Join ADAMember Log In


In a newly published systematic review from the Cochrane Collaboration, home-use tooth-whitening products were found to have short-term effectiveness in whitening teeth, but there is limited information on long-term outcomes and side effects . The systematic review received news coverage from WebMDMedical News Today and other media outlets.

The Cochrane Collaboration is an international nonprofit organization that develops evidence-based systematic reviews on health care interventions. In the new Cochrane review, researchers from the University of Michigan analyzed 25 clinical studies that measured the efficacy of OTC and dentist-dispensed tooth whiteners (tray-applied gels, whitening strips, and paint-on films) after application for two or more weeks. All tooth whiteners evaluated in the Cochrane review used carbamide or hydrogen peroxide, two commonly used agents in home-use products for vital tooth bleaching. The study did not evaluate whitening toothpastes, which remove surface stains through the polishing effect of mild abrasives (e.g., silica, baking soda) or by enzymes or other chemical action.

A primary objective of the Cochrane review was “to investigate the effectiveness and relative effectiveness of tooth-whitening products with chemical, bleaching action, that are available for use at home.”1 The review found that, after 2 weeks of use, tooth-whitening products worked better than no whitening treatment, and that differences in product efficacy were mainly due to the levels of active ingredients.

After assessing the available scientific evidence, the authors noted that the tooth-whitening studies identified in their evidence review had moderate to high levels of bias, since each was conducted or sponsored by whitening product manufacturers. The authors also cited the complexity of conducting a systematic review of clinical trials for home-use whiteners, given the significant variation in whitening products, concentrations of active ingredients, study designs and application methods.

Over the past two decades, tooth whitening has grown dramatically as a dental treatment, and today many OTC and dentist-dispensed whitening products are available for use by consumers. The Cochrane reviewers cautioned that two common side effects of home-use products for chemically-induced whitening of teeth are “mild” to “moderate” tooth sensitivity and gingival irritation. However, as noted in the Cochrane review and the ADA Statement on the Safety and Effectiveness of Tooth Whitening Products, tooth sensitivity and soft tissue irritation are usually temporary and stop after treatment.

Importantly, the Cochrane review did not identify any long-term studies that provided independent evaluations of potential harms or long-term side effects to tooth whiteners. The reviewers emphasized this call for further study “given the higher concentration of peroxide-based agents being used in clinical application.”1 To fill this evidence gap, the reviewers strongly recommended more independent long-term evaluations (over 6 months) of home-use whiteners to further evaluate their long-term effectiveness and any potential health effects.

The ADA recommends that patients receive a thorough oral examination, performed by a licensed dentist, to determine the most appropriate whitening treatment. This allows the dentist to determine if the patient has any contraindications to the procedure and to supervise the use of bleaching agents within the context of a comprehensive, appropriately sequenced treatment plan.


1. Hasson H, Ismail AI, Neiva G. Home-based chemically-induced whitening of teeth in adults. Cochrane Database of Systematic Reviews 2006, Issue 4. 

Additional Resources

Science in the News is a service by the American Dental Association (ADA) to present current information about science topics in the news. The ADA is a professional association of dentists committed to the public's oral health, ethics, science and professional advancement; leading a unified profession through initiatives in advocacy, education, research and the development of standards. As a science-based organization, the ADA's evaluation of the scientific evidence may change as more information becomes available. Your thoughts would be greatly appreciated.

Page Posted November 2006