Despite significant improvements in resin composite materials and adhesives since their introduction, posterior composite restorations still require a careful placement technique in order to avoid less than ideal anatomy, microleakage and postoperative sensitivity. The insertion of a Class 2 resin composite restoration requires proper matricing for contact formation, correct placement of enamel and dentin bonding agents, incremental placement of the resin composite material, and careful finishing. Marginal adaptation and microleakage prevention is most critical at the gingival margin. The formation of an adequate contact during the insertion of a Class 2 resin composite restoration can be particularly challenging and several matricing systems are available for this purpose. The objective of this article is to outline basic principles and issues related to the placement of a Class 2 resin composite restoration, with special attention given to the issue of resin insertion and creating anatomically correct, tight interproximal contacts.
Hybrid resin composite materials are highly filled to provide strength, wear resistance and relatively low polymerization shrinkage as required for restorations in the posterior teeth1. The most common reasons for the failure of posterior composite restorations are secondary caries and marginal deficiencies2. Studies show that the bond to gingival margins is poorer than to axial margins in Class 2 restorations3. The presence of enamel is still the most effective means of minimizing leakage at the gingival margins. The application of a dentin bonding agent is required to form a resin-infiltrated hybrid layer to form a seal against microleakage and to help retain the restoration. Despite the introduction of simplified adhesives, the 3-step total-etch dentin bonding system remains the gold standard4.
Insertion strategies to decrease polymerization shrinkage stresses and microleakage at the tooth margins have been proposed. These include incremental filling techniques, such as the use of diagonal layers to decrease the C factor, and different light application methods such as directed, ramp or pulsed light curing techniques to control the rate of polymerization shrinkage. However, the study results for these techniques are mixed5-8 and there is no strong evidence to support anything other than a careful adaptation technique to avoid marginal gaps and to avoid the development of voids or incremental defects6-8.
It has been hypothesized that a layer of resin-modified glass ionomer at the gingival margin in a "sandwich" technique could reduce the incidence of secondary caries development because of its fluoride release properties9. However, the potential advantage of the glass ionomer layer must be weighed against the increased technique-sensitivity of the additional material layer and possible dissolution of the resin-modified glass ionomer material. The use of flowable composites has also been advocated as an easier material to apply at the gingival margins of proximal boxes. However, flowable composites have greater polymerization shrinkage, weaker mechanical properties, less radiopacity than conventional composites10 and void entrapment is still possible with the use of flowable composites. No significant advantages in marginal quality or microleakage have been demonstrated to support the routine use of flowable composites as an initial composite increment11.
An interproximal posterior tooth contact is composed of two adjacent tooth surfaces that are closely approximated to resist food impaction and maintain tooth position in a mesio-distal direction. The contact area is generally 2-3 mm occlusal-gingivally, beginning 1 mm below the crest of the marginal ridges and ending within the middle third of the tooth. The bucco-lingual width of the contact should be broad, approximately 1/3rd the buccolingual width of the tooth. The contact area should be surrounded by and flow into occlusal, gingival, buccal and lingual embrasures.
Anatomically correct and tight contacts are difficult to achieve with resin restorations because resin composite materials are not “condensable”. The use of amalgam matrix bands for resin composite restorations generally leads to straight point contacts that are located in the occlusal third of the tooth. Matrix systems for resin composite materials are designed to create curved proximal surfaces and tight contact areas. These are generally comprised of thin contoured matrix bands and tooth separators. Tooth separation can be accomplished by rings which have tines that exert separating forces on the teeth, applied instruments and/or wedges. A contact forming instrument can also be used for tooth separation. Contact forming instruments should not be used passively. Some force is necessary to press the matrix band against the adjacent tooth and create tooth separation. The resin composite material at the gingival aspect of the contact area is photopolymerized while the contact forming instrument is held in place. This sets the matrix position and tooth separation, and the remainder of the proximal box can then be restored. Technique difficulties associated with the use of contact forming instruments include management problems with the first layer application and control of exuded material, and difficulty in removing the instrument after material set.
