In vitro evaluation of the ability of nanohydroxyapatite toothpastes to enhance remineralization of enamel caries lesion

Abstract

Objectives: Previous studies has shown that hydroxyapatite (HAP) in oral care formulations could serve as a favorable fluoride alternative for caries management. The present study compared the efficacy of different hydroxyapatite-containing toothpastes in remineralizing early caries lesions.

Methods: Early enamel caries lesion were produced on one hundred and sixty bovine enamel blocks by 3-day demineralization using a multispies microbial caries model. Following this, the 160 lesion-bearing blockswere randomly assigned to eight treatment groups (20/group): Crest cavity protection (1100 ppm fluoride), ClinPro 5000 (5000 ppm fluoride), Fygg (20 % nanoXIM), Boka (nanoXIM; concentration not disclosed), Dr. Jen (10 % nanoHAP), Risewell Regular (10 % microHAP), Risewell PRO (5 % nanoXIM + microHAP), and Just-Ingredients Powder (15 % microHAP). The blocks were subjected to remineralization by daily pH-cycling consisting of a 2-minute acidic challenge, three 2-minute toothpaste treatments, and then storage in artificial saliva for the rest of the time for 14 days. Surface microhardness (SMH) of each lesion was measured before and after remineralization. Data was analyzed statistically (α = 0.05) by paired t-test (intragroup comparisons) and ANOVA/Tukey tests (intergroup comparison).

Results: Every product achieved significant (p < .001) increase in SMH (remineralization). Tukey multiple comparison test indicated that Fygg (39.81 ± 24.07; 95 %CI 26.99-52.64) had a statistically significantly higher percentage remineralization than Boka (19.5 ± 10.56; 95 %CI 14.25-24.75, p < .01), Dr. Jen (21.68 ± 6.72; 95 %CI 18.45-24.92, p < .05), and Risewell Regular (21.80 ± 7.88; 95 %CI 18.11-25.49, p < .05), but did not differ significantly from the other products. There were no significant differences in the percentage remineralization among the rest of the toothpastes.

Conclusions: Within the limits of this in vitro study, there are differences in the ability of HAP toothpastes to enhance remineralization of early enamel caries lesions. It demonstrated that combining nanoXIM and nanoHAP in a toothpaste significantly enhanced the effectiveness of HAP to remineralize early caries lesion.

Keywords: Fluoride alternative; Hydroxyapatite; Nanohydroxyapatite; Remineralization; Toothpaste; nanoXIM.