Direct Posterior Composite Restoration I.
st
Fissure sealant as 1 choice before posterior composite restorations:
Pits and fissures typically result from an incomplete i ncomplete coalescence coalescence of enamel and are particularly prone to caries, by using a low-viscosity fluid resin, these areas can be sealed following acid etching of the walls of the pits / fissures and a few mill millimeters imeters of surface enamel bordering these faults .
Steps in application of sealant
Fissure in occlusal surface of mandibular molar with area isolated by rubber dam
Brush
Pumice
Cleaning surface with pumice and bristle brush
Sealant inserted and finished
90
Sealants are most effective when they are applied in children to the pits and fissures of permanent posterior teeth immediately upon eruption of the clinical crowns, Adults also can benefit from the use of sealants.
Recent clinical studies shown that sealants can be applied even over small cavitated lesions with no subsequent progression of caries.
A recent bitewing radiograph should be made and evaluated prior to sealant placement to ensure that no caries is evident that penetrates pulpal of the dentino enamel junction (DEJ).
Typical failures of early composite restorations of occlusal and proximal surfaces
Occlusal wear with loss of centric stops in central fosse
II.
III.
Color changes no proximal contacts and marginal leakage
Limiting factors to provide " ideal dentistry:
Patient preferences. preferences.
Operator skill.
Laboratory support.
Economic considerations.
Esthetics.
Amalgam – Composite replacement ethics:
The American Dental Association 139th annual session, October 2000 (San Francisco) Francisco) Considered the indiscriminate replacement of amalgam restorations on the basis of alleged toxicity with any other materials as unethical and irrational conduct
91
Sealants are most effective when they are applied in children to the pits and fissures of permanent posterior teeth immediately upon eruption of the clinical crowns, Adults also can benefit from the use of sealants.
Recent clinical studies shown that sealants can be applied even over small cavitated lesions with no subsequent progression of caries.
A recent bitewing radiograph should be made and evaluated prior to sealant placement to ensure that no caries is evident that penetrates pulpal of the dentino enamel junction (DEJ).
Typical failures of early composite restorations of occlusal and proximal surfaces
Occlusal wear with loss of centric stops in central fosse
II.
III.
Color changes no proximal contacts and marginal leakage
Limiting factors to provide " ideal dentistry:
Patient preferences. preferences.
Operator skill.
Laboratory support.
Economic considerations.
Esthetics.
Amalgam – Composite replacement ethics:
The American Dental Association 139th annual session, October 2000 (San Francisco) Francisco) Considered the indiscriminate replacement of amalgam restorations on the basis of alleged toxicity with any other materials as unethical and irrational conduct
91
IV.
Newer composite formulations posses the general composition features and improved properties:
Raidopaque filers
Smaller size of primary filer particles and the inclusion of dispersed microfiller and even nanofillers.
Increased amounts of filler and a corresponding decrease in the resin matrix.
Greater strength and stiffness.
Reduced porosity.
Reduced water sorption.
Compatibility with new enamel / dentin bonding agents.
Polymerization Polymerization by visible light and reduce shrinkage.
Ormocers are organically modified ceramics as new category to reduce the organic fraction (BISGMA or UDMA) with an organosilane to get less shrinkage and high mechanical properties.
Universal nanofilled composite were recently introduced for both anterior and posterior restoration having very small filler particles that provide greater wear resistance less marginal ditching, bulk fracture and better color matching.
V.
In fact the ADA Council of Dental Materials, Instruments and Equipment has given:
Acceptance status to several composite materials for limited use in conservative Classes I and II preparations in the absence of significant occlusal stress. However, ADA has not yet recognized any composite material as an amalgam substitute.
VI.
Advantages:
Advantages of bonded direct composite restoration (versus dental amalgam) for class I, II & VI cavity preparation are as follows:
Esthetics.
Conservation of tooth structure (no extension for prevention).
Improved resistance to microleakage.
Strengthening of remaining tooth structure. 92
VII.
Low thermal conductivity.
Completion in one appointment.
Economic, less extensive compared to gold or porcelain restorations.
No corrosion.
Disadvantages:
The following features of present direct posterior (Class I, II & VI) composites are considered disadvantages (Compared with dental amalgam).
VIII.
Very technique sensitive.
Higher coefficient of thermal expansion than tooth structure.
Low modulus of elasticity.
Biocompatibility of some components unknown.
Limited wear resistance in high stress areas.
Indications:
Classes I and II cavities that can be appropriately Isolated and where some centric contact(s) on tooth structure is (are) present.
