Concerns regarding the safety of all bleaching treatments and products have long existed, but were heightened since the introduction of at-home bleaching.5-8 Discussions in this section focus on peroxides and their use as active ingredients in tooth bleaching materials. Important concerns related to patient examination and diagnoses are addressed elsewhere in this report.
A variety of peroxide compounds, including carbamide peroxide, hydrogen peroxide, sodium perborate and calcium peroxide, have been used as active ingredients for bleaching materials; however, essentially all extracoronal bleaching materials currently available for whitening of vital teeth in the United States contain carbamide peroxide and/or hydrogen peroxide. Recently, products containing chlorine dioxide were introduced in the United Kingdom, but there is no evidence that tooth bleaching products using chlorine dioxide as the active ingredient are safer than peroxide-based materials. In fact, safety concerns have been documented with chlorine dioxide and its use for tooth bleaching treatment due to the low pH of the material and resultant tooth etching.9
Most OTC bleaching products are hydrogen peroxide-based, although some contain carbamide peroxide. Carbamide peroxide decomposes to release hydrogen peroxide in an aqueous medium: ten percent carbamide peroxide yields roughly 3.5% hydrogen peroxide. In-office bleaching materials contain high hydrogen peroxide concentrations (typically 15-38%), while the hydrogen peroxide content in at-home bleaching products usually ranges from 3% to 10%; however, there have been home-use products containing up to 15% hydrogen peroxide. Safety issues have been raised regarding the effects of bleaching on the tooth structure, pulp tissues, and the mucosal tissues of the mouth, as well as systemic ingestion. Regarding mucosal tissues, safety concerns relate to the potential toxicological effects of free radicals produced by the peroxides used in bleaching products. Free radicals are known to be capable of reacting with proteins, lipids and nucleic acids, causing cellular damage. Because of the potential of hydrogen peroxide to interact with DNA, concerns with carcinogenicity and co-carcinogenicity of hydrogen peroxide have been raised, although these concerns so far have not been substantiated through research.5,10,11 However, studies have shown that hydrogen peroxide is an irritant and also cytotoxic. It is known that at concentrations of 10% hydrogen peroxide or higher, © 2009 American Dental Association. All rights reserved. 3
the chemical is potentially corrosive to mucous membranes or skin, and can cause a burning sensation and tissue damage.5,12,13 The amount of products applied during office bleaching treatment and other formulation variables can change the potential to cause damage. However, severe mucosal damage can occur if gingival protection is inadequate with high strength tooth whitening products. Clinical studies have also observed a higher prevalence of gingival irritation in patients using bleaching materials with higher peroxide concentrations.14,15
Data accumulated over the last 20 years, including some long-term clinical study follow up16,17, indicate no significant, long-term oral or systemic health risks associated with professional at-home tooth bleaching materials containing 10% carbamide peroxide (3.5% hydrogen peroxide). However, these data were collected from studies which include examinations by dental professionals, and there is no safety evidence on bleaching materials that do not involve such examinations by dental professionals, regardless of hydrogen peroxide concentration or application venue. Additionally, consumers are not generally aware of how to report adverse events through FDA’s Medwatch system. If a licensed dental professional is not consulted when patients use OTC bleaching products, adverse effects due to product abuse may go unreported.
Regarding hard tissues, transient mild to moderate tooth sensitivity can occur in up to two-thirds of users during early stages of bleaching treatment.18 Sensitivity is generally related to the peroxide concentration of the material and the contact time; it is most likely the result of the easy passage of the peroxide through intact enamel and dentin to the pulp during a five- to 15-minute exposure interval. However, there have been no reported long-term adverse pulpal sequellae when proper techniques are employed. The incidence and severity of tooth sensitivity may depend on the quality of the bleaching material, the techniques used, and an individual’s response to the bleaching treatment methods and materials. To date, there is little published evidence documenting adverse effects of dentist-monitored, at-home whiteners on enamel, but two clinical cases of significant enamel damage have been reported, apparently associated with the use of OTC whitening products.19,20 This damage may be related to the low pH of the products and/or overuse.
To address the safety of bleaching materials, the ADA convened a panel of experts in 1993. The ADA subsequently published its first set of guidelines for evaluating peroxide-containing tooth whiteners.22 These guidelines have been revised periodically.
In March 2005, the European Scientific Committee on Consumer Products (SCCP) concluded the following: ―The proper use of tooth whitening products containing >0.1 to 6.0% hydrogen peroxide (or equivalent for hydrogen peroxide-releasing substances) is considered safe after consultation with and approval of the consumer's dentist.‖13 The © 2009 American Dental Association. All rights reserved. 4
SCCP, in January 2008, again recommended that up to 6% hydrogen peroxide is a safe limit to use for at-home tooth bleaching; however, it did not recommend use of such products without dental consultation.23
In summary, available data indicate that extracoronal bleaching treatment in the dental office or at home may cause short-term tooth sensitivity and/or gingival irritation. More severe mucosal damage is possible with high hydrogen peroxide concentrations. While available evidence supports the safety of using bleaching materials of 10% carbamide peroxide (3.5% hydrogen peroxide) by dental professionals, there are concerns with the use of at-home bleaching materials with high hydrogen peroxide concentrations. Studies designed specifically to assess the long-term safety of high hydrogen peroxide concentration in at-home bleaching materials are needed, especially for repeated use of these products. There appears to be insufficient evidence to support unsupervised use of peroxide-based bleaching materials.
Similar to other dental and medical interventions, questions have been raised about the safety of tooth whitening treatments during pregnancy. In the absence of such evidence, clinicians may consider recommending that tooth whitening be deferred during pregnancy.
The safety of tooth bleaching for children and adolescents is also a consideration. More research is needed to establish appropriate use and limitations for these patients. However, bleaching is a conservative approach compared with restorative options when tooth discoloration causes significant concern. If possible, delaying treatment until after permanent teeth have erupted is recommended, as is use of a custom-fabricated bleaching tray to limit the amount of bleaching gel.24 Close professional and parental/guardian supervision are needed to maximize benefits and minimize adverse effects and overuse. studies suggest that dental restorative materials may be affected by tooth bleaching agents.1,21 These findings relate to possible physical and/or chemical changes in the materials, such as increased surface roughness, crack development, marginal breakdown, release of metallic ions, and decreases in tooth-to-restoration bond strength. Such findings have not appeared in clinical reports or studies.