Influence of cervical margin relocation with direct restorative materials on the marginal integrity of CAD-CAM composite inlays

Purpose: To evaluate the in vitro marginal integrity of CAD-CAM composite inlays with the proximal box margin relocated with different direct restorative materials before and after thermomechanical aging. Methods: Standardized 4 mm-wide Class II cavities were prepared in 40 sound human upper molars. The mesial cervical margin was located in enamel (control) and 1 mm occlusal to the cemento-enamel junction (CEJ), while the distal cervical margin was located in dentin (experimental) and 2 mm apical to the CEJ. In the experimental groups (n=10), the distal margins were relocated up to the CEJ level by using a highly viscous conventional glass ionomer cement (Equia Forte), low-viscosity bulk-fill composite (SureFil SDR Flow), highly viscous nanofilled composite (Filtek Supreme XT), or a highly viscous bulk-fill composite (Filtek Bulk Fill). The inlays were milled from CAD-CAM nanohybrid composite blocks (Brava Block) and luted with dual-cure resin cement (Allcem). The specimens were submitted to thermocycling (5-55 degrees C, 7,800 cycles) and fatigue loading (50 N, 1 Hz, 240,000 cycles). Epoxy resin replicas of the margins were obtained before and after aging and evaluated through scanning electron microscopy. The percentage of continuous margin in relation to individual assessable margin was calculated as the marginal integrity. The data were statistically analyzed using Wilcoxon and Kruskal-Wallis tests (alpha=.05). Results: The marginal integrity before and after aging was not significantly different (P> 0.05). Similarly, no significant differences were observed between margins relocated with different restorative materials in comparison to enamel margins (P> 0.05).