Class V defects: o
Hypoplasia and hypocalcification.
o
Carious lesion that is cavitated.
o
Abrasion and erosion.
Class VI cavities (faulty pits on selected occlusal cusps.
Veneers for metal restorations.
Repair of Fractured areas (tooth and or restorations).
Restoration of a weakened tooth that can be reinforced by bonded composite.
IX.
Contraindications:
Composite materials generally are not recommended for direct posterior (Classes I, II and VI) restorations under the following conditions.
The operating site cannot be appropriately isolated.
All occlusal contacts will be in composite materials.
Heavy occlusal stresses.
Deep subgingival areas that is difficult to prepare or restore. 93
X.
Case selection:
Amalgam and \ or gold posterior restorations provide an excellent service for maPOSTERIOR
COMPOSITE RESINS
A CURRENT ASSESSMENTHISTORY
The use of posterior composite resins has been increasing for some time du e to patients’ expectations
for esthetics and the lingering concern over mercury toxicity despite decad es of formal proceedings on
the safety of dental amalgams that produced no sound scientific evidence o f chronic toxicity in humans.
The quest for composite resins with sufficient strength and
durability for posterior placement actually began nearly four
decades ago, shortly after this class of materials was introduced to
the dental profession as an extraordinarily successful alternative to
silicate cements and direct filling resins.
1,2
Earlier materials showed
relatively high rates of wear and secondary caries after a couple of
years.
3,4
Figure 1 shows a cast of an earlier composite resin in tooth Figure 1
number 19 after two years. The occlusal wear along the margins is
apparent and measured approximately 400 microns.
For the most part, these problems have been overcome due to evolutionary advances in composite
resin technology that included improved adhesion to dentin resulting in less mic roleakage and
secondary caries development, a reduction in the size of inorganic filler pa rticles resulting in less wear,
and visible light curing resulting in improved adaptation due to an unlimite d working time as well as 94
increased physical properties due to the elimination of voids incorporated during the mixing process.
ADVANTAGES
The advantages posterior composite resin restorations offer over dental amalgam are many:
Esthetics
Most modern day composites are made available in numerous shades and s everal variations in opacity
making possible excellent optical matches to tooth structure. The figures b elow (series courtesy Dr. Jeff
Blank) show a commonly used composite layering technique that can resul t in a high level of esthetics
when restoring posterior teeth. Figure 1. Cavity preparation
Figure 2. Flowable composite liner placed
Figure 3. Body layer placed up to DEJ
Figure 4. Enamel layer placed –
finished restoration
(2)Conservative Cavity Preparations
A major benefit to using composite resins is the ability to prepare very con servative cavity preparations.
When coupled with the strong bonds that can be formed with enamel and d entin, the result is less
weakening of tooth structure. There is usually no need for undercuts or ext ending cavity preparations
into self cleansing areas. Line angles are rounded and occlusal bevels are o ften not necessary. Figures 5
and 6 show an array of conservative cavities prepared to receive composite resin restorations.
Figure 5 Figure 6
Increased Wear Resistance
At a recent meeting of the International Association of Dental Research, da ta were presented on a
packable posterior composite resin, SureFil
® 95
High Density Posterior Restorative, DENTSPLY/Caulk,
Milford, DE, showing mean marginal wear of only 142 microns after ten y ears.
5
Considering this is less
than wear measurements recorded for posterior enamel cusps,
6,7
it is apparent that contemporary
composite resins matrerials can withstand the challenges posed in the poste rior region of the mouth.
Reparability
It has been shown that composite resin can bond to previously cured mater ial, even after the oxygen
inhibition layer is removed, if the cured surface is first etched with phosph oric acid and then coated with
a chemically compatible bonding agent.
8
Lower Coefficient of Thermal Conductivity
Teeth often become more sensitive to temperature fluctuations following o perative procedures, and
restorative materials capable of rapidly conducting heat can only add to the problem. Dental amalgam is
more than 30 times more conductive than dentin and gold is approximately 500 times more
conductive;
9
therefore insulating bases are required when these materials are used in de eper
restorations. While the minimal thickness of an insulating material has not been specified, anything less
than 0.5 mm would be considered of little help.
10
Filled resin materials are not good conductors of heat
and in fact offer greater insulation than dental enamel, 96
11 a desirable property that obviates the need for
insulating bases.
(3)Lower Incidence of Cusp Fractures?
Numerous statements and implications have been made that composite resi n restorations in posterior
teeth are less likely to be associated with fracturing of remaining cusps bec ause they can be bonded so
well to tooth structure. The argument makes sense from the standpoint of material science, however, it
is not well supported with evidence. One study that observed 10,869 poster ior teeth with amalgam or
composite resin restorations in 1,902
patients found no significant difference in the prevalence
of cusp fractures between the two restorative
materials.
