Composite Resins 2.0: Entering a New Age of Posterior Composites

INTRODUCTION
Dental practitioners have been placing composite resin restorations for more than 50 years,¹ and throughout this time, scientists around the world have invested numerous resources to create materials with great physical properties. Unfortunately, while physical properties of composite resin have improved, the time-consuming technique required to place these tooth-colored restorative materials has undergone little change. In fact, bulk fill composites first made their debut with the original paste-paste system. These composites were placed in larger increments, taking a few minutes to harden. In the 1970s, microfilled composites made their way into dental practices, and these single-paste systems needed to be polymerized with an ultraviolet dental curing light. This advancement essentially offered the benefit of being able to set the composite on command; however, the practitioner needed to utilize a time-consuming layering technique to minimize the problems of sensitivity, cuspal flexure, and marginal failure that were evident when these materials were bulk-filled and cured.²
In an ideal world, a composite resin would be developed that would allow bulk filling while giving the practitioner complete control over the hardening of the composite via light polymerization. During the last few years, manufacturers have thought of various ways to address this need; one way is by giving the clinician the ability to place a large volume of a low-viscosity, low-shrinkage resin as a base (or primary layer) to be followed by a traditional capping layer. Some composite materials (such as SureFil SDR flow [DENTSPLY Caulk] and Venus Bulk Fill [Heraeus Kulzer]) allow the practitioner to place an initial layer of resin at 4 to 5 mm in depth, and then place a capping layer of traditional composite over the top. This capping layer, needed for high to moderate stress areas, is a recommended step by the manufacturers. This is because the modulus of elasticity and hardness of these materials tend to be lower than traditional nanohybrid and microhybrid resin-based composites.³ The initial bench studies of these materials show favorable results of low shrinkage stress;⁴ however, the actual process of restoration placement is an incremental advancement to traditional layering techniques.

Sonic Composite Placement Technique Introduced
In 2010, Kerr released its answer to efficient posterior composites with the creation of a system named SonicFill. This composite system allows sonic energy to be transferred, via a specially designed handpiece, to a proprietary composite resin. In addition, the restorative material can be cured in 5.0 mm increments with no capping layer.
The SonicFill system includes a handpiece (Figure 1), as well a proprietary composite resin that undergoes an 87% drop in viscosity while the sonic energy is being applied. The practitioner can titrate the rate of flow of the material through a combination of a one to 5 speed setting (one being the slowest setting) on the handpiece, as well as control the amount of pressure placed on a standard rheostat. As the practitioner decreases the energy applied by the handpiece via the rheostat, the composite resin will slowly regain its original viscosity. During this period of time, the practitioner has ample time to sculpt and contour the material before polymerizing it with a standard LED (or halogen) dental curing light.

Author’s Experience
I was first introduced to the SonicFill system in 2010 and served as the principal investigator for a pilot clinical study, comparing SonicFill restorations placed in bulk by dental students versus traditional layering techniques at the University of the Pacific’s Arthur A. Dugoni School of Dentistry. The patients within the study were evaluated at 6 months, 12, months, and 18 months, and during the course of this time, it became apparent that SonicFill restorations were holding up just as well as traditional layered composites. It was through this experience that I became fond of the system and now use it routinely for posterior restorations in my own private practice.

Review of the Clinical Steps
Once the preparation of the cavity form is completed, the practitioner will routinely check the maximum depth of the cavity preparation using a periodontal probe (Figure 2). The manufacturer’s instructions state that the SonicFill resin should only be placed in 5.0 mm increments or less, compared to a recommendation of 2.0 mm or less, as stated for traditional composites. In the event that the cavity form exceeds these dimensions, the clinician can simply place a second layer on top of the first. After cavity preparation depth is confirmed, the SonicFill compule is placed within the cavity form to assure that access is not an issue in getting to the base of a conservative box form (Figure 3). In the author’s experience, if the tip of the compule is within 2.0 mm of the gingival margin, the dramatic viscosity drop of the material upon sonic activation will allow the material to completely adapt to the gingival margin. If the practitioner would like to blend composites, it is acceptable to place a small layer of flowable composite near the gingival margin, followed by the application of the SonicFill resin. After checking for proper access, the practitioner would then utilize a total-etch or self-etch technique, as preferred, and then proceed to place the composite resin. The material would flow into place and slowly regain a more viscous state. During this time, the practitioner could sculpt the resin to the preferred contour. Then, the resin would be polymerized with a curing light from the occlusal, buccal, and lingual surfaces.⁵ Finally, the restoration could be completed with the usual finishing and polishing techniques.

