Crowding

ORTHODONTICS Part 1: Epidemiology of Malocclusion Crowding -incisor crowding tends to increase in children as permt teeth erupt b/c permt incisors require more space than primary incisors -lower incisor crowding continues to worsen into adulthood -15% of adolescents and adults have severe crowding which requires extraction of permt teeth to create space Angle Classes Prevalence 1) Class I normal occlusion: 30% of population 2) Class I malocclusion: 50% of population (most common) 3) Class II malocclusion: 15% of population -presence of more than 5mm overjet -class II more common in whites of northern European descent 4) Class III malocclusion: 1% of population (least common) -presence of reverse overjet -more prevalent in Asian populations -have difficulty making “f” and “v” sounds Malocclusion -most often is hereditary -less frequently is caused by thumb-sucking/tongue-thrusting, or trauma “Sunday Bite” -occurs when ppl w/ class II profile try to adopt forward postural position of mandible to improve esthetics Mouth Breathing Characteristics 1) Skeletal open bite (“long face syndrome”) 2) Narrow face 3) Chronic tonsillitis 4) Narrow oropharyngeal space 5) Chronic rhinitis 6) Deviated nasal septum Symptoms of Thumb-Sucking Habit 1) Anterior open bite -most common result of thumb sucking 2) Crossbite 3) Constricted maxillary arch -caused by increased pressure from buccinators muscle during sucking 4) Proclined max. incisors 5) Retroclined mand. incisors 6) Class II malocclusion -from hand resting on chin which retards growth of mandible Part 2: Growth and Development Theories of Growth Control 1) Direct genetic control: bone is directly under control of genetics 2) Epigenetic growth control: cartilage is primary determinant of skeletal growth and thus indirectly controls growth of bone -cartilage grows and then is replaced by bone 3) Environmental growth control (Functional matrix theory): growth of bone is influenced by adjacent soft tissues through environmental changes in forces exerted on bones that stimulate their growth

Endochondral vs Intramembranous Bone Formation 1) Endochondral: bone formed first as cartilage, then transformed to bone -bones formed this way are less susceptible to environmental influences during growth and are under more genetic control -bones of cranial base (ethmoid, sphenoid, temporal) are endochondral 2) Intramembranous: bone formed by secretion of bone matrix directly within CT, w/o intermediate formation of cartilage -bones formed by this way are more influenced by environmental forces around them -flat bones of cranial vault, maxilla, and mandible formed intramembranously Growth of Cranial Vault -bones of cranial vault form intramembranously -at birth, bones are widely separated by loose CT at fontanelles -apposition of bone along edges of fontanelles eliminates open spaces but bones remain separated by cranial sutures -as brain growth occurs, cranial bones are pushed apart and apposition of new bone occurs at sutures -remodeling also occurs with new bone added on external surfaces and removed on internal surfaces Growth of Cranial Base -cranial base forms by endochondral method -ethmoid, sphenoid, and occipital bones formed initially in cartilage and later transformed into bone -as ossification occurs, 3 bands of cartilage remain which are impt growth centers called synchondroses 1) spheno-ethmoid synchondrosis 2) intersphenoid synchondrosis 3) spheno-occipital synchondrosis -each synchondrosis acts like a 2-sided epiphyseal plate w/ growing cartilage in middle and bands of maturing cartilage cells extending in both directions, which will be replaced by bone -eventually, these synchondroses become inactive -bones of cranial base not affected by brain growth Growth of Maxilla -maxilla grows intramembranously -growth occurs at sutures posterior and superior to maxilla at its connections to cranium and cranial base -maxilla migrates downward and forward away from cranial base and undergoes significant surface remodeling -remodeling includes resorption of bone anteriorly and apposition of bone inferiorly -much of anterior movement of maxilla is negated by anterior resorption, while downward migration is helped by inferior apposition of bone -addition of new bone can only occur at the surfaces and not interstitially -thus, increased space for eruption of posterior teeth occurs by addition of bone posteriorly at tuberosity as maxilla migrates downward and forward Growth of Mandible -growth of mandible is both endochondral and intramembranous -major site of growth is condylar cartilage -cartilage is transformed into bone at condyle as mandible grows downward and forward, away from cranial base -most growth of mandible occurs by new bone forming at condyle and by resorption of anterior part of ramus w/ apposition posteriorly

Embryonic Development of Mandible -mandible develops in the same area as cartilage of 1st pharyngeal arch (Meckel’s cartilage), but development of mand. itself proceeds lateral to Meckel’s cartilage and is entirely intramembranous in nature -Meckel’s cartilage disintegrates and its remnants are transformed into a portion of inner ear (malleus and incus) -condylar cartilage develops independently and is initially separated by a gap from body of mandible -it later fuses w/ developing mandibular ramus Mandibular Growth Rotation -as growth of condyle facilitates movement of mand. downward and forward, a gap is available btw maxilla and mand. in which the max. and mand. teeth erupt 1) Average closing rotation: condylar growth exceeds molar eruption and mand. rotates slightly closed over time (most common) -this helps make chin more prominent as child ages -allows posterior face height to increase more than anterior face height 2) Severe closing rotation: condylar growth greatly exceeds molar eruption and mand. rotates more substantially closed -leads to development of shorter face and deep anterior overbite 3) Opening rotation: condylar growth is less than molar eruption and mand. rotates open during growth -results in longer lower face and tendency for anterior open bite Cephalocaudal Growth Gradient -structures farther from the brain grow more and later in time -in fetus, head is 50% of body; -at birth it is 30%; -at adult, it is 12% of body -mand. is farther from brain than maxilla and thus grows more and later in time Scammon’s Growth Curves 1) Lymphoid tissues (tonsils, adenoids): grow quickly, reaching 2x adult size by age 10, then involute during puberty to reach adult size 2) Reproductive tissues: don’t grow much until puberty, and then rapidly increase to adult size corresponding to pubertal growth spurt 3) General body tissues (muscle, bone): grow rapidly after birth, then slow somewhat during childhood, then accelerate again at same time as reproductive tissues proliferate (puberty) 4) Neural tissues (brain, nervous system): continue to grow rapidly after birth until age 7 when they are already 100% adult size 5) Maxilla: located closer to brain so grows earlier and follows pattern close to neural tissues 6) Mandible: grows later than maxilla and exhibits growth that parallels general body tissues Growth Velocity Curve -growth in height is very rapid after birth but decelerates quickly to a lower, more constant level in childhood -around puberty, growth accelerated again, reaching a pubertal growth peak before slowing and stopping at maturity -predicting timing of this growth spurt may be impt for ortho txt Sex Differences -girls reach growth peak around 2 yrs earlier than boys -avg growth peak for girls in 12 yrs, boys is 14 yrs -there is considerable individual variation in this -generally, earlier the growth peak, the shorter the duration of growth spurt will be and less overall growth that will occur -girls will generally start growth sooner, grow for shorter amt of time, and grow less than boys

