The Potential of Hydroxyapatite Toothpaste to Prevent Root Caries: A pH-Cycling Study

Purpose: The effectiveness of a hydroxyapatite (HAP) toothpaste and a fluoride toothpaste in preventing root tissue demineralization (root caries) was compared using an established pH-cycling caries model. Materials and Methods: Sixty dentin blocks were produced from the root tissue of extracted human teeth and were assigned to 3 test groups (n=20/group): 10% hydroxyapatite toothpaste (HAP), 1450 ppm fluoride toothpaste (fluoride), and artificial saliva (artsaliva). Early root caries lesions were developed in each sample by 7-day demineralization using a pH-cycling caries model. The daily cyclic treatment regimen consists of two 2-minute toothpaste-slurry treatment periods, one 6-hour acid challenge using acidified gel (pH 4.5), and then storage in remineralizing solution (artsaliva) for the rest of the time. Demineralization was assessed as the amount of mineral loss (Delta z) using transverse microradiography (TMR). Pairwise comparisons (between treatments) were performed using analysis of variance (ANOVA), and then Tukey's HSD for multiple comparisons. All p-values are considered significant if p<0.05. Results: Both ANOVA and Tukey's HSD indicated no significant (ANOVA; n=20) difference in mean Delta z among the groups, with least Delta z (+/- Sd) in the HAP (1117 +/- 366) compared to fluoride (1392 +/- 334) and artsaliva (1406 +/- 223). Relative to control, HAP and fluoride inhibited root demineralization by 21% and 6%, respectively. Conclusion: Within the limit of the present study, the tested toothpaste containing 10% HAP is an effective root caries control toothpaste. Toothpaste containing 10% HAP was slightly more effective in preventing tooth demineralization than 1450 ppm fluoride provided as sodium fluoride. Thus, this study shows that HAP toothpastes can serve as an effective alternative to fluoride toothpastes for root caries management.