Balancing biological and mechanical performance of bioactive restorative materials in permanent class II restorations: Clinical relevance

Objectives The growing emphasis on minimally invasive and biologically oriented restorative strategies has driven the development of bioactive materials to enhance material-tissue interactions. Despite being the second in frequency after Class I, Class II restorations remain more challenging due to anatomical, biological, mechanical, material, and substrate-related factors, including leathery and firm dentin. In this context, this review evaluates the biological and mechanical performance of contemporary bioactive restorative materials and their clinical applicability as definitive restorations in permanent Class II cavities. Data sources and study selection A literature search was conducted to identify relevant in vitro studies, randomized clinical trials, and relevant systematic and narrative reviews on bioactive restorative materials, comprising glass ionomer systems and contemporary bioactive materials. Emphasis was placed on mechanisms of bioactivity, ion release potential, biological performance, mechanical properties, bonding performance, and clinical applicability in Class II restorations. Conclusions Current literature suggests a persistent trade-off between biological functionality and mechanical durability. While conventional materials demonstrate robust mechanical performance (resin-based composites) or bioactivity (glass ionomer cements), contemporary bioactive materials attempt to combine both. However, their effectiveness remains variable, with limited and inconsistent long-term clinical data, particularly in stress-bearing posterior restorations. No currently available restorative material consistently achieves an optimal balance between biological and mechanical performance for Class II restorations. Clinical significance While contemporary bioactive restorative materials aim to combine biological functionality and mechanical durability, their routine use as definitive restorations in stress-bearing areas should not yet replace conventional ones but be approached with caution until more long-term clinical data become available.