Fluoride bioavailability in close proximity to professional fluoride applications

Recent evidence, recommendations and a new CDT code have created the desire for more evidence of the anticaries potential of fluoride varnishes. Most varnishes include naturally-occurring, alcohol-soluble resins that cure to a durable coating in the presence of saliva. Because varnishes also aim to provide a physical coating for the relief of dentin hypersensitivity, the durability and reduced permeability of the film are paramount. OBJECTIVE: The objective was to evaluate fluoride bioavailable adjacent to (rather than under) different fluoride varnishes, relative to a conventional, professionally-applied fluoride gel and a placebo dentifrice. METHODS: Carpobol and lactic acid lesions were prepared on 3mm diameter bovine enamel specimens (White,1987). Specimens (N=4) were placed next to (approximately 6.5mm) other specimens that were 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 a single 4-minute application of 1:3 slurries of product:water; varnish applications consisted of a thin layer applied using the manufacturer-supplied application brush. After application, specimens were rinsed with deionized water and placed in artificial saliva (ten Cate, 1988) for 48hrs. Specimens were then removed, cleaned and fluoride-uptake microdrill biopsy was performed. RESULTS: Fluoride uptake into demineralized enamel (post-fluoride minus pre-fluoride) was expressed as mean micrograms of fluoride per centimeter cubed enamel (±SEM) with (a)42±12, (b)49±13, (c)3616±427 and (d)3335±447 and (e)2634±255 and a = b < e £ d £ c (Student Newman-Keuls, p>0.05). CONCLUSIONS: Varnishes exhibited greater fluoride bioavailability adjacent to the application than did gel. This was likely due to their ability to hold and release fluoride for long periods of time in this static model. These results suggest fluoride varnishes need not be applied directly to white-spot lesions. The rapid “paint-technique” used in the dental office is likely sufficient to effectively deliver fluoride to the entire dentition.