Polymerization shrinkage and shrinkage stress development in ultra-rapid photo-polymerized bulk fill resin composites

To determine the polymerization shrinkage (%) and stress (MPa) characteristics of ultra-rapid photo-polymerized bulk fill resin composites. Two (URPBF) materials: PFill PFlow were studied, along with their comparators ECeram EFlow. contains an addition fragmentation chain transfer (AFCT) agent. The URPBR materials irradiated using two different 3 s high irradiance protocols (3000 3200 mW/cm2 based on Bluephase PowerCure VALO LCUs, respectively) one 10 standard protocol (1200 a LCU). Bonded disk Bioman II instruments used to measure Polymerization % MPa, respectively, for 60 min at 23 ± 1 °C (n = 5). Maximum shrinkage-rate maximum stress-rate also calculated 15 via numerical differentiation. data analyzed multiple One-way ANOVA Tukey post-hoc tests (α 0.05). groups, regardless protocol, showed significantly lower PS than comparator, (p < However, protocols, was comparable EFlow > consistently produced results which 0.05) both only exhibited higher when polymerized sVALO strain-rate (%/s) in PFill-10s PFill-3s groups (using LCU) compared ECeram. no differences seen between irradiation as well comparator High over ultra-short periods led slightly strain but stress, possibly due reduced network mobility. AFCT agent incorporated composite seemed reduce development, even protocols.