Fracture resistance, marginal integrity, and microleakage of indirect composite and computer-aided designed–computer-aided manufactured ceramic inlays in Class II MOD cavities: An in vitro study

Context: Restoration of Class II MOD cavities is biomechanically challenging due to extensive loss of tooth structure and disruption of marginal ridges. Indirect inlay restorations fabricated from composite and computer-aided designed–computer-aided manufactured (CAD-CAM) ceramics are widely used; however, their comparative performance in terms of fracture resistance, marginal integrity, and microleakage remains an important clinical consideration. Aim: This study aims to evaluate and compare the fracture resistance, marginal integrity, and microleakage of indirect composite, CAD-CAM zirconia, and CAD-CAM lithium disilicate inlays in Class II MOD cavities restored using the indirect technique. Materials and Methods: Random allocation of extracted mandibular molars was done into five groups ( n = 7): intact teeth, prepared cavities without restoration, zirconia inlays, lithium disilicate inlays, and indirect composite inlays. Inlay restorations were fabricated using CAD-CAM technology or light-polymerized indirect composite resin. Following adhesive cementation and thermocycling, a universal testing machine was used to record fracture resistance. Marginal integrity was analyzed with scanning electron microscopy, while microleakage was evaluated through 1% methylene blue dye penetration under an optical microscope. Statistical Analysis: Data analysis was done using one-way ANOVA with post hoc test and Kruskal–Wallis test ( P < 0.05). Results: Among the restored groups, zirconia inlays showed the highest fracture resistance, followed by lithium disilicate and indirect composite inlays. Indirect composite inlays exhibited significantly lower marginal gaps and a tendency toward reduced microleakage. Conclusions: Ceramic inlays demonstrated superior fracture resistance, whereas indirect composite inlays showed improved marginal adaptation. The selection of restorative materials should consider both mechanical strength and marginal sealing ability.