Deep Margin Elevation With Various Resin Composites: Effect of Thermomechanical Aging on the Marginal Gap of CAD / CAM Inlays

OBJECTIVE: This in vitro study evaluated the effects of composite material type, margin design (deep margin elevation vs. control), and thermomechanical aging on the marginal gap of CAD/CAM inlay restorations. MATERIALS AND METHODS: Standardized mesio-occluso-distal (MOD) inlay cavities were prepared in extracted human molars, with mesial margins located at the cemento-enamel junction (control) and distal margins extended 2 mm apical to the CEJ and elevated using three resin composite materials (bulk-fill, packable, and flowable). CAD/CAM inlays were fabricated and luted. Marginal gap values were measured using scanning electron microscopy at baseline and after thermomechanical aging simulating 1 year of clinical service. Data were analyzed using mixed repeated-measures ANOVA to evaluate the effects of material type, margin design, aging condition, and their interactions (α = 0.05). RESULTS: Thermomechanical aging significantly increased marginal gap values (p < 0.001). Margin design showed a significant effect (p = 0.015), whereas the main effect of material type was not statistically significant (p = 0.205). Significant interactions were observed between material type and margin design (p = 0.008) and among material type, margin design, and aging condition (p < 0.001). CONCLUSIONS: Within the limitations of this current study, thermomechanical aging significantly increased marginal gap values of CAD/CAM inlays. Material type alone did not show a significant main effect on marginal gap. However, significant interaction effects were observed between material type and deep margin elevation, as well as between material type and aging condition.