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Purpose: To evaluate the fracture resistance and failure modes of endodontically treated mandibular molars restored with different designs of inlays, onlays and endocrowns. Materials and Methods: Extracted mandibular third molars (n = 180) were used. An access cavity was prepared on the occlusal surface of each tooth and the roots were obturated with gutta percha. All specimens were randomly divided into 6 groups (n = 30/group) according to the cavity design and the restoration material used. C: control group without access cavity preparation. IE: MOD inlay preparation with Ev-erX Posterior (GC Europe) in the pulp chamber. IG: MOD inlay preparation with G-aenial Universal Flo (GC America) in the pulp chamber. OE: onlay preparation with EverX Posterior (GC Europe) in the pulp chamber. OG: onlay preparation with G-aenial Universal Flo (GC America) in the pulp chamber. EC: endocrown with an empty pulp chamber. All restorations were fabricated with CAD/CAM system using CERASMART ® (GC Dental products Europe, Belgium) CAD/CAM blocks. Specimens were thermal-cycled and were subjected to a compressive load applied at 30°a ngle relative to the long axis of the tooth with a universal testing machine. Results were statistically analyzed by ANOVA followed by Tukey post hoc tests. Chi-square test and Fisher Exact tests were used for the comparisons among groups.Results: The mean fracture strength was significantly different between the groups (p < 0.001); it was significantly highest for intact teeth, followed by endocrowns (p = 0.021). The strength was significantly lower for inlays (with G-aenial Universal Flo and EverX Posterior), intermediate for onlays with EverX Posterior followed by onlays with G-aenial Universal Flo. Conclusions: Endocrowns exhibited higher fracture resistance than other tested composite resin groups. Endocrowns and onlays showed a more favorable failure mode than inlay restorations.

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Objective Problems in the confection of indirect restorations may increase the marginal and internal gap. This study aimed to quantify the marginal and the internal fit of overlays fabricated with three different materials. Materials and methods Standardized cavities were prepared on endodontically treated human third molars and digital impressions were done using an intraoral camera (Trios 3). Restorations were designed (n = 15) and fabricated with three materials: Hybrid ceramic (Cerasmart; GC Corp, EUROPE), high‐strength lithium disilicate (GC Initial® LiSi Press; GC Corp, Tokyo, Japan), and zirconia reinforced Lithium Silicate Glass Ceramic (Vita Suprinity; Vita, Germany). Axial, marginal, pulpal, and gingival gaps were calculated by measuring the distance between the restoration and the tooth at several reference points. Two‐Way analysis of variance was used for statistical analysis. The significance level was set at α = 0.05. Results Mean gap was significantly influenced by the material (p < 0.001), gap localization (p < 0.001), and interaction between the factors (p = 0.002). For all materials, the highest gap was observed at gingival and pulpal surfaces (p ≤ 0.015). LiSi Press achieved the overall lowest values at axial values measurements (p ≤ 0.003). Conclusions The performance of a CAD/CAM system relative to marginal adaptation is influenced by the restorative material used. High‐strength lithium disilicate seems to be showed the best marginal adaptation. Clinical significance Marginal and internal adaptation of CAD/CAM restorations could be influenced by the type of material chosen.