III elastics • Class III elastics effects on continuous archwires • Indication of Class III elastics • Clinical applications of Class III elastics • Clinical problems with Class III elastics • TMD and Class III elastics • Pain and Class III elastics • Orthognatics and Class III elastics

CHAPTER VIII: Particular Intermaxillary Elastics....................... • The Rectangular elastic • The U shape elastic • The Delta elastic • The V shape elastic • The M or W shape elastics • The Accordion elastics • The Class II Triangular elastic • The Class III Triangular elastic • Squeeze elastics • The cross bite elastics - Cross bite classification - Homolateral crossbite elastic - Controlateral crossbite elastic

p 97

• Elastics and dental asymmetries - Canted anterior occlusal plane - Unilateral posterior cross bite - Midline shift deviation - Asymmetric arch form • Elastics in condylar fractures

CHAPTER IX: Elastics and Extra Oral Forces..............................

p 128

• The twenty commandments of E. O. F. • The Class I elastic headgear • The Class II elastic headgear • The Class III elastic headgear • The whiskers headgear • Postero anterior elastics - The PHILIPPE’s Circummandibular Arch - The Facial Mask of: DELAIRE-VERDON PETIT GRUMMONS NANDA - The J. HICKHAM’s Chin Cup - The M. LANGLADE’s Reciprocal Mini Chin Cup - Orthopedic Class III Chin Cup

CHAPTER X: Rationale for Elastics Prescription.........................

p 159

• Before using intra oral elastics • How to prescribe elastics • Clinical example • Quiz of clinical situations

CONCLUSION............................................................................

p 178

BIBLIOGRAPHY........................................................................

p 180

CHAPITER I

Definitions

CHAPTER I: Definitions

DEFINITIONS • ELASTICITY: It is the property of a material to return to its original form.

• ELASTIC MATERIAL: Presents usually 3 properties: 1 - a distorsion not going beyond its limit of elasticity 2 - physically homogeneous 3 - isotrop, giving the same force in any direction ( see Fig I. 1 ).

Fig I. 1: A 3 ounce elastic in different clinical situations.

• LIMIT OF ELASTICITY: It is the amount of forced distorsion without deterioration and loss of elasticity .

• CLAPEYRON’S THEOREM OF RECIPROCITY When an elastic force is applied to two identical solids ( for instance two central incisors ) the moving force is identical and reciprocal.

• ELASTOMERS General term encompassing materials returning to their original dimensions immediately after substantial distorsion. Under this term are: - natural rubber or latex coming from hevea trees - synthetic rubber polymers such as styren butadien rubber, butyl, polyisopren, polybutadien, ethylpropylen, teflons, hypalon, silicons. 1


PRESENTATION OF ORTHODONTIC ELASTICS For a long time rubber elastics have been offered to the Orthodontic community in: - different sizes - different shape forces giving a precise applied force. They are presented in a plastic bag decorated with various symbols to help patients recognize which elastic was received for the last prescription. All elastics are sold in packages of 100 with a rapid zip and forces are indicated with:

colour coding first name sports

countries animals plants

fruit toys objects

Some Ortho manufacturers have even proposed mint flavoured elastics in order to improve patient compliance in elastic wear. Orthodontic elastics can be designated as: - intraoral - extraoral

Usually,the prescribed force is obtained when the elastic is stretched out three times its diameter. To check the elastic forces, the orthodontist can use CORREX or DONTRIX gauges ( see Fig I.3 ).

ADVANTAGE OF ELASTICS: • placed and removed by the patient • discarded after worn out • no activation required by the orthodontist • effect increased by mandibular movements ( mastication, phonation ) • can be changed upon prescription one, two, three times a day or even worn at night.

DISADVANTAGE OF ELASTICS: The orthodontist must be aware of: • deterioration and loss of elasticity: Any elastic worn in mouth is affected by: ➩ PH of oral environment ➩ saliva 2


➩ dental plaque ➩ time ➩ foods and drinks. • moisture absorption makes the elastic swollen and odoriferous. • non odor free when worn after 24 hours. • unpredictably variable forces exerted if the prescription is not well explained and controlled. • the exerted force is not constant and depends on patient compliance • elastics can be placed incorrectly, upsetting biomechanic effects of the appliance. • patient motivation. The more the rubber elastic is worn, the less the elasticity memory stays, as E. HIXON 4 et. al. have demonstrated ( see Fig I.2 ).

After 2 hours in the mouth, the module elastic force decreases about 30%, and after 3 hours about 40%.

It means that in clinical uses, elastics must be changed regularly according to the orthodontist’s prescription.

Fig I.2: Percentage of elastic force lost in mouth from E. HIXON 5 et. al. A. J. O. Vol 57 N° 5. p 481 1970. 3


ELASTICS FORCE USE Keep in mind: 1 - Components forces 2 - Anchorage 3 - Hooked point of force application 4 - Clinical objectives 5 - Biomechanic systems used 6 - Elastic types 7 - Patient cooperation

FACTORS IN ANCHORAGE LOSS in extraction cases treated with continuous archwires 1 - Friction 2 - Anterior torque 3 - Poor canine root control 4 - Excessive pressure 5 - Cooperation

Fig I.3: To check the elastic forces the Orthodontist can use CORREX or DONTRIX gauges. 4

CHAPITER II

History of Elastics Forces

CHAPTER II: History of Elastics Forces The first known elastic was the natual rubber used by INCAN and MAYAN civilizations extracted from Hevea trees.

☛ 1728: ☛ 1756: ☛ 1803: ☛ 1839: ☛ 1841: ☛ 1892: ☛ 1904:

☛ 1907:

☛ 1948:

☛ 1958:

☛ 1963:

Pierre FAUCHARD in his book “ Le Chirurgien Dentiste ou Traité des Dents ” proposed to close anterior diastema with silk ligature.

P. BOURDET used a “ bandeau ” with golden or silk ligatures to move teeth, prefiguring the straightwire era.

F. CELLIER introduced for the first time the “ Chin Cup Fround ” with rubber bandages.

Charles GOODYEAR discovered vulcanization.

J. M. A. SCHANGE, in his “ Précis sur le redressement des dents ” published in Paris, used elastic threads to move teeth.

Calvin CASE was the first to use intermaxillary elastic forces to correct malocclusions.

H. BAKER published in the International Dental Journal an article entitled “ Treatment of protruding and receding jaws by the use of intermaxillary elastics ”.

Edward H. ANGLE in his book “ Treatment of malocclusion of teeth ” proposed a classification of malocclusions and the use of corresponding elastic forces: Class I ; Class II ; Class III.

Charles TWEED initiated the Class III elastic use to reinforce the anchorage preparation of Class II malocclusion before using Class II elastics.

Fred SHUDY recommended short Class II elastics coming from the upper first molar and in association with a high pull anterior extraoral force in order to control the vertical sense.

J. JARABAK and FIZZEL in their book “ Technique and treatment with the light wire appliance ” page 70 to 82 from Mosby were describing the biomechanics of Class II elastics for the first time. 5

CHAPTER II: History of Elastics Forces

☛ 1965: ☛ 1964-1970:

☛ 1972:

☛ 1973-1996:

R. BEGG in his book “ Begg orthodontic theory and technique ” used Class II elastics which were changed every five days.

Robert M. RICKETTS originated the Bioprogressive segmented light square wire technique advising the closing elastics conduct in open bite cases.

Ron ROTH recommended short Class II intermaxillary elastics to help the curve of SPEE leveling associated with high pull headgear to control the vertical sense.

Michel LANGLADE developed the clinical applications of elastic forces in different situations such as occlusal elastics or controlateral crossbite elastics, proposing biomechanics comparison in clinical uses.

6

Elastomers Intraoral Elastics Only pure, natural latex is used in producing GAC elastics. Precise wall thickness and predictable forces are consistent characteristics of our full line of elastics. Our Travel Pack recognition system makes it fun and easy for patients to remember the correct size and force. In addition to size and force designation, each smudge-proof bag has a landmark, symbol, or activity associated with a specific country. Each pack of GAC intraoral elastics contains a bright white placer to help patients properly and easily use their elastics.

EXTRAORAL

INTRAORAL Inside Light Diameter Red /1.8oz 3mm (1/8Ó) 4mm (3/16Ó) 6mm (1/4Ó) 8mm (5/16Ó) 10mm (3/8Ó) 12mm (1/2Ó) 14mm (9/16Ó) 16mm (5/8Ó) 18mm (11/16Ó)

11-100-03 Australia 11-100-04 Holland 11-100-06 China 11-100-08 Canada 11-100-10 England

Medium

Heavy

Super Heavy

XH

XXH

Green/2.7oz

Blue/4oz

Black/6oz

Brown/6oz

Black/8oz

11-101-03 Germany 11-101-04 Mexico 11-101-06 USA 11-101-08 Italy 11-101-10 Spain

11-102-03 India 11-102-04 Switzerland 11-102-06 Japan 11-102-08 Scandinavia 11-102-10 France

11-103-04 Thailand 11-103-06 Korea 11-103-08 So. America

11-100-16 Ireland

11-104-08 Greece 11-104-10 Greece 11-104-12 Greece 11-104-14 Greece 11-104-16 Greece 11-104-18 Greece

11-105-04 Africa 11-105-06 Kenya 11-105-08 Argentina 11-105-10 Peru

Light, Medium, Heavy, and SH are packaged in boxes of 50 zip lock bags of 100 elastics. XH and XXH are packaged in boxes of 25 zip lock bags of 50 elastics.

ELF Ð Latex Free Elastics Eliminate rashes, irritation, and other allergic reactions with GAC's Latex Free Elastics. ELF Elastics are made from a surgical material that is hypoallergenic and exerts a more consistent force at up to 500% elongation. Available in a variety of sizes, in boxes of 50 bags of 100 ELF Elastics in each bag. Get the performance you want without the risk of allergic reaction.

Light

Medium

Heavy

Super Heavy

Red/1.8oz.

Green/2.7oz.

Blue/4oz.

Black/6oz.

1/8" 3/16" 1/4" 5/16" 3/8" 5/8"

11-201-03 / Panama 11-200-06 11-200-08 11-200-10 11-200-16

/ / / /

11-201-04 / Belgium Philippines 11-201-06 / Russia Singapore 11-201-08 / Indonesia Malaysia 11-201-10 / Finland Guatemala

11-202-03 / Columbia 11-202-04 / Brazil 11-203-04 / So. Africa 11-202-06 / Chile 11-203-06 / Saudi Arabia 11-202-08 / Luxembourg 11-203-08 / Hungary

CHAPITER III

Elastics Forces Classification

ELASTIC DISPOSITION

ELASTIC CLASSIFICATION

MOVEMENT FORCE

INDICATION

COUNTER INDICATION

• Space closure • Distal movement • Mesial movement • Tipping • Extrusion • Intrusion

NO

Dental and

Class III and

Class I Monomaxillary

Contraction • horizontal • vertical • transversal

7

Class II

→ Distal max → Mesial mandible

Skeletal

Regular

→

Class II

Class II skeletal open bite

Closing

→ Distal max

Open bite

Class III and

Class II

Class II deep bite

Extrusion

→ Mesial mandible Class II

Close the bite

CHAPTER III: Classification of Orthodontic Elastic Forces

Monomandibular


Class III

→ Mesial max

INDICATION

Class II and

→ Distal mandible

Skeletal Class III

Extrusion Ø

COUNTER INDICATION

Dental and

→

Regular

MOVEMENT FORCE

Skeletal open bite ( normal vertically )

8

Closing

Short closing

Dental

Class II and

→ Distal mandible

Deep bite

→

Class III

→ Mesial max

Class III

Skeletal open bite

Open bite

Class II and

Class III

deep bite

Extrusion

→ Mesial max canine → Distal mandible

Class III

Close the bite


ELASTIC DISPOSITION

ELASTIC DISPOSITION


MOVEMENT FORCE

INDICATION

COUNTER INDICATION

Oblique pull

Midline correction

Skeletal

extrusion

canine relationship

open bite

Oblique pull

Midline

extrusion

shift correction

Oblique pull

Canted occlusal plane

extrusion

with

of one side

midline shift

Class II

and

Class III

9 Diagonal

Oblique

Anterior

Triangular

Deep bite ?


Anterior


MOVEMENT FORCE

Posterior

→ Distal max

triangular

→ Mesial mandible

10

Anterior

deep bite

Class II

Extrusive

Dental

Extrusion

COUNTER INDICATION

Dental

→ →

Class II

INDICATION

Open bite

Deep bite U shape

force

open bite

Contraction Anterior

Dental and

rectangular

Deep bite open bite

extrusion


ELASTIC DISPOSITION

ELASTIC DISPOSITION


MOVEMENT FORCE

INDICATION

Intermaxillary

Extrusive

Vertical

COUNTER INDICATION

Open bite vertical elastic

force

extrusion

11

Vertical +

elastic

Open bite extrusion

light contraction

Vertical extrusion W and M

Extrusive

Skeletal to

elastic

force

open bite squeeze the bite


Extrusive force Delta


MOVEMENT FORCE

Accordion

Contraction ++++

INDICATION

COUNTER INDICATION

Open bite Skeletal with

Extrusion ++++

elastic

12

Posterior

→ Mesial max

open bite spaces to close

Deep bite Skeletal

triangular

→ Distal mandible

dental open bite

→

→ →

Class III

Extrusion

Homolateral

Class III

Edge to edge Transversal force +

cross bite

Skeletal cross bite

Extrusion + + + elastic

open bite degree 1


ELASTIC DISPOSITION

ELASTIC DISPOSITION


MOVEMENT FORCE

INDICATION

COUNTER INDICATION

Horizontal transversal force + + + +

Degree 2 to 3

Skeletal

Extrusion

cross bite

open bite

Controlateral

cross bite

elastic

Tranversal ectopic tooth

occlusal elastic

contraction position

See and check Class I + Class II Class I + Cross bite Class II + Cross bite Etc.......( see chapters ).

Combined

elastics

CR ▼ Individual clinical Objective


13

Too buccal O shape


CLINICAL STATEMENT

Name:

N°:

Date:

A / TRANSVERSAL: RIGHT

Crossbite

NORMAL

Crossbite

LEFT

Maxillary

Maxillary

Mandible

Mandible

Grade by a figure 1, 2, 3 the malposed teeth

B / VERTICAL: 3SD 2SD 1SD Class :

Deep bite

3SD 2SD 1SD Normal

Open bite

Skeletal Dental Grade by 1 SD, 2 SD, 3 SD . Use an arrow for tendency

C / SAGITTAL: Right A N C H O

R A G E

Right

yes no Loose yes no

Maxilla yes no Mini yes no

yes no Mean yes no

yes no Maxi yes no

yes no Maxi yes no

Mandible 14

Left yes no Mean yes no

yes no Mini yes no

yes no Loose yes no

A N C H O

Left

R A G E


FORCE DELIVERY Force application plays a strategic influence on orthodontic movement by means of wires and elastic rubber bands. Histologicaly optimum orthodontic movement had been related to an intact vascular supply. An optimum force should not exceed the capillary blood pressure ( 20 to 25 gm/cm2 ). If forces are above this level, clinical observations demonstrate possible ligament strangulation and sometimes root resorption.

Many authors had concluded that one of the major factors, if not the principal, governing bone resorption during tooth movement is the presence of an intact vascular system. Z. DAVIDOVITCH 3 had proposed intermittent forces as more suitable because their duration would not be sufficient to produce anoxic destruction of the ligament. According to this author, osteoclasts, which were stimulated to function by the force application, would continue to resorb bone for a brief period of time mobilizing the necessary bone removing cells.