12
There was a higher prevalence of cusp
fractures in teeth with more than one surface restored
and in older individuals but these were independent of
the specific restorative material used.
Figure 7. Fractured DB cusp #3 (Courtesy Dr. Jeff Blank)
DISADVANTAGES
Despite the many advantages offered by composite resins and the vast improvements that have been
made in the properties of these materials over the past three plus decades, i ssues remain with their use
in the posterior region of the mouth, particularly for larger restorations. In 1998 the American Dental
Association (ADA) issued a position statement on posterior resin ‐based co mposites that in general
supported their use, but not in teeth with heavy occlusal stress, in sites that cannot be isolat ed or in 97
patients who are allergic or sensitive to resin ‐based composite materials.
13
While a more recent position
statement has not been published, the ADA did host a panel discussion on posterior composite resins,
the proceedings of which appeared in the summer, 2006 issue of the ADA Professional Products
Review.
14
The panelists noted that while the reports on the performance of posterior composites have
generally been favorable, concern remains regarding use of the material in large restorations and the
durability of the bond to tooth structure since bonds have been shown in th e laboratory to deteriorate
over time. It was further suggested in the panel discussion that posterior co mposite resins not be placed
in situations where good isolation is not possible, in patients with a high ca ries rate and/or poor oral
hygiene or in patients who clench or brux their teeth.
Some disadvantages associated with the placement of composite resin rest orations in the posterior
region of the mouth are as follows:
Technique Sensitivity
It has long been recognized that placing posterior composites resins is a m ore demanding clinical
procedure compared to dental amalgam and may require twice the time for completion, particularly in
multi‐surface restorations.
15
Adequate light curing is essential for maximal physical properties, and
incremental placement is necessary due to polymerization shrinkage stress and depth of cure
98
limitations. Obtaining proper anatomic form and marginal adaptation is mo re difficult with composite
resins due to their plastic consistency compared to the carving characteristi cs associated with dental
amalgam. Isolation becomes more critical when using composite resins tha n with dental amalgams or
glass ionomer cements since moisture contamination during the polymeriz ation process can result in
reduced physical properties.
(4)Obtaining proximal contact is also more difficult since even the heavies t bodied composite resin
formulations have difficulty holding an extended matrix band in position, a nd specialized matrix systems
are normally required (Figure 8).
Perhaps the greatest source of technique sensitivity in
using composite resins is the need to bond to enamel and
dentin. Modern day adhesives can bond adequately to
both hard tissues even though they vary considerably in
the number of steps involved, the type of solvent used
and, in the case of self ‐etch adhesives, the pH value which
can greatly influence the Figure 8. Sectional matrix in place (Courtesy Dr. Mark
Latta)
aggressiveness of the etching pattern. Most of the documented clinical trial s on adhesives have been in
non‐carious cervical erosion lesions since their non ‐retentive nature presen ts a formidable clinical
challenge to the strength and durability of an adhesive bond. These trials h ave shown good results with
both etch‐and‐rinse and self ‐etch adhesives, but the most consistent results seem to be associated with
the three‐step etch‐and‐rinse systems and the two ‐step self ‐adhesive sytem s.
99
16
Non‐antimicrobial
Unlike dental amalgam, composite resins are unable to arrest the growth of microorganisms, which
could result in a more rapid progression of recurrent or secondary caries.
15,20
Polymerization Shrinkage Stress
The resin matrix of composite resin materials is composed of monomer mo lecules that upon
polymerization convert to a polymer network wherein molecules are packe d closer than in their free
state leading to bulk contraction.
17
If the resulting stress is greater than the bond strength to tooth structure, debonding could occur leading to marginal gap formation and irr itation of the pulp due to
microbial colonization.
18
The extent of shrinkage and the resulting stress will depend upon the dyna mics
of the polymerization reaction and the level of inorganic filler loading. At the clinical level, the degree of
stress placed on restorative margins is most influenced by the bulk of mate rial being cured and the
configuration of the cavity into which the material is placed. The potential for a given cavity
configuration to cause stress at the margins of a restoration is known as the “C” factor and is calculated
very simply by dividing the number of bonded internal cavity surfaces by t he number of non‐bonded
surfaces. Below are shown the C factors for the various cavity classes (Co urtesy Dr. Jeff Blank).
