Dental whitening is one of the most wanted for procedures for the improvement of the aesthetics of smiles, and it is considered a safe, efficient and conservative method. However, according to the literature, the application of whitening agents on the dental surface may lead to morphologic alterations on enamel surface due to the oxidizing process and the pH of the substances involved in the whitening process.
Presently, some studies have demonstrated that the addition of calcium ions to the whitening gel formula reduces the adverse effects caused by dental tissue whitening, decreasing mineral loss and increasing resistance to enamel demineralization. It is important to point out that the addition of small amounts of calcium to acid solutions may decrease the loss of minerals in up to 50%. Another advantage of the whitening gels containing calcium is the capacity to maintain a stable pH during the whole procedure, minimizing alterations in the dental structure and side effects such as dentine sensitivity and gingival irritation.
Quagliatto et al. (2013)* analyzed the pH of four hydrogen-peroxide based whitening gels at high concentrations every two minutes, starting from zero (from product manipulation) to the end of 45 minutes. They also studied the pH of two very popular drinks among the population: natural orange juice and Coca-Cola.
Measuring the pH
The products were placed in disposable test tubes. They were agitated together with the electrode of the pH meter to assure uniform contact between the product and the tip of the electrode during the 45 minutes, at a room temperature of 25 ± 2°C to allow for the pH value to stabilize.
The result data were tabulated and submitted to simple arithmetic average analysis.
G1 whitening gel showed neutral initial pH (pH=7.00), decreased slightly (pH = 6.98) and maintained the characteristics of basic pH (pH = 7.05) until the end of the test. G2 showed basic initial pH (pH = 8.90) and maintained the characteristics of a basic pH (pH = 8.50) throughout the duration of the test. G3 showed neutral initial pH (pH = 7.0) and then became acid, undergoing a gradual decrease until it reached pH = 5.40; as well as G4, which initially showed a basic pH (pH = 7.15), became acid and underwent a gradual decrease until reaching pH = 5.49.
The values of the pH of the natural orange juice (pH = 3.72) and of the Coca-Cola (pH = 2.66) were maintained acid throughout the test.
After the study, it was identified that both products analyzed showed acid pH values between 5.8 and 5.5, which can cause light demineralization of the surface of the dental enamel. The other two whitening gels did not show risk of demineralization of the enamel, since their pH values were above 7.
The whitening gel Whiteness HP Blue, G2, which contains calcium in its formula, stood out, proving to remain stable throughout the duration of the measurements with an alkaline behavior at all measurements, with and average pH of 8.5.
Whitening gels that maintain a basic pH or a pH close to neutral may be used on the dental surface without replacement, remaining in contact with the surface of the tooth for a maximum of 45 minutes with no alteration in the dental enamel morphology. The ones that show a gradual pH decrease require gel change during the whitening session.
In conclusion, it was proved that the mineral loss in dental whitening procedures is low when compared to the mineral loss resulting from the consumption of fruit juices and soft drinks. However, it is important to consider the duration of the exposure and how frequently the product is used, as well as the cleaning and buffer action of the saliva, which can reduce the undesirable effects produced by the contact of acid substances with tooth surface.
*Quagliatto PS, Duarte JI, Moura GF, Dutra MC, Mendonça LC. Análise do pH de bebidas ácidas e de géis clareadores dentários utilizados em consultório. Rev Dental Press Estét. 2013 jul-set;10(3):70-5.[Analysis of the pH of acid beverages and dental whitening gels used in the office.]