Sunburstª Elastics GACÕs Sunburst Elastics are made from the finest quality latex. They are clean-cut, durable, hygienic, and made with regulation coloring. Available in a wide range of sizes and force values, Sunburst provides the precise degree of required control with a continuous force. Like our regular intraoral elastics, Sunburst is packaged with a bright white placer in each bag for easier use and greater patient cooperation. Colors are randomly assorted and are not available in specific colors. Sold in boxes of 50 zip bags, 100 elastics per bag.

Description 2.7 oz. 4.0 oz. 6.0 oz.

3/16" 11-001-04 11-002-04 11-003-04

Catalog Number 1/4" 5/16" 11-001-06 11-002-06 11-003-06

11-001-08 11-002-08 11-003-08

Elastics Racks Our aluminum anodized elastics rack is durable, light weight, and has holes for mounting on a wall. Holds four boxes of GAC elastics. Aluminum Elastics Rack

15

97-300-30


CLASSIFICATION OF FORCES

O R T H O D O N T I C

O R

P

T

E

H

D

O

I

C

OUNCES

GRAMS

FORCE

0.5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 48

14.17 28.35 56.6 84.9 113.2 141.5 169.8 198.1 226.4 254.7 283.0 311.3 339.6 367.9 396.2 424.5 453.6 907.2 1360.8

very light

Table III.1

16

O R

light

T H O D O

medium

N T I C

heavy

very heavy

O R

P

T

E

H

D

O

I

C


BASIS FOR PRESCRIBED PRESSURES According to the Brian LEE theory, the value of 200 g. per square centimeter of enface root surface could be an average of sagittal malocclusion. R. M. RICKETTS 2 had advocated a lighter force at 150 g./ cm2 for biological efficiency ( see Table III.2 ).

Root rating scale in transversal movements: Root surface

1.20

.55

.75

.75

.40

.50

Total 4.15 cm2

Necessary force

180

85

110

115

60

75

Total 635 g.

Necessary force

Root surface

175

1.10

90

.60

90

.60

115

.75

40

.25

40

Total 635 g.

.25

Total 3.55 g.

Table III.2: Root ratings with a 150 grams use / cm2.

The size of enface root surface exposed to sagittal movement is measured in square centimeters. Every tooth can be evaluated as to the necessary force based on its root surface involved. That means, on average, a force of: ➩ 635 g. in maxilla ➩ 550 g. in mandible to move all of the teeth. With friction, continuous archwires used with ceramic bracketts, it’s easy to understand that heavy forces may be needed to move teeth. In order to use lighter forces, a frictionless biomechanic system may be advised with segmented archwires. Doing so, orthodontic movement with elastic forces should be faster and more efficient. 17


Root rating scale in transversal movements:

Maxilla forces Mandible forces

1.05

1.35

.50

.50

.70

.65

.70

155 105 95 140

205 135 105 155

75 50 60 90

75 50 60 90

105 70 70 105

100 65 50 75

105 70 50 75

.95

1.05

.60

.60

.70

.50

.50

Table III.3

Root rating scale in vertical movements:

Maxilla forces Mandible forces

.70

.80

.30

.30

.45

.30

.40

105 70 95 140

120 80 105 155

45 30 60 90

45 30 60 90

65 45 70 105

45 30 50 75

60 40 50 75

.95

1.05

.60

.60

.70

.50

.50

Table III.4 18


ANCHORAGE

STATIC

DYNAMIC

FIXED

MOBILE

RIGID

DIFFERENTIAL

WITH FRICTION

>

FRICTION LESS

CONTINUOUS ARCHWIRES

SEGMENTED ARCHWIRES

MEASURABLE

NON MEASURABLE

MECHANIC

BIOLOGIC

ABSOLUTE COOPERATION

WITH OR WITHOUT COOPERATION

HEAVY FORCES

LIGHT FORCES

Table III.5 19

CHAPITER IV

Elastics Wearing Motivation

CHAPTER IV: Elastics Wearing Motivation

PATIENT COMPLIANCE WITH ELASTICS As a clinical statement patient compliance is difficult to evaluate before the treatment. However as a useful predictor evaluation, some factors must be taken in account:

- Girls are usually more cooperative than boys. Of 10 studies relating gender to various aspects of compliance, 5 reported that girls were more cooperative, but 5 found no sex difference. - Children under age of 10 years are more cooperative than older children. - Socio-economic status may be a predicting factor. Less cooperation is experience with patients from lower socio-economic status; but that does not mean that high class patients are more concerned. - Personality is a better factor to consider for uncooperative patients, characterized as being concerned with appearance, having conflicts with a mother, a father, or both, and needing the presence of authority to enforce ethical behaviour. - Cooperation is not related to severity of the malocclusion. - Embarrassment may be given as an excuse, forgetfulness, nuisance for low motivation, or apathy. - Pain is sometimes underestimated in the clinical setting of elastics bearers. Its importance should not be dismissed since pain is one of the most frequent reasons for not wearing intra oral or extra oral rubber bands. Some patients will require more communication regarding the amount of discomfort and progressive elastic forces to get accustomed with.

In conclusion, communication is essential. So, three rules to keep in mind: 1 Explain

2 Explain

3 Explain

20


MOTIVATION OF ELASTICS WEARERS During some phases of orthodontic treatment, elastics or rubber bands are used to move teeth or jaws or sometimes both. Sometimes elastics are absolutely necessary to keep anchorage in order to move the good tooth. Patient compliance is essential: ➩ to maximize cooperation ➩ to avoid headgear use, if possible ➩ to avoid mechanic problems ➩ to avoid relapse.

Remember that the Motivation key is to dramatize any little problem:

Fig IV.I

21

CHAPTER IV: Elastics Wearing Motivation Elastics prescription needs: 1 - a written prescription on a motivation card to reinforce the message . 2 - to explain why, when, and how to wear elastics (see Fig IV.3 ). 3 - to check that the patient understands well the message and is able to place properly the prescribed elastics (see Fig IV.4 ). 4 - to keep an eye on motivation, ask to the patient to put on his elastics in front of you. 5 - to evaluate patient cooperation with: ∑ weakness of progress correction ∑ improvement of motivation means ∑ threats of complications: ➨ increased treatment time ➨ possibilities of extractions ➨ possibilities of surgery ➨ increased fees ...

“ Please follow your elastics prescription exactly as we asked you: you’ll get faster and better results ”. “ Change them and wear them as indicated. Stay with your elastics even if you have some discomfort particularly during the first two days ( as with a new pair of shoes ) ”. “ Remember that well worn elastics mean you are speeding your treatment time ”.

“ Bring back your worn out elastics at each visit ”, said R. BEGG 27, as a good way to educate a recalcitrant patient. 22

CHAPTER IV: Elastics Wearing Motivation FRONT of Motivation card Dr. STRAIGHT 1057 Paradise Av.

• Wear your elastics EXACTLY as has prescribed on the back.

L. A. CALIFORNIA

• If you have any difficulties in placing them, please come back to our office. We will help.

INSTRUCTIONS FOR ELASTICS WEARING Now you have elastics to wear to help us to straighten your teeth. They are used to exert light forces to move dental arches. The different elastics sizes and prescription correspond to various tractions that will be used in succession of the correction of your teeth. At the beginning of elastic wearing, you may have some light tenderness during one or two days. Don’t be afraid, go on wearing them, you’ll be accustomed to them very quickly !

• In order to brush your teeth and your gums correctly, remove the elastics and put them back on immediately after brushing. • Always have some extra elastics in your pocket to use in the event of breakage.

FAILURE to follow instructions may result in biomechanic complications and POSTPONE the FINAL RESULT. BACK of Motivation card

PLACE ON your elastics IN FRONT of a MIRROR. Wear them: Change them: ❏ day and night ______ time(s) a day ❏ only at night. If you need elastics, please call our office immediately.

FOLLOWING INSTRUCTION and GOOD COOPERATION MAKE YOUR TREATMENT FASTER. 23


Fig IV. 2: Example of an elastic worn around two upper incisors with initial diastema. The elastic went up in the gingiva with periodontal damage.

Fig IV.3: Clinical example of an exaggerated movement given by Class II elastics changing a Class II in Class III. 24


Fig IV.4: Example of a misunderstood prescription of elastics. To correct the Class II canine we need a closing Class II elastic.

Fig IV.5: A supply of elastics on the watch of a well motivated patient. During school hours, elastics can be changed. 25


APPOINTMENT INTERVAL OF ELASTICS WEARERS It is always difficult to give a rule, because any patient at any visit during treatment time presents a clinical situation to which the orthodontist has to offer an appropriate and individual therapeutic solution. During the course of a treatment the practitioner has to ask himself the following questions: - What is the actual clinical situation ? > Use the chart in chapter 10 to lay down the problem. - What are the objectives to reach for the next visit ? - How do I meet those objectives ? - With what kind of biomechanic systems can we reach those objectives ? - Which elastics should the patient wear to accomplish good results ? On a general basis, an appointment visit is subject to different factors: 1- Importance of movement to obtain The appointment interval may be regulated according to the gravity of the malocclusion. The more the sagittal Class II canine relationship is important the longer the intervals of the first visits. Generally, when starting the Class II discrepancy, the interval of the first two or three visits may be every 8 weeks. Then in succession of interarch correction the interval may be 6 or even 4 weeks, according to the clinical exams. There is no absolute rule because the orthodontist may slow down elastics wearing in prescribing them full time at the beginning and during night time only at the end of correction (see Table IV.1 ).

APPOINTMENT INTERVAL OF ELASTICS BEARERS

Skeletal Class II

Skeletal Class I

➨

every 8 wks ➝➝➝➝➝➝➝ 8 wks ➝➝➝➝➝➝➝ 6 wks/ 4 wks ➝➝➝➝➝➝➝ 2 wks Elastics changes: X3 per day ➝➝➝➝➝➝➝ X2 per day ➝➝➝➝➝➝➝ X1 per night

Dental Class II

Dental Class I

every 6wks ➝➝➝➝➝➝➝ 4 wks ➝➝➝➝➝➝➝➝➝ 2 wks ➝➝➝➝➝➝➝➝➝➝➝➝ Elastics changes: X2 per day ➝➝➝➝➝➝➝➝➝➝➝➝ X1 per night Table IV.1 26

➨

CHAPTER IV: Elastics Wearing Motivation 2- The clinical goal to reach The Orthodontist may advise the patient to schedule his next visit only when the goal will be reached. For instance, if the patient has to wear a delta elastic to bring down an upper ectopic canine, you can ask him or her to wear elastics until the canine contact with antagonists, and then call for a new visit.

FRICTIONLESS LIGHT FORCES + SEGMENTATION = Minimum EFFORT for a MAXIMUM EFFECT 3- In exaggerate correction risks Some clinical cases have to be watched. Particulary some Class II discrepancies, who are used to well wear their elastics, are sometimes able to go in an excessive Class III and even with the caution of the Orthodontist. Explain to the patient about the danger of undesirable movement. Do not hesitate to reduce the interval of clinical visits or to reduce elastics wearing in an alternate way-night time only or every other night for exemple. Visit intervals and elastics wearing depend on: ➤ anchorage used ➤ importance of movement ➤ patient typology ➤ patient motivation ➤ biomechanic archwires technique used ➤ patient growth ➤ parodontal situation.

Be carefull: Badly or incorrectly hooked elastics may change biomechanics effects and complicate the treatment.

Risks of excessive elastics wear: • an excessive correction ( a Class II becoming a Class III as shown in fig IV.3 ). • an exaggerate tipping of lower or upper incisors ( backward / forward ). • anchorage lost. • undesirable extrusion / overbite. 27

CHAPTER IV: Elastics Wearing Motivation • exaggerate rotation. • parodontal problem, such as Class II worn too much, may give lower incisors dehyscence.

Be carefull: To dual bite Class II elastics wearing for a long time may simulate a corrected malocclusion. The patient may exhibit a misleading convenience bite ( dual bite ). So, check centric relation at any appointment before any elastics prescription.

CENTRIC RELATION OUTLINE 1 - CR is a necessary treatment. 2 - Patient must be seated at 90°. 3 - In absence of pathology, CR is not static but a dynamic relationship. 4 - With muscle pathology, CR does not exist ! 5 - 85 % of TMD’s are muscular problems. 6 - CO - CR discrepancies are the result of muscle pathology or internal derangement. 7 - Sliding CO - CR may change. 8 - When healthy, TMJ are flexible, adaptable and have the capacity to compensate. 9 - Think chronologicaly: 1 - muscles 2 - TMJ 3 - occlusion 4 - MRI 5 - articulators. 10 - Use deprogrammation splint, if pain exists. 11 - Use sagittal range of motion to detect dual bite. 12 - Screen TMD: ➩ pain ( dynamic vs static ) ➩ functional restriction ➩ noise ? ? ➩ dyskinesia ➩ muscle tenderness. 13 - Choose pain reduction first ( ultrasounds, Tens, stress management, pharmacology). 14 - Instruct the patient. 15 - Patient’s eyes closed. 16 - Sting the soft palate with a probe. 17 - Ask the patient to swallow with the tongue placed on the soft palate sting. 18 - Stop the closing mouth at the first interdental contact. 19 - Check the CR occlusion. 20 - Use a Moyco wax bite to register CR.

28


LIMITATIONS AND WARNING SIGNAL OF ELASTICS WEARING 1 - Muscular fatigue ? ➝ myalgia. 2 - TMJ arthralgia ➝ pain. 3 - Functional mandible limitation. 4 - Mandibular dyskinesia. 5 - Increased noise: - clicking - ligament laxity - crepitus. 6 - Excessive dental tipping: - molar anchorage - forward / backward incisors. 7 - Teeth interferences: - mobility - dental pain - parodontal problems. 8 - Condylar loading signals with: - Class III elastics - chin cup/facial mask - excessive molar extrusion. 9 - Improper incisor guidance: - open bite - overbite. 10 - Insufficient arch coordination ( 3 D ) transverse first! 11 - Multiple root resorption ( extrusion / intrusion ). 12 - Chronic tongue interposition ( thumb sucker ). 13 - Chronic respiratory problems ( apnea or sleep disorders ). 14 - Excessive growth. 15 - Insufficient growth.

29


HEADGEAR INSTRUCTION CARD Headgear therapy is ordinarily used when the upper jaw has out grown the lower jaw. This easy correction is going to modify the skeletal maxilla and your appearence, in slowing the upper growth and allowing the lower jaw to catch up: 1 - Handle everything carefully, especially when removing or inserting the inner bow. 2 - Never try to pull the headgear off without first unhooking elastics or the strap which is attached to the outer bow. 3 - If a molar band becomes loose, come immediately to our office as an emergency appointment. 4 - Wear your appliance from: ❒ 12 to 14 hours

❒ 16 to 20 hours

5 - Discomfort is temporary; wear your appliance faithfully. 6 - Use your score card to keep record of the number of hours you are wearing your appliance night and day. 7 - Recording the wearing hours allows your orthodontist to determine needed forces for proper correction. 8 - To put on your headgear is quite simple in front of a mirror, or have someone help you. 9 - Don’t twist or distort your inner or outer bow by playing with it. 10 - Please don’t wear your headgear during rough play, sports, cycling.... This could result in injury to you.

Very important: Remember to bring your appliance to any appointment to give us a chance to properly adjust it. 30


MOTIVATION SCORING CARD HOURS 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10

S

M

T

W Th

F

Sat

S

M

T

W Th

F

Sat

...

