Insights into restoring teeth with deep preparation outline: thinking outside the box

This dissertation investigates the performance of partial adhesive restorations, with special attention to the challenge of bonding these restorations when the preparation margins are located below the cemento-enamel junction (CEJ). Deep Margin Elevation (DME) in combination with a partial indirect restoration is an extensively studied aspect of this dissertation. Through literature, laboratory, and clinical research, various aspects of partial restorations with and without DME are evaluated, including material comparisons and the influence on fracture strength. The dissertation provides a step-by-step overview of the application and indication of DME and offers clinical guidelines to approach deep subgingival cavities. Furthermore, it examines the influence of DME on the fracture strength of lithium disilicate restorations, finding that DME does not affect the fracture strength nor fracture type of lithium disilicate, regardless of the type of preparation (inlay/onlay). It also analyzes the clinical survival of various restoration materials and identifies the risk factors for the failure of such restorations. The results show that the risk of failure of glass-ceramic restorations increases with a high caries risk, in non-vital teeth, and in males, but that the preparation margin ending in dentin or enamel has no effect on the failure risk of the partial glass-ceramic restoration. Finally, the studies demonstrate that indirect restorations with or without DME perform well in the medium to long term, but further studies are needed since degradation is seen over time. Findings, limitations, and future research suggestions are discussed in the final chapter of the dissertation.