Long-term dentin remineralization from Ca-PO₄–releasing, whisker-reinforced polymeric composites

Resin-based cements containing calcium-phosphates have been shown in-vivo and in-vitro to remineralize mineral-deficient dentin. More recently, stronger whisker-reinforced composites have been developed for Atraumatic Restorative Treatment of carious teeth. These composites release calcium, phosphate, and fluoride ions in amounts that produce supersaturation with respect to hydroxy/fluoroapatite. OBJECTIVE: To report the 8wk remineralization of artificially demineralized dentin from 5 experimental composites, a positive (GIC-Fuji-LCII), and a negative control (TPH-Dentsply); to compare the results to the 4wk data, and explore the hypothesis that the remineralization is related to the ion release these composites produced in saline solution. METHODS: Cavities (3mm-width, 6mm-length, 1mm-depth) were drilled into occlusal dentin of extracted caries-free human molars. The teeth except the cavity were varnish-coated and exposed to demineralizing solution (pH=4.3, 48h). Each cavity was restored with one of the materials. The tooth was sliced into 180µm sections, contact microradiographs were taken and digital image analysis was performed to determine the ‘mineral-loss-before'. Each section was sandwiched between parafilm and a plastic cover exposing only the restoration edge, and incubated in 25mL artificial saliva for 4wk. Contact microradiographs were retaken, and the mineral loss after treatment was determined. This procedure was repeated after 8wk incubation. The %-remineralization was calculated from [(1-‘mineral-loss-after'/'mineral-loss-before') x 100]. RESULTS: The mean %-remineralization ± s.d. (n³3) after 8wk are: B1: 37±16; B3: 41±7; B4: 37±7; B6: 47±13; U3: 42±11; GIC: 42±3; TPH: 19±3. Analyzing for incubation time and treatment, 2-way ANOVA indicated a significant effect of time on the %-remineralization with increases over 4wk data of 6% (TPH) to 15% (B6). All experimental groups and GIC had significantly higher remineralization than TPH (p<0.05). CONCLUSION: The experimental composites and GIC have a high time-related potential to remineralize artificially demineralized human dentin. However, the measured remineralization cannot be predicted from saline ion concentrations. Support: ADAF; NIST; NIDCR-Grant-DE13298.