Proanthocyanidin Effect on Tensile Strength, FTIR Spectrum of Demineralized Dentin

Proanthocyanidin (PA) is an antioxidant/cross-linking agent that can strengthen the collagen network of demineralized dentin associated with dentin bonding. Objectives: This study aimed to analyze the effects of PA on collagen's mechanical properties and stability, and understand PA/collagen interactions using chemical characterization. Methods: 0.8mm x 0.8mm dentin beams were demineralized in 0.5M EDTA for 3 days, then subjected to 3.75% PA in sterile water for 0hrs, 1hr, or 8hrs at room temperature (N=6/time). Beams were then exposed to 0.2% collagenase in TESCA buffer for 0hrs or 2hrs at 37°C. Tensile strength and elastic modulus were obtained using a universal mechanical tester. Beams (N=15) not used for mechanical testing were used to determine average (dry) % weight change for each condition. 0.8mm thick slabs of dentin were demineralized in 0.5M EDTA for 7 days and then subjected to PA for 0hrs, 1hr, 4hrs, or 8hrs (N=1/time). Slabs were then rinsed, dried, and subjected to FTIR analysis along with PA powder. Results: A 2-factor ANOVA and Tukey's post hoc indicated that tensile strength and elastic modulus of demineralized dentin were significantly increased with increasing PA exposure time (p<.05). Strength and modulus both decreased after exposure to collagenase for most PA conditions (p<.05). Weight decreased after collagenase exposure in non-PA-exposed beams, but PA-exposed beams did not experience a significant weight decrease (<5% weight change). FTIR spectra of PA-exposed collagen were different from the spectra of collagen and PA alone. The peaks at 1400 and 1082 cm-1 in the spectra of collagen disappeared after interacting with PA. Conclusion: PA increases the mechanical properties of demineralized dentin and prevents weight loss associated with collagenase exposure. FTIR spectra indicate interactions between PA and collagen resulting in altered chemical structure which may account for mechanical property changes. Funded by UMKC SOD Summer Scholars Program.