Low and high degrees of saturation for remineralization of dentin

Introduction: Remineralization of dentin can occur either by precipitation of mineral between the collagen fibers or functionally, bound to its structure. It has been proposed that the elastic properties of the dentin matrix cannot be restored by increasing the mineral concentration alone without the formation of mineral apatite within the collagen structure. Objective: In this study we evaluated different degrees of saturation (DS) of calcium and phosphate solutions to achieve an optimal interaction of mineral with the collagen of dentin, and thus recover the properties of simulated caries lesions. Methods: Experiments used dentin substrates (12mm2) partially demineralized with a 0.05M acetate buffer in pH=5.0 for eight hours. Remineralization utilized the constant solution composition approach, which allowed the continuous growth of apatite at relative sustained conditions for mineral growth, such as pH, temperature and ionic concentration. Remineralizing solutions had either high (10.6) or low (8.9) degree of saturation (DS). Specimens were remineralized for 4, 8 and 24 hours (n=3). Elastic moduli (E) of the hydrated tissues were measured using AFM nanoindentation before and after remineralization. Mean values were analyzed by ANOVA and Tukey HSD (p<.05). Micro-structural changes were studied using AFM high-resolution imaging while mineral formation was evaluated with Raman spectroscopy. Results: Specimens remineralized using low DS did not statistically recover the properties of simulated carious dentin (0.2±0.1GPa) after four (0.2±0.1GPa), eight (0.4±0.2GPa) or tweenty-four hours (0.4±0.3GPa). The mechanical recovery was highest in samples remineralized at high DS, but still less than normal dentin (20±1.9GPa) after four(1.1±0.7GPa), eight(7±1.3GPa) or twenty-four hours (5.6±1.9GPa). Raman spectroscopy suggested the formation of apatite on the dentin matrix. Conclusion: Mineral formation under constant composition allowed greater recovery of dentin properties using a higher DS (10.6). The results suggest approaches to provide functional remineralization of carious dentin lesions.

Support-NIH/NIDCRR01DE16849.