Please score how many hours you have worn your headgear per 24 hours Name: Adress:

Don’t forget to bring this card to each appointment.

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Description Elastics Placers

31

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CHAPITER V

Class I Elastics Forces

CHAPTER V: Class I Elastics Forces

1 - Definition The Class I elastic can be a chain, a rubber band, a ring or a thread placed on a single arch and having a vertical or a horizontal force movement. The Class I elastic has a reciprocical biomechanic action in a straight line

2 - Disposition The Class I elastic can be placed: • one tooth to another tooth • one tooth in opposite way as a couple of forces • one tooth to an archwire, a loop • one point to another point of the archwire • one tooth to an auxilary appliance such as Quad Helix, a palatal bar, a bite plate etc... The Class I elastic is a monomaxillary or monomandibular elastic which can be used with other elastics in the same time.

3 - Biomechanics of a Class I elastic Whatever it is a chain, a ring or a thread, the Class I elastic has reciprocal action in straight line. The force exerted depends on clinical objectives, considering the STABLE force or anchorage used and the MOBILE force to move the teeth, we must always have:

STABLE force

>

MOBILE force

That means, for example, that if you have, as in Fig V.8, to move distally a 41 and to close a diastema, an elastic thread ligature around 42 and 41 will move both equally in the space. To move distally the 41 you should placed the thread elastic on two or more teeth or thru the utility helix to keep the stable force higher than the mobile one.

Be careful: Elastics not well hang on or worn by the patient can complicate treatment objectives.

32


Fig V. 1: Different Class I elastics uses. 33


Fig V.2: Buccal upper incisor tipping for adult in typical Class II.2. The elastic thread is tied on a .045 wire.

Fig V.3: Intrusion of a molar or cuspid with a thread elastic, tied on utility arch.

Fig V.4: Intrusion of lower incisors in adult, with a thread elastic, on a R. BENCH lower arch.

34


Fig V.5: Class I elastic ligature used to rotate and bring forward the left lateral incisor in the opened space by the M utility.

Fig V.6: Class I elastic to slide backward the right lower lateral incisor. The elastic is changed 3 times a day. 35


Fig V.7: Example of elastic ligatures tied to rotate the 24 with an opposing force couple.

Fig V.8: Example of a Class I elastic ligature thru an utility Helix to close a lower incisor diastema in moving distally the 41. 36


Fig V.9: Example of Class I elastic chain and ligature to rotate a canine and an upper first premolar with a force couple.

Fig V.10: Example of Class I elastics on a bite plate to correct a midline deviation and close diastemas. 37


Fig V.11: Example of a tongue thruster who had reopened a diastema after a treatment. Class I elastic is placed on a bite plate.

Fig V.12: Detail of the Class I cross elastic to close diastemas.

38


Fig V.13: Class I elastic ligature tied on the 4T4 to close the lower diastema. The patient was already in retention.

Fig V.14: Result obtained with the Class I cross elastic and lower elastic ligature. Permanent retention with Ribbond was made. 39


Fig V.15: Example of space reopened after treatment. The patient does not want to have braces any more.

Fig V.16: A bonded hook is made distal to the upper lateral incisor. 40


Fig V.17: An upper bite plate with an “ O ” occlusal elastic is worn to close the diastema.

Fig V.18: Detail of the “ O ” occlusal elastic used to close the diastema. 41


Fig V.19: Frontal view showing the diastema closure with the “ O ” elastic.

Fig V.20: The bonded hook is removed and the upper incisors are splinted with a ribbond wire. 42


Fig V.21: Class I elastics used on a crossway on a bite plate ( intraoral view ) for space closing.

Fig V.22: Class I elastics used on a crossway on a bite plate for space closing.

43


4 - Class I elastics effects with continuous archwires Most of Class I elastics can have a contraction movement effect which may be horizontal, vertical, or transversal. The effects may include: • space closure • distal movement ( retraction ) • mesial movement ( advancement ) • tipping • extrusion • intrusion. Again, the Class I elastic may be used in association with other elastics to reinforce a movement or anchorage ( see Fig V.23 and 24 ).

5 - Class I elastics indications According to most practioners, utilization of elastic thread has proven to be one of the simplest and most efficient way to methods: ➨ to rotate of a single tooth or reciprocal teeth ( see Fig V.1 and 9 ) ➨ to achieve space closure ➨ to use force couple maintaining the centroïd axis of a tooth during rotation control ➨ to move a tooth which is difficult to tie in the archwire ➨ to intrude a tooth or a group of teeth ( cuspid intrusion ) ➨ to extrude a tooth which is impacted or in ectopic position. In finishing and detailing occlusion, an elastic thread can be helpful to get an overcorrection of a canine, a molar, etc.

6 - Clinical applications of Class I elastics Clinical applications are numerous: 1 - SPACE CLOSING as diastema, the Class I is used as a contraction system ( see Fig V.11 - 14 ). 2 - DENTAL MOVEMENT for retraction of a tooth or a forward advancement of a posterior segment ( see Fig V.23 and 24 ). 3 - EXTRUSION of a single tooth in ectopic position ( buccally or palatally ). 4 - INTRUSION of incisors ( the elastic is placed on from a reciprocal 0.45 arch ). 5 - TIPPING CORRECTION of a tooth axis. 44

CHAPTER V: Class I Elastics Forces Influence of elastic association used - in extraction cases - on continuous archwires

Fig V.23: A: A Class I elastic on maxillary arch to retract the upper canine can certainly move it backward, but a slight forward movement of the upper molar can be seen if M1 is not anchored by an auxilary such as a palatal bar, a headgear... B: A Class I elastic on maxillary arch anchored on the second molar is a better anchorage than can achieve a retraction of the upper canine. C: A Class I elastic used simultaneously on maxilla and mandible moves forward the upper molar with the lower during the retraction of the upper canine. 45


Fig V.24: D: The association of a maxillary Class I with a Class II elastic moves forward slightly the maxillary molar when the lower goes forward E: The association of a bimaxillary Class I elastic with a Class II one moves the molar forward and the upper canine backward. F: The association of a maxillary Class I with a short Class II allows retraction of the upper canine without moving the upper molar. Then the lower molar can be brought forward without losing maxillary anchorage. 46

CHAPTER V: Class I Elastics Forces 6 - ROTATION with one Class I or with force couple of two opposed Class I ( see Fig V.9 ). 7 - STRENGTHENING FORCE such as to increase: • the loosening anchorage, a Class I can be added to a Class II or III according to the clinical objectives. • the maximum anchorage, a Class I can be also added for differential forces to increase the stable force. • the midline shift correction.

7 - Elastomeric chains Polyurethane chain elastics are commonly used in daily orthodontics as Class I elastics. They are made by Ortho manufacturers in: - long filament chain - short filament chain - closed loop chain. Elastomeric chains are mainly used for intra arch tooth movement and for spaces closing, because placement and removal requires little chairtime and no patient cooperation. More than 50 studies had been done on elastomeric chains; a consensus of clinicians may be summarized as follow: • a permanent deformation may result after extension of plastic module • the degradation of force is increased over time • the force exerted is unpredictable and inconstant • the configuration of chain affects the behaviour of the force • after 3 weeks, the residual force is generally about 5 %. • oral environment ( such as PH, light, saliva, drinks, foods, dental plaque ) has been associated with degradation of the polyurethane elastomer • extension or prestretching has been advocated before inserting the chains • the elastomeric chains must be kept in a container and protected from light.

The elastomeric chains must be changed at least every 3 weeks.

47


Fig V.25: Configuration of elastomeric chains: A - long filament chain B - short filament chain C - closed loop chain.

The longer the chain’s filament, the lower the initial force

8 - Clinical problems with Class I elastics Clinical problems are very rare. The most important one is that usually the force decreases rapidly. So the thread or chain must be changed at least every 3 weeks.

As with any system in Orthodontics, Class I elastics may give complications such as: - abnormal tipping - exaggerated rotation - exaggerated extrusion - anchorage lost - minor or insufficient displacement... Since more and more practitioners are using straight wires, some of them have undesirable effects in using a continuous elastic chain on too light archwire < 0.016. 48


Undesirable effects of continuous elastic chain 1 Mesial molar rotation with too light wires 2 Light wires do not sustain the chain force 3 Posterior expansion of archwire 4 Wilson’s curve is threatened ( molar crossbite ) 5 Undesirable root tipping 6 Increased Class II elastic forces 7 Risk of weakening anchorage 8 Molar tipping ➩ interferences 9 Incisors extrusion ➩ Torque lost 10 Lateral pterygoïd tenderness 11 Lower incisor retroversion with mandibular arch contraction 12 Increased overbite.

9 The « O » shape occlusal elastic The “ O ” shape occlusal elastic had been introduced by M. LANGLADE in 1975 to correct dental transverse malposition, which is most of the time unitarian. This elastic is placed occlusally on the maxillary or mandibular arch in order to correct: • a buccal tooth position which is in buccal cross bite degree 1 or 2 (see Chapter VIII Table VIII.1 ). Sometimes it may be a second molar. • an arch asymmetry • spaces or diastemas • a lack of canine contact in maxillary arch ( see Fig V.26 ). Biomechanically, the “ O ” shape elastic moves one tooth or a limited group of teeth transversaly. That could be a canine, a premolar, or a molar. Usually, it can be worn on a simple way or in criss cross according the clinical objectives ( see Fig V.29 ). The “ O ” shape occlusal elastic: ➨ must be worn during night only ➨ must be worn during a short time because of its efficiency ➨ must be controlled every week. 49


Fig V.26: Occlusal elastic placed on upper canine to correct a retarded occlusal contact function. The light contraction is usually obtained in a week.

Fig V.27: Correction of a too buccal position of first upper bicuspids with an occlusal elastic. 50


Fig V.28: Clinical example of the application of an occlusal elastic worn on the lower molar which became too buccal. This kind of “ O ” elastic is worn during night only and for a short time ( 2 to 3 weeks ) to correct the lower buccal cross bite degree 2 (see text ).

With a mandibular reverse arch curve, don’t use a continuous elastomeric chain... Prefer a segmented chain to allow a buccal tipping of retruded incisors !

Chain segmentation: [R Molar - R canine] [incisors] [L canine - L Molar]

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Fig V.29: Clinical example of bilateral buccal upper canine corrected with cross “ O ” shape elastics. 52

CHAPITER VI

Class II Elastics Forces

CHAPTER VI: Class II Elastics Forces

1 - Definition Class II elastics are intermaxillary elastics placed on the maxilla anteriorly, and on the mandible posteriorly.

2 - Disposition Class II elastics may be placed differently on: ➨ the mandibular arch posteriorly buccally, lingually or simultaneously from: • different teeth M2, M1, Pm2, Pm1 • distal to a molar tube • a hook • a loop • a JARABAK or KAYABASHI ligature tie • a buccal hook coming from a lingual arch • a bite plate with a distal hook. ➨ the maxillary arch anteriorly from: • a sectional archwire • a Class II utility arch • a continuous archwire with anterior loop • a sliding hook • a JARABAK or KAYABASHI ligature tie • a bracket hook • a Jig • a Class II headgear • a reciprocal archwire 0.45 with hooks • a reciprocal Mini Chin Cup.

3 - Biomechanics of a Class II elastic Let us take an example of a Class II elastic _ inch, heavy placed on the distal buccal part of the lower archwire and on an anterior loop in front of the upper canine. In occlusion, if this elastic makes a 20 degree angle with the upper continuous archwire and a 100 g force, the elastic effect has: ➩ a horizontal component force of: 100 X cos 20° = 93.90 g. ➩ a vertical component force of: 100 X sin 20° = 34.20 g. 53


Centric occlusion

Opening 10 mm

Opening 25 mm

Fig VI.1: Biomechanic influence of mouth opening on Class II elastic force ( see text ). 54

CHAPTER VI: Class II Elastics Forces • With a mouth open 10 m/m at the incisors level, the force varies with different angulation of the Class II elastic and has different effects upon: - the maxillary arch ➩ The vertical component of extrusion is: 160 X sin 29° = 77.60 g. because the elastic has now a 29° angulation with the upper arch ( see Fig VI.1 ). ➩ The horizontal component of distalization is: 160 X cos 29° = 139.90 g. - on the mandible The elastic has a 35 degree angulation with the lower archwire. So we have: ➩ A forward component force of: 160 X cos 35° = 131 g. ➩ A vertical component of extrusion force which is: 160 X sin 35° = 91.8 g.

• With a mouth open 25 m/m, which can happen when the patient is speaking, smiling or yawning, the elastic force can be again increased to 190 grams. But this force cannot be constant and is going to decrease with time, in the saliva. This maximum force occasionally exerted has again different effects upon: - the maxillary arch ➩ The vertical component of extrusion force is: 190 X sin 38.5° = 118.3 g. ➩ The horizontal distalizing force is: 190 X cos 38.5° = 148.7 g. - the mandibular arch ➩ The horizontal forward force is: 190 X cos 52.5° = 115.7 g. ➩ The vertical component of extrusion force is: 190 X sin 52.5° = 150.7 g.

From those figures, it is now easy to notice that by opening of the mouth from 10 to 25 m/m, the forward mandibular force drops down from 131 to 115.7 g.That means it decreased about 10% despite the patient opened his mouth more. Notice also that the extrusive mandibular force went from 91.8 to 150.7 g. That means it increased 64% ! From this biomechanic explanation, the clinician must understand that the use of Class II intermaxillary elastics has to take into account the facial type in order to avoid a facial pattern aggravation.

During day: Intermaxillary elastics have a vertical component of extrusion that is much more significant than the horizontal component. During night Intermaxillary elastics have an equivalent vertical and horizontal component.

55


Fig VI.2: Facial type influence with Class II elastic use and consequences on the antero superior occlusal plane when using continuous archwires. ( See text ). 56


Fig VI.3: Ch. TWEED’s Class II elastics are worn on continuous arches (with tip back) and headgear.

Fig VI.4: F. SHUDY’s Class II elastics are placed on three points in a closing way with High Pull Headgear to control anterior occlusal plane and reinforce maxillary anchorage.

Fig VI.5: R. ROTH’s Class II elastics are short and used with headgear according to the facial type.

57


Fig VI.6: The R. RICKETTS’s bioprogressive technique. Class II elastic on sectional maxillary archwire.

Fig VI.7: R. RICKETTS’s utility arch with Class II hook for maximum anchorage.

Fig VI.8: J. PHILIPPE’s circummandibular arch to protract the mandibular arch. Unfortunately, when the patient opens his mouth, the Class I elastic becomes a Class II with extrusion consequences.

58


4 - Class II elastics effects with continuous archwires The Class II elastics have different effects. ➨ Effects upon the maxillary arch • backward movement of the upper arch • extrusion and downward movement of anterior occlusal plane ( see FigVI.2 ) • upper incisors are more vertical • all teeth are distallized. ➨ Effects upon the mandibular arch • entire mandibular arch is brought forward • the lower molar can be extruded • buccal tipping of lower incisors. ➨ Effects upon occlusal plane • sagittal correction of Class II relationship • downward tilting of the anterior occlusal plane. ➨ Effects upon facial pattern • the mandible is brought forward with a posterior rotation • chin goes forward • the lower facial height is increased according to the amount of elastic force used and wearing time.

