Bleaching of Endemically Fluorosed Teeth

Most patients love their postbleach smiles but not the side effects that can accompany them. While adding remineralizing agents to bleaching gels can mitigate these side effects, there have been concerns that these agents may affect whitening efficacy.

But research presented last month at the International Association for Dental Research (IADR) meeting in San Diego found that adding calcium and fluoride to bleaching gels does not interfere with the whitening effect of the gels.

Adverse effects related to the use of bleaching agents on enamel include a reduction in enamel microhardness and some mineral alterations after bleaching procedures, Alessandra Bühler Borges, PhD, an assistant professor in the department of restorative dentistry at the University Estadual Paulista told DrBicuspid.com.

Previous studies have reported a decrease in the calcium concentration of enamel surface when high-concentrated hydrogen peroxide gels are used, she said. However, the resulting reduction in microhardness of bleached enamel can be reversed through exposure to saliva, she added.

"Nevertheless, these side effects can be reduced by adding fluoride or calcium to the bleaching gels," Borges said. "Besides, remineralizing agents are added in bleaching gels as an attempt to reduce enamel solubility and tooth sensitivity."

Although the addition of remineralizing agents on bleaching gels has been proposed with the aim to reduce side effects, the effect of these agents on bleaching efficacy of gels has not been properly studied, noted Borges and her colleagues.

"The action mechanisms of fluoride and calcium on enamel remineralization are based on the formation of a calcium-fluoride-rich surface layer and the precipitation of calcium-phosphate mineral phase on enamel surface, respectively, and these factors were supposed to interfere with the penetration of bleaching agents inside tooth structure, maybe reducing the bleaching efficacy of gels," they noted. "This motivated us to investigate the bleaching efficacy of hydrogen peroxide-based whitening gels that contains fluoride and calcium."

The addition of fluoride has previously been reported in the literature, but the bleaching efficacy of calcium-added bleaching gels represents new data, Borges added.

Calcium gluconate

Different forms of calcium can be added to bleaching gels; for this study the authors used calcium gluconate.

They prepared 45 enamel-dentin disks from bovine incisors and divided them into two groups. The groups were divided according to the concentration of bleaching agent which included 7.5% and 35% hydrogen peroxide gels.

Each group was then subdivided into three subgroups:

Control group with no remineralizing agents
Addition of 2% calcium gluconate
Addition of 2% sodium fluoride
The bleaching gel was applied on the specimens for one hour a day for the home bleaching and 40 minutes a week for in-office bleaching, both for 14 days. In the intermediate periods, the specimens were immersed in artificial saliva. Color assessments were made 24 hours after the end of treatment. The color measurement was performed by a spectrophotometer using the CIE L*a*b*system.

The data showed no significant differences for the presence of remineralizing agents, gel concentration, and interaction factors, Borges and her team noted.

"The addition of calcium and fluoride in the bleaching gels does not interfere with their whitening effect, and both concentrations tested presented similar whitening effects," the authors concluded.

These results can be considered favorable for the clinical performance of bleaching agents since the advantageous effects of adding remineralizing agents to reduce the possible adverse effects to enamel did not impair the bleaching result of gels tested, Borges noted.

"Dentists can choose calcium or fluoride-enhanced bleaching gels to perform whitening treatments in order to combine the protective remineralizing action of these agents on enamel without reducing the bleaching efficacy of treatment," she concluded.