Making Contact Just Got Easier: Making Class II Composite Restorations More Predictable

INTRODUCTION
One problem that is an all too common occurrence with the Class II composite resin restoration is gaining a positive proximal contact that is anatomically acceptable.^1,2 This problem is born from the properties of the material itself; often viscous in nature and not predictably compactable. While placing the Class II restoration, even the most viscous packable composite resins cannot adequately and predictably move the matrix band to establish a proper contact form.^3-6 The development of an anatomically correct proximal contact is critical to the success of a Class II composite resin restoration. According to Hancock et al,⁷ there is a direct correlation between the type of proximal contact and food impaction; and between pocket depth and food impaction. Class II caries initiates just below the proximal contact, and just as there is a correlation between pocket depth and food impaction in the proximal area, there is also a correlation between food impaction and recurrent caries at the gingival margin of existing Class II restorations.

Figure 1. Pre-op (clamped) tooth No. 31.	Figure 2. Pre-op radiograph of tooth No. 31.

The Class II posterior composite resin is agreeably one of the more challenging restorations to place consistently for clinicians. Throughout the years, many different matrix designs have been introduced in the hope of eliminating the problem of poor proximal contacts with composite resin restorations. Some strategies used have been: types of metal used, thickness of metal, and redesign of the retainer system. Other ancillary instrumentation, to disperse light into the interproximal area and to tighten the contact, have been introduced as well.

The purpose of this article is to explore current clinical techniques and instrumentation in order to minimize the frustrations associated with this restorative procedure so that the operator may obtain predictable and consistent results.

Issues to Consider
There is clinical evidence to suggest that Class II composite resin restorations may demonstrate higher rates of recurrent decay than amalgam restorations.^8-10 As Hinoura et al¹¹ suggest, the higher failure rates at the gingival margins of Class II composite resins can be related, but not limited to, the following: the technique sensitivity of some dentin bonding systems; polymerization shrinkage of composite resin; challenges in techniques placing highly viscous composite resin into proximal boxes without trapping air bubbles (leading to poor marginal adaptation); contamination of the tooth surfaces due to poor field isolation; and poor polymerization of the resin adhesive and composite due to inadequate curing light output^11,12 and the distance of the light guide from the gingival margin.^13-15

Figure 3. Pin forceps holding Palodent Plus (DENTSPLY Caulk) matrix band.	Figure 4. Palodent Plus Wedgeguard (DENTSPLY Caulk).
Figure 5. Side view of Palodent Plus matrix ring, band, and wedge in place.	Figure 6. Palodent plus matrix ring (DENTSPLY Caulk).

Xu et al¹⁶ investigated composite resin adhesion as the distance from the light guide increased. Their investigation was prompted by the number of studies demonstrating poor marginal seal and increased microleakage at the gingival margin of these restorations when compared to the occlusal enamel margins. Their conclusion was that the curing time should be increased to 40 to 60 seconds to ensure optimal polymerization, when curing adhesives in deep proximal boxes with a curing light set at 600 mW/cm².¹⁶

Considerations for Light-Curing Class II Restorations
Check the light output on your curing light. If less than 600 mW/cm² of output, it will require doubling the curing time in the proximal box of a Class II restoration. At least 1,200 mW/cm² is the preferred light output.
Light tip contamination is a common area overlooked in the dental office. Clean the light tip probe of any contaminants. Have a protective sheath covering the light probe and rest the probe on the posterior cusps.
When placing the light guide, the light guide should be at a right angle (90°) to the tooth being restored, with the light probe touching the tooth.

Historical Approach to Creating Proximal Contact
Historically, the most commonly used approach for obtaining proximal contacts has been the application of thin dead-soft stainless steel matrix bands that circumferentially fit around the teeth (Table 1). These bands are available for use in a Tofflemire-type matrix retainer, such as the HO band (Young Dental), a 0.001-inch dead-soft stainless steel band; Microbands (Dental Innovations), a conventional Tofflemire-type matrix band that has been machined to be ultrathin in the contact area; or as a circumferential retainer-less matrix, such as the Automatrix (DENTSPLY Caulk) or SuperMat (Kerr Corporation). These circumferential-type matrix systems have been used with Class II MO/MOD/MODL(B) preparations. The biggest drawbacks in using these systems are time in preparation of the matrix band, inconsistent resulting contacts, and occasionally, instances in which you cannot use rubber dam isolation with the circumferential matrix band system.

