Despite material advancements in almost every aspect of direct resin placement, Class II composite restorations are still tedious and time-consuming to complete for practitioners. To ensure a positive outcome for Class II composite restorations, dentists must overcome such factors as open interproximal contacts, poor anatomical contour, inadequate marginal seal, postoperative sensitivity, marginal staining, recurrent caries, and fracture.1
With more than 70 restorative composites and more than 50 flowable composite brands currently on the market (not including dual-cure composites), clinicians now have a potentially confusing array of materials from which to select.2 Since the introduction of resin-based, light-cure composite in the 1970s, practitioners have attempted to leverage materials and techniques to achieve successful placement of composite restorations in all clinical situations. Because placement of composite restorations is an exacting and tedious process, unique challenges such as isolation, adhesion, materials selection, and polishability can directly impact the outcome of the procedure. Combining these factors with issues of overhead costs and insurance reimbursement means that dentists must not only work expeditiously but efficiently. Dr. Ron Jackson summed up the daily challenge for practicing dentists: “Given today’s overhead per hour, dentists need material and technology advancements so that posterior composites can be placed faster, easier, and profitably without taking compromising shortcuts.”3
To this point, many dentists have put varying equipment and materials together to assemble their own Class II restorative system using the “this works best in my hands” argument based on completion of repetitive procedures and clinical observation. However, this approach is not entirely consistent with the principle of evidence-based dentistry, which involves 3 domains: the best available scientific evidence, a dentist’s clinical skill and judgment, and each individual patient’s needs and preferences.4 With so many sources of evidence being thrust upon the dentist, including articles and newsletters, live and Web-based presentations, information from sales representatives and consultants, Web sites, and advice from colleagues, it can be overwhelming to decipher what can truly improve clinical practice.
Incorporating existing dental literature into current practice is especially important when considering direct composite restorations. One example illustrating this involves a paradigm shift in recent dental literature from advocating incremental placement to suggesting the use of bulk-fill materials; with more focus on polymerization stress and less on volumetric shrinkage.5 In doing so, bulk-fill materials offer the possibility of decreasing procedural steps involved in direct composite placement and thereby allowing for faster placement.
In addition, recently, manufacturers have begun introducing product solutions involving products and systems designed to be used in sequence to achieve consistent positive results. Examples of product solutions currently available include 3M ESPE’s Trifecta Method for indirect restorations, and DENTSPLY Caulk’s Class II solution for direct restorations.
The intent of this article is to review the existing dental literature on bulk-fill flowable composites as a means to decrease procedural steps, and highlight important factors involved in achieving positive results during Class II restorations.
DO BULK-FILL FLOWABLES PERFORM?
Shrinkage of flowable composites can compromise the success of the restoration and contribute to a poor marginal seal, microleakage, microfracture, and recurrent caries.6 If the flowable resin is placed into a confined space and then shrinks during polymerization, stress will develop. According to Hooke’s law, stress is determined by the stiffness of a material when subject to a given strain.7 In this case, the shrinkage stresses are transferred to the surrounding tooth structure because the elastic modulus (ie, rigidity) of the tooth is far greater than the restorative material.8 As a result of shrinkage stresses being transferred to the tooth, deformation of the tooth can occur. This may result in postoperative sensitivity, opening of microfractures, bond failure, microleakage leading to recurrent caries, and deterioration of the restorative margin.9-11 Several factors have been identified as influencing the shrinkage stress of a restoration: the size and geometry of the restoration (ie, the C-factor, depth and diameter), materials used, and the curing protocol.12-14
Incremental filling techniques have been proposed as a means to reduce shrinkage stress of composite restorations. There has been disagreement among authors recently on this issue. Versluis et al10 and Abbas et al15 showed that deformation and cuspal deflection could be minimized when bulk-filling techniques were used. Lee et al16 and Park et al17 showed that incremental techniques should be used to mitigate polymerization shrinkage and cuspal deformation. Despite differing conclusions, incremental filling techniques are generally recommended, and dentists may choose to restore composite restorations in this manner on the basis of additional factors such as acceptable depth of cure, proper adaptation, and adequate bond formation.10,18
The new category of bulk-fill flowable composites promotes the effective use of 4-mm increments while decreasing shrinkage stresses generated during polymerization.19,20 In 2009, the first bulk-fill flowable resin (Surefil SDR flow [DENTSPLY Caulk]) was introduced (Figure 1). Currently there are 4 bulk-fill flowable composites on the US market: Surefil SDR flow, Filtek Bulk Flow (3M ESPE), Venus Bulk Flow (Heraeus Kulzer), and x-tra Base (VOCO America). A comparison of the 4 currently available bulk-fill flowables is presented in the Table.19,21-30