Predictors of Growth 1) Chronological age: not perfect predictor of when peak growth will occur 2) Dental age: even less reliable -children whose teeth erupt early don’t necessarily grow early 3) Skeletal age: physical growth correlates well a) hand-wrist radiograph is standard for assessing skeletal development -ulnar sesamoid and hamate bones used as landmarks for timing adolescent growth spurt b) evaluate vertebral bones from Ceph radiograph c) plot increases in body height over time d) successive Cephs can be superimposed to determine when growth spurt has started/ended 4) Sexual development: sexual development and growth in height are very well correlated -sex hormones have direct effect on endochondral ossification Directions of Growth in Jaws 1) Width: growth in width of jaws is completed before adolescent growth spurt begins 2) Length: growth in length of jaws continues through the growth spurt 3) Vertical: vertical growth continues longer than growth spurt Cleft Lip and Palate -is most common craniofacial defect -is 2nd only to clubfoot in all congenital deformities -cleft lip occurs when there is failure of fusion btw medial nasal (frontonasal) process and maxillary process -this fusion includes lip and alveolar ridge/primary palate -cleft palate occurs when palatal shelves fail to fuse -closure of secondary palate occurs 2 weeks after closure of primary palate -so, cleft lip occurs before cleft palate Part 3: Development of Occlusion Gum Pad Stage -begins at birth and goes until 6 months (ends w/ eruption of first incisor) -future position of teeth can be observed by elevations and grooves on alveolar ridge Primary Dentition Stage -starts w/ eruption of first tooth and lasts until about 6 yrs old when first permt. tooth erupts -primary max. anterior teeth are about 75% the size of permt successors -primary mand. anterior teeth are about 6 mm narrower mesiodistally than their successors -conditions: 1) Overbite: vertical overlap of mand. teeth by max. teeth -can be measured in mm but preferably done in percentages (overbite normally ranges 10-40%) 2) Open bite: lack of overbite where there is space btw max. and mand. teeth -not unusual in primary dentition due to habits (thumbsucking) 3) Overjet: horizontal distance btw max. and mand. teeth -normal variation from 0-4mm -habits can cause increased overjet 4) Spacing: primary dentition often has generalized spacing -especially noted in two locations called primate spaces a) btw lateral incisor and canine in max. b) btw canine and 1st primary molar in mand. 5) Crowding: uncommon to have crowding in primary dentition

Primary Molar Relationships 1) Flush terminal plane: distal aspect of 2nd primary max. and mand. molars are at same level -develops into class I (56%) or class II (44%) permt molar relationship 2) Mesial step: distal of mand. 2nd molar is mesial to distal of max. 2nd molar -develops into class I most often but can be class III depending on severity 3) Distal step: distal of mand. 2nd molar is distal to distal of max. 2nd molar -develops into class II occlusion -by age 5, 90% of children have flush terminal place or are 1+mm in mesial step -1st permt molar is guided along terminal plane during eruption, so the primary molar relationship will determine permt molar relationship Mixed Dentition Stage -starts around age 6 with eruption of first permt tooth -as each permt tooth erupts, it is expected its antimere (contralateral tooth) will erupt within 6 months -“ugly duckling stage”: as two max. central incisors erupt, they move facially and temporary diastema often present (present in 98% of 60 children) -when permt canines erupt, the centrals move mesial to close diastema -mand. incisors erupt lingual to primary incisors and then move facially -transient open bite may be present on partial eruption permt anteriors, but resolves -normal characteristics of mixed dentition: 1) molar and canine relationships are class I 2) leeway space present 3) well-aligned or slightly crowded incisors 4) tight proximal contacts Leeway Space -difference in mesiodistal size btw primary canine to primary 2nd molar and their permt replacements (permt canine to permt 2nd premolar) -leeway space larger in mand. arch (2.5-4mm per side) where max. arch is around 1.5-2.5 mm per side -leeway space can affect eventual permt molar relationship or may aid in resolution of crowding Permanent Dentition Stage -begins when last primary tooth is lost -max. teeth should overlap mand. teeth vertically and buccolingually -overbite is generally 10-20% -overjet should be 1-3mm -arches have two curvatures: 1) Curve of Spee: curvature in sagittal plane (Front – back) 2) Curve of Wilson: curvature in frontal plane (Left – right) -permt dentition relationships fairly stable once established -exception in 2nd-4th decades of life when tendency for anterior crowding to develop or worsen

Dimensional Changes in Dental Arches 1) Width a) Max. intercanine width: increases by about 6mm btw ages 3-13 and 1.7mm until age of 45 b) Max. intermolar width: increases 2.2mm btw 8-13 and decreases by 1mm by age of 45 -increase in max. arch due to alveolar bone growth being divergent c) Mand. intercanine width: increases 3.7mm from 3-13 and decreases by 1.2mm from 13-45 d) Mand. intermolar width: increases 1mm from 8-13 and decreases by 1mm from 13-45 2) Length -arch length measurement is at midline from a point midway btw central incisors to tangent touching distal surfaces of 2nd primary molars or mesial of 1st permt. molars a) Maxilla: small decrease in arch length w/ age b/c incisors become more upright b) Mandible: similar decrease in arch length due to uprighting of incisors and loss of leeway space 3) Circumference/Perimeter -measurement of amt of space available for dentition -measured from distal aspect of 2nd primary molar (mesial of 1st permt molar) on one side to distal aspect of 2nd primary molar (mesial of 1st permt molar) on other side a) Maxilla: increases very slightly over time b) Mandible: decreases significantly due to mesial shift of permt dentition to fill leeway space, interproximal wear, and lingual positioning of incisors Sequence of Eruption 1) Primary dentition -begin calcification btw 3-4 months in utero -mand. teeth start calcification before max. -eruption of first primary tooth occurs at about 6-7 months and continue to erupt until 2-3 yrs old -typical sequence: CI, LI, 1M, C, 2M 2) Permt dentition -permt teeth begin calcification shortly after birth -1st permt molar: calcification begins at 2 months -3rd molars calcify at 8-9 yrs old -max. sequence: 1M, CI, LI, 1PM, 2PM, C, 2M, 3M -mand sequence: 1M, CI, LI, C, 1PM, 2PM, 2M, 3M 3) Gender: females have eruption around 5 months earlier than males Eruption Patterns 1) Incisors: permt tooth buds lie lingual and apical to primary incisors 2) Canines: permt canine is more facially than primary but usually right in line 3) Permt teeth move occlusally and buccally during eruption 4) Maxillary arch is slightly longer (128mm) than mandibular arch (126mm) Ectopic Eruption -tooth erupts in wrong place -most likely to occur in max. 1st molars and mand. incisors -treated by placing brass wire btw primary 2nd molar and permt 1st molar -more common in maxilla and assoc. w/ skeletal class II pattern