5 - Class II elastics indications Class II elastics may be used for main or secondary objectives according to the individual clinical case such as: • skeletal and/or dental Class II malocclusions • anchorage reinforcement • backward movement of the upper incisors • mandibular arch advancement • bite opening • buccal tipping of retruded lower incisors • midline deviation correction • dual bite correction. 59


Fig VI.9: Example of a Class II elastic placed on a sliding hook to compress a spring for minor distalization.

Fig VI.10: Example of a Class II elastic placed on a sliding Jig to correct a molar relationship.

60


Fig VI.11: Example of a Class II elastic placed on a Class II utility arch to correct a midline shift.

Fig VI.12: Example of a Class II elastic placed on a contraction utility arch to correct an upper incisor protrusion and close anterior spaces. 61


Fig VI.13: Example of a Class II elastic placed on a continuous archwires.This kind of intermaxillary elastic has an extrusion component on the occlusal plane ( see text ).

Fig VI.14: Clinical case of one Class II elastic placed on the upper sectional to settle the canine relationship and one other Class II elastic placed on the contraction utility archwire to help the incisor retraction and torque. 62


Fig VI.15: Clinical example of a Class II canine relationship associated with a Class I molar relationship before treatment.

Fig VI.16: After treatment of a Class II elastic placed on a sectional maxillary arch.

63


Fig VI.17: Example of clinical dental Class II 1 deep bite before treatment. Notice the canine Class II relationship.

Fig VI.18: After 3 months the canine relationship had been corrected with a Class II elastic worn on a reciprocal maxillary arch. 64


In incisor overclosure, the use of Class II elastics is recommended only after: ➩ the correction of the vertical sense ( overbite ) ➩ the segmentation of the maxillary archwire.

6 - Clinical applications of Class II elastics ➨ In dental Class II malocclusions Any kind of elastics can be used whatever they are Class I postero anterior, regular Class II or combined with different ones. In case of dental open bite, closing Class II elastics are recommended to close the bite (see Fig 24 ). ➨ In skeletal Class II patterns We must differentiate: • vertically normal: where the Class II elastic has a light effect of posterior mandibular rotation. • deep bite: the extrusion component of Class II can be used with the combination of triangular Class II.

Remember:

➩ correct the overbite before the overjet ➩ level the curve of Spee before using the Class II elastic ➩ segment the maxillary arch. In some cases, the bite plate can help to open the bite when using intermaxillary elastics. • open bite: in those cases the use of Class II elastics must be avoided because their effects increase the mandibular rotation even when using closing Class II. It’s better to use Class I elastics associated with judicious extraction strategies and/or surgery. The vertical component of Class II elastics extrusion depends on: ➤ the facial type ➤ the occlusal plane orientation ➤ the curve of Spee ➤ cases with or without extraction ➤ the mandibular anchorage posterior point of the elastic( M2, M1, Pm2, Pm1 ) ➤ the force exerted ( day and/or night ).

65


7 - Clinical problems with Class II elastics Many clinical problems may be observed even with careful clinical watching on: • insufficient wearing • excessive wearing • parodontal problems such as: - lower incisors dehyscence - abnormal rotation and fenestration, etc... • biomechanic complication such as: - space opening - space closing - anchorage lost - abnormal tipping - exaggerated rotation - exaggerated extrusion.

Be aware of the DUAL BITE ! The Class II elastic wearing can simulate a corrected malocclusion and disappoint someone’s hopes. Some patients have worn Class II elastics for so long that they can develop a convenience bite and cheat their Class II correction. Before stopping Class II elastics check the centric relationship and look at the patient occlusion.

8 - T. M. D. and Class II elastics Some clinical cases are true temporomandibular disorders and some have only a predisposition or a dysfunctional recurrence of TMD. Most of the time they can have separately or all together: ➩ a premature contact giving a mandibular shift ➩ a muscular hyperactivity resulting from stressed life ➩ an instability of the collateral condylar ligament with a disc interference. In this kind of patient it’s better to tripod the mandible.

The Class II elastics with mandibular tripod must consider: • to segment the maxillary arch • segmented tripod to keep posterior wedges • to distalize lateral segments, try to obtain overcorrection • to intrude incisors • to advance the lower arch.

66


9 - Pain and Class II elastics Some dysfunctional patients have difficulties tolerating intermaxillary elastics, because wearing may increase the tenderness and pain. For this kind of patient a splint must be recommended to control muscular or articular pain resulting from the muscular hyperactivity coming from the elastics use. Tripodization of the mandible can be a helpful solution as noted by D. GRUMMONS 29. For example, some Class II Div. 1 clinical patients may develop excessive buccal lower incisors tipping and going on with Class II elastics, particularly in those with deep overbite, awaking the sleeping cat - PAIN- because the incisor contact with exaggerate use of Class II elastics may give again a condylar compression. In those kinds of clinical cases the mandibular tripod is very useful and allows intrusion of lower incisors and/or upper incisors. Then the segmentation of the splint may help the segmentation of archwires and may go on with intermaxillary elastics. Extrusion of lateral segments must be done with a parodontal approach in order to avoid bone lose by elongating teeth. Usually, this elongation must not go beyond 2 mm for each arch, according to D. GRUMMONS 29. Not every patient should have their vertical dimension of occlusion increased. Some skeletal Class II micrognatia patients may have vertical deficiencies due to overclosure in jaw position in closed mouth. A modest increase does not appear to be detrimental, and addresses: - molar tipping or rotation - forwarding incisors - intruding incisors - advancing lower arch - surgery. Remember that an excessive thickness of the tripod beyond the freeway space or mandibular postural position can lead to detrimental intrusion of the posterior teeth.

The orthodontic management of cases with lack of posterior support involves: 1 - reestablishment of the vertical support 2 - elimination of the anterior excessive contacts due to overbite. This can be done by: • uprighting posterior teeth • extruding posterior teeth • intruding incisors and/or? • buccal tipping of incisors to correct incisal angulation and overbite • surgery.

67


10 - Orthognatics and Class II elastics Surgerised orthognathics cases may need some Class II elastics for different reasons:

➩ to maintain a good skeletal relationship during healing and consolidating phase ➩ to overcorrect dental relationship ➩ to correct midline deviation ➩ to seat the canine occlusal relationship. The practitioner must consider the patient on an individual basis and the kind of surgery undertaken. The Class II elastics should be used: • to avoid bone mobilization, even in rigid fixation cases • to segment the surgerised arch to its opposing arch, if possible • to prefer short closing Class II elastics • to use segmented archwires instead of continuous ones, with frictionless forces. • to keep posterior wedges and avoid posterior mandibular rotation.

In orthognatics cases, the control of the vertical sense is fundamental in maintaining the advantages of sagittal correction.

11 - Influence of the archwire and hooked point To make more comprehensive this notion, let us see the Fig VI.19 where we have a dental Class II malocclusion with a locked second premolar. Different biomechanic systems could be used: ➨ WITH FRICTION In using a continuous archwire with an opened coil spring for Pm2 space, we can place the Class II elastics as follows: 1 - behind the lower molar, which is going to be extruded and advanced with the whole mandibular arch without opening the Pm2 space. 2 - on the mesial hook of the lower molar which is going to be advanced without extrusion, but without opening the Pm2 space. 3 - distal to Pm1 on a KOBAYASHI tied ligature. The Class II elastic is going to advance the mesial part of the mandibular arch before the Pm2, with a friction system which is better than Fig.VI.19 n° 1 or 2, but less efficient than Fig.VI.19 n° 6. 68

CHAPTER VI: Class II Elastics Forces ➨ FRICTIONLESS Using an archwire with an activated M loop with tip back, we can place the Class II elastic: 4 - behind the lower molar to advance the whole mandibular arch with less extrusion than in Fig. n° 1. 5 - on the mesial hook of the lower molar to help the activation of the M loop and open the Pm2 space and advance the mandibular arch with more efficiency than in Fig. n° 2. 6 - distal to Pm 1 on a KOBAYASHI tied ligature, the Class II elastic is going to help the M loop to give a reciprocal effect in opening quickly the Pm2 space and advancing the mandibular arch in a very efficient way.

There are other biomechanic systems that could be used such as segmented arches with utility arch etc; but the principle remains mainly the same.

In LINGUAL TECHNIQUES all biomechanic principles remain the same, except that elastics are placed on lingual side.

69


1

4

2

5

3

6

WITH FRICTION

FRICTIONLESS

Fig VI.19: Influence of biomechanic archwires systems and the hooked point of the Class II elastics ( see text ).

70


12 - Bioprogressive torque Class II elastics Class II elastic placed on the anterior part of a contraction utility arch has an effect of increasing the TORQUE during the incisor backward movement ( see Fig VI.20 ). In fact, the Class II elastic pulls downward and backward the anterior loop which raises the anterior segment of the arch and increases the anterior torque progressively with the contraction. This is a big difference between a continuous contraction arch and the RICKETTS’s segmented technique. Remember that when a continuous contraction arch is activated, the anterior occlusal plane goes downward during the contraction. If you need to control it, you have to use a high pull anterior headgear with good patient compliance. This bioprogressive torque, in using Class II elastics, is a very innovative biomechanic system.

Fig VI.20: Biomechanics of Progressive Torque with the RICKETTS’s utility arch. The Class II elastic pulls downward and backward the anterior loop which raises the anterior segment of the arch increasing progressively the torque with the contraction. A bodily movement of the upper incisors is the result. See text.

71


Fig VI.21: Clinical example of Class II elastics placed on a Class II utility maxillary archwire and a sectional to correct Class II molar and canine relationship on one side.

Fig VI.22: Clinical example of Class II elastic on right side to correct a midline deviation and help to close the space between upper canine and lateral incisor. 72


Fig VI.23: Clinical example of U shape anterior elastic to close the bite. Notice the controlateral crossbite elastic to move the first bicuspid palatally.

Fig VI.24: Clinical example of closing Class II elastics to help closing the bite. Notice the extrusion Class I elastic placed from right to left hook of the lateral maxillary sectional archwires. 73


13 - The Class II molar extrusion elastic This Class II elastic is hooked over the cinched distal end of the upper archwire, both strands are hooked under the cinched distal end of the lower end of the archwire, and the other is hooked mesial to the upper canine ( see Fig VI.25 ). This kind of elastic had been dubbed by R. HOCEVAR 22 “ The check elastic ” according to its upside down V shape. Its clinical indication is mainly: • skeletal and/or dental deep bite • expansion which must be used in conjunction with thoses elastics... or may be hooked palatally on the maxillary molar. The vertical component on the lower molar is between three to four times greater with the check elastic according to R. HOCEVAR.

14 - How to diminish the extrusion component force with the Class II elastics use According to many authors, about 15% of Class II Div.1 malocclusions have a potentially vertical excess dimension. Some of those cases are usually treated with extraction of bicuspids that results, when using Class II elastics, in an increased extrusion component force ( see Fig VI.28 ). There are different means to diminish the extrusion force such as: • wearing elastics only during sleeping hours • more horizontal elastics with hooked point more posterior in the mandible and more anterior for the maxilla.

In using: ➩ molar M2 banding ➩ Class II headgear ➩ .045 reciprocal arch ➩ reciprocal mini chin cup.

Before RETRACTION, the more vertical the upper incisors are, the more TORQUE is needed.

74


Fig VI.25: The R. HOCEVAR “ Check elastic ” is a Class II molar extrusion.

Fig VI.26: Class II molar extrusion elastic indicated in deep bite cases.

Fig VI.27: Triangular Class II elastic with a double component of Class II and extrusion for deep bite tendency cases.

75


Fig VI.28: Influence of the hooked point of the Class II elastic: A - In extraction case. B - In non extraction case from M1. C - In non extraction case from M2. Notice the difference of the vertical component of extrusion. 76


A

Fig VI.29: A, B, C, Class II 1 malocclusion before treatment.

B

C

77


D

Fig VI.30: D, E, F, After correction with Class II elastics placed on an . 045 upper reciprocal arch.

E

F

78


Fig VI.31: Example of oblique and Class II elastics to correct midline shift with a segmented frictionless mechanism. 79


Fig VI.32: Example of a Class II elastic headgear with anterior welded hooks opened anteriorly.

Fig VI.33: Intraoral example of unilateral Class II elastic headgear for midline shift and Class II correction. 80


Fig VI.34: M. LANGLADE’s reciprocal maxillary arch used with a Class II elastic on a .016 X .022 lower utility arch.

Fig VI.35: With a maxillary sectional arch and a LANGLADE’s reciprocal arch the patient can wear two Class II elastics on each side.

Fig VI.36: With the same system we can add a LANGLADE’s reciprocal mini chin cup to reinforce the Class II effect according the degree of difficulty of the clinical case (3 X 100 g. force on each side → mandibular protraction effect ). See Chapter IX.

81


15 - The Split elastic positioner The Split elastic positioner was developed by G. and B. KAPRELIAN 25 to improve results when compared to the traditional one piece tooth positioner ( see Fig VI.37 ). This appliance, as its name indicates, is a two piece positioner occlusally flat, with buccal hooks for Class II elastics. The advised force ranges from 100 to 150 g. depending on the prescription and the final growth potential of the child. The benefits of the Split elastic positioner are: • improvement of occlusion • elimination of breathing problems • sleep disorders assistance • no adjustment needed • good patient acceptance • can be worn independently • clinching prevention • stops deep bite return • long term retainer.

Fig VI.37: KAPRELIAN “ K 2 P ”. A split elastic positioner, worn with Class II elastics, during home hours and sleeping.

82

CHAPITER VII

Class III Elastics Forces

CHAPTER VII: Class III Elastics Forces

1 - Definition Class III elastics are intermaxillary elastics placed posteriorly on the maxillary arch and anteriorly on mandibular arch.

2 - Disposition According to the clinical problem, Class III elastics may be placed: Posteriorly • buccally • palatally ➩ to help expansion • buccally and palatally ➩ to increase the force • from the distal part of the archwire ( Fig VII.4 ) • from a molar hook ( Fig VII.5 ) • before the maxillary molar, even from Pm2 or Pm1 • from a Class III headgear • from a bite plate distal upper hook. Anteriorly • a loop on archwire • a JARABAK or KOBAYASHI ligature • from a Class III bite plate with anterior hooks and inclined plane to help to jump the bite ( see Fig VII.6 ).

3 - Biomechanic of Class III elastics Let us take an exemple of a 100 g. Class III elastic put on continuous arches (see Fig VII.1 ). In occlusion, the elastic having a 20 degree angle with horizontal plane is developing: ➩ a vertical component force of 100 X sin 20° = 34.20 g. ➩ a horizontal component force which can be written 100 X cos 20° = 93.90 g. In a mouth open 25 mm, the elastic force becomes 190 g. with a reciprocal action: - on maxilla: vertical component of 136.67 g. horizontal component of 131.98 g. - on the mandible: horizontal component of 92.11 g. vertical component of 166.17 g. With those figures, it is easy to understand the effect of incisors elongation anteriorally and to appreciate the vertical effect of such an elastic! 83


Centric occlusion

Opening 10 mm

Opening 25 mm

Fig VII.1: Class III elastics biomechanics. See text. 84


Fig VII.2: Influence of conventional Class III elastics on the occlusal plane tilting when using continuous archwires ( see text ). 85


Fig VII.3: Influence of conventional Class III elastic forces with facial type and consequences on the vertical component of extrusion, when using continuous archwires. See text. 86

CHAPTER VII: Class III Elastics Forces Influence of Class III elastics on occlusal plane tilting with continuous archwire: When a regular Class III is placed distally to the upper molar and mesially to the lower canine with continuous arches, the resulting force depends on the tilting of the occlusal plane -in other words on the facial type: - in a normal vertical dimension the resultant is a 50% forward movement of the maxilla of applied Class III elastic ( see Fig VII.3A ) with an extrusion on upper molar and an extrusion with lingual tipping of the lower incisors. - the more the vertical dimension is increased ( see Fig VII.3B and C ), the less the mesial movement of the upper molar from 33% to 25% with an increased extrusion worsening the open bite. So, it is very important to keep the posterior wedge in a patient with a potential borderline open bite. Segment the arch behind the first upper premolar and use short closing Class III elastics. The vertical component of extrusion of Class III elastics depends on: • the curve of Spee • the cases with or without extractions • the point where the elastic is placed • the facial type: the more the open bite, the greater the extrusion component

4 - Class III elastics effects on continuous archwires The use of Class III elastic has different effects: Effects upon maxillary arch ➩ forward mesial tipping and extrusion of the first molar ➩ light maxillary advancement ➩ buccal tipping of upper incisors. Effects upon mandibular arch ➩ lower incisors extrusion ( see Fig VII.2 ) ➩ lower lingual tipping of lower incisors ➩ lower arch distalization. Effects upon occlusal plane ➩ sagittal correction of occlusal relationship ➩ upward tilting of lower anterior occlusal plane ( see Fig VII.3 ). Effects upon facial type ➩ backward rotation of the mandible ➩ the chin goes downward and backward ➩ the lower facial height is increased.

