Methacrylate-functionalized proanthocyanidins as novel polymerizable collagen cross-linkers - Part 2: Effects on polymerization, microhardness and leaching of adhesives

Dent Mater. 2021 Jul;37(7):1193-1201. doi: 10.1016/j.dental.2021.04.010. Epub 2021 May 6.

Abstract

Objective: The aim of the study was to investigate the effects of a novel polymerizable collagen cross-linker methacrylate-functionalized proanthocyanidins (MAPA) on the polymerization, microhardness and leaching of a HEMA-based experimental dental adhesive system.

Methods: Three MAPAs were synthesized using different methacrylate (MA) to proanthocyanidins (PA) feeding ratios of 1:2, 1:1, and 2:1 to obtain MAPA-1, MAPA-2, and MAPA-3, respectively. The resulting three MAPAs and PA were added to an experimental adhesive formulated with HEMA and a tri-component photoinitiator system (0.5 wt% CQ/EDMAB/DPIHP) at 1%, 5% and 10% MAPA or PA concentrations (wt%). The adhesive polymerization kinetics was measured continuously in real-time for 10 min using a Fourier-transform infrared spectroscopy (FTIR) with an attenuated total reflectance (ATR) accessory. Degree of conversion (DC) and Vickers microhardness (MH) of cured adhesives were measured at 72 h post-cure. The leaching of cured adhesives in DI water was monitored using UV-vis spectrophotometer. Statistical analysis was performed using one-way and two-way ANOVA, Tukey's (p < 0.05).

Results: The adhesive formulations with 1%, 5% and 10% MAPAs-1, -2, -3 all generated higher rate of polymerization and 10-min DC than the formulations with PA at the same concentrations. At 72 h post-cure, the adhesive formulation with 5% MAPA-2 exhibited significantly higher DC (99.40%) and more than doubled MH (18.93) values than the formulation with 5% PA (DC = 89.47%, MH = 8.41) and the control (DC = 95.46%, MH = 9.33). Moreover, the cured adhesive with 5% MAPA-2 demonstrated significantly reduced PA leaching in comparison with cured adhesive with 5% PA.

Significance: Synthesized MAPA is a novel class of polymerizable collagen cross-linker that not only stabilizes dentin collagen via its PA component, but also improves polymerization, mechanical properties and stability of HEMA-based adhesives via its MA component. By inheriting the benefit while overcoming the drawback of PA, MAPA offers a revolutionary solution for improved bond-strength and longevity of dental restorations.

Keywords: Degree of conversion; Dental adhesive; Grape seed extract proanthocyanidins (PA); Kinetics; Leaching; Methacrylate functionalized proanthocyanidins (MAPA); Polymerizable collagen cross-linker; Polymerization; Rate of polymerization; Vickers microhardness.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bisphenol A-Glycidyl Methacrylate
  • Collagen
  • Dental Cements
  • Light-Curing of Dental Adhesives
  • Materials Testing
  • Methacrylates*
  • Photoinitiators, Dental
  • Polymerization
  • Proanthocyanidins*

Substances

  • Dental Cements
  • Methacrylates
  • Photoinitiators, Dental
  • Proanthocyanidins
  • Bisphenol A-Glycidyl Methacrylate
  • Collagen