Class IV C= 0.5 Class III C= 1.0 Class I C= 5.0 Class II C= 2.0
(5) 100
Class IV C=0.5
Class III C=1.0
Class I C=5.0
Class II C=2.0Little clinical evidence exists to support a relationship betwe en negative outcomes and polymerization
shrinkage stress; however, direct effects relative to bond stability can be shown in the labora tory. It is
therefore prudent to at least bear in mind that shrinkage stress is likely an u ndesirable property for a
restorative material and practical steps that could minimize shrinkage stres s should be considered. Such
steps include vertical rather than horizontal layering of composite resins an d avoiding the placement of
bulk amounts of the material prior to light curing.
POSTERIOR RESIN COMPOSITE FAILURE AND CAUSES
Since composite resins were first considered as a potential replacement for dental amalgam, questions
have been raised as to their suitability for such a critical role in dentistry. T here are many reports
comparing the success rates of the two materials, and by and large compos ite resins have shown
acceptable performance even if not quite to the level of dental amalgam. M atching the efficiency of
dental amalgam as a public health measure is indeed beyond the reach of most restorative materials.
Table 1 shows the results of one comprehensive study that followed over 1 700 posterior restorations for
a seven year period. Half of the patients received composite resin restorati ons while the other half
received amalgam.
TABLE 1
MEAN ANNUAL SURVIVAL RATES OF COMPOSITES AND AMAL GAMS
AFTER SEVEN YEARS (%)
CHARACTERISTIC AMALGAM COMPOSITE 101
TOOTH TYPE
Premolar
Molar
94.5
94.4
85.7
85.5
RESTORED SURFACES
1
2
3
4 or more
98.8
90.5
88.5
81.8
93.6
80.6
66.2
50.0
SIZE
Small
Medium
Large
98.9
93.3
89.5
93.6
84.9
74.3
ALL 94.4 85.5
Adapted from Bernardo M et al
19
102
As evident from the table, amalgam restorations did demonstrate fewer fail ures than composite resins
over the seven year period, particularly in restorations with three or more s urfaces where composite
resins experienced a 50% failure rate in the largest restorations. This study also reported that the main
reason for restoration failures in both groups was secondary caries. However, the proportion of failures
due to secondary caries was higher in the composite resin group (88%) co mpared with the
(6)amalgam group (66%). It has been reported that the most frequent sites for secondary caries are th e
gingival margins of all classes of restorations.
20
This is not terribly surprising given the difficult access many of these areas present as well as the challenges posed by bonding to dentin and cementum as
compared with enamel.
While the main cause for failure of posterior composite resin restorations a ppears to be secondary
caries in the area of the gingival margin, the specific reasons for caries dev elopment are far less clear.
Certainly a low level of oral hygiene is considered by many as causative, y et the evidence is scant. It is
known that the replacement rate for posterior composite resins is higher in adolescents compared with
adults, perhaps owing to poorer oral hygiene and higher sugar intake in the younger cohort. The
technique sensitivity of composite resin placement and associated bonding procedures have been
thought to contribute to a reduced survival rate compared with amalgam, b ut evidence here is also
103
lacking. One study had Class II restorations placed in teeth destined for ext raction, following which the
restorations were observed on radiographs and under scanning electron mi croscopy.
21
It was reported
that only 27% of gingival margins were free of defects, a finding that woul d support the technique
sensitivity involved with placing composite resins in posterior teeth and pe rhaps also the higher risk
these areas face with respect to secondary caries. Surprisingly, the study al so found that none of the
following variables had an effect on the quality of gingival margins:
• Experience level of the operator
• Horizontal versus vertical layering of restorations
• Type of adhesive; one ‐step etch‐and‐rinse, two‐step etch‐and‐rinse or two‐ step self ‐etch
While this study highlighted the gingival margin as an area that should rec eive focused attention, it did
not suggest that experience, layering technique or adhesive selection woul d help remedy the observed
defects. Another study that evaluated the longevity of posterior resin composite res torations cast a
shadow of doubt over the insistence on the part of some that rubber dam is olation is essential for a
successful restoration since it did not result in significantly higher survival rates than isolation by cotton
rolls.
22
LINERS
104
Some comments regarding the use of liners ‐ and flowable composites in pa rticular‐ beneath posterior
composite resin restorations are in order since a recent survey
23
indicated that 90% of dentists have
used a flowable composite in the past twelve months, and that 82% of flow able users apply them as
liners. The use of flowable composite liners has been claimed to increase marginal adaptation in the
gingival marginal area of Class II restorations thereby reducing microleaka ge. It has also been claimed to
mollify polymerization shrinkage stress on the part of the composite resin due the more more elastic
nature of flowable composite resins. Recent work has shown that t he use o f a flowable liner showed
fewer voids at the interface of the restoration and tooth structure in the cer vical area of Class II
restorations when compared with bonding agent and resin composite alone .