Ilie and Hickel31 examined Surefil SDR flow compared to other composites and found that the contraction stress generated by Surefil SDR flow was 1.1 mPa compared to 5.3 mPa and 6.5 mPa for Esthet•X (DENTSPLY Caulk) and Filtek Supreme Plus Flow (3M ESPE), respectively. The authors31 theorized that the stress-relieving properties of Surefil SDR flow in part were the result of a delayed gelation phase and slower polymerization, allowing for increased flow. Compared to the other composites, Surefil SDR flow showed the lowest Vickers hardness, which may be due to its having the lowest filler content by volume (44%). For this reason, the Surefil SDR flow directions for use recommend that a 2.0 mm occlusal cap be placed using a universal/posterior restorative composite.32
C-factor is an estimation of the stresses generated through a given cavity configuration by a ratio of bonded to unbonded surfaces. According to Feilzer et al32 the higher the C-factor (ie, the higher the number of bonded surfaces), the higher the stress generated (eg, Classes I and II). Conversely, a cavity with a higher ratio of unbonded surfaces should result in lower shrinkage stress (eg, Classes III and IV). Two recent studies have also suggested that cavity depth and diameter may impact shrinkage stress and resulting microleakage.13,33 Examining the effect of bulk-filling high C-factor cavities with a low shrinkage flowable composite (Surefil SDR flow), Van Ende et al34 and de la Macorra and Gomez-Fernandez,35 showed that 4-mm increments placed in high C-factor preparations (mimicking Class I and II preparations) did not compromise bond strength secondary to shrinkage stress. The authors34,35 concluded that if bulk-fill techniques are desired for restoration of high C-factor cavities, the dentist should consider low-stress materials to avoid adhesive debonding and microleakage. These conclusions appear to agree with the conclusions of Roggendorf et al36 that bulk-fill low-shrinkage flowable resin can be used in an open sandwich technique without a negative impact on marginal integrity.
A STEP-WISE APPROACH TO PLACING CLASS II RESTORATIONS
The gold standard for isolation of prepared teeth prior to composite resin placement is a rubber dam. However, in the case of Class II composite restorations, isolation with a matrix system is the challenge. Not only does the selected matrix system need to seal the preparation to help achieve marginal integrity, it needs to mimic natural tooth contour and facilitate interproximal contact.1 Historically, circumferential matrices (Tofflemire Type, AutoMatrix) have been used but have inherent limitations. While effective in sealing the preparation, Tofflemire matrices provide little help in creating proper interproximal contact, both in the shape and position of the contact or the actual strength of contact, all of which influence the potential for food impaction.37,38
It was not until 1986 and the introduction of the BiTine sectional matrix system (Darway/DENTSPLY Caulk) that a better system for creating Class II contacts in composite resin was introduced.39 Currently, sectional matrix systems such as Palodent Plus (DENTSPLY Caulk), V3 (Triodent), and the Composi-Tight 3D (Garrison Dental Solutions) are designed to overcome the inadequacies of the circumferential matrix and the shortcomings of the BiTine system (eg, tooth separation, seating and stabilizing the ring, preventing the ring from collapsing the matrix on a wide bucco-lingual preparation) (Figures 2 and 3). In addition, the previously mentioned sectional matrix ring systems all include anatomically shaped wedges to facilitate proper interproximal contour and contact creation. Figure 4 shows a radiograph of Class II composites placed with a circumferential matrix and wooden wedges, and a sectional matrix system using anatomic wedges.
Since 1955, Buonocore’s40 acid-etching technique has made bonding to enamel successful. However, achieving consistent dentin bonding has been more challenging based on factors such as microleakage, resin infiltration and penetration, hydration versus desiccation, and postoperative sensitivity.41 To mitigate these factors, the evolution of dentin bonding has included a shift from total-etch techniques involving placement of 30% to 40% phosphoric acid on both enamel and dentin sufaces (ie, etch-and-rinse), to self-etch techniques where phosphoric acid esters are contained within the bonding agent and no etchant gel is placed on the preparation.42
Recently, a third bonding technique has emerged that allows for hybridization of the remaining dentin smear layer and includes phosphoric etching of exposed enamel to maximize bond strength and prevent marginal discoloration. The selective-etch technique is designed to harness the positive attributes of both techniques for improved clinical outcomes. In 2 recent studies, selective-etch adhesives were found to have increased enamel bonding while reporting no postoperative sensitivity.43,44 In a meta-analysis by Heintze and Rousson,45 it was their conclusion that restorations placed with rubber-dam isolation and enamel-etching technique showed the best overall performance. There are currently (at the time of writing this article) 3 universal adhesives on the market that can be used in all 3 etching modes: Prime&Bond Elect (DENTSPLY Caulk), Scotchbond Universal Adhesive (3M ESPE), and All-Bond Universal (BISCO Dental Products).
