In vitro fluoride dose-response study of sterilized enamel lesions

Currently our intra-oral model uses enamel specimens that have been disinfe cted by soaking in buffered formalin (pH 6.8). However, because of increasi ng emphasis on infection control, it is important to identify a way to ster ilize these specimens. The aim of this study was to determine if autoclaved , or gas sterilized, lesioned enamel responds to fluoride (F) in the same w ay alcohol-disinfected enamel lesions do. Seventy-two formalin-disinfected, human enamel specimens (3 mm) were lesioned in demineralizing solution for 96 h and were then divided into three groups. One group was autoclaved; on e group was gas sterilized (ethylene oxide), end the remaining 24 specimens were further disinfected in 70% ethanol for 10 min. Specimens in each grou p were then treated 4 times/day for 4 weeks with 0, 250 or 1,100 ppm F dent ifrice slurries in an in vitro cycling, remin/demin model. Following treatm ent, fluoride up take was analyzed by microdrill biopsy, and lesion depth a nd mineral content changes (BM) were determined by transverse microradiogra phy, Data were analyzed by one-way ANOVA analysis. In all three groups of s pecimens there were significant (p<0.05) differences in fluoride uptake in response to different fluoride treatments. Autoclaved lesions failed to pro vide dose-response data with regard to changes in lesion mineral content, B ecause formalin and 70% alcohol are only disinfectants, and autoclaving alt ered the responsiveness of enamel lesions, results from this study suggest that, of the methods tested, gas sterilization is the preferred method for sterilizing enamel specimens that will be used in intra-oral studies. Copyr ight (C) 2000 S. Karger AG, Basel.