Figure 7. Prepped distalocclusal tooth No. 31. Very large intercuspal position area to fill.	Figure 8. Palodent Plus in place, restoration placed.

Another class of matrix system is the sectional matrix, in combination with a ring. Traditionally, these systems have been limited to 2-surface Class II preparations restoring only a single proximal surface. The “weak link” in these systems is the design of the ring. Made in either metal or plastic, the thin and often poorly shaped ring-tines that fit between 2 teeth on the buccal and lingual surfaces slip off, eliminating their ability to be used on shorter clinical crowns and more extensive tooth preparation into either the buccal or lingual cusps.

A NEW APPROACH INTRODUCED
A new class of sectional matrix (Palodent Plus Sectional Matrix System [DENTSPLY Caulk]) has recently been introduced. Entirely redesigned, this matrix system incorporates some unique features: it utilizes an ultra-thin dead-soft stainless steel sectional matrix in combination with a ring that, when placed, is designed to achieve some additional tooth separation; and fit so as to adapt the sectional matrix to form an anatomically correct contact with the adjacent tooth. Also, because of the redesigned ring, this matrix system allows utilization of the matrix with virtually all sizes of restorations including MOD and MODL(B). In addition, the clinician can place an anatomically correct wedge before or after placing the ring. The wedge comes in 3 different sizes and is designed to not impinge the interdental papilla, pushing the matrix band against the cervical portion of the box to create a better marginal seal. The rings, sectional matrices, and wedges are uniquely designed for easy handling, pick-up, and control during placement and removal, created with built-in holes to accommodate specially designed forceps. Because of this incredibly unique sectional matrix design, the Palodent Plus Matrix System, in the author’s hands, is faster and easier to place than previously introduced matrices. The author also finds an accurate and anatomically-shaped proximal contact can be created more consistently.
Besides matrix bands, other devices have been introduced to assist in achieving an anatomically correct proximal contact with Class II composite resins (Table 2). Some of these devices (eg, contact formers [American Eagle Instruments] and Contact Pro [CEJ Dental]) allow the clinician to push against the matrix band while light-curing. While these devices can achieve the desired result, they are limited in that they do not fit all preparations. Other devices include the Light-Tip (Denbur) and ProxiCure tips (Ultradent Products), which are fitted over the curing light tip and can be inserted into the proximal box of the cavity preparation, allowing light penetration into the critical gingival area of the tooth preparation.¹⁵ However, because of the design of the tip, it will not form the contact predictably in the correct anatomic location, and in some instances its size precludes use in more conservative cavity preparations. 
A smaller, more anatomically shaped tip (Trimax [AdDent]) was introduced to enhance light dispersion into all aspects of the proximal box, while at the same time allowing for pressure on the matrix band to achieve a positive anatomic proximal contact. In the author’s hands, it is found to be easy to control. Furthermore, if necessary, it can be modified for minor variations in preparation size and shape. This single-use disposable tip solves problems associated with a decrease in light penetration through the tip due to repeated autoclaving. Another benefit of using a light-conducting device is that there will be a reduction in the amount of composite resin being cured in the proximal box at the gingival margin, thereby reducing the polymerization shrinkage gaps that can occur.^12,13 The light-transmitting device directs the curing light to the depths of the composite resin in the proximal box.

