Linear and volumetric shrinkage displacements of resin composite restorations with and without debonding

The study aimed to compare shrinkage displacements of fully and partially bonded resin composite restorations (RCRs). Two groups (n=5) Class-I RCR evaluated: Group 1 (G1) fully bonded and Group 2 (G2) debonded at the floor. Experimental results were compared with predictions from simple theory and finite element analysis (FEA). The experimental linear surface displacement (LSD) was G1 62.5±5.2 µm and G2 32.8±4.0 µm. Theoretically-predicted LSD for G1 60.1±7.4 µm and G2 31.3±7.5 µm. FEA-predicted LSD were G1 65.2 µm and G2 34.6 µm. The experimental volumetric surface displacement (VSD) was G1 1.22±0.2 mm³ and G2 0.63±0.2 mm³. Theoretically-predicted VSD for G1 1.36±0.2 mm³ and G2 0.67±0.2 mm³. No significant difference (p>0.05) was found in LSD and VSD among the experimental, theoretical and FEA in the same group. Significant differences (p<0.05) were noted between the two groups, with LSD and VSD of G2 values being almost half of G1. This pattern gave an insight of a debond restoration characteristics.