An in vitro and in vivo study of fluoride uptake by dentine following application of various topical fluoride regimens

Restoration of severely worn dentitions frequently involves the use of overlay dentures. Such treatment can lead to the rapid development of caries. Topical fluoride regimens, including sodium fluoride, amine fluoride or stannous fluoride, have been used to reduce this risk. Sodium fluoride is regarded as effective but the other two compounds to be evaluated have benefits such as deposition of acid insoluble salts on the tooth surface. However stannous fluoride can be unstable and it has been suggested that amine fluoride/stannous fluoride combinations may be more effective. This study investigated the three fluoride containing compounds both alone and in combination to measure the effects on the fluoride content of dentine both in vitro and in vivo. The effect in vivo on caries incidence and on bacteria flora in plaque and saliva (Appendix 7) in patients wearing overlay dentures was also evaluated. Techniques for biopsy of dentine were assessed and a novel method was developed and evaluated for harvesting dentine in vitro and in vivo for fluoride analysis. The in vitro study examined the uptake of the three materials in paste and rinse, gel or solution. The results showed that all the regimens significantly increased the fluoride content of dentine except an amine fluoride/stannous fluoride (AmF/SnF2 gel. SEM analysis of the treated dentine surface showed deposition of solid material except following the AmF/SnF2 gel. The latter behaved inconsistently. This suggested that complexing of the fluoride ion might occur. The in vitro study also found that demineralised dentine took up fluoride ions but in this instance the AmF/SnF2 gel produced a greater fluoride uptake. The in vivo investigation showed that in a double blind trial using patients wearing overlay dentures, biopsied dentine samples exhibited significantly increased fluoride levels following sodium fluoride and Amf/SnF2 paste and rinse regimens. No statistical difference was apparent between the treatments. The use of the products in vivo resulted in a significant increase in new cavitated carious lesions in patients using the AmF/SnF2 regimen compared to the sodium fluoride regimen. The three monthly evaluation of plaque and saliva samples indicated no statistical difference in bacterial counts between the treatments