CASE REPORTS
Case 1
A 33-year-old female patient presented with an amalgam restoration on tooth No. 30 that exhibited a marginal discrepancy near the mesial pit and approximal caries extending under the mesial marginal ridge. The patient demonstrated ideal cuspid rise in right lateral movement, and no signs of excessive occlusal wear were present on the adjacent or opposing teeth. Based on these factors, a decision was made to place a direct mesial-occlusal composite restoration.

Figure 1. The SonicFill (Kerr) handpiece has built-in speed regulation.	Figure 2. In this case, the greatest depth measures less than 5.0 mm.
Figure 3. The cavity prep is checked to see that the SonicFill tip has proper access to box form.	Figure 4. (Case 1) Tooth No. 30: Preoperative condition.
Figure 5. Caries and existing alloy have been removed.	Figure 6. A 37% phosphoric acid-etching gel (Ultra-Etch [Ultradent Products]) was applied.

Clinical Protocol
After anesthetizing the patient, teeth Nos. 28 to 31 were isolated with a rubber dam (DermaDam [Ultradent Products]) and a 12A clamp (Hygenic [Coltène]) (Figure 4). The alloy restoration and approximal caries were then removed to achieve cavosurface margins on sound tooth structure. Next, a sectional matrix (V3 Matrix [Triodent]), wedge (Wave-Wedge [Triodent]), and ring (V3 Universal Ring [Triodent]) were then placed on the mesial proximal surface of tooth No. 30 (Figure 5). After confirming that the matrix was properly sealed, a total-etch adhesive technique was utilized. The enamel was etched for 20 seconds and the dentin was etched for 15 seconds utilizing a 37% phosphoric acid (Ultra-Etch [Ultradent Products]) (Figure 6). After rinsing the etchant and blot drying with a cotton pellet, a fifth-generation adhesive (OptiBond Solo Plus [Kerr]) was applied, air-thinned, and then light-cured for 20 seconds utilizing an LED curing light (Demi [Kerr]) (Figure 7). The deepest portion of the preparation measured slightly greater than 4.0 mm in depth, so it was decided the entire volume of the restoration could be filled with one increment of SonicFill composite. The SonicFill system was set at a flow rate of 4 and the entire preparation was filled. After letting the resin settle for approximately 10 seconds, an acorn burnisher was moistened with wetting resin (Composite Wetting Resin [Ultradent Products]), and the anatomically correct form was sculpted. Upon completion of the sculpting, the resin was then light-cured from the occlusal surfaces for 20 seconds utilizing the LED curing light. After removing the sectional matrix system, the restoration was further cured from the buccal and lingual surfaces for an additional 20 seconds each. After removing the rubber dam, a minor occlusal adjustment was made utilizing a 16-fluted carbide composite finishing bur (ET Series [Brasseler USA]). Finally, the restoration was polished utilizing a 3-step silicone-impregnated rubber point system (Jiffy Polishers [Ultradent Products]). The final result can be seen in Figure 8.

Figure 7. A fifth-generation adhesive (OptiBond Solo Plus [Kerr]) was applied, air-thinned, and then light-cured for 20 seconds utilizing an LED curing light (Demi [Kerr]).	Figure 8. Restored with SonicFill and polished.
Figure 9. (Case 2) Tooth No. 14: Preoperative condition showing fractured mesial marginal ridge.	Figure 10. Protection device placed in the interproximal space.
Figure 11. Caries and existing alloy removed and clear through sectional system placed.	Figure 12. Maximum depth of restoration measured with periodontal probe.
Figure 13. Adhesive applied and light-cured.	Figure 14. View of restorations immediately after curing and removing sectional matrix system.