24 The study also showed that thicker (2mm) flowable pre‐cured liners showed more marginal leakag e when compared with
thinner (0.5‐1mm) liners. This finding would obviously refute the notion th at flowable liners could
counteract the effects of polymerization shrinkage stress from the composi te resin. Finally, this study
showed that a lining technique originally presented by Jackson and Morga n
25 involving placement of a packable composite over a thin uncured flowable liner resulted in the best marginal sealing of all groups
105
tested.
(7)REFERENCES
1. Phillips RW, Avery DR, Mehra R, Swartz MI, McCune J. Observations on a composite resin for Class II
restorations: two‐year report. J Prosthet Dent Aug 1972;26:68 ‐77.
2. Phillips RW, Avery DR, Mehra R, Swartz MI, Mc Cune J. Observations on a composite resin for Class II
restorations:three‐year report. J Prosthet Dent Dec 1973;30:891‐7.
3. Eames WB, Strain JD, Weitmann RT. Williams AK. Clinical compariso n of composite, amalgam and
silicate restorations. JADA 1974;89(5):111 ‐7
4. Leinfelder KF, Sluder TB, Santos JFF, Wall JT. Five ‐year clinical evalu ation of anterior and posterior
restorations of composite resin. Oper Dent 1980;5(2):57‐65
5.Wilder AD, Bayne SC, Heymann H, Perdigao, J, Swift EJ. 10 ‐year clinic al performance of packable
posterior composite. 2008 IADR Abstract #0238.
6. Molnar S, McKee JK, Molnar IM, Pryzbeck TR. Tooth wear rates amon g contemporary Australian
Aborigines. J Dent Res 1983;62:562 ‐5.
7. Lambrechts P, Braem M, Vuylsteke ‐Wauters M, Vanherle G. Quantitati ve I vivo wear of human
enamel. J Dent Res Dec 1989;68(12):1752 ‐4.
8. Blank JT, Latta MA. Bond strength of composite to composite simulatin g clinical layering. 2003 IADR
Abstract #2003.
9. Craig RG, Peyton FA. Thermal conductivity of tooth structure, dental ce ments and amalgam. J Dent
Res May‐June 1961;40:411‐8.
10. Jeffrey IWM. The relationship of lining thickness and thermal insulatin g efficiency. J Oral Rehab
1984;11:429‐39.
106
11. Saiho M et al. Thermal properties of dental materials. Part 10. Crown a nd bridge resins containing
high concentrations of filler. J Japan Soc Dent Mat Dev 2000;19(5):441 ‐7.
12. Wahl MJ, Schmitt MM, Overton DA, Gordon KM. Prevalence of cusp fractures in teeth with amalgam
and with resin‐based composite. JADA August 2004;135:1127 ‐32.
13. ADA Council on Scientific Affairs; ADA Council on Dental Benefit P orgrams. Statement on posterior
resin‐based composites. JADA Nov 1998;129:1627 ‐8.
14. Hilton TJ, Ferracane J, Liebenberg W, Sarrett DC, Swift EJ. Posterior composites: expert panel
discussion. Summer 2006;1(1).
15. Leinfelder KF. Posterior composite resins: the materials and their perfo rmance. JADA May
1995;126:663‐76.
16. De Munck J, Van Landuyt K, Peumans M, Poitevin A, Lambrechts P, Braem M, Van Meerbeek B. J
Dent Res 2005;84(2):118‐32.
17. Davidson CL, Feilzer AJ. Polymerization shrinkage and polymerizatio n shrinkage stress in polymer ‐
based restoratives. Journal of Dentistry 1997;25(6):435‐40.
18. Roulet JF. Benefits and disadvantages of tooth ‐coulored alternatives to amalgam. Journal of
Dentistry 1997;25(6):459‐73.
19. Bernardo M, Luis H, Martin MD, Leroux BG, Rue T, Leitão J, De Rou en TA. Survival and reasons for
failure of amalgam versus composite posterior restorations placed in a rand omized clinical trial. JADA
June 2007;138:775 ‐83.
20. Mjör IA, Clinical diagnosis of recurrent caries. JADA Oct 2005;136:14 26‐33.
21. Opdam NJM, Roeters FJM, Feilzer AJ, Smale I. A radiographic and sc anning electron microscopic
107
study of approximal margins of Class II resin composite restorations place d in vivo. Journal of Dentistry
1998;26(4):319‐27.
