In vitro analysis of the pH stability of dental bleaching gels during in-office procedures

BACKGROUND: Previous studies have shown that acidic bleaching gels could lead to worse collateral effects during an in-office bleaching procedure, while neutral or basic products leads towards a better experience. Considering this fact, the main purpose of this study was to evaluate the pH behavior of 6 in-office bleaching gels, compared to the information provided by their manufacturers. MATERIAL AND METHODS: Thirty enamel discs of bovine teeth were prepared, the initial colors of which were measured by a spectrophotometer and then divided into 6 groups. A pH meter was used to measure the pH every 30 seconds until the end of each procedure, when a new color evaluation was then made. The Tukey test was used for statistical analysis of the results. RESULTS: There was no difference in the color variation (ΔE) between the groups (p> 0.05). In two groups, the pH variation (ΔpH) showed neutral stability, with initial and final pH averages of 7.04 and 7.11 (p = 0.08) and 7.21 and 7.19 (p = 0.55), respectively; in another, there was alkaline stability, with an initial and final pH average of 8.54 and 8.37 (p = 0.14). In the other three brands, however, the results showed acidification, with initial and final pH averages of 6.14 and 5.22 (p = 0.001), 6.05 and 5.16 (p = 0.001) and 7.14 and 5.83 (p = 0.001), respectively. CONCLUSIONS: In 3 of the evaluated gels, a discrepancy existed between the manufacturer’s information and the data obtained, which could lead, considering previous studies discussed throughout this article, to unexpected collateral effects on the patients, especially dental sensitivity. Thus, clinicians and researchers should be aware about pH stability studies of in-office bleaching gels for better predictability and safety on their clinical usage. Key words:Tooth bleaching, Bleaching agents, Hydrogen-ion concentration, Dentin sensitivity, Hydrogen peroxide.