Part 4: Ortho Diagnosis Angle Classification 1) Class I normal occlusion: MB cusp of max. 1M fits in buccal groove of mand. 1M and intra-arch relationships among teeth are correct -max. CI overlap mand. CI -max. canine lies btw mand. canine and 1st PM 2) Class I malocclusion: MB cusp of max. 1M fits in buccal groove of mand. 1M but intra-arch relationships among teeth are abnormal (incorrect line of occlusion) 3) Class II (distocclusion): MB cusp of max. 1M is anterior to buccal groove of mand. 1M -max. canine mesial to mand. canine a) Division 1: maxillary incisors flared/protruded (labioversion) b) Division 2: max. incisors upright/retruded (laterals flared/protruded) and deep overbite present 4) Class III (mesiocclusion): MB cusp of max. 1M posterior to buccal groove of mand. 1M -max. canine distal to mand. canine -pseudo-class III malocclusion: mand. incisors forward to max. incisors when in centric occlusion, but pt can bring mandible back w/o strain so mand. incisors touch max. incisors Signs of Incipient Malocclusion 1) Lack of interdental spacing in primary dentition 2) Crowding or permt incisors in mixed dentition 3) Premature loss of primary canines Crossbite -teeth are on wrong side of opposing dentition -types” a) skeletal: has smooth closure to centric occlusion b) functional: has deviation as pt closes -causes: hereditary, jaw-size discrepancy, oral habit (thumb-sucking, not tongue-thrusting), supernumerary teeth, or trauma Posterior Crossbite 1) Normal: max. lingual cusps fit into mand. central fossa 2) Crossbite (Lingual crossbite): max. buccal cusps fit in mand. central fossa -if bilateral, is called a “scissor bite” 3) Complete lingual crossbite: whole maxillary tooth lingual to mandibular tooth 4) Complete buccal crossbite: whole max. tooth buccal to mand. tooth Crossbite Treatment -crossbites treated in 1st stage of txt as transverse dimension is first to stop growing -posterior crossbites corrected w/ palatal expansion (rapid palatal expander) 1) expander activated 2x/day (0.25mm per turn) 2) after activation completed, expander remains in place for 3-6 months for bone to form -after expansion, diastema usually forms btw central incisors which closes spontaneously -nasal floor expansion also occurs Open Bite -should be diagnosed early b/c it is not self-correcting and worsens w/ time

Facial Proportions 1) Lip posture/competence: with teeth together and lips at rest, the lips should lightly touch or be slightly apart -a gap of more than 3-4mm indicates lip incompetence b/c of long lower face, protruding incisors, large overjet, or short lips 2) Incisors at rest (Lip-to-tooth): amt of upper incisor showing below upper lip -2-4mm is considered esthetically pleasing 3) Gingiva at smile: up to 1-2mm of gingiva showing on smiling is esthetically pleasing, w/ any more being excessive Profile Examination 1) Facial convexity a) Convex: indicates class II (retrognathic) b) Straight: indicates class I (orthognathic) c) Concave: indicates class III (prognathic) or midface deficiency 2) Lip prominence: evaluated by Rickett’s Esthetic Line (E-line) which extends from tip of nose to chin -lips should be slightly behind this line for esthetics -anterior-posterior position of incisors affects lip prominence a) Full: protrusive b) Average c) Flat: retrusive 3) Nasolabial angle: angle btw base of nose and upper lip -should be perpendicular or slightly obtuse Skeletal Relationships (Cephalometrics) 1) Cephalometric reference planes a) S-N plane: anterior cranial base b) Porion (Po)-Orbitale (Or): Frankfort horizontal plane -best horizontal orientation to assess lateral skull c) Gonion (Go)-Gnathion (Gn): mandibular plane -steep mand. plane yields long anterior facial height and anterior openbite -flat mand. plane yields short anterior facial height and deep bite 2) Cephalometric measures a) SNA: anterior-posterior position of maxilla -larger angle means max. is more anterior (prognathic max.) b) SNB: anterior-posterior position of mandible -larger angle means mand. is more anterior (prognathic mand.) c) ANB: anterior-posterior difference btw max. and mand. -2-4 degree ANB indicated class I skeletal occlusion -more positive angle indicates skeletal class II -more negative angle indicates skeletal class III 3) “Poor man’s ceph”: done by facial profile analysis Moyer’s Mixed Dentition Analysis -uses size of erupted mand. permt incisors to predict size of unerupted canines and premolars -max. incisors not used b/c they have too much variability in size Molar Uprighting -long-term loss of mand. 1st molar causes tipping, migration, and rotation of adjacent teeth into edentulous space -txt done by tipping 2nd molar distally and opening up space for pontic to replace missing tooth -should band 2nd molar to prevent shearing of brackets -timetable is 6-12 months -stabilization should last until lamina dura and PDL reorganize

-slow progress in adult pt most likely caused by occlusal interferences Impacted Canines -can be brought into arch through ortho traction after being surgically exposed -retained primary tooth should be extracted -during exposure, flaps should be reflected so tooth is pulled through keratinized tissue, not alveolar mucosa -adequate space in arch should be created before attempting to pull impacted canine into position Part 5: Treatment Planning Prioritizing the Problem List 1) Systemic disease/pathology -must be controlled before ortho txt can begin 2) Impacted teeth 3) Esthetic or occlusal problems a) Interarch relationships take priority over intra-arch relationships 4) Habits 5) Growth potential/tendencies Part 6: Biology of Tooth Movement Fundamental Principles -ortho movement results from application of a force system to the tooth and the transduction of that mechanical signal into a biological signal and response -a force system is applied at the crown of a tooth and the mechanical signal is transmitted to the supporting structures of the tooth (bone, PDL) -for movement to occur, force must not necessarily be continuous, but must be applied for minimally acceptable period of time to elicit biological response needed -amt of force (heavy or light) determines the biological pathway of tooth movement and formation or lack of formation of a hyalinized zone w/ undermining resorption -the PDL, a well-organized CT, remodels significantly during ortho movement Pressure vs Tension Sides of Tooth Movement 1) Pressure/Compression side: side toward which tooth is moving against -where bone resorption takes place as result of osteoclastic activity -resorption lacunae created is called Howship lacunae 2) Tension side: side opposite that which the tooth is moving against -apposition of bone occurs on this side -difft. types of tooth movement are characterized by difft. patterns of stress distribution in PDL and corresponding areas of bone resorption and apposition a) Intrusion: when tooth is intruded, area of compression of PDL is concentrated at apex of tooth b) Tipping: crown and apex move in opposite directions, creating two areas of compression i) cervical area on side toward which tooth is tipping ii) apical region on side opposite which tooth is tipping -tension areas located on opposite sides where compression occurs -tipping best accomplished by use of finger springs c) Translational/bodily movement: one side of PDL experiences compression (side toward which tooth is moving) and other side experiences tension Biological Control of Ortho Tooth Movement -during tooth movement, tension and compression occur in PDL and its two interfaces: 1) with bone on alveolar side 2) with cementum on tooth side -when an ortho force is applied to a tooth, two scenarios can develop depending on if force is heavy or light

