Erosion Potential of Tooth Whitening Regimens as Evaluated with Polarized Light Microscopy

Aims: Tooth whitening is a widely utilized esthetic treatment in dentistry. With increased access to over-the-counter (OTC) systems concerns have been raised as to potential adverse effects associated with overuse of whitening materials. Therefore, this study aimed to evaluate enamel erosion due to different whitening regimens when used in excess of recommended guidelines. Materials and methods: Extracted human teeth (n = 66) were randomly divided into 11 groups (n = 6/group). Specimens were exposed to OTC products: Crest Whitestrips and 5-minute natural white and a do-it-yourself (DIY) strawberry whitening recipe. Within each regimen, groups were further divided per exposure time: specimens receiving the recommended product dosage; 5 times the recommended dosage; and 10 times the recommended dosage. Negative and positive controls were treated with grade 3 water and 1.0% citric acid, respectively. Specimens were nail-varnished to limit application to a 1 × 4 mm window. Following treatment, specimens were sectioned and erosion (drop in µm) measured using polarized light microscopy. Two-sample t-test was used to detect difference in amount of enamel erosion between negative and positive groups, while one-way analysis of variance (ANOVA), followed by post hoc Dunnett’s test was used to detect difference between set of treatment groups and negative control groups or among all experimental groups. Results: There was significant difference in mean amount of enamel erosion (p<0.0001). Mean enamel erosion for positive control group was significantly greater than that for negative control group (23.50 vs 2.65 µm). There was significant effect for type of treatments on enamel erosion [F(9,50) = 25.19; p<0.0001]. There was no significant difference between the negative control and each of treatment groups (p > 0.05 for all instances), except for Natural White_10 times treatment group (p<0.0001) that was significantly greater than the negative control group (14.82 vs 2.65 µm). Conclusion: Caution is advised when using certain over-thecounter products beyond recommended guidelines as there is potential for enamel erosion. Clinical significance: Enamel erosion due to the overuse of whitening products varies for different modalities and products. Therefore, caution is advised when using certain over-thecounter products beyond recommended guidelines, as there is potential for enamel erosion.