(8)22.Brunthaler A, König F, Lucas T, Sperr W, Schedle A. Longevity of direct resin composite restoration in
posterior teeth. 2003 Clin Oral Invest;7:63‐70.
23. Council on Scientific Affairs of the American Dental Association. Spri ng 2009;4(2).
24. Chuang S ‐F, Jin Y‐T, Chang C‐H, Shieh D‐B. Influence of flowable co mposite lining thickness on Class II
composite restorations. Operative Dentistry 2004;29(3):301 ‐8.
25. Jackson RD, Morgan MM. The new posterior resins and a simplified pl acement technique. JADA
March 2000;131(3):375‐83.
(9)ny years, whereas posterior composite restoration may not serve as long.
Amalgam and \ or gold posterior restorations have adequate strength and wear resistance to support occlusion in high stress areas, whereas wear of posterior composite restoration may be greater.
It is important that the occlusion be, evaluated preoperatively to determine the bite relationship and type of occlusal function.
To maintain proper vertical dimension, at least one centric holding contact should be located on sound tooth structure or on the same type of restorative material that has wear rate approximately that of tooth structure.
Articulating paper point Occlusal centric stops
108
During evaluation of occlusion centric stops and functional patterns are marked articulating with paper. Classes I posterior restorations could be placed in selected areas of these premolar maxillary teeth.
XI.
Cavity preparation designs: A. Conventional Preparation Design:
These boxlike cavity designs have slightly converging (toward the
occlusal) external walls, basically flat floors and undercuts in dentin for retention form.
Although the conventional type of preparation can be used with
posterior composites for Classes I, II or VI cavities, it is usually not employed in its entirety because of the benefits of beveling most enamel walls.
109
Conventional cavity preparation for amalgam or composite restorations
Moderate size class I cavity preparation
Large class II cavity preparation
B. Beveled conventional preparation design:
The Incorporation of an enamel cavosurface bevel in preparations for composite is recommended, because it provides more surface area for bonding and it allows for the more preferred end on etching of the enamel rods. These features increase retention, reduce leakage and provide greater potential for strengthening the remaining tooth structure. The bevel is prepared with a coarse, flame shaped diamond instrument, approximately 0.5 mm wide, and at an angle of approximately 45 to the external enamel surface. Beveling is particularly beneficial when placed along facial and lingual walls of proximal box because the enamel rods run parallel to these cavity walls:
It increases the surface area along the end of the enamel rods, resulting in improved retention and resistance to leakage.
110
It is most frequently used for restoration of class I & VI cavities, when there is a need for increased resistance form to resist occlusal forces.
(A) Marginal configuration for beveled conventional preparation. (B) Occlusal bevel are less beneficial due to enamel rod orientation.
C. Modified preparation design:
Typically dictated by the extent of the lesion or defect, conserving as much
intact tooth structure as possible, and in some rare instances the preparation can be restricted entirely to enamel.
Modified preparations are characterized by:
The conservative removal of only the defective or carious tooth structure.
The establishment of a beveled configuration on all enamel cavosurface margins.
Extensive modified designs for Classes I and II cavities can incorporate
unique preparation features such as: Reverse Bevels, Secondary flares and Brace-Type Skirting at the axial transitional tooth corners to enhance
retention and resistance form.
Large preparations of this type should not be
considered routine and are contraindicated except in specific compromise situations. Modified Class I cavity preparation for posterior composite restorations Some undermined enamel is maintained Extension strengthen remaining tooth structure
Extensive cavity preparation.
111
XII.
Preventive Resin Restoration (PRR) or class one conservative composite restoration:
This design allows for restoration of the lesion or defects with minimal removal of
tooth structure and often may be combined with the use of composite or sealant to seal radiating non-carious fissures or pits that are at high risk for subsequent caries activity. It is referred to as a conservative composite restoration or preventive risin restoration PRR.
An accurate diagnosis is essential prior to restoring the occlusal surface of a
posterior tooth. The critical factor in this clinical assessment is whether or not the suspicious pit or fissure is cavitated, therefore requiring restorative intervention.
After deciding that cavitations has occurred, it usually must be determined
whether to use amalgam or composite; important factors related to this decision include:
Ability to isolate the tooth \ teeth.
Occlusal relationship.
Esthetics.
Operator ability.
Environmental amalgam restriction.
Advantages of preventive resin restoration (PRR) over amalgam are:
Conserving tooth structure.
Enhancing esthetics.
Bonding tooth structure together.
Sealing the prepared tooth structure.
