Does the pH of the grape seed extract interfere in the biomodification capacity of dentin collagen?

The aim of this study was to verify the biomodifying action of 6.5% grape seed extract solutions, with different pH, when applied on dentin collagen. Dentin bars (1.7 mm x 6.0 mm x 0.5 mm) were demineralized for 5 hours in 10% phosphoric acid, and distributed into the following groups: acid solution (pH=4.42); neutral (pH=6.96); alkaline (pH=11.92) and distilled water (pH=6.75). Three-point flexural test (n=10) and mass variation (n=10) were assessed at different periods (baseline, after biomodification, 7 and 14 days of remineralizing solution storage). For qualitative analysis, similar dentin bars were prepared and analyzed using Fourier transform infrared spectroscopy (FT-IR) and Raman Spectroscopy (FT-Raman) before and after 1 hour of immersion in biomodifying solution with different pH. Data were subjected to Shapiro-Wilk normality tests, followed by two-way ANOVA for repeated measures and Tukey's post-test (p<0.05). Alkaline solution was effective in increasing the modulus of elasticity, showing a decrease after 7 days and subsequent stabilization after 14 days of storage. Acid solution group showed a greater increase in the modulus of elasticity immediately after biomodification, but it was not stable over storage. Regarding mass variation, only the acid solution showed an increase in mass after biomodification and 14 days of storage. In relation to FT-IR and FT-Raman, all solutions showed interaction with collagen at some level. Therefore, pH of the solution directly influences the action of the grape seed extract, with satisfactory results being found in both acidic and alkaline solutions.