IADR Abstract Archives
Thio-Urethane Oligomers Reduce Polymerization Stress in Dental Cements
Objectives: Thio-urethane additives increase conversion and strength, while significantly reducing polymerization stress (PS) in unfilled resins (Pfeifer, 2012). This study evaluates the efficacy of such additives in reducing stress in highly filled composites.
Methods: Oligomers were synthesized by combining 1,6-Hexanediol-diissocyante (aliphatic), 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) or Dicyclohexylmethane-4,4'- diisocyanate (cyclic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 20wt% to BisGMA-UDMA-TEGDMA (5:3:2), camphorquinone/Ethyl-4-dimethylaminobenzoate (photoinitiators, 0.2/0.8wt%) and di-tert-butyl hydroxytoluene (inhibitor, 0.3wt%). 70wt% silanated inorganic fillers were added (85% Barium glass, 0.4 microns; 15% OX-50, 50nm). Volumetric shrinkage (VS) was assessed with dilatometry. Polymerization stress (PS) was measured on the Bioman. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (BluePhase, 800mW/cm2). Results were analyzed with two-way ANOVA/Tukey’s test (α=5%).
Results: Results in the Table with the same superscript are statistically similar. In general, conversion was similar to the control for all TU tested, whereas the polymerization rate was significantly lower. Delayed vitrification likely led to the reduced stress values observed, since shrinkage was statistically similar for all groups.
Conclusions: Thio-urethane oligomers favorably modified conventional dimethacrylate networks with minimal disruption to existing curing chemistry, in highly filled composites. Stress reductions of up to 75% were observed.
Methods: Oligomers were synthesized by combining 1,6-Hexanediol-diissocyante (aliphatic), 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) or Dicyclohexylmethane-4,4'- diisocyanate (cyclic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 20wt% to BisGMA-UDMA-TEGDMA (5:3:2), camphorquinone/Ethyl-4-dimethylaminobenzoate (photoinitiators, 0.2/0.8wt%) and di-tert-butyl hydroxytoluene (inhibitor, 0.3wt%). 70wt% silanated inorganic fillers were added (85% Barium glass, 0.4 microns; 15% OX-50, 50nm). Volumetric shrinkage (VS) was assessed with dilatometry. Polymerization stress (PS) was measured on the Bioman. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (RP) during photoactivation (BluePhase, 800mW/cm2). Results were analyzed with two-way ANOVA/Tukey’s test (α=5%).
Results: Results in the Table with the same superscript are statistically similar. In general, conversion was similar to the control for all TU tested, whereas the polymerization rate was significantly lower. Delayed vitrification likely led to the reduced stress values observed, since shrinkage was statistically similar for all groups.
Conclusions: Thio-urethane oligomers favorably modified conventional dimethacrylate networks with minimal disruption to existing curing chemistry, in highly filled composites. Stress reductions of up to 75% were observed.