Objectives: The purpose of this in vitro study was to investigate the pH of 21 commercially available tooth-whitening products.
Methods: Tooth-whitening products were divided into four categories: dentist supervised-home bleaching products (n = 5); in-office bleaching products (n = 5); over-the-counter bleaching products (n = 4) and whitening toothpastes and rinses (n = 7). The pH of three samples of each product was measured using an Orion Expandable Ion Analyzer EA940 with a Sure-Flow, Epoxy-body combination pH electrode. The group data were analysed using one way ANOVA (significant at p < 0.05).
Results: The five dentist supervised-home bleaching products had a mean pH of 6.21 +/- 0.76 and ranged from 4.88 to 6.81. The five in-office bleaching products had a mean pH of 6.26 +/- 1.19 and ranged from 5.30 to 7.85. The four over-the-counter whitening products had a mean pH of 5.07 +/- 1.74 and ranged from 3.76 to 8.03 and the seven whitening toothpastes had a mean pH of 7.66 +/- 1.19 and ranged from 6.61 to 9.68. The pH of the over-the-counter category was significantly lower (more acidic) than all other categories (p < 0.05). The whitening gel of Rapid-White had the lowest acidic pH of 3.76 and Colgate Advanced Whitening toothpaste showed the highest alkaline pH of 9.68.
Conclusions: The pH of all tooth-whitening products showed a wide range from 3.76 (highly acidic) to 9.68 (highly alkaline). Over-the-counter whitening products showed the lowest pH levels and in general these can be expected to damage enamel more than the other products. Dentists should be vigilant with regards to products used outside their surgeries and should warn their patients accordingly.
Clinical implications: The acidic pH of many of the whitening products other than in-office bleaching products is of concern and the general public should be better informed by the dental professionals of the dangers of these products.