Effect of a Novel Light-curing Unit and Bulk Fill Composites on Polymerization Shrinkage Vectors

Objectives: The present study evaluated the effect of a novel light-curing unit and experimental bulk fill composites on filler displacement compared to regular bulk fill materials, through polymerization shrinkage vectors, seen by micro-computed tomography scans.
Methods: Spherical radiopaque zirconia fillers were homogeneously incorporated in the resin composites. The evaluated groups were: TEB (Tetric EvoCeram Bulk Fill) and TBF (Tetric EvoFlow Bulk Fill); FLB (experimental flash light bulk fill composite) and FLF (experimental flash light flowable bulk fill composite), with a high-power intensity curing light. Twenty-four tooth models with standardized class I cavities (4 mm depth×4 mm length×4 mm wide) were fabricated with a 3D printing machine and restorations were performed using each specific adhesive system. Cavities were filled in a single increment with the designated resin composite, and micro-computed tomography scans were obtained before and after light-curing using a high-resolution μ-CT (Bruker Skyscan 1172). The data were imported into open source software (3D Slicer–Version 4) and filler particle movement were identified by polymerization shrinkage vectors, at five depths (from 0 up to 4 mm): top, top- middle, middle, middle-bottom and bottom.
Results: Overall displacement of group FLF was the lowest of all groups (3.29 µm), being statistically different from other groups, followed by TBF (11.37 µm), group TEB (20.76 µm) and group FLB (23.13 µm), respectively, all statistically different within each other (P < 0.05).
Conclusions: Group FLF showed the lower vector displacement between all groups, being localized in top occlusal surface, that in a clinical situation, could be covered by a cap layer. New high intensity curing lights associated with specific restorative materials showed to be viable option as a fast curing material with similar, or better, results of vector displacement compared to commercial bulk fill composite materials.