Polymerization of HEMA-based Adhesive Containing Methacrylate Functionlized Grape Seed Proanthocyanidins

Objectives: To investigate the effects of three different versions of methacrylate functionlized proanthocyanidins (MAPA) of different concentrations (1%, 5% 10%) on the degree of conversion (DC) and polymerization rate (PR) of a HEMA-based model dental adhesive.
Methods: Three versions of MAPAs were synthesized with different MA to PA ratios, including MAPA1(MA:PA=1:2), MAPA2(MA:PA=1:1) and MAPA3(MA:PA=2:1). An experimental model dental adhesive was formulated with HEMA monomer and CQ-based photo-initiator (CQ/EDMAB/DPIHP) at 0.5wt% concentration (control group). Three versions of MAPAs and grape seed PA were added to the model adhesive at concentrations of 1%, 5% and 10wt% (four test groups).
Each group (n=3) was light-cured using a LED curing light (1200 mV/cm²) for 100s. Polymerization behavior of adhesive was monitored by real-time FT-IR, with an attenuated total reflectance (ATR) attachment. The spectra were recorded at a resolution of 4 cm^-1 in the wave number range between 700 and 4000 cm^-1. Degree of conversion (DC) at 10min and polymerization rate (PR) (maximum slope of linear region of the DC curve) for all groups were calculated and statistically analyzed (repeated one-way ANOVA, Tukey’s. p<0.05).

Results: PA inhibited the polymerization of the model adhesive, and the inhibition effect increased with PA concentration. At 1% concentration, three MAPA groups and PA group showed similar DC (82.96-83.22), all significantly lower than the DC of control group (84.98). At 5% and 10% concentrations, three MAPA groups showed significantly higher DC than PA group, in the following order and values (DC): 5%PA(76.47)<5%MAPA1(78.80)<5%MAPA2(80.17)<5%MAPA3(81.94)Conclusions: PA inhibited the polymerization of HEMA-based model adhesive while MAPAs improved the adhesive polymerization when compared to PA at the same concentration.