Class III elastics have a counterclockwise effect on the occlusal plane anteriorly and posteriorly.

87


5 - Indications of Class III elastics Before using Class III elastics, the Long Range Growth Forecast is recommended for predicting the mandibular dimension and position in the face in the growing patient. Knowing the final mandibular position during the Class III elastic use, it is possible to get a posterior mandibular rotation in cases with deep bite skeletal pattern with: - dental overbite - closed labio nose angle - collapsed labial esthetics In such a way camouflage becomes possible. In normal vertical cases, it becomes dangerous to open the bite with an extrude fulcruming maxillary molar which may increase T. M. J. tenderness. Regular Class III elastics may increase patient mandibular growth ( see Chapter IX ). For normal vertical Class III cases, it’s better to keep posterior wedges, if you want to treat your patient orthodontically. Evidently, for open bite skeletal Class III patterns, treatment should include surgery. Finally the Class III elastics indications may include: • dental Class III occlusal relationship with deep bite skeletal pattern • anterior crossbite going edge to edge in centric relation • retromaxilla deep bite with • incisor overbite Class III allowing a possibility of camouflage by posterior mandibular rotation • mandibular incisors protrusion in which you need closing and retraction space • maximum mandibular anchorage with monomandibular extraction of the first premolars • midline deviation correction.

Camouflage with posterior mandibular rotation in Class III squeletal pattern depends on: ➩ growth potential (use Long Range growth Forecast ) ➩ dental overbite ➩ collapsed labial esthetics ( see Table VII.1 ) 88


CHILDREN

ADULTS

GROWTH POTENTIAL

LONG RANGE FORECAST

CANINE FUNCTION

NO GROWTH

Class III Mandibular • Dimension • Position

limited by

POSTERIOR ROTATION

DENTAL OVERBITE

NOSE LABIAL ANGLE

T.M.J.

VERTICAL DIMENSION

KEEP POSTERIOR WEDGE

89

LABIAL ESTHETICS


Fig VII.4: Conventional Class III elastic placed behind the upper molar. A high component of extrusion exists on the occlusal plane.

Fig VII.5: Regular Class III elastic placed on maxillary mesial molar hook. The extrusion component force still exists. 90


Fig VII.6: Example of Class III elastics placed on behind the maxillary molar posteriorly and on anterior hook of a lower inclined bite plate in order to bring forward the upper arch and jump the bite.

Fig VII.7: Example of a Class III elastic to correct a midline shift.

91


Fig VII.8: In this Class III, almost edge to edge incisor relationship, the vertical sense is critical and must not be opened. The posterior wedge must be kept.

Fig VII.9: Notice that the arch is segmented behind the 14th, and the patient is wearing a closing short Class III elastic to jump the bite. 92


6 - Clinical applications of Class III elastics In order to recognize the risky prognathic true Class III, remember to use the long range growth forecast. In deep bite cases it is useful to: • protract the maxillary arch • procline maxillary incisors: bond them upside down to advance Point A • use inclined 45° bite plate with Class III elastics • use utility M loop to advance upper arch • use brackets with buccal crown torque on lower incisors to resist the extrusion and lingual tipping elastic force ( to avoid gingiva dehyscence ). In borderline or open bite cases it is useful to: • segment the maxillary archwire behind the first upper premolar • keep the posterior wedges • avoid increasing the vertical sense • use short closing anterior Class III elastics ( see Fig VII.9 ) • check and watch T. M. J.

The deeper the overbite, the better the prognosis in Class III malocclusions.

7 - Clinical problems with Class III elastics Many clinical problems may be observed even with careful clinical management such as: • insufficient wearing • excessive wearing • parodontal problems such as lower incisors dehyscence • biomechanics problems like lingual tipping or excessive extrusion of lower incisors. The distal lower tipping of the mandibular canine may increase the retroversion of lower incisors, when using Class III elastics with light memory archwires. For example, when a Class III elastic is placed on an 0.016 X 0.016 lower Niti or TMA, the lower canine can be distally tipped, inducing an increased extrusion of lower incisors already subject to the vertical component of extrusion of the Class III elastic. 93


8 - T. M. D. and Class III elastics Some clinical cases are true temporomandibular disorders but are very rare in this kind of malocclusion. The excessive use of Class III elastics may bring a recurrence of T. M. D. problems by a condylar compression. According to the clinical problem, the treatment can be done: ➨ without mandibular tripod: • watch lower incisors extrusion • fight against lingual tipping of lower incisors ( use buccal crown torque brackets ) • use segmented maxillary archwires • keep posterior wedges • don’t open the bite anteriorly. ➨ with mandibular tripod: • optimize condyle disc relationship • use mandibular tripod • keep posterior wedges • segment maxillary archwire behind the upper canine or the first premolar • grind the tripod progressively to control the occlusal situation three dimensionaly • use short anterior closing Class III elastics.

9 - Pain and Class III elastics Some dysfunctional patients have difficulties tolerating intermaxillary elastics. The wearing may increase the tenderness and even become painful due to the condylar compression loading. For these patients, a splint may be recommended for control of the muscular hyperactivity coming from the elastics use. Tripodization of the mandible can be a helpful solution as noted by D. GRUMMONS 29. Class III elastics forces can be associated with postero anterior elastics in order to advance the retruded maxilla.

94


10 - Orthognatics and Class III elastics Surgerised Class III cases may need some Class III elastics for different reasons:

➩ to maintain a good skeletal relationship healing and consolidating phase ➩ to overcorrect dental relationships ➩ to correct midline deviation ➩ to seat the canine occlusal relationship. Most of the time the orthodontist has to consider the patient on an individual basis without forgetting the kind of surgery undertaken. Class III elastics should be used: • to avoid bone mobilization, even in rigid fixation cases, using light forces • to segment the antagonist arch to the surgerised one, if possible • to prefer short closing Class III elastics • to keep posterior wedges • to control vertical dimension • to use segmented archwires instead of continuous ones with frictionless forces.

In orthognatics cases: Extrude teeth on an unitarianly way in order to avoid moving bone fragments.

In some OPEN BITE cases with

TONGUE INTERPOSITION, vertical intermaxillary elastics can be

LINGUALLY placed on cleat lugs, bonded buttons, to provide an

ANTI-TONGUE SCREEN.

95


Centric occlusion

Opening 10 mm

Opening 25 mm

Fig VII.10: Triangular Class III biomechanics with a _, light elastic in 10 cm opened mouth. We have: • at the maxilla: an extrusion force of 119.1 g. a forward force of 32 g. • at the mandible: an extrusion force of 115.1 g. a backward force of 44.3 g. 96

CHAPITER VIII

Particular Intermaxillary Elastics

CHAPTER VIII: Particular Intermaxillary Elastics Many intermaxillary elastics may be used for a specific extrusion component associated in conjunction with others such as contraction, in a horizontal or vertical way. Among them let us see:

1 - THE RECTANGULAR ELASTIC This elastic has a rectangular shape adding a contraction and extrusion force movement ( see Fig VIII.10 ). It is well indicated for closing spaces and extruding a segment of the dental arch. So it can be placed: - posteriorly - anteriorly in order to close the bite and to close remaining spaces at both arches.

2 - THE

U SHAPE ELASTIC

The U shape elastic has a contraction and extrusion effect on only one arch. So it can be used with a segmented arch to the antagonist arch and can be used in U shape or upside down ( see Fig VIII.1 ). Most of the time, this elastic is used anteriorly, but it can also be used posteriorly.

3 - THE DELTA ELASTIC This elastic has a delta shape, a short triangle using a vertical component of extrusion for a single ectopic tooth, most of the time an upper canine ( see Fig VIII.7 ).

4 - THE

V SHAPE ELASTIC

This elastic has a vertical component of extrusion without a light contraction. It can be worn to bring a tooth on the occlusal plane in a V shape or upside down according to the clinical need.

5 - THE

M OR W SHAPE ELASTICS

These elastics are used for extruding a group of teeth in order to squeeze the bite in an effective closing way. Heavy elastic up to 300 g. may be used ( see Fig VIII.3 and 4 ).

6 - THE ACCORDION ELASTICS They have the same purpose as the M or W ones, but they add a contraction component that could be interesting for closing spaces when extruding a group of teeth ( see Fig VIII.3 and 4 ).

7 - THE CLASS II TRIANGULAR ELASTIC This elastic has a triangular shape with a Class II orientation, indicated for its vertical component of extrusion of deep bite Class II clinical cases. 97

CHAPTER VIII: Particular Intermaxillary Elastics

Fig VIII.1: Example of the U shape vertical closure elastic on segmented arch. 98


ELASTICS CONDUCT IN OPEN BITE CASES

Fig VIII.2: From R. M. RICKETTS and al. Bioprogressive Therapy. RMO Editor. 1979 99


Fig VIII.3: Example of M and W elastics to close the bite faster than locking up the maxillary teeth in a straight wire.

Fig VIII.4: Two weeks later, the bite is closed with the M and W vertical elastics.

100


Fig VIII.5: Clinical example of a squeeze of the bite with M and W shape elastics ( see text ).

Fig VIII.6: Post surgery TMJ patient wearing a splint with lateral rectangular elastics to extrude lower molar and first bicuspid. 101


Fig VIII.7: Example of an upside down V elastic to bring down a right upper canine instead of locking it up with a straight wire.

8 - THE CLASS III TRIANGULAR ELASTIC This kind of elastic has also a triangular shape used for its vertical component of extrusion of the posterior part of the maxillary arch as Class III sagittal correction of occlusion ( see Chapter VII. Fig VII.10 ).

9 - SQUEEZE ELASTICS In some borderline surgery open bite cases, R. M. RICKETTS 2 had advocated heavy elastics forces ranging from 800 to 1500 g. to close the bite (see Fig VIII.5 ). Those elastics are worn 24 hours a day, and changed three times during two weeks, to obtain the bite closure.

10 - THE CROSS BITE ELASTICS They must be differentiated in: A - homolateral cross bite B - controlateral cross bite But, before seeing their clinical application, we must look at a new international classification. 102


CROSS BITE CLASSIFICATION Most authors have identified the unilateral posterior cross bite occlusion only in terms of transversal relationship of the maxillary molar. The term “ cross bite ” means an abnormal labio lingual, edge to edge or bucco lingual relationship of the antagonist teeth. This incomplete definition has caused some confusion since apparent tooth relationships can hide underlying skeletal discrepancies sagittally and/or transversely. The reality of clinical and functional exams of patients, presenting a unilateral posterior cross bite occlusion with three dimensional cephalometric analysis, axiography and study models, has shown to M. LANGLADE that the lower molar can be affected in 19.36 % of those cases in a sample of 280 orthodontic patients. Since 1988, the author has used an international classification based on the responsible molar ( upper or lower ) with a figure 1, 2 or 3, expressing the transversal unwedging by degree of difficulty: - normal is 0 - 1 is edge to edge - 2 is a one cusp unwedging - 3 is the complete jump of the bite Doing so, it is possible to establish the true pathologic situation which opens concretely on the appropriate therapeutic solution. For instance, all third degree cross bites must be corrected with a bite plate on the antagonist arch. See Table VIII.1

MAXILLA: UB3 = upper buccal 3 cross bite UB2 = upper buccal 2 cross bite UEE1 = upper edge to edge 1 UL2 = upper lingual 2 cross bite UL3 = upper lingual 3 cross bite

MANDIBLE: LB3 = lower buccal 3 cross bite LB2 = lower buccal 2 cross bite LEE1 = lower edge to edge 1 LL2 = lower lingual 2 cross bite LL3 = lower lingual 3 cross bite

103

CHAPTER VIII: Particular Intermaxillary Elastics Buccal →→→→→→→→→→→ Edge to edge →→→→→→→→→→→ Lingual

Table VIII.1

International Classification of posterior unilateral cross bite: Grade the pathologic situation according to the unwedging cusp: 1 - for edge to edge 2 - for one cusp 3 - for the jump of the bite

Buccal →→→→→→→→→→→ Edge to edge →→→→→→→→→→→ Lingual 104


Fig VIII.8: Differential posterior cross bite occlusion diagnosis must distinguish A - a dental malocclusion B - a narrow maxilla C - a mandibular latero deviation ( functional shift ). 105


A / HOMOLATERAL CROSS BITE ELASTIC Definition: The homolateral cross bite elastic is usually used to jump the bite of a tooth or a group of teeth. It is placed opposing teeth, for instance a palatal cleat lug of an upper molar in lingual cross bite degree two, to the buccal hook of the lower molar of the same side ( or contrary ). This kind of intermaxillary cross bite elastic can be used on any kind of tooth from the palatal side to the buccal side or conversely. Biomechanism: The Biomechanism of a homolateral cross bite elastic may explain a clinical example of such an elastic developing a 90 g. horizontal force in occlusion. This elastic, as in Fig VIII. 9, gives a rotation moment written: M = 90 X 16 = 1440 g. If the distance of elastic insertion to the center of resistance is 16mm: ➩ the upper molar undergoes a palato buccal rotation ➩ the lower molar undergoes a bucco lingual rotation. When the patient opens his mouth to 30 mm, the 90 g. force becomes a 180 g. If we suppose that each molar has an 8 mm width and the jump of the bite is 4 mm, the elastic is obliquely stretched exerting a force of rotation on each molar, which is decomposable in a vertical and a horizontal force. We have now a triangle with two known sides: a = 30 mm b = ( 8 + 4 ) = 12 mm According to the Pythagorian theorem, the hypotenuse is: c2 = a2 + b2 or c = √( 30 )2 + ( 12 )2 = 39.8 mm So, the exerted force in the mouth is dependent on: - a horizontal force ➩ Fh = 180 X (12/39.8) = 54.3 g. - a vertical force ➩ Fv = 180 X (30/39.8) = 171.7 g. This oblique force exerted on each molar in inverted sense has moments which can be written: - for the horizontal force ➩ Mh = 54.3 X 16 = 868.8 g.mm - for the vertical force ➩ Mv = 171.7 X 8 = 1573.6 g.mm It is clear now that an intermaxillary homolateral cross bite elastic in an open mouth gives an extrusive force three times greater than the original horizontal force. This biomechanic demonstration shows that such elastics are to be avoided in open bite cases.

