Efficacy and safety of whitening mouthrinse on enamel: randomized clinical trial and in vitro study

Whitening mouthrinses have become very popular because they are easy to use and are accessible. However, there is no evidence of the effects and safety of this product on sound and demineralized enamel. The proposal comprised in two parts. The first one was a randomized clinical trial that evaluated the efficacy and safety of the whitening mouthrinse. Participants (n=45) were randomly allocated to three treatment groups: LWE (Listerine Whitening Extreme–2.5% hydrogen peroxide); PL (placebo mouthrinse); and OPF (Opalescence PF–10% carbamide peroxide). The treatment was performed 1x/day for 14 days during 2h for OPF, and 2x/day for 90 days during 30s for LWE and PL. Tooth color was measured using shade guides (DUEC) and spectrophotometer. Tooth sensitivity, gingival condition, enamel demineralization potential, and participant satisfaction were analyzed. The analyses were performed in different times. For shade guides, Kruskal-Wallis showed a significant difference between treatments in the evaluated times (p<0.05). LWE showed higher DUEC values compared to PL after 60 days. PL and OPF exhibit constant values, being significantly higher for OPF. For spectrophotometer, RM-ANOVA showed significance for the groups and interaction (p<0.05). LWE showed higher color difference values than PL from T14. OPF exhibited the highest values throughout the study. After 2 years, there was maintenance of tooth color for all groups. There was lower intensity of sensitivity for LWE and OPF. No participant exhibited gingival inflammation. LWE and OPF promote a significant decrease in calcium concentration, but after 1 week the values were intermediate. Phosphorus concentration did not alter over time. All participants of OPF group were satisfied with the treatment and 67% of the participants of LWE group showed satisfaction. The second part of the study consisted of an in vitro study that compared the effect of whitening mouthrinse on enamel demineralization and on initial caries lesions. Bovine enamel/dentin specimens (n=120) had their surface divided into three areas [control sound enamel, enamel treated (ET); and initial caries lesion treated (ICLT)] and were randomly assigned to the experimental groups: LWE; PL; OPF; and deionized water (DW). The treatments (2min for LWE, PL and DW; and 2h for OPF) were performed during a 28-day pH cycle (6x60min demineralization). Surface reflection intensity (rSRI), mineral loss, and fluoride concentration (additional specimens) were performed. For ET, a higher value of rSRI was observed in LWE (89.99%±6.94) and a greater decrease in rSRI was observed for OPF and DW. There was no mineral loss in the groups (p>0.05). For ICLT, rSRI was significantly significant after cycling for all groups with no difference between them (p>0.05). Higher fluoride concentration was found in OPF. LWE and OPF exhibited similar effects on the mineral loss with intermediate values. There was whitening efficacy for both LWE and OPF and color maintenance after 2 years. There was a protective effect of the mouthrinse during cycling