A list of sectional and circumferential matrix bands is provided in Table 1. A list of separating rings is provided in Table 2.
|Composi-Tight (Garrison Dental Solutions)||.033 mm||curved|
|Contact (Danville Materials)||.038, .058 mm||curved|
||.038, 051 mm
|Hawe Adapt (Kerr)||.038 mm||different degrees of curvature|
|V3 (TrioDent Katikati, New Zealand)||.03 mm||curved and contoured|
|Dixieland Ultrathin Getz Contour (Water Pik)), used with Tofflemire retainer||.038 mm and .05 mm||curved|
|Micro band (Dental Innovations)||Areas .01 mm surrounded by.038 mm||flat|
|OptraMatrix (Ivoclar Vivadent) ), used with Tofflemire retainer||Areas .01 mm surrounded by .038 mm||flat|
|Omni-Matrix (Ultradent), attached to plastic matrix||.025, .038 mm||
|Ho Band (Young Dental) ), used with Tofflemire retainer||.025 mm||Only 9.5mm is curved|
Hawe SuperCap (Kerr), “auto-retaining”
|.038, .030 mm||5.0, 6.3mm|
RELATIVE SEPARATION FORCE 12
G-ring and 3D-ring (Composi-Tight, Garrison Dental Solutions,)
Gold- higher separation force
Silver-lower separation force
Gold- higher separation force
Silver-lower separation force
Gold- wider oval tine
Silver- thinner round tine
3D-ring: Adaptable silicone on tine, V-shaped, Bifurcation accommodates wedge
|Contact Ring (Danville Materials)||0.38 kg/mm||Stackable, Rectangular converging tines|
|Palodent BiTine ring(Dentsply) and BiTine ii||0.55 (BiTine) and 0.38 (BiTine ii) kg/mm||
Rectangular parallel tines
BiTine ii is elongated and hence stackable with original BiTine
|V ring and V3 Ring (TrioDent)||60-80 um separation (company information)||
V ring: V shaped tine
V3: glass fibre-reinforced plastic curved tine
Bifurcation accomodates wedge
|Hawe Adapt Shapers (Kerr)||low||Translucent plastic system|
The rubber dam is essential to provide optimal tooth isolation. A carefully placed rubber dam will prevent blood, saliva and gingival crevicular fluid contamination, and improve visibility. Prewedging in a Class 2 situation is useful to initiate tooth separation.
Conventional tooth preparation methods are used to remove decay and/or existing restorations. The main aim of the tooth preparation is to remove diseased tissue only. In a Class 2 situation, a proximal enamel shell serves to protect the adjacent tooth from damage during drilling procedures. This shell is subsequently removed using gingival marginal trimmers. Sufficient access is required to assess the carious lesion. A smooth slightly rounded outline and internal preparation form should make the subsequent composite insertion and adaptation easier. Clinical judgment is required to decide if decay removal is complete. Decayed tooth structure can be removed using slow speed instrumentation or a spoon excavator until a relatively solid base is reached. Obviously, infected and softened dentin should be removed. Harder, drier, inactive carious dentin may not need removal, especially if the cavity is deep. The cavity margins should be smooth and well-delineated. Occlusal bevels, which are prone to fracture under occlusal load, and proximal bevels that will be difficult to access are not routinely recommended. When an amalgam is being removed, all peripheral stain that may show through after composite restoration should be removed.
Matrix system application
After tooth cavity preparation, the matrix system is selected based on operator preference, cavity location and size. If the contact is not opened during tooth preparation, conventional matrix materials may be simpler to use rather than curved matrix bands and separating rings. Metal matrix bands are preferred over clear ones, which are difficult to use because of their thickness. The matrix band is placed into the interproximal space. It is important that the matrix band is not deformed during placement. This is particularly a concern when dead soft matrix materials are used because the deformation will lead to a similarly defomed interproximal contour. The height of the matrix band should slightly exceed the height of the adjacent tooth marginal ridge.