Heavy Force -use of heavy ortho forces does not make tooth movement more efficient and actually delays tooth movement by causing a lag period after initial movement of tooth within PDL 1) Initial period of tooth movement -bone bending and creation of piezoelectric signal occurs in less than 1 second -pizoelectric signal characterized by quick decay rate and production of equivalent signal of opposite direction when force is released -PDL then compressed and fluid is expressed from area of compression, resulting from instant movement of tooth within PDL in 1-2 seconds -as fluids expressed from PDL, pain is felt as result of pressure applied within 5 seconds -tooth is now compressed against bone surface and no further movement will occur until resorption takes place -resorption occurs within alveolar bone in marrow spaces and moves toward PDL area -appearance of osteoclastic cells in marrow spaces is first indicator of resorption -resorption can last a few weeks and no movement will occur until resorption is completed when heavy ortho forces are applied -compressed PDL undergoes significant tissue changes -on compression side of PDL, hyalinized zone starts to develop (PDL lost all organization and necrosis seen) -cells from surrounding bone marrow start to migrate into area from marrow spaces within days and resorption simultaneously starts within marrow spaces 2) Secondary period of tooth movement (after resorption) -hyalinized PDL is in process of healing -secondary movement occurs after a lag period during which resorption takes places Light Force -use of light force causes a smooth, continuous tooth movement without formation of significant hyalinized zone in PDL -teeth subjected to light forces start to move earlier and in more physiological way -initial rxn include partial compression of blood vessels and distortion of PDL -within minutes, blood flow altered, oxygen tension changes, and prostaglandins and cytokines released within PDL -metabolic changes start to appear in this area of PDL after a few hours of initial movement -PTH, calcitonin, fibroblast distortion, substance P, prostaglandins, and neurotransmitters -within a few hours, a signal transduction starts in PDL and c-AMP levels increase -cellular differentiation takes place in PDL and coupling btw osteoclast/osteoblasts activities results in frontal resorption of bone Adverse Effects of Ortho Forces 1) Mobility -forces cause bone and PDL to undergo remodeling and PDL is temporarily widened -moderate mobility occurs and resolves with completion of therapy as long as there is no active perio dx -if tooth is in traumatic occlusion or pt has parafxnal habits, mobility is significantly increased 2) Pain -heavy forces cause pain as soon as PDL is initially compressed -pain typically occurs within few hours if initiation of force and lasts for 2-4 days -pain after heavy forces is due to development of areas of ischemia or necrosis (hyalinization) in PDL (these areas will remodel and pain will decrease) -best way to minimize pain is to minimize amt of force applied -pts should be given Tylenol rather than aspirin or ibuprofen 3) Tissue inflammation -usually results from poor hygiene, but can also be allergic rxn to latex or nickel

4) Pulpal effects -mild pulpitis or loss of vitality are rare -loss of vitality seen in teeth that had trauma, restorations, or moved with heavy forces over long distances -if apex is moved out of alveolar bone, blood supply may be severed and tooth loses vitality 5) Root resorption -as PDL experiences hyalinization, the adjacent cementum shows signs of resorption as well -heavy continuous forces have more potential for root resorption -resorptive defect can repair depending on size of defect created -risk factors for root resorption include: a) genetic factors (family hx of root resorption) b) heavier forces c) single rooted teeth d) trauma, bruxism, heavy mastication e) tooth already had signs of resorption prior to ortho f) movement of roots into cortical plate -teeth with substantial root resorption but intact marginal periodontium will not experience any more mobility than unresorbed teeth Part 7: Mechanical Principles in Tooth Movement Forces -forces are vectors and have direction and magnitude -forces can act anywhere along their line of action -the point of force application also influences tooth movement -a force acting thru the center of resistance of a tooth will cause pure translation of tooth in direction of force -pure translation is movement of all points on tooth in same direction in same amt (no rotation) -pure translation also called bodily movement -a force applied that is not at center of resistance causes rotation of tooth -for a free body floating in space, the center of resistance is the same as the center of mass or gravity -for a tooth, the location of center of resistance depends on size and shape of tooth and quality and level of supporting structures (bone, PDL) -in a healthy tooth, center of resistance presumed to be ½ the distance from alveolar crest to root apex -this is about 10mm from where ortho bracket would be placed on crown of tooth -center of resistance is more apical for tooth that is perio compromised Moments -moment is defined as a tendency to rotate and may refer to rotation, tipping, and torque in ortho -moment of force is equal to magnitude of force x distance of force from center of resistance (M=Fd) -3 orders of tooth movement: 1) First order: rotation 2) Second order: tipping 3) Third order: torque -if force is applied at any point other than center of resistance, a moment is created -the center of rotation is the mathematical point about which the tooth appears to have rotated after movement is complete -increasing magnitude of force or applying the same force farther from center of resistance will increase tendency for rotation Couples -a couple is two equal and opposite forces -a couple applied to a tooth produces pure rotation without translation -tooth rotates about its center of resistance regardless of point of application of couple

-magnitude of moment created by couple depends on magnitude of force x distance btw forces (M=Fd) -couples usually applied by engaging a wire in an edgewise bracket slot Types of Tooth Movement 1) Pure rotation -when a couple is applied to a tooth, it rotates around its center of resistance -center of rotation is at center of resistance 2) Tipping -when force is applied at bracket, center of resistance moves in direction of force and crown tips in direction of force (apex moves in opposite direction) -center of rotation is apical to center of resistance -this is easiest and fastest tooth movement, but least desirable 3) Crown Movement -force is applied at bracket and small couple is also applied to partially negate tipping of crown caused by the force -center of rotation is at root apex -is a slightly difficult tooth movement and occurs slowly 4) Pure Translation -force applied at bracket and larger couple also applied to exactly negate tipping of crown -center of rotation is so far apical to tooth that tooth translates w/o tipping -is difficult and slow type of tooth movement 5) Root Movement -force applied at bracket and an even larger couple is applied to more than negate tipping of crown so only root moves in direction of force -center of rotation is at crown of tooth -is most difficult and slowest tooth movement Static Equilibrium -all ortho appliances obey Newton’s 3rd law (for every action there is an equal and opposite rxn) -for each appliance, the sum of forces and sum of moments acting on it equal zero -it is impossible to design an appliance that defies this law of physics Anchorage -defined as resistance to movement -anchorage value of any tooth is equal to its root surface area 1) Reciprocal tooth movement: 2 equal anchorage value teeth are moved against each other and move same amt toward/away from each other 2) Reinforced anchorage: adding additional teeth to a unit to distribute force over greater area slows movement of anchor unit -ex. Headgear or interarch elastics 3) Stationary anchorage: teeth meant to be the anchor are activated to undergo difficult, slow movements which distribute forces over large areas of PDL 4) Cortical anchorage: anchor teeth roots are moved into cortical bone which resorbs more slowly than medullary bone 5) Implants for anchorage: implants, including palatal implants and miniscrews, can serve as absolute anchorage for holding or moving teeth -a stable implant will not move since it has no PDL

