Re-Treatment of a Failing Posterior Amalgam Restoration

Partial coverage preparations in posterior teeth that are restored with all-ceramic materials, such as lithium disilicate, have been shown to demonstrate similar fracture resistance to that of natural teeth,² and if morphology-driven preparation technique guidelines¹ are followed, the restoration will demonstrate predictable clinical results.

From a bonding perspective, immediate dentin sealing is a technique that has been widely recommended and used for the past 15 years.³ The benefits of using this technique include better bond strength to freshly cut dentin, less marginal gaps, less bacterial leakage, reduced sensitivity, and more. All of these principles are applied in the following clinical case.

A patient presented to the office with a failing amalgam restoration and fractured distobuccal cusp on the upper right first molar (Figure 1). Following the history and examination, an esthetic analysis was performed to determine the ideal location for the margins (Figure 2). The failing amalgam restoration was then removed in a conservative manner (Figure 3). After final amalgam removal, a deep discolored dentin base with minor undercuts was revealed in an area close to the pulp. The immediate dentin sealing technique³ was performed to protect it from contamination and promote adhesion, and then the final preparation was completed (Figure 4). Next, a self-etch bonding technique was performed using a light-cured dental adhesive (All-Bond Universal^®, BISCO, Inc.), and the core was reconstructed using a nanohybrid universal composite (Venus^® Diamond, Kulzer) (Figure 5). This step helps reduce the esthetic challenges for both the laboratory and the clinician. After the preparation and core reconstruction were complete, an impression was taken and sent to the laboratory for the fabrication of a lithium disilicate crown (Figure 6).

At the seating appointment, the restoration was tried-in to check for proper fit and occlusion. The preparation was kept as conservative as possible, avoiding the unnecessary removal of tooth structure in order to place the crown (Figure 7). In combination with a proper bonding technique, this conservative approach provides a durable and predictable restoration.^1,4

The restoration was cemented using a dual-cure resin luting cement system (Duo-Link Universal^™, BISCO, Inc.). After the margins were tack-cured for 3 seconds to facilitate  proper cleaning and the removal of excess cement, a final light activation was performed for 20 seconds on each surface of the tooth (ie, buccal, lingual, occlusal). Complete poly-merization of the material was achieved via chemical curing (Figure 8). At a 14-month follow-up consultation, the restoration exhibited excellent marginal adaptation and proper occlusal function (Figure 9).

Nikhil Sethi, BDS
Private Practice
London, England