Volumetric Isothermal Polymerization Contraction of Model Quaternary-Ammonium-Methacrylate (-Acrylate) Resins

Objectives : To determine the volumetric polymerization contraction of a range of quaternary ammonium-methacrylates (QAMs) at 25°C.  Methods: A range of commercial QAMs were added to comonomer mixtures of TEGDMA (30 wt%), HEMA (2 wt%), and BisGMA (40-60 wt%) in water and rendered photocurable by addition of 1% wt TPO: ATA (5, 10, 15 wt%); MCMS (5, 10, 15 wt%), METMAC (5, 10, 15 wt%); MAPTAC 5 wt%, DDAC 5 wt%; a custom non-QAM control (NQC); and a commercial control (Scotchbond Multipurpose Adhesive (SBMP). Thin films of uncured fluids (160 microns) were placed in a volumetric shrinkage device (Watt's Bonded Disc apparatus) and heated to 25°C for 2 min prior to  application of 60s light curing (Optillux 401). Real-time shrinkage values were derived (1/s) and total shrinkage 10 minutes following light application was determined (n=5). Data were analyzed by 1-way ANOVA with the Tukey post-hoc test (a=0.05). Results: Control BisGMA/TEGDMA resin shrank 6.7 ±0.5%, while SBMP shrank 7.4 ±0.1%.  QAM shrinkage values ranged from a low of 7.0 ±0.7% for 15% METMAC  to a high of 8.2 ±0.4% for 5% DDAC. Each statistical grouping included the commercial, non-QAM resin adhesive (SBMP) as a control. Parallel monomer degree of conversion (DC) studies (not shown) indicated that all resin blends gave DC values between 65-67% for control and SBMP, respectively, and between 72-89% for QAM-containing BisGMA/TEGDMA blends.  Table presents mean and SD of volumetric shrinkage and statistical groupings.

Resin abbreviations defined in J Dent Res 2011;90:535-540.

 

Conclusions : Isothermal volumetric photopolymerization shrinkage of model QAM-containing resins fell within the range measured for a non-QAM, commercial resin adhesive. The results indicate promise for all QAM-containing groups as potential successful candidates for experimental adhesive resin blends.