Objectives: This exploratory study sought to evaluate the utility of nanoindentation in determining the extent to which an enamel pretreatment of sodium fluoride (NaF) could reduce the effects of an acid challenge on the nanomechanical properties of enamel.
Methods: Human coronal enamel was polished stepwise through 0.25 micrometers and the atomic force microscope (AFM) based wet nanomechanical properties (indentation modulus, E, and hardness, H) were measured. Half of each specimen was masked and the specimens were treated with a range of solutions of fluoride (as NaF) for set time periods followed by measurement of E and H. After removal of the masks, the specimens were exposed to 1.0% citric acid (pH 3.8) for 10 minutes and E and H were again measured. A repeated measures design was used and the results were analyzed with ANOVA.
Results: No significant changes in E and H values were observed following NaF pretreatments. All NaF treatments resulted in a reduced change in the nanomechanical properties of enamel after acid challenge compared to the no-treatment condition.
Conclusion: This AFM based nanoindentation study suggests that fluoride confers some protection to the near-surface nanomechanical properties of enamel following exposure to 1.0 % citric acid (pH3.8).
Acknowledgement: Supported by GlaxoSmithKline.