Nanomicrohybrid Composites Make Posterior Placement Easier

Creating direct posterior restorations requires the utilization of instruments, techniques, and materials that result in increased longevity, functionality, and aesthetics, goals highly desired by both patients and practitioners. Compared to amalgam, the restoration of teeth with resin composites is laborious and technique sensitive. Common concerns and challenges include the achievement of good proximal contact, proper contour, and sensitive-free postoperative restorations. Nowadays, many products, techniques, and instruments are available to the dentist in order to obtain consistent and easily attainable results in daily practice. However, proper utilization and understanding of these materials and techniques is imperative to achieve such goals.
The purpose of this article is to describe the technique and utilization of a nanohybrid resin composite to restore a Class II cavity preparation.

CASE REPORT
Diagnosis
A 35-year-old male patient presented for a hygiene and recall examination. The clinical and radiographic examinations revealed a defective amalgam restoration with recurrent decay and caries in the mesial aspect of a lower first molar (Figure 1). The patient had not experienced pain or sensitivity prior to the appointment. The tooth responded positive to pulp testing, perio probings were within normal limits, and the use of “tooth slooth” did not reveal any cracklike symptoms. The patient’s occlusion was within normal limits and no parafunctional habits were identified.

Clinical Protocol
First, a local anesthetic was administered, and then the tooth was cleaned with a slurry of pumice prior to selecting a shade. The A1 shade was selected from the middle third of the tooth and isolation was then achieved using a rubber dam (Figure 2). Note that achieving proper isolation is important when placing composite restorations, since bonding is negatively affected by contamination with saliva or blood.^1-2 The existing amalgam restoration was removed using diamonds (Figure 3), revealing remaining decay in the mesial and pulpal floor.
All infected and soft dentin were removed from the deepest portions of dentin (Figure 4). The textured appearance at the bottom of the preparation represents dentin affected by the caries process but was firm to probing. The crack in the mesial aspect was not followed because the tooth was vital and no periodontal pocket or pain was evident. The size and extension of the cavity preparation should be dictated by the removal of any existent restorative material and caries, with the ultimate goal of preserving as much healthy tooth structure as possible. Upon inspection, the final preparation should present round internal line angles and a smooth cavosurface margin; any severely undermined thin enamel should be removed. A slight divergence or flare is attained over the occlusal aspect with a flame-shaped fine diamond bur (8862.31.012 [Brasseler USA]). This ensures no loose enamel rods are present at the enamel margin.³ Interproximally, the preparation should be carried below the contact point, because proximal caries initiate slightly below the contact point. If the facial and lingual aspects of the contact are not removed during cavity preparation, they are slightly opened or lightened with a fine grit safe-sided strip (VisionFlex Diamond Strips [Brasseler USA]) in order to facilitate the insertion of the proximal matrix.

Figure 1. Preoperative view showing the patient’s defective amalgam restoration with recurrent decay in the mesial.	Figure 2. Isolation was achieved with a rubber dam.
Figure 3. After removing the old amalgam restoration, decay remained in the mesial and pulpal floor.	Figure 4. The textured appearance at the bottom of the preparation represents dentin affected by the caries process.
Figure 5. A resin-modified glass ionomer liner (RelyX Luting Plus [3M ESPE]) was carefully placed over dentin surface. Note that this liner did not cover the enamel in order to ensure enamel adhesion.	Figure 6. A band, sectional matrix, separation ring (V3 Ring Universal separation ring [Triodent]), and wooden wedge were placed to close the gingival area.

A resin-modified glass ionomer liner (RelyX Luting Plus [3M ESPE]), was carefully placed over the deep dentin surfaces and then light-cured for 20 seconds (Figure 5). (The liner should not extend to the enamel in order to ensure sealing of the cavosurface margin via enamel adhesion.)
A sectional matrix (V3 Ring Universal Separation Ring [Triodent]) and a wooden wedge were placed before application of the adhesive. It is important to consider that the wedge has the purpose of closing the gingival embrasure; the ring has the purpose of separating the teeth to compensate for the matrix thickness and to obtain a tight proximal contact; and the band has the purpose of containing the material and reproducing proper anatomical proximal contour. Contoured sectional matrices represent a better alternative to conventional matrices used for amalgam because of their anatomical shape. Proper gingival-occlusal placement of the sectional matrix should be achieved to create ideal contour and to minimize any finishing procedures, especially interproximally where access is difficult. When placing the matrix, the occlusal curvature of the sectional matrix should match the adjacent marginal ridge to achieve proper proximal occlusal contour of the final restoration. While holding the matrix in place, the wedge is inserted, and then the ring is placed.
The sectional matrix was burnished against the adjacent tooth to replicate the position and extension of proximal contact, about 1.0 mm below the marginal ridge (Figure 6). A total-etch 3-step adhesive (OptiBond FL [Kerr]), was used to bond the composite to the enamel and dentin. The entire preparation was etched with 37% phosphoric acid gel. Due to the different composition of enamel and dentin, the etchant needs to be applied to enamel longer than to dentin; as such, the etchant was then applied to enamel first and subsequently to dentin in such a way that dentin is etched for no more than 10 seconds.⁴ The preparation was then rinsed and left moist. Multiple coats of primer were applied for 30 seconds and then thoroughly dried to remove residual water and solvent. Next, a coat of adhesive was applied and light-cured for 20 seconds.
Two increments of Tetric EvoCeram A1 Enamel (Ivoclar Vivadent) were placed to fill the proximal box (Figure 7). The first increment was applied to a thickness of about 2.0 mm using a smooth, round-ended condenser, pressing and adapting the material into the proximal box. A microbrush was used to smooth the composite surface before polymerization to facilitate adaptation of the subsequent increment, thus preventing voids between increments. Each increment was individually cured for 40 seconds. The final resin increment should be taken to full contour without excess or minimal excess to facilitate contouring and limit the use of rotary instruments during finishing.

