The effect of strontium and combinations of strontium and fluoride on the remineralization of artificial caries lesions in vitro

Objective: To determine the effect of relatively low strontium concentrations on enamel remineralization and investigate the dose-response effects of strontium and fluoride combinations on the remineralization of artificial caries lesions in vitro. Method and Materials: Artificial caries lesions were created in 135 bovine enamel specimens. Lesion severity was analyzed using transverse microradiography (TMR) and quantitative light-induced fluorescence (QLF). The specimens were randomly assigned to nine treatment groups based on lesion volume after lesion creation, as measured by TMR. Treatment groups were based on a 3 × 3 factorial design (0/0.05/0.1 ppm fluoride and 0/10/15 ppm strontium). Lesions were remineralized at 37°C for 14 days in artificial saliva, which was supplemented or not with NaF and/or SrCl2 × 6H2O. Lesion remineralization was assessed using QLF and TMR. Data were analyzed using ANOVA. Results: For the TMR data, lesion remineralization in the 10 ppm strontium + 0.05 ppm fluoride group was significantly higher than in all other groups (P .05) except the 0 ppm strontium + 0.05 ppm fluoride group (P = .06). The 10 ppm strontium + 0 ppm fluoride group exhibited significantly less remineralization than the 0 ppm strontium + 0 ppm fluoride group (P = .048). For the QLF data, intergroup differences were not the same as for the TMR analysis. The QLF measurement was only moderately correlated with TMR mineral loss (r = -0.37). Conclusion: Strontium alone did not improve the remineralization of artificial caries lesions under the chosen in vitro conditions. However, a synergistic effect between the combination of fluoride and strontium was found at specific concentrations. Keywords: bovine teeth, dental caries, enamel, fluoride, remineralization, strontium