Grape Seed Proanthocyanidins Increase Collagen Biodegradation Resistance in Dentin Bonding

Contemporary methods of dentin bonding may create hybrid layers containing voids and exposed, demineralized collagen fibers. Matrix metalloproteinases and bacterial enzymes may degrade collagen fibers over time, reducing bond integrity. Proanthocyanidins (PA), a class of plant compounds, have been shown to crosslink and strengthen demineralized dentin collagen, but their effects on collagen degradation within the hybrid layer have not been widely studied. Objectives: The purpose of this study was to qualitatively compare the morphological and chemical differences of hybrid layers created by BisGMA/HEMA model adhesives with and without the addition of grape seed extract PA under conditions of enzymatic collagen degradation. Methods: The occlusal third of the crown was removed from eight extracted human third molars. BisGMA/HEMA model adhesives formulated with and without 5% grape seed extract were bonded to the acid etched dentin. Slabs were cut from each bonded tooth. Five-µm-thick sections cut from the slabs were stained with Goldner's trichrome and analyzed by light microscopy. The slabs were then exposed to 0.1% collagenase solution for zero, one, or six days. Following collagenase treatment, the slabs were analyzed with SEM and micro-Raman spectroscopy. Results: Staining with Goldner's trichrome did not reveal a difference in the hybrid layers created with the two adhesives. Micro-Raman spectroscopy indicated the presence of collagen in hybrid layers following collagenase treatment of specimens bonded with adhesive without PA. SEM showed the presence of intact collagen fibrils in all collagenase treatment conditions for specimens bonded with adhesive containing PA. Specimens bonded with adhesive lacking PA showed no collagen fibrils after one or six days of collagenase treatment. Conclusions: The presence of grape seed extract PA in dental adhesives may inhibit the biodegradation of exposed collagen fibrils within the hybrid layer. Funded by NIH/NIDCR DE015281.