Case 2
A 40-year-old male patient presented at his 6-month recare examination with a fractured mesial marginal ridge on tooth No. 14. Radiographic examination did not reveal any obvious signs of caries on the mesial approximal surface; however, the fractured mesial segment was clearly visible on clinical examination. The patient was informed that a fair amount of tooth structure would need to be removed, and the ideal treatment of choice would involve cuspal coverage utilizing an indirect restoration. The patient had a history of cuspal fractures due to clenching; however, finances happened to be a concern for the patient. As a result, he opted to have a direct restoration placed in the interim. In addition, the patient was also informed that he had a restoration on tooth No. 12 that could benefit from a more ideal contour but opted not to purse treatment at the time.
After anesthetizing the patient, teeth Nos. 12 to 15 were isolated with a rubber dam, and a 12A clamp was placed on tooth No. 15. The mesial fracture was clearly evident once the tooth was isolated (Figure 9). A protection wedge (Wave Guard [Triodent]) was placed between teeth Nos. 14 and 13 to allow for prewedging as well as protection of the adjacent approximal surface (Figure 10). Once the caries and existing restoration were removed, a clear metal matrix was placed (ClearMetal Matrix [Triodent]) and a gingival seal was created utilizing a wedge (V4 Wedge [Triodent]). A separating ring (V4 Molar Ring [Triodent]) was then placed to apply buccal and lingual pressure, allowing for a temporary increase in interproximal space between teeth Nos. 13 and 14 (Figure 11). A perio probe was then utilized to measure the area of the preparation that exhibited the greatest depth. The mesial proximal box form at its greatest depth measured 4.5 mm from the base of the gingival floor to the cavosurface (Figure 12). Since this measurement was within the manufacturers’ recommendation (5.0 mm or less), it was decided that a single increment of the restorative material could be placed. A total-etch technique was utilized, and the Optibond Solo Plus adhesive was applied to all surfaces of the cavity form and light-cured (Figure 13). A single increment of the SonicFill composite was placed at an extrusion speed of 5. After waiting for approximately 10 seconds for the SonicFill material to regain viscosity, an acorn burnisher was moistened with the composite wetting resin, and the anatomical form was sculpted in less than 30 seconds. Once proper form was reached, the restoration was polymerized from the occlusal, buccal, and lingual surfaces for 20 seconds each using the Demi LED curing light. Once the matrix band was removed, the approximate final contour of the restoration was present. At this point it was apparent that the central to mesial pit was slightly oversculpted, and a gray hue was visible through the restoration (Figure 14). To minimize this issue, a small amount of the SonicFill composite was added, and then blended into the underlying composite and polymerized. Note in hindsight, a small amount of opaque flowable composite could have been placed over the stained dentin to block this gray hue out in its entirety. The rubber dam was removed, the occlusion was checked, and the restoration was polished utilizing a 3-step silicone-impregnated rubber point system (Figure 15).

