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Meta-analysis shows effectiveness and safety of OTC whitening strips Critical Summary Prepared by: Shukan Kanuga DDS, MSD 

OVERVIEW

  • Systematic Review Conclusion:

    Teeth can be safely and effectively whitened at home with the use of 6 percent hydrogen peroxide whitening strips.

  • Critical Summary Assessment:

    Based on a meta-analysis of seven randomized control trials (RCTs) at a single center, the use of 6 percent hydrogen peroxide tooth whitening strips improved yellowness and lightness of teeth in adults after two weeks.

  • Evidence Quality Rating:

    Limited

A Critical Summary of:

Single site meta-analysis of 6% hydrogen peroxide whitening strip effectiveness and safety over 2 weeks

Gerlach RW, Barker ML, Karpinia K, Magnusson I. Journal of Dentistry. 2009;37(5):360-5

  • Clinical Questions:

    Is bleaching teeth with 6 percent hydrogen peroxide whitening strips effective and safe in comparison to baseline?

  • Review Methods:

    The meta-analysis included data from seven different RCTs conducted over a 4-year period at a single dental school. Each study involved two weeks’ use of 6 percent hydrogen peroxide whitening strips for 30 minutes twice daily as one of the treatment groups. Adults with no bleaching history and current tooth sensitivity were included. Those with acute dental treatment or extensive anterior restorations were excluded. Researchers collected efficacy and safety measurements at baseline and again after one and two weeks of treatment for six studies and at baseline and 2-week intervals for only one of the studies.

  • Main Results:

    The authors included seven RCTs that had been conducted over a 4-year period. All of the RCTs had been conducted at a single dental school with a total of 148 subjects (ranging from 18 to 71 years of age, mean age 32.8 years; females made up 72 percent of the sample) in the treatment group at baseline and 141 subjects at the respective 2-week follow-up interval. The test product in all the studies was 6 percent hydrogen peroxide strips while the control product varied between studies, consisting of a marketed combination, experimental strip, marketed tray, or marketed paint-on whitener. The individual studies and the pooled sample exhibited whitening (less yellow, brighter and less red) across all color parameters beginning at Week 1 and continuing through Week 2. After two weeks, the adjusted mean for Delta-b* (change in yellowness) was -2.3 (Standard Error, SE = 0.07), differing significantly from Week 1 (p<0.0001). The estimated correlation between Weeks 1 and 2 for Delta-b* was 0.74. Results were similar for Delta-L* (change in lightness). The estimated correlation between Weeks 1 and 2 for Delta-L* was 0.75. Individual study means ranged from 1.9 to 2.6 for Delta-L*, with overall 95 percent confidence intervals of 1.8 to 2.3 at Week 2. Study-to-study variation contributed approximately 7.2 percent of all Delta-L* variability at Week 2. Oral irritation and tooth sensitivity were the most common adverse events and were transient. The authors did not report any serious adverse events. They noted a significant relationship between age and baseline tooth color (p < 0.0001).

  • Conclusion:

    Adult teeth can effectively and safely be bleached with 6 percent hydrogen peroxide whitening strips.

  • Source of funding:

    Procter and Gamble provided partial research support for the included studies.

Commentary:

  • Importance and Context:

    Teeth whitening is a cosmetic treatment for which patients commonly inquire and seek treatment. With a multitude of bleaching options available for at-home and in-office treatments, the practitioner should be equipped to offer treatment options based on the best current evidence for each modality. With convenience and cost-effectiveness being a major advantage for whitening strips, it is important to understand the safety and efficacy of this commonly preferred intervention.

  • Strengths and Weaknesses of the Systematic Review:

    The authors did not carry out a comprehensive search of databases for this meta-analysis; rather they included seven studies that were conducted with a homogenous RCT design at a single dental school. The research used a common, unbiased, reproducible instrument and method to measure whitening response across trials. Although the authors did not provide a list of studies, they summarized key characteristics of individual studies in a table. The authors were unclear about the comparison group and how many participants there were in each group of the trials at the beginning and end of each study. The characteristics of the comparison groups were not described, therefore no inter-group comparisons were reported. They clearly indicated their affiliations and provided conflict of interest statements.

  • Strengths and Weaknesses of the Evidence:

    All the included studies were RCTs with a homogenous study design of interventions conducted at a single dental school. Entrance criteria, test product, safety and efficacy methods (digital image analysis, clinical exam and interview), time points and study conduct site were common across studies. The analysis was inclusive of studies, subjects and observations. The pooled data showed significant outcomes in terms of whitening color improvement relative to the baseline. The studies only provided intra-group comparisons; comparisons between the experimental and control groups were missing in all studies. The authors did not mention how randomization was conducted or whether the studies were double-blind. The sample size of seven RCTs is small. The authors failed to mention how the drop-out subjects were treated and how this affected the outcome. They did not discuss the outcomes from a patient satisfaction standpoint or whether the statistically significant results of whitening were of clinical significance to the subjects. The researchers received financial compensation for these studies.

  • Implications for Dental Practice:

    Based on limited evidence, 6 percent hydrogen peroxide strips that are available over-the-counter are a safe and effective at-home bleaching technique. Better safety and efficacy studies need be conducted to determine the safety and efficacy of these strips in comparison with other available modalities.

  • Critical Summary Publication Date: 10/21/2013

These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association ©

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