Toothbrush abrasion, simulated tongue friction and attrition of eroded bovine enamel in vitro

Objectives: Enamel erosion results in the formation of a softened layer that is susceptible to disruption by mechanical factors such as brushing abrasion, tongue friction and attrition. The aim of this study was to investigate the individual contribution of those mechanical insults to the enamel loss caused by dental erosion. Methods: Forty two bovine enamel samples were randomly divided into seven groups (n=6 per group) that were submitted to 3 cycles of one of the following regimes: erosion and remineralization (er/remin); toothbrush abrasion and remineralization (abr/remin); erosion, toothbrush abrasion and remineralization (er/abr/remin); attrition and remineralization (at/remin); erosion, attrition and remineralization (er/at/remin); simulated tongue friction and remineralization (tg/remin); erosion, simulated tongue friction and remineralization (er/tg/remin). Erosion took place in a demineralization solution (50 mM citric acid, pH 3) for 10 min under agitation. Brushing abrasion, tongue friction and attrition were simulated for 1 min using a home-made wear device. Remineralization was carried out in artificial saliva for 2 h. Enamel loss was quantified using optical profilometry. Results: One-way ANOVA indicated a significant difference between the amounts of enamel lost due to the different wear regimes (p≤0.001). Multiple comparisons with Bonferroni procedure showed that the wear depths found for the er/at/remin (p≤0.001) and er/tg/remin (p≤0.001) were significantly higher than the amount found for the er/remin group (4.4±0.7 μm). This was not the case for er/abr/remin group (p=0.075). Conclusions: The results suggest that the three forms of mechanical insults remove to varying extent the softened layer formed by the erosion challenges.