Including other suspicious areas on the occlusal surface with either the composite restorative material or a sealant material.
When caries is limited to enamel, there is no need to prepare into dentin as is necessary for amalgam restoration.
Small cavities could be restored with flowable composite that may also act as a fissure sealant or composite resin followed by fissure sealants to seal the adjacent fissures. This procedure is considered less traumatic to the patient and minimally invasive to the tooth structure.
112
XIII.
Simple proximal box preparation: 1) It's used to restore a small proximal lesion without either occlusal
fissure or previously inserted occlusal restoration. It's limited to teeth with narrow interproximal contact. 2) The outline could have rounded margins as in resinous material or
could be in the form of definite walls as in case of amalgam restorations. 3) It's mainly used whenever there's a need to avoid cutting into sound
occlusal surfaces. 4) Buccal and lingual walls of the boxes should be almost facing each
other to maximize retention. It's done without an occlusal step. 5) To compensate to the lack of occlusal portion that allows retentions,
proximal retentive groves on the expense of facial and lingual walls having 0.5 mm at the gingival point angles and taper to 0.3 mm at the occluso surface are done. 6) Using amalgam or resin composite according to cavity design.
Pear shaped proximal box prepared for resin restoration or GIC.
XIV.
Proximal box prepared for amalgam.
Slot preparation: 1) Used in old patient who have gingival rescission
and often experience cavities on the proximal exposed cementum on the root surfaces that is gingival to the contact area. Or whenever wide embrasures are encountered that allow easy access to the proximal lesion sparing the marginal ridges and the occlusal surfaces. 2) The approach to perform this design is buccally or lingually in the
form of a slot.
113
3) Offers better esthetics, does not alter occlusal relationships, may
preserve a natural proximal contact and enjoys greater patient acceptability than traditional approach. 4) The occlusal and gingival walls should be perpendicular to the long In
a cavity with buccal approach, the buccal wall must flare suffiently to allow access and visibility while the lingual wall should face buccally as much as the caries extension allows resisting the condensation forces. 5) Two retentive grooves could be placed along the occluso-axial and
gingivo-axial line angles if retention is required for non-bonded restoration. 6) Could be restored using amalgam, resin composite or glassionommer
and its modifications.
XV.
Tunnel preparation: 1) Also termed internal fosse, internal
oblique preparation, internal occlusal diagnonal preparation or simply internal preparation. 2) The tunnel approach for a proximal
lesion preparation allow preservation of the marginal ridge; access could be directly on the lesion by trepanning the occlusal enamel in the fosse near the marginal ridge keeping it untouched, a diagonal inclination of the cutting tools is then done to keep the occlusal marginal ridge without undermining it. 3) Air abrasion has proven effectiveness lately in performing such a
design. 4) The decayed tissue is then removed with or without involvement of a
proximal enamel .this is referred to, as 'partial tunnel' preparation when this proximal enamel is left undisturbed as it's neither carious nor cavitated but left supported by sound dentine. 114
5) The 'total tunnel' preparation is that when the proximal enamel has
been perforated by the carious lesion and removed during the preparation. 6) The most suitable restorative material used in conjunction with this
modality is the cavity has to be filled to the level of DEJ with GIC and the rest is filled with composite. Other restoratives can also be used with this technique like compemers, cement or any high resisting GIC. 7) Molars failed 5 times as often as premolars did. It's thus recommended
that tunnel technique be used for premolars. 8) The tunnel preparation and restoration are still until now controversy
as no firm data have been given to support its use unrestrictedly.
XVI.
Ultra conservative cavity preparation:
It is determined by the size and shape of the carious lesion rather than by cutting an outline per sec. Conservative outline vary according to the tooth type, occlusal pattern, oral hygiene and cares risk tests. The width of the cavity has decreased enormously from 1/3 to 1/4 the inter cuspal distance to 1/8 to 1/6 of the inter cuspal distance and sealing fissures and retentive grooves with fissure sealant.
XVII.
Class II cavity preparations for moderate composite restoration: 1. Even though the ADA has not endorsed composite:
As a substitute for amalgam in posterior teeth, composite restorations in Classes I and VI (as already presented) are excellent when done properly. 2. Composite may be used successfully in restoring class II cavities:
When the potential to seal the tooth and strengthen the remaining tooth structure by bonding composite to the tooth, along with the obvious esthetic benefits are taken in consideration. Recall that a conservative beveled conventional cavity preparation is recommended for most moderate Class II composite restorations. 3. Limiting factors for the use of composites in Class II applications are: i.
