Biomimetic Remineralization of Radicular Dentin Collagen Matrix
Objectives: This Ex Vivo study aimed to analyze and characterize the remineralization process of demineralized human radicular dentin in a bioceramic/Phosphate-buffered Saline (PBS) system. Methods: Twenty-two radicular dentin slices (2mm thickness) were prepared and partially or completely (n=10) etched with 37% H3PO4 solution for 30s. Each slice (n=18) and a standardized Biodentine® disk were placed into opposing sides of a glass vial containing 20mL of calcium-free PBS (pH 7.2) at 37°C. For comparison, two sound dentin slices and partially or completely (n=2) acid-etched slices were studied as controls. The calcium ion release and pH of the solutions were monitored at 12h, 1-15 days. The composition of the precipitates and ultrastructural examination was evaluated by Micro-Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) after 1-3 days, and 1-4 weeks. Results: Precipitation began in the first 30 minutes after immersion, increasing turbidity with time. The pH profiles showed a rapid initial rise, being the highest pH value recorded on day 3 (9.2-10.4) followed by a gradual decline with time. The higher value of calcium release recorded was on day 3 (32.42 mg/L) and 5 (26.40mg/L). Raman spectra obtained from precipitates and remineralized dentin showed distinctive bands at 955 and 1063cm-1 assigned to bending vibration ν1 (PO43–) of carbonate hydroxyapatite. SEM-EDAX indicated that the precipitates contained mainly calcium and phosphorus (Ca/P 1.40-1.70). FESEM revealed the migration to dentin of pre-nucleation clusters spherules within the first 24h. After 3 days was observed petal-like precipitates along the dentin surface with some discontinuous regions. With time, agglomerate (corn-on-the-cob) and compact precipitates mimicked the original structure of dentin. There was nearly no deposition of precipitates on mineralized dentin. Conclusions: Controlled apatite nucleation on collagen fibrils was achieved with this biomimetic mineralization system, promoting a remineralization process comparable to radicular dentin microstructure.