Correlation between marginal accuracy and fracture resistance of indirect composite restorations varying cavity preparation design

This study evaluated the correlation between marginal accuracy and fracture resistance of laboratory-processed resin composite (LPRC) restorations with different cavity preparation designs. Eighty human third mandibular molars were selected and divided into 8 groups (n=10): G1 conservative (-c) inlay; G2 extensive (-e) inlay; G3 onlay-c with mesio-buccal cusp coverage (CC); G4 onlay-e with mesio-buccal CC; G5 onlay-c with buccal CC; G6 onlay-e with buccal CC; G7 onlay-c with total CC; G8 onlay-e with total CC. Indirect composite restorations (SR Adoro, Ivoclar-Vivadent) were manufactured and positioned over each respective preparation. Marginal accuracy was assessed using a stereomicroscope at 3 points on buccal, lingual, mesial and distal regions (40x magnification). After adhesive cementation (Adper Single Bond 2 and Rely-X ARC, 3M ESPE) a load compressive test (0.5mm/minute) was performed. Data were recorded in mm (marginal accuracy) and Kgf (fracture resistance). In general, Pearson correlation coefficient (a=0.05) did not show significance between factors in study (r=0.073; p=0.520) but it showed significance only on G6 (r=0.702; p=0.024). Irrespective of the preparation design it seems difficult to state the clear correlation between marginal accuracy and fracture resistance of LPRC restored teeth. In this study the effect of one variable on another was negligible