In vitro evaluation of marginal adaptation and microleakage in CAD/CAM and direct composite restorations for permanent molars with extensive substance loss

This study was conducted to evaluate the marginal adaptation and microleakage of resin nanoceramic, composite, and zirconium-reinforced lithium disilicate ceramic restorations produced with computer-aided design/computer-aided manufacturing (CAD/CAM) compared with direct resin composites in permanent molars with extensive loss of tooth structure. Mesio-occluso-distal (MOD) cavities were prepared on 44 extracted molars and randomly divided into four groups ( n = 11). Group 1: CERASMART nanoceramic (GC Corp., Tokyo, Japan); Group 2: BRILLIANT Crios composite block (Coltene/Whaledent, Altstätten, Switzerland); Group 3: Celtra Duo zirconia-reinforced lithium disilicate (Dentsply Sirona, Konstanz, Germany); Group 4: GC Essentia direct composite (GC Corp., Tokyo, Japan). Restored teeth embedded in acrylic were examined for marginal adaptation and continuity under a Quanta FEG 250 scanning electron microscope (FEI Company, Hillsboro, Oregon, USA) at 400x magnification. Microleakage was assessed using 0.5% basic fuchsin solution, followed by longitudinal sectioning and dye penetration scoring at 20x magnification with a stereomicroscope (Olympus, Tokyo, Japan). Normality was assessed using the Kolmogorov–Smirnov test; the Mann–Whitney U test was used for comparisons between two groups, the Kruskal–Wallis test for multiple group comparisons, and the Pearson chi-square test for categorical variables ( p < 0.05). The mean marginal adaptation values ranged from 16.92 ± 14.27 μm to 69.97 ± 41.15 μm. The percentage of continuous margins was significantly greater in the CERASMART group ( p < 0.05). CERASMART group also demonstrated significantly lower microleakage compared to other groups ( p < 0.05), while no significant difference was observed among other materials. All materials demonstrated marginal adaptation values within clinically acceptable limits. CERASMART resin nanoceramic showed superior marginal adaptation and lower microleakage than the other tested materials. These findings may provide clinical insight into restorative options in permanent molars with extensive loss of tooth structure; however, further clinical studies are required to confirm these results.