Intermaxillary homolateral cross bite elastic can be used: • in normal or deep bite skeletal cases • in deep bite cases where expansion is desired.

106


Occlusion

Open 30 mm

Fig VIII.9: Biomechanics of homolateral cross bite elastics ( see text ). 107


B / CONTROLATERAL CROSS BITE ELASTIC Definition: The controlateral cross bite elastic is an intermaxillary elastic placed on opposite sides of dental arches; for example from a left upper molar buccally to a right lower molar, or vice versa. Biomechanics: We can, for instance, use the same demonstration with a 130g. elastic force in a closed mouth ( see Table VIII.2 ). If the patient opens his mouth again to 30 mm: ➩ the transversal force is 273 g. ➩ the vertical force is 115.38 g. Now, we have a new situation with a horizontal force which is three times the extrusive one. That means that the controlateral cross bite elastic is much more effective transversaly than any other. TABLE VIII.2 In maxilla

In open mouth 30 m/m

H O M O In closed mouth occlusion F = 90 g.

L A T E R A L

Fh transversal: 54.3 g.

Fv extrusion: 171.7 g.

In mandible In maxilla

In open mouth 30 m/m

C O N T R O L A T E R A L

In closed mouth occlusion F = 120 g.

Fh transversal: 273.3 g.

Fv extrusion: 115.38 g. In mandible

108


Fig VIII.10: Posterior rectangular elastic ( see text ).

Fig VIII.11: Short vertical elastics have a tendency to narrow the transversal dimension

Fig VIII.12: GRUMMONS double cross bite used for molar extrusion in TMD patients to unload the condyle.

109

CHAPTER VIII: Particular Intermaxillary Elastics Clinical applications: The clinical application of this kind of controlateral cross bite elastic suggests it is helpful in various transverse corrections, more especially in posterior unilateral crossbite situations. In 1990, M. LANGLADE 39 did a comparative study on cross bite correction of unilateral palatal upper molar in two degree cross bite wearing a Quadhelix with or without the help of a controlateral cross bite elastic (see Table VIII.3 ). The treatment time was shortened from approximately 270 to 60 days with the controlateral elastic !

Unilateral expansion Quadhelix Maxillary lingual degree 2 cross bite Without any elastics 8 Male 4 Female Average age: 12.4 years

With controlateral elastics N12

N12

6 Male 6 Female Average age: 10.9 years

Transverse unwedging 4.91 mm

Transverse unwedging 5.58 mm

Range from 3 to 6 mm

Range from 3 to 7 mm

Treatment time 267.25 days

Treatment time 60.33 days

Table VIII.3: Comparison of Unilateral posterior cross bite correction from M. LANGLADE. Foundation for Orthodontic Research 1990.

The intermaxillary controlateral cross bite elastic is very helpful in correcting unilateral posterior cross bite.

Clincal indications of the controlateral cross bite can be summarized as: • mandibular functional side shift • posterior unilateral cross bite: 1 - for helping an expansion 2 - for helping a contraction 3 - for helping an expansion and a contraction 4 - for helping a contraction and an extrusion. 110


Fig VIII.13: Use of a controlateral cross bite elastic to correct a right maxillary buccal degree 2 with a unilateral contraction Quadhelix. The elastic is reinforcing the stable force and helping to increase the moving force.

Fig VIII.14: The controlateral cross bite elastic has a double action on the unilateral movement of the Quadhelix by: 1 - increasing the molar anchorage on the right side 2 - increasing the expansion force of the Quadhelix with a transversal elastic helping to jump the left molar bite ( mobile force ). 111


Fig VIII.15: Controlateral cross bite elastic used to correct a lingual maxillary molar degree 2 with a unilateral expansion Quadhelix.

In DISTRACTION OSTEOGENESIS, the practitioner can use all biomechanic principles in order to correct maxillo mandibular anomalies using intermaxillary elastics such as: U N I L A T E R A L

● vertical rectangular, M, W etc ● diagonal, oblique etc ● controlateral cross bite ● homolateral cross bite ● Class I, Class II, Class III ● combination

112

B I L A T E R A L


Fig VIII.16: Example of buccally ectopic canines with anterior open bite.

Fig VIII.17: A cross controlateral elastic is going to palatally move each canine in a week. 113


Fig VIII.18: One week later the bite is closed and the upper canines are settled transversally and vertically ( see Fig VIII.16 and 17 ).

Fig VIII.19: Example of a controlateral elastic helping the correction of a cross bite degree two with a unilateral Quadhelix force. 114


Fig VIII.20: The palatal ramp unilateraly on a bite plate can be used to guide the mandible in functional shifts: A - without occlusal plate B - with bilateral bite plate C - with unilateral bite plate. Controlateral or intermaxillary elastics can be placed to help the midline shift correction. 115


11 - ELASTICS AND DENTAL ASYMMETRIES Many dental asymmetries exist and can be divided into:

1 - CANTED ANTERIOR OCCLUSAL PLANE With a tilting in the frontal plane associated with: ➩ unilateral divergent ➩ unilateral convergent ➩ inclined divergent ➩ inclined convergent The association of segmented biomechanic archwires with oblique or anterior triangular elastics could help to correct the anterior occlusal plane (see Fig VIII.22 and 23).

2 - UNILATERAL POSTERIOR CROSS BITE It can be corrected with a Quadhelix developing unilateral force movement associated with an homolateral or a controlateral cross bite elastic, according to the degree of difficulty (see Fig VIII.13 to 15).

3 - MIDLINE SHIFT DEVIATION It is usually corrected by three means: A / Different module force elastics: For example, you can have on one side a Class II changed one time a day and on the other side a closing short Class II changed three times a day that means you have double force on that side. B / Different elastic disposition: Such as a Class II on right side and a Class III on left side. But you may have also a cross bite and Class II elastics on the same side in an opposite one ( see Fig VIII.22 ). C / Segmented arch form: It is very helpful to correct the dental midline deviation using frictionless forces associated with intermaxillary elastics. But one can also use a different arch form of the archwires in using the transversal loop.

Continuous archwires don’t work in a dental asymmetric arch or with facial asymmetry. Mandibular functional shifts can be corrected with the help of a guiding bite plate (see Fig VIII.20) and controlateral cross bite or associated intermaxillary elastics. Usually the cross bite elastic is placed in opposition to the side of mandibular shift (see Fig VIII.22) 116


4 - ASYMMETRIC ARCH FORM: It may exist in different planes: • vertically • horizontally • transversely • sagittally. Some practitioners are not well aware of the straight wire limitations to correcting such asymmetric dental arch form. Most of the time, the segmentation of archwires and/or the different arch form given by a transversal loop associated with combined elastic forces may be the therapeutic solution for those difficult clinical cases.

Midline shift diagnosis summary

✸ Check Mdb centric relation. ✸ Set the Mid sagittal plane of reference. ✸ What has caused the Midline deviation ? ✸ How does the deviation affect the occlusion ? ✸ Is it necessary to correct it ? and how ? ✸ Do 4 D dental arches analysis.

Midline treatment summary

➩ Mandibular reposition with: ● functional appliance ● palatal Ramp ( Fig VIII. 20 ) ● surgery ? ➩ Dental arch coordination: ● particular extraction (controlateral ? unilateral ? ) ● reproximation / stripping ● segmented archwires ● asymmetric mechanics ( transversal loop ) ● special intermaxillary elastics

117


DENTAL MIDLINE DEVIATION

N: Normal: Check CR

A: Opposed midline deviation: • oblique elastics • Class II / III elastics • cross bite elastics • cross stripping ?

B: Unilateral bimaxillary midline deviation ( Right ): • left extractions ? • left Class II elastics • right Class III elastics • unilateral stripping ?

C: Unilateral maxillary midline deviation ( Left ): • right max extraction ? • right Class II elastics • left Class III elastics ? • unilateral Mx stripping ?

D: Mandibular midline deviation • check CR ? • bite plate with ramp ? • Class III left elastics ? + • cross bite elastics • unilateral Mdb stripping ?

Fig VIII.21: Elastics use and possibilities of correction. Check: - Fronto facial / profile esthetics - Frontal cephalometric analysis - CR occlusal relationships. 118


MANDIBULAR SHIFT and MIDLINE DEVIATION 1) Choose Mandibular Reposition with: ● functional appliance ● bite plate ramp ● surgery ? Then reconsider midline deviation and choose clinical options:

A: 2) Use Class III elastic on opposite side to the Mdb shift ? 3) Unilateral Mdb maximum anchorage on opposite side Mdb shift. 4) Unilateral Mdb stripping opposite to Mdb shift ? 5) Combination ?

B: 2) Mx extraction on opposite to midline deviation, and also 3) Maxi anchorage. 4) Class I elastic on opposite side to midline deviation. 5) Unilateral Mx stripping on opposite midline deviation.

C: 2) Mx extraction on opposite midline deviation. 3) Unilateral arch advance on side of midline deviation. 4) Class III elastic on opposite to Mdb shift (anterior diagonal + vertical). 5) Cross stripping ?

D: 2) Mx and Mdb unilateral extractions on side of Mdb shift. 3) Class II elastics on Mdb deviation side. 4) Unilateral stripping on opposite midline deviation. 119


MANDIBULAR SHIFT and MIDLINE DEVIATION 1) Choose Mandibular Reposition with: ● functional appliance ● bite plate ramp ● surgery ?

Then reconsider midline deviation and choose clinical options:

E: 2) Mdb extraction on Mdb side shift ? 3) Class III elastic on opposite side of Mdb shift. 4) Unilateral Mdb arch maximum anchorage. 5) Stripping and/or combination of above.

F: 2) Unilateral Mx and Mdb extraction on side of Mdle shift. 3) Class II elastic ( anterior or diagonal ) on Mdb side shift. 4) Unilateral Mx maximum anchorage opposite to Mx midline deviation. 5) Stripping and/or combination.

G: 2) Cross extractions 14 / 34. 3) Cross maximum anchorage. 4) Anterior diagonal elastic and/or Class II elastic on opposite side of Mdb shift. 5) Stripping and/or combination.

H: 2) Mx unilateral extraction on opposite side of Mdb shift. 3) Latero vertical and/or Class I elastics. 4) Unilateral stripping on opposite side Mdb shift. 5) Stripping 120


Fig VIII.22: Midline shift correction

121

CHAPTER VIII: Particular Intermaxillary Elastics A: Inclined divergent: • segmentation of archwires • triangular anterior elastics

B: Unilateral divergent open bite: • segmentation of archwires • unilateral M and W elastics

C: Maxillary anterior open bite: • U shape elastics • segmentation of archwires • anterior squeeze elastics • rectangular anterior elastic

Fig VIII.23:

CLASSIFICATION OF VERTICAL ASYMMETRY OF ANTERIOR OCCLUSAL PLANE 122


D: Inclined convergent: • bite plate • segmentation of archwires • unilateral triangular elastics • Class II / III elastics

E: Unilateral convergent: • unilateral bite plate • unilateral rectangular elastics

F: Deep anterior overbite: • anterior bite plate • utility intrusion archwires • segmentation • Class II elastics and/or • postero rectangular elastics

Fig VIII.23:

Elastics use and possibilities of correction Check:: - Fronto facial / profile esthetics - Frontal cephalometric analysis - CR occlusal relationships.

123


A: Anterior and left closing Class II elastics with unilateral left segmented maxillary archwire. Objectives: to correct left Class II to close the bite and correct maxillary midline.

B: Triangular anterior elastic and anterior segmented maxillary archwire. Objectives: to close the bite and to close lower incisors spaces.

C: Oblique and left Class II elastics with maxillary segmented archwire. Objectives: to correct midline deviations and close the bite.

D: Triangular anterior elastic and segmented utility Class II in a left maxi anchorage. Objectives: to correct left Class II, to close the bite and correct maxillary midline.

Fig VIII. 24: Elastic use in canted anterior occlusal plane: 1 - check sagittal plane of reference 2 - determine midline deviation 3 - look at vertical dimension 4 - prefer maxillary archwire segmentation 5 - use elastics combination. 124


12 - ELASTICS IN CONDYLAR FRACTURES Sports and automobile accidents frequently involve condylar fractures.

In the growing patient, treatment for the fractured condylar, either unilateral or bilateral, is usually a conventional functional appliance.

In the adult case, elastics may be a part of an orthodontic treatment such as:

A / IN UNILATERAL CONDYLAR FRACTURE where the condylar neck is anteromedialy displaced with an opening deflexion on the affected side ( see Fig VIII. 25 ). The treatment should be: ● a unilateral bite plate on the controlateral fractured side, to help condylar distraction. ● segmented archwires on affected side with ● rectangular vertical elastics.

B / IN BILATERAL CONDYLAR FRACTURE the mandible is rapidly rotating posteriorly with an anterior open bite and limited mouth opening ( see Fig VIII. 26 ). The treatment should be: ● a bilateral posterior bite plate to help the condylar distraction for healing. ● anterior segmented archwires with ● anterior vertical elastics.

In any case, the elastics are worn for two to three months and progress can be checked with Xrays.

125


Fig VIII. 25: ELASTICS AND UNICONDYLAR FRACTURES ( see text ). ● a unilateral bite plate on controlateral fractured side, to help distraction. ● segmented archwires on affected side with ● rectangular vertical elastics. 126


Fig VIII. 26: ELASTICS AND BILATERAL CONDYLAR FRACTURES ( see text ). ● bilateral posterior bite plate to help the condylar distraction for healing. ● anterior segmented archwires with ● anterior vertical elastics. 127

CHAPITER IX

Elastics and ExtraOral Forces

CHAPTER IX: Elastics and ExtraOral Forces

The Twenty Commandments of E. O. F. 1 - The E. O. F.is a biologic orthopedic appliance 2 - Don’t use it with an occlusal 0.45 molar tube ( extrusion / tipping ) 3 - Use an expansion of the inner face bow 4 - Use the natural muscular effect of cheecks 5 - Control the molar rotation 6 - Expand maxillary arch to avoid buccal eruption of M2 7 - Keep away archwires when using E. O. F. 8 - Don’t use any maxillary bite plate with E. O. F. 9 - Ask for 15 hours daily wear 10 - Don’t use excessive forces 11 - Don’t limit the treatment to E. O. F. only 12 - Don’t use E. O. F. in maxillary incisor overbite 13 - Don’t use E. O. F. in every Class II. With Long Range Growth Forecast, you may choose to use: - extractions - activators - surgery 14 - Don’t stop the E. O. F. abruptly. 15 - Do overcorrect 16 - Time is needed to obtain growth correction 17 - Don’t use E. O. F. on a patient who is still thumbsucking ? 18 - Encourage patient motivation 19 - Don’t stop treatment after the orthopedic correction 20 - Don’t underestimate the simplicity of E. O. F.

128


Extra Oral Force Delivery ➩ Juvenile preventive phase: 350 g. ➩ Interceptive phase: 400 - 500 g. ➩ Adolescent corrective phase: 750 g. • in vertical excess tendencies: 1000 g. • in true vertical excess E. O. F. is not advisable.

The convexity reduction decreases with age; after 12 years the reduction in point A is about 1 mm only.

In high convexity cases with a protrusive maxilla, it’s advisable to begin E. O. F. before 8 years old.

129


Fig IX. 1: The same malocclusion can be seen in different facial types. A different extra oral pull must be appropriate to it. 130


Long

Medium

Short

High

Horizontal

Low

tion

rac wt

Lo

Fig IX. 2: Biomechanical diagram of LOW pull. ( From M. LANGLADE in “ Therapeutique Orthodontique ” 3rd edition. Maloine. PARIS 1986 ).

