In vitro dentin tubule occlusion and remineralization competence of various toothpastes

Objectives: The purpose of this study was to evaluate dentin tubule occlusion and remineralization competence of various toothpastes containing fluoride, bioactive glass (BG), and hydroxyapatite (HAP) as active ingredients.

Materials and methods: Sixty dentin discs that were etched with ethylene-diamine-tetraacetic acid (EDTA) were randomly divided into nine groups. The first five groups containing eight dentin discs corresponded to subsequent brushing experiments: control, distilled water, fluoride toothpaste, BG toothpaste, and HAP toothpaste. Scanning electron microscopy (SEM) was used to demonstrate tubule occlusion after 7 days of simulated brushing (twice a day for 2min), which was followed by a citric acid challenge. The discs were stored in freshly prepared artificial saliva (AS) after every brushing cycle. The remaining four groups that contained five discs each received the following treatment: discs kept in distilled water (control), discs kept in a mixture of AS (pH 7.2) and 2g fluoride toothpaste, discs kept in a mixture of AS and 2g BG toothpaste, and discs kept in a mixture of AS and 2g HAP toothpaste. These discs were left in the mixture for one week at 37°C and were then examined under SEM. The pH of the leftover mixture was analyzed using a pH meter. The Wilcoxon signed-rank test was used to identify any statistically significant differences (p<0.05).

Results: All toothpastes demonstrated tubule occlusion after simulated brushing experiments. However, after the citric acid challenge, particles of fluoride toothpaste were completely washed away from the tubules whereas HAP and BG toothpastes demonstrated tremendous resistance to the acid challenge. After immersion of the discs in the mixture of AS and toothpaste, HAP and BG toothpastes again showed superior tubule occlusion in comparison to the other groups, but the highest pH increase was observed for fluoride toothpaste after mixing the toothpastes in AS.

Conclusion: The results of this study demonstrate that the highest tubule occlusion competence (both pre-and post-citric acid challenge) was achieved by HAP toothpaste, followed by BG toothpaste. After mixing the toothpastes in AS, the highest pH increase was observed for fluoride toothpaste, showing its superior remineralization and buffering capacity.