Enamel Strontium after in situ application of Sr/F toothpaste

Mineralized dental tissues have been known to retain strontium chloride with resulting inhibition of destruction processes. Recent studies have revealed that strontium is incorporated into the structure of synthetic apatites and contributes to its increased resistance to acid induced demineralization. Objectives: the aim of the study has been to analyze strontium contents on the surface and in deeper layers of artificially demineralised enamel following application of strontium-fluoride supplemented experimental toothpaste. Material and methods: Twenty healthy premolar teeth extracted for orthodontic reasons from children aged 12-14 years were used as the study material. The teeth were cut into samples and demineralized. The samples were placed in the oral cavity environment on buccal surfaces of the first molars of volunteers who used Ca2+, P043- Sr+2 (group I) and Ca2+, P043-, F-, Sr2+ (group II) supplemented toothpastes for 3 and 6 months. The contents of strontium on the surface and on the lateral side of the enamel at preselected depths of 15, 30, 60 and 100 μm was assayed with EDS microanalysis. Non-parametric ANOVA was used in statistical analysis of the results. Results: After 3 and 6 months of Sr-F toothpaste exposure (group II) no significant differences in Sr contents on the enamel surface could be detected as compared to the control enamel assayed immediately after demineralization. On the lateral enamel side there was significant Sr contents decrease (p< 0.01) at 60 μm depth, compared to the depth of 15 and 30 μm, after 3 month of the study, while after 6 months, Sr contents significantly increased (p< 0.01) reaching the highest value at 100 μm depth. No other changes could be observed in group I either on the enamel surface, or on the lateral walls. Conclusion: Strontium incorporation into the sub-superficial enamel layers is a process which can be facilitated by fluorides.