Part 8: Ortho Materials Wire Material Properties 1) Stress-strain relationship a) stress is the internal response of a wire to application of external forces b) strain is deformation or deflection of archwire as consequence of stress -defined as dimensional change divided by original dimension 2) Ideal wire characteristics 1) high strength 2) low stiffness 3) high working range 4) high formability 3) Wire properties -doubling length of wire decreases its strength by half, makes it 8x less stiff, and 4x the range -doubling diameter of wire increases strength by 8x, increases stiffness by 16x, and decreases range by half 4) Wire Selection a) Large ortho movements: wires w/ low load/deflection rate desirable b/c produce constant low forces b) Small ortho movements: wires w/ high load/deflection rate desirable -load/deflection rate is proportional to modulus of elasticity of material -stainless steel has highest modulus of elasticity (highest load/deflection rate) -nickel-titanium has lowest modulus of elasticity (lowest load/deflection rate); most flexible wire -load/deflection rate varies directly to 4th power of diameter of round wire and to 3rd power of width of rectangular wire -load/deflection rate varies inversely to 3rd power of length of wire -increasing interbracket distance decreases load/deflection rate Ortho Archwire Materials 1) Nickel-titanium: a) low modulus of elasticity b) extremely wide working range 2) Beta titanium (TMA/titanium-molybdenum alloy): a) intermediate modulus of elasticity (half of stainless steel and double Ni-Ti) b) excellent resilience c) wide working range d) high formability (bendable) e) high coefficient of friction (undesirable) 3) Stainless steel a) good mechanical properties b) excellent corrosion resistance c) low cost d) highest elastic modulus (stiffest) and lowest springback -composed of 18% chromium (gives corrosion resistance) and 8% nickel

Part 9: Ortho Appliances Straightwire (Preadjusted) System -original design: orientation of bracket slot is at right angles to long axis of tooth and thickness of bracket base was same for all types of teeth 1) 1st order bend: bend placed to position each tooth individually in buccal-lingual direction 2) 2nd order bend: bend placed to provide proper angulation in mesiodistal direction 3) 3rd order bend: bend to provide proper angulation in buccal-lingual direction -in new straightwire appliance system, this info is incorporated into brackets for each individual tooth which eliminates need for 1st, 2nd, 3rd order bends -these built-in attachments help achieve proper position of an individual tooth -built-in adjustment of each bracket system is called the bracket prescription -pre-adjusted appliances allow the following: 1) Rotational control 2) Horizontal control 3) Mesiodistal tip control- Bracket slot is angulated relative to the base of the bracket to provide the proper tipping movement of each tooth 4) Torque- Bracket slot is angulated labiolingually to provide the proper root and crown movt Brackets 1) Metal brackets: made of stainless steel -disadvantage is poor esthetics 2) Ceramic brackets: made of monocrystalline/polycrystalline ceramics -highly esthetics, but prone to fracture -also have high frictional resistance to sliding mechanics so can cause abrasion of opposing teeth 3) Self-ligating brackets: special locking mechanism incorporated into bracket system to engage archwire to eliminate need for ligatures -shorten txt time by reducing friction b/c wire is kept engaged in bracket slot Bands -all of teeth, including molars, can be bonded but it is still preferred to band the molars -prior to banding, separators are placed btw teeth to create space for band fitting and cementation -types of separators: 1) elastomeric 2) metal -glass ionomer cement used b/c fluoride-releasing properties Bonding -brackets attached to enamel using bonding resins 1) Direct bonding: direct attachment of ortho appliances to teeth using chemical or light-cured adhesives 2) Indirect bonding: brackets first positioned on study casts and then transferred to mouth using custom tray -more technique-sensitive but less chairside time needed and more precise -principles mechanism of attachment btw tooth and resin is mechanical interlocking of bonding agent and etched enamel -bonding procedure: 1) enamel prophylaxis to remove pellicle and enhance wettability of enamel for acid etching 2) enamel etching w/ 37% phosphoric acid 3) bracket positioning and secured w/ resin adhesive and light-cured When to Use Bands Over Brackets 1) Need to resist breakage (heavy mastication of cuspal interference 2) Teeth that need lingual and labial attachment 3) Teeth w/ short clinical crowns 4) Tooth surfaces incompatible w/ bonding (amelogenesis imperfect, stainless steel crown)

Major Components of Removable Appliances 1) Retentive component: Adams clasps, ball clasps, etc. 2) Framework/baseplate: made of acrylic and provides anchorage 3) Active/tooth-moving component: springs, jackscrews, elastics 4) Anchorage component: resists force of active component (acrylic baseplate, labial bow) Advantages/Disadvantages of Removable Appliances 1) Advantages a) improved hygiene b) increased pt comfort c) lab fabrication decreases chair time 2) Disadvantages a) dependent of pt compliance b) can’t achieve two-point tooth contact, so bodily movement impossible c) can only achieve tooth tipping Components of Fixed Appliances 1) Bands 2) Brackets 3) Arch wires 4) Auxiliaries (elastics/ligatures) Appliances to Modify Growth of Maxilla and Mandible -these appliances allow differential growth of jaws -in adolescence, mandible has more potential for growth than maxilla -growth modification is most successful in pre-adolescent children w/ good compliance and growth potential -appliances: 1) Headgear 2) Fxnal appliances (Herbst, activator, bionator, twin block) Headgear -uses: 1) modify growth of maxilla (restrain growth to allow mand. to catch up) 2) retract (distalize) or protract maxillary teeth 3) reinforce anchorage -usually used in skeletal class II growing pts -headgear should be worn at least 8 hrs per day (preferable 14 hrs) -for orthopedic/skeletal changes, force of 250-500 g/side recommended -for dental changes, force of 100-200 g/side recommended High-Pull Headgear -used in pts w/ class II malocclusion, increased VDO, minimal overbite, and gummy smiles -consists of high-pull headstrap and facebow which inserts into headgear tubes of max.1st molar attachments -objectives of appliance: restrict downward and anterior max. growth -places distal and intrusive (upward) force on maxilla Cervical-Pull Headgear -used to correct class II malocclusion w/ deep bite -consists of cervical neckstrap and facebow which inserts into tubes of max 1st molar attachments -objectives: 1) restrict anterior growth of maxilla 2) distalize and erupt maxillary molars -places distal and extrusive (downward) force on maxilla

