IADR Abstract Archives
Proanthocyanidins Compatible With Monomer Chemistry can Increase Degree of Conversion
Objectives: Proanthocyanidins (PACs) as natural collagen cross-linkers can elicit more robust and durable resin-dentin bonds. Thus, PACs are promising contenders for optimizing the resin adhesive chemistry for desirable therapeutic capabilities at the resin-dentin interface. This study evaluated the polymerization behavior of a model adhesive in the presence of selective epi-catechin PAC oligomers.
Methods: A BisGMA-based monomer blend was formulated with TEGDMA as a diluent monomer and a typical two-component (camphorquinone/ tertiary amine) photoinitiator (PI) system. To the neat resin, trimeric (namely AA, AB, and BB) and tetrameric (BBB) PACs were added (separately) via ethanol-PAC aliquots to produce solvated resins with PACs at 0.4% (4 mg/mL), 1% (10 mg/mL), and 2.5% (25 mg/mL). Monomer conversion was analyzed using Fourier transform infrared (FTIR) spectroscopy in conjunction with attenuated total reflectance (ATR). Uncured and cured sample absorbance spectra were recorded at a resolution of 4 cm-1 with 32 accumulations. The degree of conversion (DC) of methacrylic double bonds was determined by monitoring the decrease in absorbance at ~ 1637 cm-1 (C=C stretching) after light curing. Absorbance at ~ 1715 cm-1 (carbonyl, C=O) was used as an internal reference for normalization purposes.
Results: Compared to the control mean (72.2% ± 1.6), the DC values were remarkably higher for resins formulated with the highest concentration of trimers AA (85.2% ± 0.4) and AB (77.8% ± 0.2). Regardless of the PAC concentration, resins enriched with B-type PACs (BB and BBB) had similar polymerization behavior to the control (the differences in the DC means were not statistically significant at the 0.05 level).
Conclusions: The DC results suggest that the selected PACs are compatible with the resin monomer chemistry and free radical polymerization mechanism. While specific PACs' free radical scavenging activity has been claimed to halt the methacrylate polymerization, secondary PAC radical formation could support/enhance the monomer-to-polymer conversion.
Methods: A BisGMA-based monomer blend was formulated with TEGDMA as a diluent monomer and a typical two-component (camphorquinone/ tertiary amine) photoinitiator (PI) system. To the neat resin, trimeric (namely AA, AB, and BB) and tetrameric (BBB) PACs were added (separately) via ethanol-PAC aliquots to produce solvated resins with PACs at 0.4% (4 mg/mL), 1% (10 mg/mL), and 2.5% (25 mg/mL). Monomer conversion was analyzed using Fourier transform infrared (FTIR) spectroscopy in conjunction with attenuated total reflectance (ATR). Uncured and cured sample absorbance spectra were recorded at a resolution of 4 cm-1 with 32 accumulations. The degree of conversion (DC) of methacrylic double bonds was determined by monitoring the decrease in absorbance at ~ 1637 cm-1 (C=C stretching) after light curing. Absorbance at ~ 1715 cm-1 (carbonyl, C=O) was used as an internal reference for normalization purposes.
Results: Compared to the control mean (72.2% ± 1.6), the DC values were remarkably higher for resins formulated with the highest concentration of trimers AA (85.2% ± 0.4) and AB (77.8% ± 0.2). Regardless of the PAC concentration, resins enriched with B-type PACs (BB and BBB) had similar polymerization behavior to the control (the differences in the DC means were not statistically significant at the 0.05 level).
Conclusions: The DC results suggest that the selected PACs are compatible with the resin monomer chemistry and free radical polymerization mechanism. While specific PACs' free radical scavenging activity has been claimed to halt the methacrylate polymerization, secondary PAC radical formation could support/enhance the monomer-to-polymer conversion.