Comparative study of the shrinkage behavior of three bulk-fill resin-based composites using the aluminium tooth model with a MOD cavity

This study evaluated the cusp tip deflection of aluminium tooth models with a mesial-occlusal-distal (MOD) cavity filled with three bulk-fill resin-based composites (RBCs), Aura Ultra Universal (Aura), Admira Fusion x-tra Universal (Admira), and Filtek One shade A2 (Filtek One), to assess the level of shrinkage stress they could produce. The models were prepared using a primer, adhesive and a single RBC increment photo-cured for 20 s at a radiance exitance 1.25 W/cm². The RBC axial shrinkage strain (ε) and stress (S) were also measured. Micro-computed tomography in combination with silver nitrate infiltration showed no interfacial debonding. The mean cusp tip deflection for Admira was found to be smaller than those for the other two RBCs. Although ε and S for Aura were higher than those for Filtek One, their mean cusp tip deflections were not significantly different. These results could be explained by the temporal behavior of their elastic modulus.