Abstract
BACKGROUND: With the advances in the adhesive science, several conservative treatment options such as non-retentive overlays have been suggested for endodontically treated posterior teeth. However, information is scarce regarding the fracture strength and adaptation of non-retentive overlays compared with endocrowns, and the effect of material type in this respect. Thus, this study aimed to assess the fracture strength and internal and marginal adaptation of lithium disilicate (LDS) and hybrid ceramic endocrowns and non-retentive overlays for endodontically treated molar teeth. METHODS: This in vitro study was conducted on 40 endodontically treated molar teeth that were randomly assigned to 4 groups based on the restoration type and material type (n = 10): LDS and hybrid ceramic endocrowns, and LDS and hybrid ceramic non-retentive overlays. The internal and marginal adaptation of restorations were assessed by the silicone replica technique. After cementation and thermomechanical loading, the fracture strength was measured, and the failure mode was determined. Data were analyzed by two-way ANOVA with pairwise comparisons with the Tukey's test, and Fisher's exact test (α = 0.05). RESULTS: The highest mean marginal and internal gaps were recorded in hybrid ceramic endocrowns, followed by LDS endocrowns, hybrid ceramic overlays, and LDS overlays. All pairwise comparisons revealed significant differences (P < 0.001) except the two endocrown groups, which were not significantly different regarding internal gap (P = 0.998). The mean fracture strength was the lowest in hybrid ceramic endocrowns, followed by hybrid ceramic overlays, LDS endocrowns, and LDS overlays. All pairwise comparisons revealed significant differences (P < 0.05) expect the two hybrid ceramic groups (P = 0.180). No significant difference was found in the failure mode among the groups (P = 0.312). CONCLUSIONS: Type of restoration and material significantly influenced both adaptation and fracture strength. Specifically, LDS overlays on endodontically treated molar teeth yielded the highest fracture strength and superior internal and marginal adaptation in comparison with other material.