Figure 7. Two increments of Tetric EvoCeram (Ivoclar Vivadent) enamel were placed to fill the proximal box.	Figure 8. One increment of Tetric EvoCeram dentin was placed to cover the pulpal floor.
Figure 9. The triangular ridges were incrementally filled using an enamel shaded Tetric EvoCeram material.	Figure 10. Anatomical contouring was accomplished using a thin-bladed instrument and brushes.
Figure 11. The restoration was polished using a composite polishing brush (Jiffy [Ultradent Products]) brush, while a No. 12 Bard Parker blade was used to remove any flash interproximally.	Figure 12. The occlusion was verified using articulating paper.

Figure 13. Postoperative view of the completed nanomicrohybrid composite resin restoration.

One 2.0-mm increment of Tetric EvoCeram A2 Dentin (Ivoclar Vivadent) was placed to cover the pulpal floor and cured for 40 seconds (Figure 8). This dentinlike increment is usually achieved using one or 2 dentin shades darker than the selected shade in order to impart chroma to the final restoration. Additionally, the use of a dentinlike material ensures adequate opacity to block any undesired coloration from the dentin. The remainder of the preparation was incrementally filled with Tetric EvoCeram T Enamel. The use of a high translucency material allows for better blending and a chameleon effect over enamel. Each triangular ridge was placed and contoured using a thin-bladed instrument and a sable brush. Careful attention should be given to adapt each increment and follow the cusp inclines and existent occlusal anatomy. A football burnisher is also very helpful to contour the material. Each increment was light-cured for 40 seconds prior to placement of the next increment (Figure 9).
The resin material used in this restorative case (Tetric EvoCeram) is a universal nanomicrohybrid composite that has a nice viscosity and handling characteristics, facilitating incremental placement, and sculptability. The material does not slump; it is not sensitive to ambient light and is not sticky, thus allowing it to be placed wherever the clinician wants to place it while maintaining its shape. This nanohybrid composite was also chosen because it demonstrates greater ease-of-use and low polymerization shrinkage rates to reduce marginal leakage and secondary caries.
The ring, wedge, and matrix were removed, and finishing and polishing were accomplished with abrasive rubber points (HiLuster [Kerr]). If necessary, fine diamond grit burs and abrasive disks can also be used to eliminate gross excess or for recontouring (Figure 10). The restoration was polished using a composite resin polishing brush (Jiffy [Ultradent Products]) to reach into all of the grooves and establish a nice smooth surface, while a No. 12 Bard Parker blade was used to remove any interproximal flash (Figure 11). The occlusion of the final restoration was verified using articulating paper (Red/Black AccuFilm II 
[Parkell]) (Figure 12).

CONCLUSION
A simplified incremental layering technique for restoration of posterior teeth using a sculptable and very polishable universal nanomicrohybrid composite resin material was described. Modern composite resins, instruments, and techniques enable clinicians to easily and predictably create sensitive-free restorations that demonstrate good anatomical form, good proximal contacts, and a good chameleon effect that will blend into the surrounding tooth structure (Figure 13). Additionally, when incremental placement follows tooth contour, and materials with excellent polishablilty are used, the clinician can easily impart a lustrous and aesthetic surface to these restorations quickly and with a minimal armamentarium.

References

1. Chang SW, Cho BH, Lim RY, et al. Effects of blood contamination on microtensile bond strength to dentin of three self-etch adhesives. Oper Dent. 2010;35:330-336.
2. Powers JM, Farah JW. Technique sensitivity in bonding to enamel and dentin. Compend Contin Educ Dent. 2010;31(3, special issue):1-8.
3. Baratieri LN, Ritter AV. Critical appraisal. To bevel or not in anterior composites. J Esthet Restor Dent. 2005;17:264-269.
4. Zhao SJ, Zhang L, Tang LH, et al. Nanoleakage and microtensile bond strength at the adhesive-dentin interface after different etching times. Am J Dent. 2010;23:335-340.

Dr. Vargas graduated from Cayetano Heredia University School of Dentistry in Lima, Peru, in 1985. He spent from 1990 to 1992 in the AEGD program at the Eastman Dental Center in Rochester, NY. He received his certificate and master’s degree in operative dentistry in 1994 at the University of Iowa, where he is currently a professor in the department of family dentistry. He also maintains a private practice limited to operative dentistry with an emphasis on aesthetic dentistry. His primary research interests are in the area of dental materials, including glass ionomers, dentin bonding, composite resins, and aesthetic dentistry. He is also recognized for his expertise of direct restorative treatment procedures and conducts numerous lectures and hands-on seminars internationally. He has been published extensively in the area of dental adhesion and resin composites for more than 20 years. He can be reached via e-mail at marcos-vargas@uiowa.edu.

Disclosure: Dr. Vargas reports no disclosures.