Technical Challenges with Posterior Composites

Recommended Technique

Use basic (occlusal) shade for smaller Class I and II composites. Mark occlusion to identify existing contact points. Administer anesthesia.

Place a rubber dam. This is not optional for predictable posterior composites. As noted above, cutting a 1-cm airhole just lingual to central incisors helps the claustrophobic patient tolerate the dam without compromising isolation. Using a new, round-end bur (such as an 1157), carefully remove old amalgam, if present (Figure 2). If there is an old composite, consider using a round-end diamond. (Using it dry allows the dentist to distinguish between tooth and composite, so that old composite is not left in the preparation, and also prevents over-preparation.)

Remove decay (Figure 3). Evaluate the internal tooth structure for cusp or pulpal floor cracks. If pulpal floor cracks are present, a crown may be the treatment of choice. Consider extending the preparation to remove cracks that are through noncarious proximal walls. Refine the proximal boxes and internal preparation with rounded internal line angles. Rounding internal line angles reduces the odds of initiating cracks and optimizes the adaptation of the composite.

Place a slight bevel or exaggerated flair on the proximal box walls. Proximal walls must be free of decay and demineralization. It is possible that in a quest to be more conservative, dentists are sometimes incompletely removing damaged tooth structure, resulting in premature failure of the composite. This is not really a composite failure; it is a technique failure. Conservative preparations are desirable, but there must be sufficient preparation to ensure complete disease removal (Figure 4).

Place a slight bevel on the proximal box floor if it is still in enamel. If it is not in enamel, ensure a clean finish line (Figure 5). Polish adjacent old fillings if they are rough, and evaluate the margins with direct vision. Select and place a sectional matrix, wedge, and ring clamp. If it is an MOD, place one wedge lightly. Place only one ring clamp to the fully wedged side. After the first box is filled, the ring is switched to the other box before completing the composite placement (Figure 6).

Adaptation of the matrix to the tooth structure apical to the proximal box is essential, as is adaptation of the matrix to the full extent of the contact. In addition, adaptation of the matrix to the proximal walls is very helpful to reduce finishing time. At this stage, there should be a totally contamination-free restorative field; there should be no blood or saliva. Any contamination jeopardizes the longevity of the restoration (Figure 6 through Figure 11). Etch as appropriate for the bonding system being used. If etching, consider using chlorhexidine 2% after rinsing.

Apply a bonding agent—usually two coats—and light-cure. Provide an extended cure for this step and the first proximal layer to ensure an adequate proximal cure, due to the increased distance from the light tip to the material in the proximal box. Carefully apply a very thin layer of flowable composite along the matrix band–tooth interface (to create a seal) and along the internal line angles. Ensure that composite has flowed smoothly along the matrix band–tooth interface before curing (Figure 7). Cure composite and flowable in the proximal box for an extended time to compensate for the increased distance of the composite from the curing light (Figure 8 and Figure 9).

If the restoration is a MOD, complete composite placement against one matrix, then engage the second wedge and move the clamp to the second proximal. If there is not a threat of bleeding, consider removing the first sectional matrix. Layer composite in three or more increments with the final increment being the enamel shade, if using a separate enamel. Be careful to ensure that each layer is well adapted. The final layer can be sculpted to near-final contour prior to cure (Figure 10). Remove the clamp, wedges, and matrix (Figure 11). Do preliminary finishing and polishing, including evaluation of contact(s). Re-etch margins and seal with a very thin layer of bonding agent or gloss. Remove the rubber dam. Evaluate and adjust the occlusion (including upright chair position). Polish and show the patient the final results (Figure 12).

Discussion

Proximal box failures are most common with Class II composites. This can be due to recurrent decay, incomplete caries removal, margin failure due to a defective margin (poor adaptation or void), or leakage (bonding agent failure caused by under-curing or high polymerization stresses). Most of these problems can be avoided with excellent technique. Patients who have active caries (not just old failed fillings) must receive treatment and/or advice aimed at stopping the active caries process or they will continue to get caries— regardless of the restorative material.

Larger composites cannot be properly completed in the timeframe that is compensated for with standard insurance fees. Consider adjusting fees for larger composites rather than doing a poor job or just moving on to a crown. Moderate to large composites can save tooth structure and cost compared to the alternative onlay or crown, and they can be profitable to the dentist if fees are appropriately adjusted for the added complexity and time required.

For offices that have the freedom to apply a higher fee for direct restorations that require more time, communication is essential to help patients understand the value behind the treatment. In the author’s practice, patients are counseled regularly on the practice philosophy of performing minimally invasive dentistry, using the finest materials and adequate time for excellent technique. Patients are also informed that this philosophy does not always coincide with insurance reimbursement rates. In cases such as this, the aim is to provide a long-lasting restoration without removing healthy tooth structure, and this procedure takes time. Patients understand that the goal is not to simply charge more; it is to do better dentistry. By adjusting fees for the added complexity and time required for these restorations, moderate to large composites can save more tooth structure than the alternative onlay or crown, they can save the patient money over the alternative indirect restoration, and they can be profitable for the dentist.