Does the restorative design and material affect marginal, internal fit, interfacial volume, and fatigue behavior of indirect restorations?

Introduction: Prosthodontists must select the restoration design and material to achieve long-lasting oral rehabilitations when restoring endodontically treated teeth. Few studies compare those factors in terms of fit, interfacial volume, and fatigue behavior. Thus, this study aims to evaluate the fatigue behavior, marginal and internal fit, and interfacial volume of CAD-CAM restorations with different designs (endocrowns and crowns) made from different materials (lithium disilicate ceramic, LD, IPS e.max CAD; and resin composite, RC, Tetric CAD).

Methods: Simplified crowns and endocrowns (n= 10) were produced using CAD-CAM technology through scanning by an intraoral scanner (Primescan), followed by milling in a 4-axis machine (CEREC MC XL), and then bonded to fiberglass-reinforced epoxy resin dies. After the restorations' finishing, surface treatment procedures, and bonding, a computed microtomography was used to assess fit and interfacial volume. A cyclic fatigue test (20 Hz, initial load= 100 N/5,000 cycles; step-size= 50 N/10,000 cycles until 1500 N, if specimens survived, the step-size=100 N/10,000 cycles until failure) was performed. Topography and fractography analysis were also performed. Two-way ANOVA and Kaplan-Meier with log-rank (Mantel-Cox) test were run (α= 0.05).

Results: Endocrowns presented a superior axio-occlusal fit, while crowns presented a better cervical-axial and occlusal fit. LD restorations had a superior occlusal fit, while RC had a better marginal fit. The interfacial volume was similar among the tested groups. Fatigue behavior was superior for RC restorations compared to LD ones, independently of the restoration design. LD restorations presented a softer topography compared to RC.

Conclusion: The restoration design affected the cervical-axial, axio-occlusal, and occlusal fit. The marginal gap was similar between designs, but it was impacted by the restorative material, as well as the occlusal fit. The fatigue behavior was not influenced by the restoration design, meanwhile RC restorations showed superior performance compared to LD ones.