Resin composite placement involves a precise and strategic process to complete. Challenges to the practitioner include: proper adaptation of material to the preparation, bulk-fill versus incremental fill techniques, polymerization shrinkage and shrinkage stress, depth of cure, and handling of the material.
Historically, practitioners have used flowable composites as liners in Class II preparations because of their increased wetting and ability to adapt to cavity walls. However, the use of flowable composites as a liner to seal the gingival margin and provide an intermediate stress-absorbing layer under Class II restorations is controversial. Some studies have shown decreased microleakage when flowable composite is used as a liner at the gingival margin,46-56 while others have discouraged the practice.57-63 Some studies have concluded that location of the gingival margin, either above or below the cemento-enamel junction, is the most important factor in determining the best restorative material. In these studies, glass ionomer cement has been suggested because of its adhesion properties and lack of shrinkage over flowable composite to prevent microleakage.64-67 When synthesizing the results of these studies, it appears that the use of flowable composite as a liner in the proximal box is preferred to increase cavity adaptation and reduce microleakage.
Because the currently available bulk-fill flowable composites are not promoted for use on occlusal surfaces, a final occlusal layer of restorative composite is needed.19 To simplify decision-making and to offer a composite that can ensure excellent performance in all clinical situations, DENTSPLY Caulk has introduced TPH Spectra Universal Composite (Figure 5). This new composite is based on the resin technology of TPH3 and contains nanohybrid and microfiller components. The result is a composite that has the potential to perform well in either the anterior or posterior, and should have toothlike translucency, improved polishability and color stability, and good wear resistance.68-70 TPH Spectra also comes in 2 handling choices: a creamy light viscosity formulation, and a packable high viscosity formulation. For both viscosities, the physical properties are similar. Because handling preference is subjective and highly individualized, practitioners are able to select the right viscosity for all clinical situations.
The final step for achieving excellent clinical results with Class II composite resin is gross contouring with a high-speed handpiece followed by finishing and polishing of the restoration.71 The polishability of a composite is based on the filler type, shape, and content, and although a recent study showed that hybrid and microfilled composites perform best clinically, the trend in composite technology is for universal applicability. The creation of ideal surface polish of a composite restoration can improve the aesthetics and the longevity of restoration by reducing stain potential, biofilm accumulation, gingival inflammation, and minimizing the wear.72 In a study by Berger et al73 examining 3 composites and polishing systems (ie, DENTSPLY Caulk, 3M ESPE, and Cosmedent) supplied by the same manufacturer, it was the authors’ conclusion that, “the polishing system from the same company as the composite resin should be used, as these showed good results in comparison with other polishers.”
In 2009, CLINICIANS REPORT evaluated composite polishing systems and graded the following polishing disks as good or excellent: Super-Snap Rainbow Technique Kit (Shofu Dental), Enhance (DENTSPLY Caulk), FlexiDisc (Cosmedent), and OptiDisc (Kerr).74
A 32-year-old female presented to the office for examination of an open interproximal contact and persistent food trap in a mandibular left tooth. The clinical exam revealed a fractured disto-occlusal composite in tooth No. 20. The patient requested the restoration be redone to more effectively close the space and prevent food impaction (Figure 6).
After local anesthesia with one carpule of 4% Articadent DENTAL with epinephrine 1:100,000 (DENTSPLY Pharmaceutical), the existing composite was removed with high- and low-speed handpieces, and Snoop Caries Detector (Pulpdent) was used to verify the preparation was free of decay (Figure 7).
