Influence of Thermal Aging on the Physicochemical Behavior of a CAD / CAM Resin Composite and a Conventional Resin Composite

ABSTRACT This in vitro study investigated the effect of thermocycling on the physicochemical properties of a conventional light‐cured nanohybrid resin composite (ATOS, Smart Dent) and a CAD/CAM resin composite (ATOS BLOCK, Smart Dent). A total of 30 specimens ( n = 10 per group and per time point) were prepared and evaluated after 24 h, 5,000 and 10,000 thermal cycles (5°C/55°C) for flexural strength (FS), elastic modulus (EM), and solvent softening (ΔKHN%), while color stability (Δ E 00 and ΔWID) was assessed only for nonaged specimens after immersion in black tea. Data were analyzed using two‐way ANOVA followed by Tukey's post hoc test ( α = 0.05), except for color stability, which was analyzed using one‐way ANOVA. The CAD/CAM composite (BLOCK) exhibited significantly higher FS values than the conventional resin at all time points ( p = 0.002). After 10,000 cycles, FS decreased to 105.0 ± 7.2 MPa (BLOCK) and 70.0 ± 6.9 MPa (ATOS) ( p < 0.0001). EM values ranged from 980.0 ± 85 to 1380.0 ± 100 MPa, with no significant differences between groups ( p = 0.072). ΔKHN% remained higher for BLOCK (33.0% ± 2.0%–18.0% ± 1.0%) than for ATOS (21.0% ± 1.8%–9.0% ± 1.1%) ( p < 0.001). No statistically significant differences in Δ E 00 ΔWID were observed between materials ( p > 0.05). Overall, CAD/CAM composites demonstrated superior physicochemical stability and surface preservation compared with conventional light‐cured composites.