Evaluation of the Effect of Teeth Whitening Strips on Dental Plaque pH

Background and aim: the present study aimed to assess the effect of teeth whitening strips on dental plaque pH in vivo. Materials and Methods: This in vivo experimental study was conducted on 21 individuals, who were requested to use Crest 3D whitening strips for 30 minutes once a day and for 14 days according to the manufacturer’s instructions. Dental plaque pH was measured using GC plaque indicator kit at baseline (before using the strip), immediately after use (upon removal of the strip), and 30 minutes after the treatment at days one, seven and 14 following the onset of bleaching treatment. The data were analyzed using Freidman test, while Dunn's post-hoc analysis was used for complete comparison. Results: At days one, 7 and 14, the plaque pH decreased immediately after the completion of the treatment compared to the baseline value, and this reduction was statistically significant (p=0.001). The pH increased to the baseline value after 30 minutes. The plaque pH decreased at the 14th day in comparison with the first day, and this reduction was statistically significant (p=0.008). Conclusion: the results of the present study showed that application of whitening strips decreases the plaque pH immediately after the completion of the treatment; however, 30 minutes after strip removal, the pH reaches the baseline level. The plaque pH decreased during the two-week treatment period; however, it did not reach the critical pH.