Fluoridated elastomers: in vivo versus in vitro fluoride release.

OBJECTIVES To compare (i) the in vivo release of fluoride from fluoridated elastomers to the in vitro release, and (ii) the residual fluoride content of the elastomers after 1 week in the mouth with and without fluoride toothpaste and mouthrinse. DESIGN A prospective, longitudinal, cross-over study. SUBJECTS AND METHOD Six subjects were recruited by poster to take part in the study. Each subject had one premolar in each quadrant to which a bracket could be fixed and exemplary oral hygiene. Elastomers were then placed on these brackets. INTERVENTION The study was divided into two parts: (i) subjects used oral hygiene products with fluoride and (ii) oral hygiene products with fluoride were excluded. Both groups of elastomers were left in the mouth for 1 week. After collection the elastomers were stored in distilled water. MAIN OUTCOME MEASURES The amount of residual fluoride in the ligatures after they have been placed in the mouth for 1 week was compared with the cumulative fluoride release in vitro over 1 week and 6 months. RESULTS Only 13 per cent of the total amount of fluoride in fluoridated elastomers was released during the first week in vitro, compared with 90 per cent in vivo. There was a significantly greater amount (P = 0.001) of residual fluoride when the elastomers were in the mouth for 1 week in the presence of fluoride toothpaste and mouthrinse, than when fluoride supplements were excluded. CONCLUSIONS (1) Higher levels of fluoride are lost from the fluoride elastomers in vivo than in vitro during the first week. (2) A significantly greater amount of residual fluoride was released from the elastomers placed in the mouth when fluoride toothpaste and mouthrinse were used.