Effect of bristle stiffness of manual toothbrushes on normal and demineralized human enamel-An in vitro profilometric study.

OBJECTIVE: To compare the brushing abrasion carried out by manual toothbrushes with different bristle types (hard and soft) on normal and demineralized human enamel. MATERIALS AND METHODS: Thirty enamel blocks (N = 30) were prepared and were randomly divided into three main groups: A, teeth kept in artificial saliva with no brushing (control, n = 2); B, teeth brushed with toothbrushes with hard bristles (n = 14); and C, teeth brushed with toothbrushes with soft bristles (n = 14). Seven teeth belonging to groups B and C were brushed normally, and the remaining seven were demineralized before brushing experiments with 6 wt.% citric acid (pH = 2.2) for 5 minutes. The brushing experiments were carried out twice a day for 2 mins for 7 days inside a toothbrush simulation machine. The changes in the surface of enamel (prebrushing and post-brushing) were evaluated using non-contact profilometry. The results were analysed statistically using Kruskal-Wallis test and the Wilcoxon signed rank test. RESULTS: For both normal and demineralized enamel, toothbrushes with soft bristles caused more abrasion. The results revealed significant differences (P = .055) in the surface roughness values between the four groups prebrushing. Within each group, the prebrushing and post-brushing surface roughness value differences were all statistically significant (P < .05). CONCLUSIONS: The results demonstrate that soft bristles caused more abrasion as compared with the hard bristles. These results could have an impact on the toothbrush recommendations for patients.