131


Long

Medium

Short

High

Low

Fig IX. 3: Biomechanical diagram of HORIZONTAL pull. ( From M. LANGLADE in “ Therapeutique Orthodontique ” 3rd edition. Maloine. PARIS 1986 ).

132


gh Hi c tra n tio

Long

Mediu

Short

High

Horiz.

Low

Fig IX. 4: Biomechanical diagram of HIGH pull. ( From M. LANGLADE in “ Therapeutique Orthodontique ” 3rd edition. Maloine. PARIS 1986 ).

133


Fig IX. 5: Recommended geometric configuration of power-arm unilateral face bow. The long arm should be placed on the favored side to receive the greater distal force and should terminate posteriorly near the first molar. It should extend laterally so that it clears the cheek by two inches when in an activated state. The short arm is placed on the other side and terminates near the canine tooth. It should extend laterally just enough to allow its tip to gently touch the soft tissue of the cheek, allowing the traction strap on that side to approximately parallel the midsagittal plane of the patient. ( From H. G. HERSHEY et. al. A. J. O. Vol 79 N° 3 page 230-249. 1981 ).

134


DIFFERENTIAL FORCE DELIVERY SYSTEMS

FORCE SYSTEM

GENERAL RANGE OF FACIAL TYPE

TIME INCREMENTS IN HOURS

FORCE DELIVERED IN GRAMS

1 - Cervical headgear

Mesofacial through brachyfacial

12 - 14 Long term

400 +

2 - Cervical headgear and 2 X 4 lower

Mesofacial through brachyfacial

12 - 14 Long term

400 +

3 - Combination headgear

Mesofacial through dolichofacial

12 - 14 Long term

1000 +

4 - Combination and 2 X 4 upper

Mesofacial through dolichofacial

20 + Short term

1000 +

GENERALIZED RESPONSE

Open facial axis Maxillary response Upright lower molars Expansion Hold or close facial axis Maxillary response Mandibular setback Expansion Hold facial axis Maxillary response No mandibular response Expansion Hold facial axis Maxillary response No mandibular response Hold arch form

From R.M. RICKETTS et. al. Bioprogressive Therapy. Book 1. R.M. 1979.

Elastics Racks Our aluminum anodized elastics rack is durable, light weight, and has holes for mounting on a wall. Holds four boxes of GAC elastics. Aluminum Elastics Rack

135

97-300-30


THE CLASS I ELASTIC HEADGEAR This is an appliance for upper incisor protrusion correction. This headgear has an inner face bow with two welded hooks distal to the canine area, opened backward for placing a Class I elastic from the right to the left hook to push backward the maxillary incisors having protrusion with spaces to close ( see Fig IX. 6 ). In an incisors diastema condition, it is indicated to using this appliance, which allows to push back and to close spaces ( see Fig IX. 7 ). This appliance is able to correct a minor clinical problem of Class II canine relationship without bonding the full arch, using only two molars bands.

Fig IX. 6: Class I elastic Headgear ( see text ). 136


Fig IX. 7: Clinical example of a Class II malocclusion corrected with only a Class I headgear elastic. Correction of canine relationship and incisor protrusion had been obtained at the same time (see text ). 137


THE CLASS II ELASTIC HEADGEAR This headgear has an inner bow with two welded hooks at the distal point of the maxillary lateral incisors. Those hooks are opened forward in order to place Class II elastics coming from the mandibular molars ( see Fig VI. 32 and 33 ). This appliance has a backward effect on the maxillary arch and a forward effect on the mandibular arch. Usely, the Class II elastic headgear is worn at home during homework and sleeping hours. Class II elastics are reinforcing the headgear effect on the maxilla and at the same time protracting the mandible.

THE CLASS III ELASTIC HEADGEAR This is a very useful appliance in cases needing simultaneously maximum anchorage in the maxilla and in the mandible. This headgear has an inner bow with a welded hook, opened posteriorly, mesial to the molar bayonet, allowing to place a Class III elastic ( see Fig IX. 8 and 9 ). This welded hook avoids placing the elastic behind the upper molar, and abstaining from an extrusion and a forward movement of the maxilla molar, as it is usually noticed with the regular Class III elastic wearing. The elastics are worn only when the headgear is worn. The Class III elastic headgear is very effective in: • Non extraction biprotrusion where bite and space closure is obtained with a maximum anchorage system using closing Class III elastic headgear. • Biprotrusion with extraction where the closure of the bite must be done without moving forward the maxillary molar. • Bimaxillary maximum anchorage in cases treated with extractions of the first premolars on both arches.

138


Fig IX. 8: Example of a Class III elastic headgear. Notice the welded hook mesial to the upper molar, on which the closing Class III elastic is placed ( see text ).

Fig IX. 9: Typical Class III elastic headgear. The Class III elastic force has no influence on posterior occlusal plane ( see text ).

139


THE WHISKERS HEADGEAR This arch was born from problems with the patient needing help placing elastics on STEINER’s arch bow or the SHUDY’s J hook. M. LANGLADE 33 proposed in 1973 the Whiskers headgear which is an extra oral bow in .045 round wire with two hooks coming under the maxillary archwire, between the central and the lateral incisors ( see Fig IX.10 to 12). This appliance may be used with 100 to 150 g. elastic force placed on helmet. Indications for the Whiskers head gear: • palatal root torque • upper incisors intrusion ( gummy smile ) • anterior occlusal plane rising upwards.

Fig IX.10: LANGLADE’s whiskers headgear. 140


Fig IX.11

The Whiskers headgear is useful for gummy smile correction.

Fig IX.12

141


POSTERO ANTERIOR ELASTICS The purpose of this kind of elastic is to bring forward the maxilla or the mandible. If the posterior support is always the first or the second molar, at the anterior level the support may be variable upon: 1 - the PHILIPPE’s circummandibular arch 26. 2 - the Facial Mask: • of DELAIRE - VERDON 62 • of H. PETIT • of D. GRUMMONS 29 • of R. NANDA 51. 3 - the J. HICKHAM’s Chin Cup 53. 4 - the M. LANGLADE’s Reciprocical Mini Chin Cup 35. 5 - Orthopedic Class III Chin Cup As we are going to see, some of those appliances have an excessive extrusion component that limits their clinical use.

1 - THE PHILIPPE’s CIRCUMMANDIBULAR ARCH It’s a .045 round wire thru the upper first molar which comes down in the lower buccal part all around the mandibular arch; two welded hooks are at the canine level, opened anteriorly for postero anterior elastics from the first or second lower molar ( see Fig VI.8 ). Unfortunately, when the patient opens the mouth, the Class I postero anterior elastic becomes a Class II elastic force with a high clockwise movement of the maxillary molar. It seems that this circummandibular arch should be recommended rather for retention of the retruded lower incisor patients, especially those who have a strong mentalis muscle. Night wearing seems better for adolescents and adult patients.

2 - THE FACIAL MASK Proposed in 1904 by Victor Hugo JACKSON with metallic lamella framework for protracting the maxilla, then made fashionable by J. DELAIRE, the facial mask is a precious and useful auxilary; but its indication is very limited. Too many orthodontists, faced with an anterior cross bite, quickly choose the facial mask use, thinking “ If it’s not good, it would not be bad for the profile concavity ”. 142

CHAPTER IX: Elastics and ExtraOral Forces The action of the facial mask which supplies a vertical counter clockwise rotation of the upper molar and palatal plane, what ever, high, horizontale, is known as the postero anterior pull.

Any sagittal movement goes with a vertical one, from which it’s impossible to escape

Disposition: This appliance is used to protract forward the retruded maxilla from: ➩ a welded buccal hook on a labio lingual wire cemented on the first premolars and first molars. ➩ the distal maxillary archwire. The advised force: According to different clinicians, heavy elastics can range from 1000 to 2000 g. Whatever the protraction force is, it should be: • parallel to the occlusal plane • 20° upward as DELAIRE and VERDON suggested, or • 20° downward as T. ITOH and S. J. CHACONAS 49 et. al. proposed. The resulting effect ( see Fig IX.13 to15 ) is an extrusion of the posterior palatal plane, a counter clockwise rotation of the occlusal plane, and a backward mandibular rotation. The effect: The facial mask effect is accompanied by: ➩ at the maxillary level: • a limited advancement of point A from 1 to 3 mm maximum, with a downward descent • a downward and forward movement of posterior palatal spine ( see Fig IX.15 ). For every forward millimeter of the point A, the posterior palatal plane goes downward 4 mm. • an upper molar extrusion of 5 mm for 1 mm of point A advancement. ➩ at the mandibular level with a postero anterior traction with a chin support it gives: • a posterior condylar compression more or less tolerated which creates an alleviation attempt by the digastric muscle with • a posterior rotation of the mandible • an aggravation of prognathic growth tendencies of the mandible in the growing patient. 143

CHAPTER IX: Elastics and ExtraOral Forces ➩ at the dental level: • a downward movement of the antero superior occlusal plane • an opening of the bite with an aggravation of the anterior incisal open bite and, sometimes, a tongue interposition as concluded the P. H. BUSCHANG et. al. studies. The use: The facial mask use shows that the more the point A goes forward, the more the anterior open bite increases. This alleviation tongue interposition reflex phenomenon is a response of the muscular chains to the posterior condylar compression. The TMJ by its numerous receptors is the regulation mechanism of the mandibular growth. By those facts, the facial mask use is much more limited than some authors had declared.

Instead of a choice in uncertain future, the orthodontist must use a RICKETTS’s Long Range Growth Forecast “ to begin with the end in mind ”. If you have a 7 year old patient with anterior cross bite, how can you make a decision at present time, if you ignore the final growth pattern of this patient ? Are you going to treat him immediately with a facial mask ? By orthopedics or with Class III elastics ? And run for a useless jump of the bite during many years to finally use surgery to treat him ?

In orthodontics, profits and winnings, as losses and relapses, are not given by the diagnosis only, but also by the prognosis. After your decision, you may suffer the consequences of your treatment, if you have no image of the final growth pattern ( see Table IX. 1 ). In using the long range growth forecast, you can predict: • the convexity • the mandibular corpus length • the mandible in the face • the esthetic profile with the three prognosis key factors: 1 - Long Range Growth Forecast 2 - anterior overbite 3 - collapsed lower facial height. You may use dental compensation or dental camouflage in some Class III cases, as D. WOODSIDE 59 or P. TURLEY 60 had shown ( see Table VII. 1 ). 144


Fig IX. 13: The facial mask use has a triple chain reaction: A - a lowering down of posterior palatal plane with a DOWNWARD and forward maxillary dental arch advancement. B - a posterior condylar loading which unlatch by reflex track. C - a posterior mandibular rotation allowing a sagittal increase of prognathic growth. Please remember that it is the vertical sense in TMJ that gives opportunity to the mandible to grow SAGITTALLY. 145


Fig IX. 14: According to R. M. RICKETTS 2, the maxillary growth is much more vertical posterior than anterior. This natural phenomenon must be taken into account in the facial mask use.

Fig IX. 15: Any kind of facial mask pull always involves a downward movement of the posterior palatal plane, increasing the vertical sense with consequences on mandibular overgrowth. 146

CHAPTER IX: Elastics and ExtraOral Forces SKELETAL CLASS I →→→

SKELETAL CLASS I → Pseudo Class III →

SKELETAL CLASS III → True Class III →

→→→

1SD 2SD 3SD 4SD DENTAL

Functional shift

CLASS III

dental

skeletal

Borderline

Elastics correction

Post mandible rotation

Extractions

Surgery

USE LONG RANGE GROWTH FORECAST Table IX. 1

“ The face mask produces orthodontic instead of orthopedic effect in most of the cases. Dental and skeletal relapse will happen due to continued mandibular growth ”. JONG HIN 58 et. al. 1993.

In deep overbite Class III cross bite: • Use anterior bite 45° inclined plate, with Class III elastics. • Bond maxillary incisors upside down to advance point A. • Procline maxillary incisors ( use M loops ). • Retrocline mandibular incisors ➩ close diastema ➩ use stripping of distal 33T43 ➩ extractions of 34T44 ? ? ( surgery ) • Extrude posterior maxillary teeth.

In Class III, the deeper the overbite, the better the prognosis.

147

CHAPTER IX: Elastics and ExtraOral Forces ● H. PETIT’s Face Mask This appliance is a little modification of DELAIRE - VERDON facial mask, with an apparent simplified wire frame work. ● D. GRUMMONS’s Face Mask 29 This is a modified face mask having a support from the forehead and cheeks instead of the chin, allowing the maxilla or the mandible arch or both to be brought forward. The author recommends a 12 hours wearing with 400 g. intra oral elastics on each side. Because this face mask has no support on the mandible, there is no impact on the T. M. J.

Fig IX.16: D. GRUMMONS 29 face mask. See text. ● NANDA’s Reverse Headgear 41 This appliance, according to his author, is recommended for maxilla retrusion. It goes posteriorly to the maxilla molar tube and is worn with the extra oral elastics placed on a HICKHAM 53 Chin Cup with postero anterior elastic forces in order to bring forward the maxilla ( see Fig IX.17 to 19 ). With a hook welded in front of the molar, an intra oral Class III elastic can be added to increase the maxilla protraction with: - intra oral forces = 150g. - extra oral forces = 500g. 148


Fig IX. 17: R. NANDA reverse headgear with a mesial molar hook for a Class III elastic to reinforce postero anterior maxilla protraction.

Fig IX. 18: R. NANDA reverse headgear worn in mouth with complementary Class III elastics on a lower Class III hooked bite plate. 149


Fig IX. 19: A

Fig IX. 19 B: The NANDA postero anterior headgear is worn with a HICKHAM Chin Cup to bring forward the maxilla.

150


Fig IX. 20: The HICKHAM chin cup for maxillary protraction.

Fig IX. 21: The HICKHAM chin cup for maxillary protraction is worn with postero anterior intra and extra oral elastics placed on a head cup. 151


3 - THE HICKHAM’S CHIN CUP 53 This chin cup has two vertical labial hooks for postero anterior elastics to protract the maxilla or the dental mandibular arch ( see Fig IX.20 and 21 ) Unfortunately, this appliance must be worn with a headgear that is difficult to keep on the head, even during sleeping hours.

