The Effect of Fluoride on Enamel wear in vitro

OBJECTIVES: The aim of this study was to investigate whether a 225ppm fluoride solution would affect erosion and attrition on enamel in vitro. METHODS: 30 flat enamel specimens were prepared from caries free, human third molar teeth. Specimens were polished and taped to leave a 2mm by 3mm window of exposed tooth surface. The enamel samples were randomised to 5 groups (n=6 per group) for 5 cycles of experimental wear. Group 1 (G1): Erosion (3% solution of citric acid at pH 3.2 for 5 min); Group 2 (G2): Attrition (customised attrition machine using human premolar cusps mounted and loaded at 300g over 60 linear strokes); Group 3 (G3): Erosion and Attrition; Group 4 (G4): Erosion and Attrition and Fluoride (225ppm sodium fluoride solution over 5 minutes); Group 5 (G5): Attrition and Fluoride. All samples were remineralised in artificial saliva for 2 hours before each wear cycle. Wear was measured using non-contacting laser profilometry before and after the initial and final wear cycles to record stepheight (SH), roughness (Ra) and Knoop microhardness (KMH). RESULTS: The following values are mean before/after differences for each group: G1 (SH 0.4µm, Ra -20.1%, KMH -39.5%); G2 (SH 1.8µm, Ra -19%, KMH -15.8%); G3 (SH 3.5µm, Ra -3.2%, KMH -30.1%); G4 (SH 3µm, Ra -10.9%, KMH –17%); G5 (SH 1.1µm, Ra -5.5%, KMH –12.9%). The following groups showed significant differences: SH G1-G3 (P<0.05); Ra G1-G3 (P<0.05), G1-G5 (P<0.05), G2-G3 (P<0.05); KMH G1-G5 (P<0.002). CONCLUSION: The different wear regimens vary in the amount of tooth wear produced with a combination of erosion and attrition producing the greatest stepheight change and erosion alone producing the greatest reduction in hardness. The addition of fluoride suggests a protective effect however these differences were small and did not approach statistical significance.