Fluoride uptake from professional fluoride applications applied directly onto lesions

Fluoride varnishes are becoming increasingly popular in-office fluoride treatments for the prevention of tooth decay. Their relatively high concentration of fluoride and tenacious resin-based vehicle render them an obvious choice for increasing fluoride delivery and retention. OBJECTIVE: The aim of this experiment was to evaluate the fluoride uptake afforded by three new fluoride varnishes when applied directly onto laboratory-prepared white-spot lesions. METHODS: Conventional white-spot lesions were prepared on 3mm diameter bovine enamel specimens using the lesion solution of White (1987). Indigenous fluoride content was determined using the microdrill biopsy technique first described by Sakkab (1984). Specimens (N=4) were then treated with either a fluoride-free dentifrice (a), 5000ppm F gel (b), Vanish® varnish (c), Enamel Pro® Varnish (d) or Prevident® Varnish (e). Dentifrice/gel treatments consisted of soaking specimens in 1:3 slurries of product and water for 4 minutes while varnish applications consisted of a thin layer of varnish painted directly on the sample with the application brush provided by the manufacturer. Specimens were immediately rinsed with water, then placed in artificial saliva (ten Cate, 1988) for 48 hours. After soaking, specimens were thoroughly cleaned and again subjected to microdrill biopsy. RESULTS: Fluoride uptake into demineralized enamel was expressed as mean micrograms of fluoride per centimeter cubed (±SEM) with (a)35±13, (b)451±54, (c)1746±196 and (d)2723±290 and (e)2225±167 and a < b < c £ d (Student Newman-Keuls, p>0.05). CONCLUSIONS: The varnishes exhibited greater fluoride uptake than the commonly used 5000ppm F gel treatment. This is likely due to both fluoride concentration and significant contact time. The varnishes exhibited different fluoride uptake results suggesting fluoride release and, more importantly retention time for sustained low-level fluoride release may not be the same for all varnishes. These static conditions may over exaggerate oral conditions as salivary flow would promote evacuation of released fluoride more rapidly.