Marginal Quality of CAD/CAM Composite vs. Ceramic Restorations

Objectives: Resin composite blocs [RCB] for dental CAD/CAM restorations are suggested as an alternative to indirect ceramic restorations. The aim of this study was to compare indirect RCB restorations to lithium disilicate ceramic restorations.
Methods: Sixty third molars received MOD preparations (one approximal box above and one below the cemento-enamel junction) with partial cusp replacement, having been scanned (Cerec 3D, Dentsply Sirona) and then restored with CAD/CAM restorations (n=10): 1. Grandio-Bloc (GB, Voco), 2. Grandio-Bloc round blanks (GRB, Voco), 3. Lava Ultimate (LU, 3M Oral Care), 4. Cerasmart (CS, GC), 5. Brilliant Crios (BC, Coltene), 6. IPS e.max (IP, Ivoclar Vivadent). Restorations were placed using the respective adhesive luting system recommended by the manufacturer. Before and after thermomechanical loading (TML) (100,000 cycles á 50N and 2,500 thermal cycles: +5/+55 ° C; CS4.8 Professional Line, SD Mechatronics) epoxy resin replicas were fabricated. Replicas were semi-quantitatively evaluated using a scanning electron microscope (SEM, Phenom) at 200x magnification (WinMes 2.0, SPSS 20.0).
Results: SEM analysis showed significantly different data (p<0.05): TML in all groups resulted in a significant decrease in marginal quality (p<0.05, Wilcoxon test). For enamel margins, the highest decrease was observed for CS (percentage gap-free margin (%): From 96.4 +/-4.3 to 68.3 +/-12.3), lowest for GRB (100 to 95.0 +/-3.9). In dentin, the highest decrease was observed for IP (94.3 +/-9 to 68.2 +/- 8.8), the lowest for LU (100 to 82.3 +/- 9.2); (p<0.05, Mann-Whitney U-test). Margins of replaced cusps showed better marginal quality than the contralateral sides without cusp replacement (p<0.05).
Conclusions: CAD/CAM RCB restorations show promising marginal quality results compared to conventional ceramic restorations. Evaluations of individual abrasion patterns and chipping characteristics will be evaluated in future studies.