J-Hook Headgear (Straight-Pull) -consists of high-pull headstrap that attaches to two hooks on anterior part of max. archwire -can be used to deliver posteriorly-directed (straight distal direction) forces to maxilla -used most often to retract canines and incisors Protraction Headgear (Reverse-Pull) -used in pts w/ class III malocclusion where there is max. deficiency -protracts maxilla -consists of 2 pads that rest of soft tissue in forehead and chin region which are connected by midline framework -anterior wire w/ hooks also connected to framework to accommodate downward and forward pull on maxilla via elastics -only headgear w/ an extraoral component Chin Cup/Cap -can be used to correct class III malocclusions from excessive mandibular growth -works by restraining mandibular condylar growth -consists of headstrap and cup that fits on chin -designed to deliver forces in superior and posterior direction to condyles via chin Functional Appliances -hold mandible in protrusive position and transmit forces created by stretch of muscles and soft tissues to dental and skeletal components to produce movement of teeth and modification of growth -designed to modify growth during mixed dentition -have dental AND Skeletal effect -used to correct class II malocclusion by restraining maxilla and displacing mandible while still allowing normal mandibular growth -appliances: A. Tooth-borne 1) Herbst 3) Bionator 2) Activator 4) Twin block B. Tissue-borne 1) Frankel appliance (only tissue-borne appliance) -alters mand. posture and contour of facial tissue -removable appliance Herbst Appliance -consists of piston and tube device that places mandible in forward position as pt closes mouth -holds mandible forward to induce growth -usually cemented or bonded to max. and mand. dental arches -max. and mand. frameworks splinted together via pin and tube device -shows increased tendency for mand. incisors to flare due to forces indirectly delivered to these teeth -can be fixed (most often) or removable Activator -consists of acrylic body that coverts part of palate and lingual aspect of mand. ridge and labial bow that fits anterior to max. incisors -on acrylic adjacent to max. posterior teeth, facets are cut to allow occlusal, distal, and buccal movement of teeth -on lingual aspect of mand. posterior teeth, facets allows occlusal and mesial movement -objectives: 1) activates mandibular growth to correct class II malocclusion 2) tip anterior teeth 3) control eruption of teeth vertically -is first removable fxnal appliance

Bionator -advances mand. to edge-to-edge position to stimulate mand. growth for correcting class II malocclusion -similar design to activator but less bulky and less impedent to speech -consists of lingual horseshoe-shaped acrylic w/ wire in palatal area -facets placed in acrylic to guide posterior teeth and hold mandible in forward position -labial bow presents anterior to maxillary incisors to eliminate pressure from buccal musculature -is a removable appliance Twin Block Appliance -has two-part design w/ interaction btw max. and mand. parts to control how much mand. is postured forward and how much max. and mand. are separated vertically -due to two-part design, it is easier to tolerate by pts -can be removable or cemented -postures mand. forward Pendulum Appliance -used to correct class II malocclusion by distalizing max. molar teeth -can also fxn to expand maxilla by incorporating expansion screw into appliance -if expanding screw used, it is called a Pendex appliance Appliances to Correct Crossbites -correct transverse discrepancies by expanding palate at midpalatal suture or by dental expansion 1) Rapid palatal expansion: occurs at rate of 0.5mm/day 2) Slow palatal expansion: occurs at rate of 1mm/week -devices: 1) Hyrax appliance 4) Quad-helix W-arch 2) Haas appliance 5) Transpalatal arch 3) Hawley w/ jackscrew Hyrax Appliance -most common type of rapid palatal expander for skeletal expansion -screw activated by at least 0.25mm/day for rapid expansion -max. arch width increased by opening midpalatal suture -expansion continued until lingual cusps of max. posteriors contact lingual inclines of buccal cusps of mand. posteriors -usually results in diastema formation btw max. central incisors, which closes on its own from pull of supracrestal fibers -retention needed for 3-6 months after active expansion completed w/ device remaining in place Haas Appliance -causes skeletal expansion of palate by use of acrylic pads placed in contact w/ palatal mucosa which allows forces from appliance to apply to underlying hard tissues to minimize dental tipping -disadvantages are inflammation of palate and difficult hygiene Hawley Appliance w/ Jackscrew -can be used for dental or skeletal expansion -used to correct mild crossbites Quad Helix/W-Arch -mostly used for dental expansion -should be used when only small amt of expansion needed Transpalatal Arch -used for dental expansion -extends from one max. 1st molar to contralateral 1st molar along contour of palate 2-3mm away from tissue

-can be used for expansion or restriction of palatal growth Appliances Used in Mixed Dentition 1) Nance appliance: used as space maintainer -has wire soldered to palatal aspect of max. 1st molars and has acrylic button that rests on palate 2) Lower lingual arch: can be used for space maintenance, anchorage, or expansion -has wire adapted to lingual surfaces of mand. incisors 3) Lip Bumper: used to control or increase mand. dental arch length, upright molars, and prevent lower lip from getting btw max. and mand. incisors -removes pressure of buccal musculature on teeth to allow lateral and anterior dentoalveolar development -problem is it does cause some distal tipping of mand. 1st molars Appliances Used to Control Vertical Dimension 1) Intrusion arch: archwire used for deepbite correction -causes extrusion at molars and intrusion at incisors 2) Extrusion arch: archwire used for openbite correction -causes intrusion at molars and extrusion of incisors Elastics -elastomeric bands used to produce forces for tooth movements 1) Class I elastics (intramaxillary): used for traction btw teeth in same arch 2) Class II elastics (intermaxillary): worn from tooth in anterior maxilla (canine) to tooth in posterior mandible (1st molar) -used to correct class II malocclusion, reduce overbite, and restrict max. anteriors 3) Class III elastics (intermaxillary): worn from tooth in posterior maxilla (1st molar) to tooth in anterior mandible (canine) -used to protract max. posterior teeth or improve overjet in edge-to-edge bites or anterior crossbite 4) Crossbite elastics: worn from palatal portion of max. teeth to buccal portion of mand. teeth -corrects crossbite -also causes extrusion of teeth so use caution in pts w/ open bite tendency 5) Anterior diagonal elastics: run from one side of max. teeth to other side of mand. teeth crossing midline -used to correct unaligned midlines

Part 10: Early Treatment Early Treatment -designed to alleviate or prevent moderate-severe ortho problems before permt dentition has fully erupted -often further comprehensive txt will be needed once full permt dentition has erupted Crowded and Irregular Teeth -caused by lack of adequate space for alignment or interferences w/ normal eruption 1) Space maintenance: used in cases where primary teeth have been lost and space is adequate -band and loop, distal shoe (before eruption of permt molar), lingual arch, Nance appliance (max.) 2) Space regaining: used for localized space loss less than 3mm -removable appliance w/ finger springs to tip teeth distally, headgear, lingual arch, lip bumper, or limited fixed appliance 3) Moderate crowding: less than 4mm a) arch expansion (controversial) b) extraction of primary canines (must be followed by lingual holding arch) c) flaring of incisors (by fixed or removable appliances) d) stripping interproximal enamel from anterior teeth 4) Severe crowding: more than 4mm a) Arch expansion (controversial) b) Serial extraction: timed extraction of primary and permt teeth; used for crowding over 10mm i) extract primary incisors ii) extract primary canines to allow permt incisors to erupt iii) extract primary 1st molars to allow permt 1st premolar to erupt iv) extraction of permt 1st premolars to allow permt canine to erupt and align -serial extraction used primarily for severe class I malocclusion -contraindicated in deep bites -increased overbite usually results as incisors tip lingually into excess space -comprehensive txt almost always needed after serial extraction to get teeth into ideal alignment Anterior Spacing 1) Max. midline diastema (less than 2mm) -usually is self-correcting but txt indicated if esthetics are concern or if central incisors are inhibiting eruption of lateral incisors and canines -large space may indicate supernumerary tooth (mesiodens) or missing lateral incisors 2) Large max. midline diastema (over 2mm) -not likely to close on its own -fixed ortho appliances may be needed -frenectomy after txt may be indicated if space re-opens or tissue bunches after txt 3) Generalized anterior spacing -postpone txt until there is an esthetic complaint -if spacing is accompanied by protrusion, a fixed ortho appliance usually required Eruption Problems 1) Over-retained primary teeth: remove primary tooth to encourage eruption of permt tooth 2) Ankylosed primary teeth: usually resorb on their own but can be removed if causing delay in permt tooth eruption -if permt successor is missing, ankylosed primary tooth should be removed to prevent vertical alveolar defect 3) Ectopic eruption: eruption of tooth into unexpected location or into adjacent tooth location a) Lateral incisors: may cause loss of adjacent primary canine or midline shift -usually indicates lack of sufficient space -treat by extracting primary canines or space regaining b) Max. 1st molars: may erupt into primary 2nd molar -treat by uprighting the erupting 1st molar

