Effect of Dilute Hydrofluoric Acid-Treatments on Enamel In Vivo

Dilute hydrofluoric acid (HF) solutions have in earlier tests been proven to reduce enamel solubility. Objectives: To examine the effect of different concentrations of dilute HF in reducing enamel solubility using an in vivo model. Methods: Four healthy anterior teeth in each subject (n=72) with intact pellicle were exposed to diluted citric acid (10mmol/l) applied using a peristaltic pump (5 ml, 6 ml/min) and the acid collected in a test tube before and after application of the respective HF preparations (etch I and etch II). Four different concentrations of HF solutions (0.20%, 0.15%, 0.10%, 0.05%) where dripped on the labial surfaces of each of 18 teeth using the peristaltic pump (1 min, 6 ml/min). The teeth where rinsed for 5s with water between applications and left for five minutes after the treatment with HF before etch II. Enamel solubility was examined by assessment of calcium content in the citric acid applied before and after the treatment with the HF solutions using atom absorption spectroscopy. The reductions in calcium content in the citric acid between etch I and etch II were calculated for each tooth. Results: A greater reduction in calcium loss was observed for the three most concentrated solutions (0.20% HF – 69.7%, 0.15% HF – 61.6%, 0.15% HF – 70.1%) compared to the least concentrated solution (0.05% HF – 41.2%). Conclusions: Even extremely diluted HF seems to provide a very promising level of protection against the effects of acid on enamel solubility. Further studies are planned to determine the clinical relevance of these findings.