Each matrix band should be secured with a wedge. A wedge is needed to maintain adaptation of the matrix to the tooth at the gingival margin to avoid overhangs. Excessive wedging forces are unnecessary when an additional tooth separator, such as a ring, will be used.
A separating ring is positioned, using a rubber dam or dedicated forceps, so that the tines are situated in the buccal and lingual embrasures of the contact area. The tension of the ring exerts separating forces to the teeth. The silicone on the tines adapts the buccal and lingual aspects of the matrix band to the tooth to avoid proximal excess. The bifurcated ends of the tines straddle the wedge. The occlusal portion of the ring can be oriented either mesially or distally depending on the space available.
Irregular tooth positions and embrasure shapes can sometimes prevent seating of the rings. It is useful for the dentist to have a variety of separating rings with different tine shapes, with round or rectangular cross sections, for a better fit in some buccal and/or lingual embrasures. When the cavity preparation is wide either buccally or lingually, the tines of the ring could collapse the matrix band into the wide tooth preparation where the matrix band is unsupported by tooth structure. In this situation, placement of the tines along the side of the wedge away from the prepared tooth prevents the tines from collapsing into the tooth preparation while still delivering tooth separation forces through the wedge. In larger cavities, a circumferential matrix band can be chosen over sectional matrix bands. Ultrathin, curved and/or self-retaining circumferential bands enhance the ability to form tight, curved contact areas and should be used rather than a traditional circumferential amalgam matrix band in a Tofflemire retainer. If a separating ring cannot be used in conjunction with the circumferential matrix system, prewedging and active wedging forces are essential.
When a matrix system and separating ring is used, the matrix position should be verified prior to application of the bonding agent and resin composite materials. A properly matrixed tooth shows no gap along the gingival margin between the tooth and the matrix band. The matrix band should rest against the adjacent tooth. If the natural inclination of the matrix band is to rest away from the adjacent tooth, the matrix band will need to be held against the adjacent tooth during composite insertion because the composite will not readily push the band out.
In the case of an MOD preparation, it is possible to place separating rings oriented in opposite directions at both mesial and distal surfaces simultaneously. Some proprietary separating rings are angled or have different tine lengths to allow “stacking” and simultaneous placement of mesial and distal rings. However, tooth separation may be less effective owing to opposing forces on the prepared tooth. Therefore, the recommended procedure is to position the ring to achieve tooth separation at one interproximal contact first, and then after the first contact area is restored, to reposition the ring at the other interproximal contact to achieve tooth separation there and to complete the restoration.
When a 3-step total-etch bonding system is used, the phosphoric acid etchant is applied to the enamel first, and then to the dentin for a maximum etching time of 15 seconds on the dentin surface. The etchant is thoroughly rinsed and excess water is removed to leave a moist dentin surface without pools of water. Primer is immediately applied to saturate the dentin surface. The primer can be applied in multiple consecutive layers and a minimum of 2 layers should be applied. A rubbing or massaging action may aid primer penetration. Inadequate priming can lead to a discrepancy in the depth of resin penetration relative to the depth of dentin demineralization. The fully-primed dentin surface is then gently dried to completely evaporate the primer solvent before the application of the adhesive component. If there is residual primer solvent at the interface, the bond will be more prone to bond degradation. An adequately primed dentin surface will appear glossy but should not actually be wet. The adhesive should be applied to form a thin uniform layer by careful brush application. The excessive use of a stream of air to spread the adhesive can create pooled areas of excessive adhesive thickness as well as bald areas of inadequate adhesive thickness, and therefore should be avoided13. Photopolymerization of the adhesive layer is essential.