CASE REPORT
The patient presented for treatment with clinical and radiographic evidence of caries on the mesial of the tooth No. 31 (Figures 1 and 2). Tooth No. 30 was scheduled to be replaced with a core and a full-coverage crown at a future date.
A rubber dam (Hygenic Flexi-Dam nonlatex [Coltène]) was placed after the administration of local anesthesia. Preparatory removal of existing occlusal composite and associated decay was initiated. The tooth was prepared with Nos. 558 and 4 round carbide burs (DENTSPLY Midwest) and a 1103R diamond bur (DENTSPLY Midwest).
A Palodent Plus Wedgeguard (DENTSPLY Caulk) (Figure 3) was used to protect the adjacent tooth. The Palodent Plus Matrix sectional matrix has a tab extension and grip holes that makes it easy to hold and place using a special pin-forcep (Figure 4).

Once the sectional matrix was placed an anatomic flexible polymeric wedge was placed to stabilize the matrix (Figure 5). This wedge has a tab extension with a grip hole to make it easy to hold and place using the same pin-forcep. Next, a silicone-covered split-ring (Figure 6), uniquely designed to place over the wedge and form the matrix to the prepared tooth, is placed. This ring, because of its design, is stable on the tooth and continues to apply pressure during restoration placement to ensure an anatomic proximal contact. Also, its shape allows for placement without interference from the gingival wedge. The wedge can be placed before or after you place the ring (Figure 7).
The matrix is then burnished with a round instrument of the clinician’s choice into the adjacent tooth to create a contact point.
Adhesive (Allbond Universal [BISCO Dental Products]) was applied and the prepared tooth was filled with a composite resin (Esthet.X HD [DENTSPLY Caulk]). Then, after light-curing (Smartlight Max [DENTSPLY Caulk]), the matrix, ring, and wedge were removed. The restoration was finished and adjusted for proper occlusion (Figure 8). (See the actual video case study by tagging this article with your smartphone.)

CONCLUSION
Because of the shift in material usage from amalgam to composite during the last 20 years, there has been a need to improve operator technique and instrumentation for Class II restorations. The concepts, instrumentation, and techniques described herein can be used to assist the clinician with useful information to make the placement of Class II posterior composite restorations easier and more predictable.

References

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3. Strydom C. Handling protocol of posterior composites—part 3: matrix systems. SADJ. 2006;61:18-21.
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10. Bernardo M, Luis H, Martin MD, et al. Survival and reasons for failure of amalgam versus composite posterior restorations placed in a randomized clinical trial. J Am Dent Assoc. 2007;138:775-783.
11. Hinoura K, Miyazaki M, Onose H. Effect of irradiation time to light-cured resin composite on dentin bond strength. Am J Dent. 1991;4:273-276.
12. Rueggeberg FA, Jordan D. Light tip distance and cure of resin composite. J Dent Res. 1991;71(special issue A). Abstract 188.
13. Felix CA, Price RB. Effect of distance on power density from curing lights. J Dent Res. 2006;85(special issue B). Abstract 2468.
14. Pilo R, Oelgiesser D, Cardash HS. A survey of output intensity and potential for depth of cure among light-curing units in clinical use. J Dent. 1999;27:235-241.
15. Pires JA, Cvitko E, Denehy GE, et al. Effects of curing tip distance on light intensity and composite resin microhardness. Quintessence Int. 1993;24:517-521.
16. Xu X, Sandras DA, Burgess JO. Shear bond strength with increasing light-guide distance from dentin. J Esthet Restor Dent. 2006;18:19-28.

Dr. Simos received his doctorate of dental surgery at Chicago’s Loyola University. Dr. Simos is the founder and president of Allstar Smiles and the Allstar Smiles Learning Center. He teaches postgraduate courses to practicing dentists on cosmetic dentistry, occlusion, and comprehensive restorative dentistry through Allstar Smiles’ state-of-the-art learning center and client facility in Bolingbrook, Ill, and throughout the country. He is nationally recognized as a leader in cosmetic and restorative dentistry, promoting awareness, communication, and education within the dental profession, and is an internationally published author on the use of innovative techniques and materials in dentistry today. He can be reached at (866) 614-8455 or via e-mail at sam@allstarsmiles.com.

Disclosure: Dr. Simos reports no disclosures.