Assessment of cuspal deflection and volumetric shrinkage of different bulk fill composites using non-contact phase microscopy and micro-computed tomography

Abstract

The understanding of cuspal deflection and volumetric shrinkage of resin composites is necessary to assess and improve the placement techniques of resin-based materials. The aim of this study was to investigate the cuspal deflection and its relationship with volumetric polymerization shrinkage of different bulk-fill resin composites. The investigation was conducted using non-contact phase microscopy and micro-computed tomography. Thirty custom-milled aluminum blocks were fabricated for microscopy analysis and thirty-six tooth models with standardized Class I cavities were used for micro-computed tomography analysis. Results showed that high-viscosity composites present higher cuspal deflection compared to bulk-fill composites. The filler loading of resin composites seems to have an effect on cusp deflection, since the higher the filler content percentage, the higher the cusp deflection. On the other hand, it seems to have an opposite effect on volumetric shrinkage, since higher filler loadings produced lower volumetric shrinkage percentages.

Shrinkage stress and elastic modulus assessment of bulk-fill composites

“…Nevertheless, a lower Young's modulus may allow stress dissipation during the polymerization process, thus reducing the stress in bigger increments. 10 , 25 , 26 , 32 , 33 …”

The effect of aging methods on the fracture toughness and physical stability of an oxirane/acrylate, ormocer, and Bis-GMA-based resin composites

“…The volume change of the resin composite samples was evaluated using the µCT evaluation method. Several studies have confirmed the validity of using µCT to evaluate the volumetric change of resin composite materials (Yoshikawa,Sadr [64],Hirata, Clozza [14], Zeiger, Sun [6], Prager, Pierce [76]). In this study, three specimens from each group were used and submitted to evaluation before and after the environmental challenge.…”

Polymerization shrinkage of light-cured conventional and bulk-fill composites —The effect of cavity depth and post-curing

“…Nevertheless, increasing the volume of increments is thought to increase the amount of polymerization shrinkage, leading to greater contraction stress. Therefore, there have been concerns regarding the development of gap formation at cavity walls with the bulk-fill technique, but several studies reported that bulk-fill RBCs did not give rise to post-operative problems, gap formation and cuspal deflection [5][6][7][8][9][10] . The manufacturers claim that bulk-fill RBCs exhibit lower polymerization shrinkage than conventional RBCs because of advanced filler technology or the addition of modulators that decrease the polymerization rate.…”