4 - THE LANGLADE’S RECIPROCICAL MINI CHIN CUP 35 This new appliance was invented by Dr M. LANGLADE in 1978 for the treatment of dental Class II malocclusions. This appliance consists of two parts: • a reciprocal maxillary arch • a mini chin cup ( see Fig IX.22 to 24 ) ● THE RECIPROCAL MAXILLARY ARCH Similar to an inner face bow, it is an .045 round wire inserted into maxillary molar tubes. A vertical step goes under the upper lip, and two welded anterior hooks are used to attach intermaxillary Class II elastics. The arch can be worn 24 hours a day, and because it has a lip bumper and headgear effect, along with Class II elastics, it can replace headgear during school hours and sometimes altogether. ● THE MINI CHIN CUP For a more severe malocclusion, the mini chin cup can be inserted in a welded .045 tube to the buccal sections of the reciprocal maxillary arch. The chin cup has anterior hooks at the level of the labial commissure for attachment of postero anterior elastics from the mandibular molars. It should be worn during homework and sleeping hours to increase the mandibular protraction effect of the elastic force. This mini chin cup is highly recommended for: • Class II dental relationships in Class I skeletal patterns ( even with no growth potential) • mandibular dental retrusion • tipped back mandibular canines with or without mesial spacing • borderline surgery cases • microdontia with deep bite and spacing • missing mandibular teeth that may cause a deepening of the bite. When spaces must be closed in those two last indications, to correct the Class II dental relationship, some contradictory biomechanical movements come into play, with any technique without a force coming from outside of the mouth. 152


Fig IX. 22: The reciprocal mini chin cup with: 1 - a reciprocal maxillary arch worn full time with Class II elastics 2 - a mini chin cup, worn at home and during sleeping hours with postero anterior elastics. 153

CHAPTER IX: Elastics and ExtraOral Forces This appliance is not cumbersome and may help to bring forward the retruded mandibular arch and open the bite despite the spaces closing. The reciprocal mini chin cup advantages are: • appliance is prefabricated • quickly adjusted ( only 5 minutes ) • does not require special bands • no lab assistance needed • easily inserted and removed • well tolerated by children and adults • invisible, not cumbersome • easily worn 24 hours a day • reinforces Class II elastics effects • may avoid headgear use. Actions of this appliance: • block / move back upper molar • control palatal plane • advance lower incisors during space closing • advance lower arch even in non extraction cases ( reciprocal effect ) • appliance of choice for rough cases with missing teeth, agenesia, or anodontia in mandibular arch • supplemental chance for conservative treatment plan in borderline extraction/surgical cases.

This appliance is most effective for its reciprocal effect allowing use two, three, or even four intermaxillary Class II elastics. Usually the reciprocal mini chin cup is worn during a short time ( from two to five months ), even in adults cases. 154


Fig IX. 23: The LANGLADE’s prefabricated maxillary reciprocal arch which is worn 24 hours a day with Class II elastics using a bumper effect. See text.

Fig IX. 24: The LANGLADE’s prefabricated reciprocal mini chin cup which goes in the lateral tubes of the maxillary reciprocal arch which can be used with two to three Class II elastics and a postero anterior Class I elastic. This appliance is very effective and easily worn by adults. 155


Fig IX.25: Clinical example of dental Class II malocclusion with a retruded mandibular arch corrected in three months with a Reciprocal Mini Chin Cup. Notice the sagittal and vertical overcorrection ( before and after ).

156


5 - ORTHOPEDIC CLASS III CHIN CUP This appliance provides a retruding extra oral force used to posteriorly rotate the mandible. Indications: It first requires a long range growth forecast to diagnose the risky true prognathic case, in order to determine treatment effectiveness (see Table IX.1 ). Use: This appliance can be used: • for functional pseudo Class III • for moderate Class III skeletal borderline cases • in primary or deciduous dentition only • with CR Æ near edge to edge incisor relationship • in very early age 2.5 - 4 years • with short vertical facial height • with normal or protrusive lower incisors • with or without an inclined bite plane • with or without Class III intra oral elastics • when the extra oral force used is between 120 to 300 g., 24 hours a day during 6 to 8 months according to W. DOYLE 61. P. D. WENDELL, R. NANDA 56 et. al. found a reduced mandibular length by 60 to 68 % advocating the chin cup as a viable mode of three years treatment for younger moderate prognathic patients. Effects: The wearing effects of orthopedic Class III chin cup are: • backward and downward mandibular rotation • increased VDO • backward tilting of lower incisors • clockwise maxilla rotation • decreased gonial angle • “ restricted ” vertical condylar growth According to L. GRABER 47, who treated 30 Class III malocclusions in patients between 5 to 8 years during a three year period, his study provided strong support for the use of orthopedic force mini chin cup appliance in the clinical management of young patients with moderate skeletal mandibular prognathism.

The deeper the overbite, the better the prognosis in Class III malocclusions.

157


Fig IX.26 : The two piece corrector from G. EGANHOUSE 57 is constructed with a sliding guide and worn with closing Class III elastics and Chin Cup. From J. C. O. Vol. XXXI. N° 4. pages 246 - 250. 1997.

158

CHAPITER X

Rationale for Elastics Prescription

CHAPTER X: Rationale for Elastics Prescrition Even with the knowledge of all elastic possibilities, it is sometimes difficult for the clinician to decide on the best elastic treatment.

Separate the different clinical objectives: - take notice of primary objective - accept or refuse, for a while, the secondary objectives.

The primary objective: It may be: • to open the bite or, • to close the bite. The vertical dimension of skeletal pattern is the main factor to consider clinically. Remember that all intermaxillary elastics have a tendency to increase the vertical dimension.

The secondary objectives: They may be numerous choices for reaching selective secondary objectives. For instance, a Class II molar relationship can exist with an edge to edge that could be corrected by placing the intermaxillary elastic buccally or palatally according to the transverse problem.

159

CHAPTER X: Rationale for Elastics Prescrition

BEFORE USING INTRA ORAL ELASTICS 1 - Consider the vertical dimension first: • How is the skeletal pattern ? Normal ? Open bite tendancy ? True open bite ? Deep bite tendancy ? Or true deep bite tendancy ? • What is the dental problem ? = Do we have to close the bite ? = Do we have to open the bite ? • What kind of biomechanics are need to reach our goals ? = continuous archwires ? = segmented archwires ? • Are we allowed to use intermaxillary elastics forces ? Or do we have to use Class I or closing elastic forces ?

Refer to the skeletal pattern and to the Long Range Growth Forecast. Look at the occlusal bite. If you have an edge to edge incisor relationship your priority will be to close the bite absolutely; so in that case you must use closing elastics and/or eventually extractions. 2 - Observe the transversal sense afterwards: Look at the centric occlusion: • Is it a normal occlusion relationship ? • How are the median lines ? Is there a midline shift ? Which one must be corrected ? • Do you have a cross bite ? If yes, what is the degree of the cross bite 1, 2, or degree 3 ? • Do you need an expansion on one side ? • Do you need a contraction on one side ? • Do you need cross bite elastics ? Closing elastics ? • Do you need a bite plate to jump the bite ? For example, a lingual crossbite relationship of a maxillary canine may be corrected in placing on the Class II elastic palatally to correct in the same time the transversal and sagittal sense. A midline shift clinical case can suggest increasing the Class II elastic force on one side by: ➩ changing three times the elastic on one side and only one time per day the other side or, ➩ using a closing elastic force on one side and a regular one on the other side or, ➩ using a heavy elastic on one side and a lighter on the other.

3 - Correct sagittal relationship at last: In good order: 1 - molar relationship 2 - canine relationship 3 - incisor relationship. 160


HOW TO PRESCRIBE ELASTICS A: Observe the malocclusion ( see next page ). B: Write down the occlusal chart. C: Lay down the problem ! Come up with objectives to reach: use arrows - Consider the vertical sense first: Observe the open bite tendency, more important on the left side of the patient’s mouth, and the edge to edge incisors relationship. This report means that we will probably need closing elastics in order to close the bite while correcting sagittal problems. - Note the midline shift of the mandible on the left side. - Notice the half cusp Class II canine relationship on the left side and the Class III canine and molar relationship on the right side.

D: Draw the needed biomechanic archwires: 1 - Determine the needed anchorage:

Right A N C H O

R A G E

Maxilla yes no Loose yes no

yes no Mini yes no

yes no Mean yes no

Right

yes no Maxi yes no

yes no Maxi yes no

Left yes no Mean yes no

yes no Mini yes no

Mandible

yes no Loose yes no

A N C H O

R A G E

Left

2 - Archwire with friction + Extra Oral forces: ❏ yes ❑ no

❑ yes ❑ no

3 - Frictionless segmented archwires: ❑ yes

❑ no

❑ asymmetric...

❑ mean

❑ minimum

4 - Needed cooperation: ❑ maximum

In using arrows on the chart and after determining the needed anchorage on each side of the maxilla, the archwires may be chosen with the elastics forces which must be used to reach clinical goals. 161

CHAPTER X: Rationale for Elastics Prescrition A: Observe the malocclusion:

B: Write down the occlusal chart:

C: Lay down the problem ! Come up with the objectives to reach. Use arrows:

D: Draw the needed biomechanic archwires:

E: Draw elastic forces necessary to reach clinical goal:

162


CLINICAL EXAMPLE A - Observe this dysfunctional patient with a painful left TMJ ( Fig X. 1A ): - on right side she has a Class II lingual degree 2 cross bite and a Class II canine relationship. - a midline shift of 3 mm with an edge to edge incisor relationship. - on left side she has an open bite with a Class III canine relationship.

B - Let us write down the problem:

C - Solution ( Fig X. 1B ): • on right side, a triangular Class II cross bite elastic is going to correct the Class II and jump the bite. • anteriorly a closing Class III elastic is going to correct the midline shift, bring forward the left upper canine, and close the bite ! • on left side, we are keeping the posterior wedge so we don’t need any elastic. D - After 8 weeks ( Fig X. 1C ): The correct prescription of elastics corrected the majority of the malocclusion and the patient is pain free.

163


A

Fig X. 1

B

C

164


TEST your clinical SKILL

Answear the following QUIZ:

● QA -

● QB -

● QC -

● QD -

Remember to follow the rationale for elastic prescription: 1 - Observe the problem. 2 - Establish the clinical statement of each case. 3 - Write down the occlusal chart on a paper. 4 - Lay down the problem 5 - Draw the needed biomechanical archwires, and your elastic prescription. 6 - After your answer, go to the solution; you’ll be rewarded. 165


QUIZ A A - Observe Fig X. 2A, 2B, 2C ): John has three missing teeth: 12 - 22 and 23. - on right side notice the Class II canine relationship: we’ll have to open the lateral upper incisor space for a future implant. - anteriorly we have an open bite tendency edge to edge with a 2 mm maxillary midline shift. - on left side 22 and 23 are missing and we have a Class II edge to edge position of the first bicuspid, we would like to use for canine function. We also need to keep a space for the upper left incisor implant. B - Let us write down the problem:

C - Solution ( Fig X. 3A, 3B, 3C ): • on right side, we need a maximum Class II anchorage with two Class II elastics, one on the sectional arch, the other on the Class II utility arch. • to correct the midline shift, we can add an oblique elastic worn during night. • to bring forward the first left bicuspid, we need a Class III elastic which is also going to help the midline shift correction.

To increase elastics efficiency, we could also use closing elastics in this case... but we don’t need too much overbite with future implants.

166


A

Fig X. 2

B

C

QUIZ A 167


A

Fig X. 3

B

C

SOLUTION A 168


QUIZ B A - Observe ( Fig X. 4A, 4B, 4C ): Jerome’s clinical problem: - on right side we have a 2 mm Class II canine relationship. - anteriorly, the mandibular midline shift is off 2 mm on the left. - on left side we are in Class II canine and premolar relationship. B - Let us write down the problem:

We need a maximum anchorage on left side. C - Solution ( Fig X. 5A, 5B, 5C ): Evidently segmentation may use: • on right side, a sectional with a Class II elastic placed the canine worn only at night. • on left side, we’ll use a double Class II elastic worn 24 hours a day and changed three times.

Notice that one elastic is placed the utility Class II and the other on the left sectional, so we have a maximum anchorage on that side, which is also going to correct the mandibular midline !

169


A

Fig X. 4

B

C

QUIZ B 170


A

Fig X. 5

B

C

SOLUTION B 171


QUIZ C A - Observe ( Fig X. 6A, 6B, 6C ): Look at Sophie’s clinical problem: - on right side, we are in Class I molar and premolar, but with a mesial space in front of the first bicuspid, the right upper canine is in total Class II relationship. - anteriorly, there is a distal diastema to the upper right lateral incisor; a maxillary midline deviation of 4 mm. - on left side, we have a maxillary ectopic canine, however in Class I, because the upper left incisor is edge to edge with the lower left canine. B - Let us write down the problem:

We need a maximum anchorage on the right side. C - Solution ( Fig X. 7A, 7B, 7C ): • on right side, a sectionnal retractor with a Class II elastic and a Class II utility arch with again a Class II elastic, worn 24 hours a day and changed three times. • notice that the utility arch is cut behind the left central for placing on oblique elastic during sleeping hours. • on left side, a sectional retractor with a Class II elastic worn 24 hours a day and changed three times is going to bring downward and backward the left upper canine.

172


A

Fig X. 6

B

C

QUIZ C 173


A

Fig X. 7

B

C

SOLUTION C 174


QUIZ D A - Observe ( Fig X. 8A, 8B, 8C ): Sylvain’s clinical problem: - on right side, the upper right canine is missing, and we would like to use the first bicuspid for canine function. - anteriorly, we have a light open bite, with a light midline maxillary deviation of 2 mm and an upper incisor protrusion. - on left side, we have a Class II canine tendency.

B - Let us write down the problem:

C - Solution ( Fig X. 9A, 9B, 9C ): With straight wires we may use closing elastics; but with the frictionless segmented technique we can use: • on right side, an M loop to bring forward the first bicuspid; and a closing loop behind the upper lateral incisor to contract the incisor protrusion. • on left side, we can have a contraction utility arch wire to close the bite and to contract the incisor protrusion with the help of a double Class II elastic, the second one placed on the canine in order to correct the Class II tendency and close the distal diastema.

175


A

Fig X. 8

B

C

QUIZ D 176


A

Fig X. 9

B

C

SOLUTION D 177

CONCLUSION

1) In treating your patient, use a whole philosophy rather than a technique. 2) Evaluate all patient’s functions: respiration - swallowing - occlusion mastication - phonation - growth - ... - and personality. 3) Individualize the patient by a 4 D diagnosis including growth potential with the long range forecast: “ Begin with the END in mind ”. 4) Do an early diagnosis of the risky patient to postpone orthodontics until after surgery. 5) Set a long range visualization of treatment objectives (the short range VTO is not enough ! ). 6) Progressive banding or bonding makes scheduling easier and reduces stress on both the patient and the doctor. 7) Take advantage of pretorqued, preangulated brackets. The double buccal tubes on the lower molars and the triple buccal tubes on the upper molar provide archwire combinations and flexibility. 8) Unlock the malocclusion in a progressive sequence and establish more normal function and growth. 9) Use expansion first, before sagittal correction. 10) Choose FRICTIONLESS biomechanics with light forces:

Resistance to sliding mechanics such as friction and binding reduces the efficiency of a fixed appliance; resist the urge to increase the FORCE which will result in excessive pain and lost anchorage along with unwanted tooth movement.

Your patient tells you: “ Please use frictionless and light mechanics to increase efficiency and comfort ”.

178

11) Treat the overbite before the overjet. 12) Prefer Progressive Torque control throughtout the treatment. 13) Increase the ease and efficiency of tooth movement with segmented archwires. 14) Diminish anchorage problems with the use of utility archwires which also allow more cases to be treated on a non-extraction basis in recovering the Lee way. 15) Use elastics forces carefully to get a mobile force without threatening anchorage. 16) In the mixed dentition malocclusion, to get early canine function, use provocation of sequences of teeth eruption ( E the first, D the second and C the last ). 17) Use the ideal patient arch form according to the facial type. 18) Recognize the benefit of the segmented technique to get intraoral adjustments and optimize elastic forces. 19) Overtreat the malocclusion. 20) Use selective retention devices to maintain treatment results until the patient reaches maturity.

179

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The BEST COOK BOOK on ELASTICS more than 100 ways to use them!

“This book provides a comprehensive detailed description of orthodontic elastic usage. A compendium of possibilities heretofore never been collectively presented”. Prof. Ram S. NANDA - DDS - MS - PhD Chairman of departement of Orthodontics University of Oklahoma

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Optimization of Orthodontics Elastics. m. Manglade

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