c) Max. canines: may lead to canine impaction or resorption of adjacent lateral incisor -extraction of primary canine indicated Missing Teeth 1) Mandibular 2nd premolars a) maintaining primary 2nd molars may be option b) some reduction in width of primary 2nd molar may be needed to attain good posterior interdigitation c) early extraction of primary 2nd molars (age 7-9) can be done to encourage closure of space 2) Maxillary lateral incisors a) substitute canine in lateral incisor position is option b) retaining space for later replacement is option c) best choice may depend on occlusion and esthetic demands Occlusal Relationship Problems 1) Posterior crossbite: usually due to mandibular shift a) equilibration to eliminate shift b) maxillary expansion w/ appliance should follow 2) Anterior crossbite: must differentiate skeletal from dental causes a) skeletal: due to deficient maxillary or excessive mandibular growth b) Dental: due to inadequate space -after creating space, teeth can be moved forward w/ ortho appliance w/ or w/o extracting adjacent primary teeth 3) Maxillary dental protrusion w/ spacing -may be due to skeletal discrepancy or thumbsucking -txt indicated if esthetics are concern or if danger of trauma -treat w/ removable appliance to upright teeth 4) Deep bite -biteplates can be used to open bite posteriorly and allow eruption of posterior teeth -intrusion can also be used 5) Oral habits and open bites -pacifiers and thumbsucking can cause increased overjet, decreased overbite, and POSTERIOR crossbite -as long as habit stops before eruption of permt incisors, most of negative changes resolve on their own -to stop habits, can use reminders (bandage on finger, habit appliance), reward system, etc. -tongue crib, bluegrass appliance can be used -if appliance must be used it should remain in place for 6 months after habit appears to have stopped -open bites that persist after habit ceases are likely due to skeletal cause and may need more txt -ortho and surgical txt Part 11: Growth Modifications Timing of Growth Modification -successful growth modification can occur only during periods of growth -early modification often requires retxt b/c unfavorable growth continues -waiting until permt dentition erupts may be too late for modifying growth, especially in girls Treatment of Mandibular Deficiency (Class II) -timing should be when mandible is actively growing (before peak adolescent growth) 1) Headgear: restrains max. growth forward to allow mandible to grow normally to catch up -puts posterior forces on max. 1st molars 2) Functional appliances: stimulate mandibular growth but long-term increase in size not seen -also puts a restraining force on max. growth -move mand. teeth anteriorly and max. teeth posteriorly

Treatment of Vertical Deficiency (Short Face) 1) Cervical headgear: has extrusive force on max. molar and it will erupt 2) Functional appliances: allow eruption of upper and lower posterior teeth Treatment of Vertical Excess (Long Face) 1) High-pull headgear: will inhibit eruption of max. posterior teeth 2) Functional appliance w/ bite blocks: blocks posterior eruption Treatment of Maxillary Deficiency 1) Expansion: treats transverse deficiency 2) Protraction or reverse-pull headgear: can correct anterior-posterior deficiency (class III) -anterior force placed on maxilla to encourage growth at maxillary sutures -ideal timing is early (8-9 yrs) to encourage maxillary growth since max. grows earlier than mandible Treatment of Mandibular Excess 1) Chin cup therapy: restrains mandibular growth -generally re-directs mand. growth downward than actually stopping it -contraindicated in long-faced pts Treatment of Facial Asymmetry -asymmetry may be due to congenital anomaly or early condylar fracture 1) Asymmetrical fxnal appliances may be useful 2) Early surgery may be indicated when asymmetry is progressively worsening Part 12: Comprehensive Treatment Comprehensive Treatment -involves complete fixed appliances once all permt teeth have erupted Extraction vs Nonextraction Decisions -need for extractions (usually 1st premolars) is dictated by amt of crowding present -when space is needed, arches can be expanded and anterior teeth flared but only to limited degree -expanding too much can leave teeth unstable due to lack of bone support -other option is to create space by extracting teeth -another indication for extraction is to camouflage a class II or III malocclusion by extracting premolars in one arch only to achieve class I canines and have normal overjet and overbite a) upper premolars would be extracted to camouflage a class II b) lower premolars would be extracted to camouflage a class III -there may be esthetic considerations to remove or not remove teeth since anterior tooth position affects lip fullness -removing premolars and uprighting incisors increases overbite, whereas aligning moderately crowded teeth w/o extractions flares incisors and decreases overbite Indications for Extractions 1) Large amount of crowding 2) Minimal overbite or presence of open bite 3) Flared incisors 4) Full/protrusive lips 5) Acute nasolabial angle 6) Anterior recession or minimal attached gingival 7) To camouflage class II or class III relationship 8) Missing or severely compromised teeth 9) Asymmetrical occlusion (unilateral class II or class III)

Indications to Avoid Extraction 1) Minimal crowding or spacing 2) Deep overbite 3) Upright incisors 4) Flat/recessive lips 5) Obtuse nasolabial angle Stages of Comprehensive Treatment 1) Alignment: use light, flexible wires initially, followed by slightly stiffer wires 2) Overbite correction: must be done before molar correction and space closure since deep overbite will prevent posterior movement of incisors to normal overjet a) extrusion of posterior teeth can help pts w/ short lower face (contraindicated in pts w/ long face) b) intrusion of anterior teeth (max. or mand.) can be done based on esthetics c) flaring of anterior teeth can decrease overbite 3) Correction of molar relationship a) growth modification b) interarch elastics c) distal movement of max. molars 4) Space closure a) interarch elastics d) headgear 5) Root correction: if spaces have been closed, teeth may have tipped into extraction space and roots will need to be paralleled to improve stability and perio health -incisors may have uprighted during retraction and roots may need to be torque lingually 6) Detailing/Finishing a) Intra-arch: final tooth positioning by re-bracketing misbracketed teeth or by small bends in wire to eliminate small discrepancies b) Inter-arch: settling of occlusion into solid relationship via light wires or vertical elastics -can also use a positioner (plastic appliance made w/ teeth reset into ideal position) 7) Special considerations a) Tooth size discrepancies: smaller/larger teeth in one arch may affect intercuspation -large teeth may require interproximal reduction (IPR) to reduce width -small teeth may require build-ups to fill space -very small spaces can be masked by tipping teeth to take up more space b) Unfavorable growth: pts w/ anticipated unfavorable growth patterns may use continued headgear at night c) Overtreatment: anticipated rebound of anterior-posterior discrepancies, crossbites, or rotations may be overcorrected in txt in anticipation that they will rebound afterwards to some degree d) Supracrestal fiberotomy: supracrestal gingival fibers exert some elastic force that may move teeth after txt -cutting these fibers has been shown to significantly reduce, but not eliminate, this tendency