|Figure 1. Surefil SDR flow (DENTSPLY Caulk).||Figure 2. BiTine (Darway/DENTSPLY Caulk) Sectional Matrix System in place for the restoration of tooth No. 4. Note that the ring helps to adapt the matrix to the tooth but does not contact the adjacent tooth and does not help to facilitate tooth separation for contact creation.|
|Figure 3. Palodent Plus Sectional Matrix System (DENTSPLY Caulk).||Figure 4. Radiograph showing maxillary premolar restored with circumferential matrix system and triangular-shaped wooden wedges. The lower premolar was restored using the Palodent Plus Sectional Matrix System and anatomic wedges. Note the improved gingival and incisal embrasures of the mandibular tooth, as well as the correct interproximal contour.|
|Figure 5. TPH Spectra (DENTSPLY Caulk).||Figure 6. Pre-op view of tooth No. 20 showing inadequate existing disto-occlusal composite restoration.|
|Figure 7. The finished disto-occlusal preparation is verified with Snoop Caries Detector (Pulpdent).||Figure 8. Isolation of tooth No. 20 using the Palodent Plus Sectional Matrix System.|
|Figure 9. Prime&Bond Elect Universal Dental Adhesive (DENTSPLY Caulk) being placed.||Figure 10. Surefil SDR flow in the Compula Tip being placed into tooth No. 20.|
|Figure 11. TPH Spectra Low-Viscosity Universal Composite is placed for the final occlusal layer.||Figure 12. Tooth No. 20 after composite placement.|
|Figure 13. Using the Palodent Plus Pin Tweezers (DENTSPLY Caulk) for easy removal of the sectional matrix.||Figure 14. After finishing and polishing, the final restoration on tooth No. 20.|
After placing a rubber dam, the entire preparation was etched with 34% phosphoric acid for 20 seconds and then thoroughly rinsed with water. Isolation of the preparation was achieved using Palodent Plus (Figure 8). Prime&Bond Elect was scrubbed into the preparation for 20 seconds and then dried with air for 5 seconds to remove the solvent. The bonding agent was light-cured for 20 seconds (Figure 9).
An initial layer of SureFil SDR flow was placed into the preparation, followed by a 20-second light-cure (Figure 10). TPH Spectra Low-Viscosity shade A2 was placed into the preparation and cured in 2-mm increments (Figure 11).
The final restoration was finished with fluted composite burs and polished with Enhance and PoGo (DENTSPLY Caulk) (Figures 12 to 14).
A female patient presented with a complaint of a lost filling. An intraoral exam revealed a lost disto-occlusal amalgam restoration on tooth No. 12 (Figure 15). The patient was experiencing no pain but did note occasional sensitivity to cold liquids. After verifying the medical history and reviewing the radiographs, a direct composite resin restoration was treatment planned.
Anesthesia was achieved with one carpule of 2% xylocaine DENTAL with epinephrine 1:100,000 via buccal infiltration. The preparation was refined using a 330 carbide bur on a high-speed handpiece and a No. 4 round bur on a low-speed handpiece. Caries removal was verified with Snoop Caries Detector.
|Figure 15. Final preparation of tooth No. 12.||Figure 16. Selective enamel etching of tooth No. 12.|
|Figure 17. Tooth No. 12 is isolated with Palodent Plus Sectional Matrix System. Because of a gagging tendency, no rubber dam could be used for this patient.||Figure 18. Prime&Bond Elect is scrubbed into the preparation of tooth No. 12.|
|Figure 19. TPH Spectra High-Viscosity is placed into tooth No. 12.||Figure 20. Tooth No. 12 after composite placement and curing, before removal of the matrix system.|
|Figure 21. Final restoration of tooth No. 12.|
Because of the depth and size of the final preparation, a selective etch technique with Prime&Bond Elect was used. This technique was chosen to maximize enamel bonding and minimize etching of dentin.44,75 The enamel was etched with 34% phosphoric acid for 20 seconds and then rinsed (Figure 16). Prime&Bond Elect was scrubbed into the preparation for 20 seconds and then dried with air for 5 seconds to remove the solvent (Figure 17). The adhesive was light-cured for 20 seconds. Isolation of the preparation was achieved using Palodent Plus (Figure 18). The patient’s shade was judged to be approximately A2 according to the VITA Classic (Vident) shade guide. TPH Spectra High-Viscosity shade A2 was selected and placed in 2-mm increments (Figures 19 and 20). Each composite increment was light-cured for 20 seconds.
The final restoration was finished with fluted composite finishing burs and white stones to achieve proper shape and contour. After occlusal adjustment, the composite was polished with Enhance and PoGo (Figure 21).
Current dental materials are technologically advanced and capable of spectacular results when utilized in a careful and precise manner. Systems exist in dentistry to provide step-by-step solutions to clinical situations that if followed, can lead to positive outcomes. These solutions have existed in implantology as kits and in fixed prosthodontics, and now, as demonstrated in this article, clinicians have a predesigned, coordinated Class II solution for the predictable placement of Class II composite restorations.
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Disclosure: Dr. Goodchild is a salaried employee of DENTSPLY Caulk.