Effect of Low Concentrations of Fluoride on Dentin and Enamel

The effects of low concentrations of fluoride (~1 mg/L F) on the enhancement of enamel remineralization and thus prevention of caries have been the rational basis of water fluoridation for many years.  The inhibition of erosion and demineralization in dentin and enamel are also important factors in the long term retention of healthy teeth.  Dental erosion is defined as the chemical removal of tooth surface mineral without microbiological aide.  Dental demineralization is defined as the loss of tooth mineral behind the surface of the tooth.  Low F concentration is considered to be the primary factor that effects erosion and demineralization progression.  Purpose:  Compare the effects of 0.5 mg/L F on dentin erosion and demineralization to that of enamel.  Method:  the continuous flow mouth model (Carey et al, JDR, 2004) was used with 0.5 mg/L F as NaF included within the saliva-like solution (SLS) at flow rate of 0.25 mL/min.  Hard tissue slices (enamel or dentin, n³3 each) with all cut edges protected by epoxy were exposed to three 1-hour demineralization challenges daily, with the SLS flowing across the samples throughout the interim cycles for a period of two weeks.  The tissue slices were evaluated for erosion and demineralization by comparing before and after x-ray microradiographs.  Results: at the low F concentration of 0.5 mg/L the amount of erosion (µm) for dentin 12.0±0.7 was significantly greater than enamel 5.7±4.2 (≤0.05).  The amount of dentin demineralization 14.4±3.0 was not statistically different than enamel 13.1±4.2 (p=0.3).  Conclusions: at low F exposure, dentin is more susceptible to erosion than enamel; however there is no difference in the demineralization of these tissues.  More data is needed to establish the concentration of F needed for protection of both dentin and enamel.  Supported by NIH Grant R01DE14707, ADAF and NIST.