Part 13: Retention Purposes of Retention 1) Allow time for reorganization of gingival and PDL fibers -reorganization of PDL occurs in 3-4 months and full-time retention is recommended for that time -part-time retention after 4 months to around 12 months is recommended to allow more complete reorganization of PDL 2) Prevent soft tissue pressures from altering post-txt tooth position 3) Hold new position of teeth until growth is completed a) Retention after class II correction: relapse may occur b) Retention after class III correction: relapse may occur due to continued mand. growth c) Retention after overbite correction: retainer w/ acrylic lingual to max. incisors usually blocks deepening of bite d) Retention after open bite correction: continuation of thumbsucking or tongue thrusting may intrude incisors e) Retention after mand. incisor alignment: pressure from lip may cause crowding of mand. incisors -late mand. growth is also possible contributor to mand. anterior crowding -no evidence that 3rd molar eruption causes incisor crowding f) Permanent retention: may be needed if teeth have been placed in inherently unstable positions Removable Retainers 1) Hawley retainer -incorporates clasps for retention and an outer bow w/ adjustment loops -acrylic on palate can act as potential biteplate to control overbite -outer bow retains incisor position and rotations -clasps or wires that cross the occlusion may wedge space open or prevent closure of spaces that remain (disadvantage) 2) Wrap-around retainer -similar to Hawley retainer but w/o wires that cross the occlusion 3) Positioner -may be used as finishing device and then as retainer -are bulky and therefore not well tolerated -not worn full-time and therefore may not retain rotations well -maintains intra-arch and inter-arch relationships 4) Essex appliance: vacuum formed -rapid, economical, and esthetic Fixed Retainers -bonded flexible lingual wires attached to individual teeth or bonded rigid wires bonded to 2 teeth (especially btw lower canines) -maintain mand. incisor position, hold diastemas closed, maintain space for pontic/implant, and keep extraction spaces closed Active Retainers -used for realignment of irregular teeth -irregular teeth are reset on a model and retainer is made to new tooth setup -retainer needs to have some flexibility to fit over irregular teeth -interproximal reduction may be required to allow space for teeth to rotate Post-Orthodontic Circumferential Supracrestal Fibrotomy -indicated for rotated max. lateral incisors -supraalveolar tissue responsible for relapse of ortho-rotated teeth -incision in sulcus made to crest of bone where collagen fibers insert into tooth root

-eliminates collagen fiber retraction and allows new fibers to form which will help retain tooth in new position Part 14: Adult Treatment/Interdisciplinary Treatment Periodontal Aspects of Adult Treatment -any perio conditions should be stabilized prior to ortho txt -good oral hygiene must be maintained b/c gingivitis in adults may progress to perio dx (this is rare in kids) -level and condition of attached gingival must be monitored to prevent recession -pts w/ hx of perio disease must be monitored on frequent schedule (every 2-4 months) -steel ligatures retain less plaque than elastic ligatures -lower forces can be used on teeth w/ reduced bone support b/c less PDL area Proper Sequence for Interdisciplinary Treatment 1) Disease control phase (caries, perio dx) 2) Ortho tooth movement 3) Definitive txt (perio bone contouring, crowns, implants, etc) Lack of Growth in Adulthood -adults don’t have benefit of mandible growth during txt so all interarch corrections must be made dentally or w/ surgery -w/o aid of growth to supplement dental changes, txt progresses more slowly even though tooth movement itself may progress at same rate Part 15: Combined Surgical and Ortho Treatment Indications for Combined Surgical-Ortho Txt -surgery indicated when problem too severe for ortho alone -adults don’t have growth modification options available and may need surgical interventions -fxnal limitations and esthetic goals may be indications for surgery even if ortho corrections alone are possible Anterior-Posterior Surgical Corrections 1) Maxillary surgery a) Advancement (to correct class III): LeForte I downfracture of maxilla mobilizes it so it can be advanced b) Setback (to correct class II): it is difficult to move entire maxilla posteriorly, so usually a premolar is extracted and anterior segment is moved posteriorly (segmental osteotomy) 2) Mandibular surgery a) Advancement (to correct class II): bilateral sagittal split osteotomy of ramus is preferred method b) Setback (to correct class III): bilateral sagittal split osteotomy is also preferred method Vertical Corrections 1) Maxillary surgery a) Superior repositioning (to correct open bite): LeForte I used to move maxilla superiorly which allows mandible to autorotate and correct open bite and long face b) Inferior repositioning (to correct deep bite): Positioning maxilla downward would rotate mandible open to reduce overbite and lengthen face -this is one of least stable surgical procedures 2) Mandibular surgery -anterior and downward rotation of mandible to correct deep bite can be done w/ sagittal split osteotomy -surgical procedures to move mandible superiorly to correct open bite aren’t recommended b/c cause downward rotation at gonial angle and stretch muscles of pterygomandibular sling

Transverse Corrections -for correction of crossbites, maxilla can be expanded or constricted during LeForte I osteotomy -changes in mandibular width are more difficult 1) Maxillary expansion: positioning of lateral segments in ideal position or by use of surgically-assisted rapid expansion -expansion proceeds w/ a jackscrew device 2) Maxillary constriction: bone removed to allow for constriction of lateral segments Genioplasty -chin can be augmented to improve esthetics by osteotomy or adding implant material -sliding osteotomy is preferred method and can be used to move chin in all 3 dimensions -reduction is least predictable method Timing of Surgery -surgery rarely performed before adolescent growth spurt except in cases of facial deformity 1) Growth excess cases (class III w/ excess mand. growth): surgery should be delayed until mand. growth is complete 2) Growth deficiency cases (class II w/ small mandible): surgery can be performed earlier in maturation Sequencing of Combined Surgical-Ortho Treatment 1) Pretreatment considerations: disease control and good gingival health should be established before txt begins -unerupted/impacted 3rd molars should be removed to allow for good bone healing 2) Ortho txt performed to align teeth within each arch 3) Surgery performed with ortho appliances in place -rigid wires placed in appliances to stabilize teeth -jaws repositioned and held by rigid internal fixation or intermaxillary wire fixation -soft diet required for 6 weeks after surgery 4) Pt returns to continue orthodontics for 6 month period to detail occlusion and finish