Comparative analysis of polymerization efficiency and degradation indicators of adhesive resin cements and preheated restorative composites

Preheated restorative resin-based composites (RBCs) have been suggested as alternative luting agents for ceramic restorations; however, their polymerization and long-term degradation behavior require further clarification. This study compared a preheated RBC with conventional light-cured and dual-cured adhesive resin cements regarding degree of conversion (DC%), monomer elution, water sorption (WSo), and solubility (Sol). Standardized lithium disilicate overlays were luted to ceramic abutments using preheated Estelite Σ Quick (EQ_55°C), Variolink Esthetic LC (VE_LC), or Variolink Esthetic DC (VE_DC). DC% was assessed by micro-Raman spectroscopy, monomer elution using high-performance liquid chromatography at 3, 10, and 17 days, and WSo/Sol per ISO 4049 at 30, 60, and 90 days. VE_DC showed the highest DC% (72.1%), while EQ_55°C presented the lowest (59.9%). Monomer elution was significantly higher for VE_LC and VE_DC compared to EQ_55°C and decreased over time for all groups. WSo peaked at day 60 but remained significantly lower for EQ_55°C. Sol followed the pattern VE_DC > VE_LC > EQ_55°C, decreasing progressively with time. These results indicate that the preheated RBC demonstrated reduced monomer release and lower hydrolytic degradation, supporting its potential use as a stable luting alternative for indirect ceramic restorations.