Fluoride-releasing elastomeric ligatures assessed with the in situ caries model

The in situ caries model was used to assess the clinical benefit of fluoride-releasing elastomeric ligatures. The design of the experiment was a longitudinal, prospective, randomized, crossover clinical trial. Fourteen individuals starting orthodontic treatment with fixed appliances were recruited. Three in situ enamel specimens, with preformed subsurface carious lesions, were prepared for each patient, from human premolars. Two were placed in customized holders and one was retained as a control specimen. A crossover design was used so that patients had two experimental periods of six weeks with either fluoridated or non-fluoridated elastomerics, and a washout between. Elastomerics were randomly allocated at the first visit and one enamel specimen was placed at the beginning and collected at the end of each experimental period. The specimens were sectioned and ground to 100 microns, and transverse microradiography was carried out. They were analysed using dedicated computer software. The outcome measure was the change in the parameters of the pre-formed carious lesion, expressed as mineral loss (delta Z), lesion depth (ld), lesion width (lw), and ratio (delta Z/ld) between the three specimens. The mean mineral loss (vol %.micron) for the control specimen was 403.7 (+/- 139.5), compared with 599.3 (+/- 515.4) for the non-fluoridated ligatures and 477.2 (+/- 298.4) for the fluoridated ligatures. A one-factor within subjects ANOVA showed no statistical difference between the groups (P = 0.376). Fluoride-releasing ligatures do not provide a significant anti-cariogenic benefit in patients undergoing orthodontic treatment. This may be due to the short-term nature of the fluoride release. However, they might affect the local environment surrounding the bracket.