Dental Tribune America

Quest for tooth whitening: Study reports extensive damage to dental cells by carbamide peroxide

By Iveta Ramonaite, Dental Tribune International
August 27, 2021

TORONTO, Canada/LONDON, UK: As the quest for having whiter teeth continues, it is crucial to fully understand the extent of damage that tooth-whitening agents could have on oral health. In the first study of its kind, researchers sought to dig a little deeper into the issue and investigated the possibly deleterious effect of hydrogen peroxide-derived free radicals on dental cells. They found that exposing teeth to certain concentrations of carbamide peroxide gel harms the dental pulp cells and that this damage is irreversible.

It has long been established that tooth whitening may cause gingival irritation and hypersensitivity of teeth. However, although dental professionals have been warning patients against tooth whitening at home, little has been known about the actual, long-term damage that tooth-whitening agents could have on dental cells.

“This study is long overdue in dentistry, and we expect that it may impact how this routine dental procedure is viewed and developed in the future,” co-author Dr. Ola Redha, a student in the Eastman Dental Institute in London, told Dental Tribune International (DTI). “Our goal has always been to increase the awareness of patients of the possible dangers of this procedure,” she added.

“This study is long overdue in dentistry”
— Dr. Ola Redha, Eastman Dental Institute

In the study, the researchers directly or indirectly exposed 30 teeth to a tooth whitening gel that contained 5% or 16% carbamide peroxide. The experiment was carried out for two weeks, and the gel was applied for 4 hours daily. They were able to demonstrate how the dental pulp cells react adversely to exposure to carbamide peroxide through a 3 mm dentin layer and how this, in turn, makes the enamel more porous, which facilitates the penetration of the whitening agents into the dentin and, eventually, the pulp.

Lead researcher Dr. Laurent Bozec. (Image: Jeff Comber)

Discussing the possibly harmful effects of tooth whitening, lead researcher Dr. Laurent Bozec, an associate professor in the Faculty of Dentistry at the University of Toronto, told DTI: “Unfortunately, because the patients cannot see any damage to their teeth, besides the immediate hypersensitivity, there is a false feeling that the procedure is harmless.”

The study found that higher concentration and longer application time of the carbamide peroxide gel directly threaten the viability of the dental cells. According to the data, applying only 10% carbamide peroxide gel on teeth reduces the enamel protein content by up to 50%, whereas applying higher concentrations of around 35% could lead to pulp necrosis.

Study limitations and take-home message

Discussing the findings with DTI, Bozec noted that the results should be interpreted with caution: “We ought to be a little careful in the interpretation of our study as we performed an in vitro study, and it is likely that the cytotoxic side effect of carbamide peroxide tooth whitening would be lessened to some extent in the patient owing to the natural mitigation strategies that exist within our dental pulp.”

Additionally, Redha commented that performing similar experiments directly on patients could jeopardize the vitality of the tooth, but that this would help provide crucial evidence and reaffirm earlier findings. “Considering the natural function of the dental pulp stem cells in the production of odontoblasts to create reparative dentin and of the pulp itself to support the vitality of the entire tooth, it is critical nonetheless to evaluate how these byproducts have an impact on the population of such a critical stem cell reservoir,” she stated.

In light of the findings, Bozec noted that patients ought to be made aware of the potential oral health risks of high concentrations of tooth-whitening gels. He also suggested that products containing high concentrations of carbamide peroxide should include warning or educational labeling. Finally, he acknowledged that, even though the concentrations of carbamide peroxide used in dental offices are much lower, dental professionals should discuss the long-term effect of tooth whitening with their patients and recommend alternative products that contain a lower concentration of carbamide peroxide or no peroxide at all.

“We would welcome any direct interactions with the industry to develop joint approaches to develop safe tooth whitening,” Bozec concluded.

The study, titled “Compromised dental cells viability following teeth-whitening exposure,” was published online on July 30, 2021, in Nature Scientific Reports.

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