Case 3
A 53-year-old female patient presented with caries on the mesial approximal surface of tooth No. 14 (Figure 16). The patient did not exhibit any substantial occlusal wear, so a direct mesial-occlusal-lingual composite restoration was treatment planned. After administering anesthesia, a rubber dam was placed and teeth Nos. 12 to 15 were isolated. Upon removing the existing restoration and caries, highly stained dentinal surfaces were noted. A clear sectional matrix (Clear [Garrison Dental Solutions]) was utilized on the mesial proximal surface, followed by the placement of a wedge (Cure Through Wedge [Garrison Dental Solutions]) and separating ring (Composi-Tight 3D XR [Garrison Dental Solutions]) (Figure 17). Upon confirmation of complete gingival seal, a similar total-etch technique utilizing 37% phosphoric acid and OptiBond Solo Plus was followed as demonstrated previously in cases 1 and 2. Noting that the dentin was highly stained, a 0.75 mm layer of opaque flowable composite (Premise Flowable [Kerr]) was placed over this area and fully polymerized with the Demi LED curing light. A single increment of SonicFill composite was then placed, contoured, polymerized, and polished in the same manner as demonstrated in the preceding cases. It is interesting to note that SonicFill composite can be layered with other composites, if the clinician feels an aesthetic and/or functional advantage can be achieved. In this case, by utilizing a small amount of opaque flowable composite, a very efficient and aesthetically pleasing restoration was still achieved. Unlike the final restoration depicted in Case 2, no gray hue is visible through the restoration (Figure 18). In a traditional approach, 3 to 4 separate increments of composite would have been placed and individually polymerized in order to achieve similar results.

Figure 15. Restored with SonicFill and polished.	Figure 16. (Case 3) Tooth No. 14: Preoperative condition depicting existing restoration and caries extending under mesial marginal ridge.
Figure 17. Caries and existing alloy removed and clear through sectional system placed.	Figure 18. Restored with SonicFill and polished.

IN SUMMARY
After 3 years of clinical use in private practice, the author has witnessed very positive results with the SonicFill system, and it is now being utilized for the vast majority of the posterior composites placed. Until this composite resin system was introduced, the author practiced a strict 2.0 mm oblique composite layering protocol and was very hesitant to initially change due to fear of sensitivity, marginal leakage, and tooth fracture. However, these fears have subsided after clinical experience with the system and, in fact, a recent dye leakage study demonstrated that the SonicFill technique demonstrated a lower degree of dye penetration compared to other bulk fill composites (as well as more traditional composites) placed with a traditional layering technique.⁶
This composite system offers the simplicity of a single-increment bulk-filling technique and also the versatility of being compatible with other composites when a blended technique may be indicated. It is the author’s finding that the SonicFill system is a tremendous time saver without sacrificing proper functional and aesthetic results.

References

1. Bowen RL, assignor to the United States of America as represented by the Secretary of Commerce. Dental filling material comprising vinyl silane treated fused silica and a binder consisting of the reaction product of bisphenol and glycidyl acrylate. US patent 3,066,112. November 27, 1962.
2. Kwon Y, Ferracane J, Lee IB. Effect of layering methods, composite type, and flowable liner on the polymerization shrinkage stress of light cured composites. Dent Mater. 2012;28:801-809.
3. Ilie N, Bucuta S, Draenert M. Bulk-fill resin-based composites: an in vitro assessment of their mechanical performance. Oper Dent. 2013 Apr 9. [Epub ahead of print]
4. El-Damanhoury H, Platt J. Polymerization shrinkage stress kinetics and related properties of bulk-fill resin composites. Oper Dent. 2013 Jul 18. [Epub ahead of print]
5. Belvedere PC. Contemporary posterior direct composites using state-of-the art techniques. Dent Clin North Am. 2001;45:49-70.
6. Poggio C, Chiesa M, Scribante A, et al. Microleakage in class II composite restorations with margins below the CEJ: in vitro evaluation of different restorative techniques. Med Oral Patol Oral Cir Bucal. 2013;18:e793-e798.

Dr. Kachalia is an associate professor and the vice chair of simulation, technology, and research and is a team leader within the University of the Pacific’s rehabilitation program. He is a Fellow of the American Dental Education Association’s leadership institute. He lectures internationally, and is a researcher and published author in the areas of dental technology, digital diagnostics, contemporary fixed prosthodontics, and financial management. Dr. Kachalia acts a consultant for many dental materials/dental technology companies. He is a member of the Pride Technology Leadership Council. Dr. Kachalia maintains a private practice geared toward restorative dentistry with his wife and fellow Pacific alum Dr. Charity Duncan. He can be reached at pkachalia@pacific.edu.

Disclosure: Dr. Kachalia received research funding from Kerr.