The inability to isolate the area (the bond may be compromised),
ii. Deep subgingival extensions (preparation, insertion, and bonding may be
compromised), and
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iii. Occlusal contact entirely on the composite (increased wear may occur). 4. Early wedging: a wedge is placed interproximally before cavity preparations: i.
Separating the teeth to compensate later for the thickness of the matrix band.
ii. Depresses and protects the rubber dam and gingival tissue when the
proximal area is prepared. iii. The presence of the wedge during cavity preparation also is a guide to
help prevent overextension of the gingival floor.
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Preoperative and postoperative views of moderate posterior compoAsite restorations
Articulating paper mark
Failing amalgam
Failing amalgam restorations are not in centric holding areas
Rubber dam
Protective base
Isolation with rubber dam, Cavity preparation with protective base in place
Initial appearance of composite restorations
After 3 years of service. Occlusion is marked with articulating paper
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5. Main variations in Class II cavity design for a composite restoration as opposed
to that for an amalgam: i.
The axial wall initial depth usually is limited to a depth of 0.2 mm into dentin. This means that the tip of the No. 245 bur would be cutting less than one half in dentin and more than one half in enamel to be most conservative. (The diameter of the bur's tip end is 0.8 mm). This decreased pulpal depth of the axial wall allows greater conservation of tooth structure since retention locks will not be used. The occlusal walls are prepared to converge occlusally.
ii. Many areas of the enamel are unsupported by dentin, but not friable.
This undermined enamel is not removed, it will be reinforced by etching and bonding. iii. Placing bevels on the occlusal and proximal cavosurface margins, if
access permit, with a coarse, flame-shaped diamond instrument. Recall that bevels on the occlusal surface may be considered optional (if not required for fissure treatment) due to enamel rod direction, especially in areas of steep cuspal inclines. Also, beveling of the proximal box enamel to cavosurface margins must be done judiciously. iv. For placement of bevels it may necessitate undue extension, which may
cause the operator to decide whether to reduce or eliminate the proximal beveling.
XVIII.
Extensive Classes I and II preparations for posterior composites:
"Real
world"
dentistry
sometimes
necessitates
esthetic
treatment
alternatives that, while representing a clinical compromise, may provide a needed service to the patient.
Large posterior composite restorations sometimes can be used as a
reasonable alternative when more permanent options are not possible or realistic.
The patient must be informed of the possible limitations of these large
posterior composite restorations; primarily excessive wear and increased recurrent caries potential.
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Most extensive Classes I and II composite restorations will utilize a
beveled conventional cavity preparation design. Increased bevel widths may assist in both the retention of the material and strengthening of the weakened tooth. A) Class I extensive modified preparations:
– Because first molars erupt at an early age, they are sometimes neglected and extensive caries may develop. When infected dentin is removed, a severely weakened tooth with unsupported cusps may remain.
– In an effort to splint the weakened facial and lingual cuspal elements together, facial and lingual extensions are made with a coarse, roundedend diamond instrument.
– The depth should be at least 1mm into enamel as the extension crosses the cusp ridge and approximately 0.5 mm deep in the facial and/or lingual enamel.
– Some unsupported, but not friable, enamel may be left because it will be reinforced by etching and bonding. When properly etched and restored, the composite material acts as a splint to lock the tooth together for resistance to fracture under masticatory forces.
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Favorable occlusion permitting extensive modified Class I cavity preparations (mandibular teeth) for composite restorations
Faulty amalgam Rubber dam isolation of teeth with fault amal am restorations.
Secondary caries
Existing amalgam restorations removed revealin secondar caries.
Undermined cusps
Facial and lingual cusps undermined b removal of infected dentin
Base
Bases inserted and preparation com leted
Model illustrating extension and bevels prepared with diamond instrument to strengthen the tooth by the splinting action of bonded com osite restoration.
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B.Class II extensive modified cavity preparations:
– Esthetics and economics were factors in the decision to replace old faulty amalgam with a composite restoration.
– A coarse, flame-shaped diamond instrument was used to reduce the severely undermined enamel of the lingual cusp approximately 1.5mm and place a reverse bevel with a chamfered margin on the lingual surface.
– The same instrument was used to reduce the facial cusp 0.75 mm and placed slight counter bevel on the facial cusp.
– Skirts were placed on all of the axioproximal walls except the mesiofacial, where a secondary flare was used.
– This wraparound design in the enamel allows the bonded composite restoration to brace the tooth to resist fracture.
– In this wraparound design note:
Reverse bevel → lingual cusp.
Counter bevel → facial cusp.
Skirt bevel → all axioproximal walls.
Secondary flare → mesiofacial wall.
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