The effect of two different toothpastes and tooth brushing timing on enamel surface microhardness after an erosive challenge – Ex vivo study

Abstract

Introduction: Excessive consumption of carbonated beverages, fruit juices, high-energy drinks, and candies are the main causes of erosive dental lesions. Several studies have shown that phosphoric, citric acids and other substances present on these products have an erosive action on enamel surface [1]. The aim of this study is to compare the effect of two different toothpastes, with fluoride or chlorhexidine, and toothbrush timing on enamel surface microhardness after an erosive challenge with Redbull^®.

Materials and methods: Sample was obtained from 10 human molars (intact, caries/fracture-free). This study was approved by Egas Moniz Ethics Committee. Each tooth was sectioned in four enamel specimens (4x3mm) giving rise to 40 enamel specimens, randomly assigned in 4 different groups (n = 10): Group A - specimens were subjected to an erosive challenge (EC) with Redbull^® 3 minutes, 4 times a day, 5 days and brushed with a fluoride based toothpaste immediately after (Oral B^® pro-expert); Group B - EC, and brushed with a chlorhexidine based toothpaste immediately after (CHX - Elgydium^® gum protection); Group C – EC, specimens were submersed two hours in artificial saliva, at 37ºC, and then tooth brushed with the same fluoride based toothpaste of group A; Group D – EC specimens were submersed two hours in artificial saliva, at 37ºC and then tooth brushed with the same chlorhexidine based toothpaste of group B. Enamel surface microhardness values were obtained with a Vickers Microhardness tester. One-way ANOVA was used for the comparison of group microhardness means and post hoc tests (Bonferroni test) for pairwise comparison of groups. Statistical significance was accepted at p < 0.05.

Results: Enamel surface microhardness mean values were: Group A – 275.36 ± 50.10 HV; Group B – 304.60 ± 36.15 HV; Group C – 361.78 ± 36.17 HV; Group D – 387.16 ± 39.01 HV. Statistical analysis of data has shown no significant differences between the means of groups A and B (p = 0.117), and between the means of groups C and D (p = 0.172). However, there is statistical evidence that means of groups A and B are significantly different than means of groups C and D (p < 0.001).

Discussion and conclusions: Our results suggest the best timing for tooth brushing after the extrinsic erosion of enamel with a high-energy drink should be two hours, rather than immediately after the erosive challenge. No significant differences were found in enamel surface microhardness mean values when brushing with the fluoride based compared with the chlorhexidine-based toothpaste, considering the same brushing time.