The first increment of composite material that is applied to the gingival seat should be no greater than 1mm thick since the gingival margin is relatively distant from the light source. Adaptation of the resin composite material to the gingival margin is difficult but critical. Marginal gaps at the gingival margins of proximal boxes must be avoided. The composite material can be applied directly from a compule tip or using hand instruments. “Pull-back” of the composite material occurs when the composite material sticks to the insertion instrument rather than the tooth surface. A lateral swipe of the compule tip toward the margins can help separate the composite increment from the compule tip. Pull-back with hand instruments occurs when the contact area of the composite-to-instrument is greater than the contact area of the composite-to-tooth and/or if heavy pressures are used during resin insertion. It is essential that the dentist develop an insertion technique that maximizes adaptation to tooth structure. A gentle but firm push and pat motion is recommended. If an initial layer of flowable composite is used at the gingival seat, the thickness of the layer should be minimized.
Composite resin increments of no more than 2-mm thickness are necessary to ensure adequate material photopolymerization. Photopolymerization should be accomplished with the light-curing tip placed as close as possible to the composite material. Each increment should be cured for a minimum of 40 seconds. When one proximal box has been filled and photopolymerized, the separating ring is transferred to the other proximal box. The second proximal box is then filled in a manner similar to the first. Incremental composite insertion techniques can be in the form of successive cusp build-ups where individual cusps are restored using small sloping increments, or in layers to successively build up the dentin followed by the enamel14. The height of the marginal ridges should be similar to the height of the marginal ridges of the adjacent teeth. The occlusal surface should include basic occlusal anatomy such as main fissures and cusp inclines. Composite insertion is complete when the tooth preparation is slightly overfilled. The separating ring, wedges and matrices are then removed. If resistance is felt during matrix band removal, it is a good indication that tight contacts have been formed. After matrix removal, further photopolymerization should be directed to the proximal boxes from the buccal and lingual embrasures.
Finishing and Polishing
A well-placed composite restoration should not require excessive contouring and finishing. Multi -fluted carbide burs can be used for gross shaping, contouring and occlusal adjustment. Floss should be used to clear the contact area from excess material as well as to assess the tightness and location of the contact area. Margination describes the specific step of the finishing process that involves the removal of excess restorative material at the cavosurface junction. The restoration margins should be smooth enough to be imperceptible to the tine of the explorer. A smooth cavosurface margin is critical to avoid plaque accumulation and maintain marginal integrity. The occlusion should be checked to ensure that no interferences are present. Final finishing and polishing can be accomplished using strips, discs, points and cups15. The use of a surface sealant as a final layer to seal surface imperfections is controversial. It was reported that commercial surface sealers were not able to totally seal controlled-size cavosurface gaps16 and that all of the sealer that was applied in a conventional manner was lost and the underlying resin composite became exposed after in vitro brushing in a conventional manner. Composite restorative procedures should therefore be performed in a manner which provides ideal surface finish and polish.
Resin composite materials can be used for restoration of posterior teeth and have the advantages of esthetics and adhesion to tooth structure. Compared with amalgams, the requirements for retention and resistance forms are not as strict with composites and therefore, the teeth can often be prepared more conservatively. The use of composites for posterior tooth restoration has steadily increased but is still contraindicated in large complex restorations that will undergo heavy occlusal stress and when adequate isolation cannot be achieved. The longevity of posterior composite restorations has been shown to be related to the number of restored surfaces, with larger restorations showing lower survival rates17,18.
Ongoing developments in materials and techniques have continued to reduce the technical difficulties associated with the placement of posterior composite restorations and improve restoration longevity. The challenge of interproximal contact formation is greatly reduced by the introduction of various matrix systems that create tooth separation and curved proximal contours. Post-operative tooth sensitivity remains an issue for some dentists and this has been largely attributed to microleakage19. Further research is needed towards the development of non-shrinkage resin composite materials which have the potential to eliminate or reduce polymerization shrinkage and microleakage issues20.
The success of a posterior composite restoration is heavily dependent on case selection and careful operator technique. Special attention must be paid to proper matricing, dentin bonding and resin insertion procedures. This video was produced to demonstrate the placement of a posterior resin composite restoration.
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