The modern trend for tooth whitening has become popular since 1989 when nightguard vital bleaching was described. Since then a range of bleaching techniques for use in the dental clinic, or at home have been in use. A wide range of over-the-counter (OTC) whitening products are also available, including gels, rinses, gums, dentifrices, whitening strips, and paint-on-films. However, not all of these products are available in all markets e.g. strips are no longer available in Europe. The aim of this review was to compare the efficacy and safety of over-the-counter whitening strips to the ADA-recommended home-bleaching technique using 10% carbamide peroxide gel.

Methods

Searches were conducted in the PubMed and Cochrane Central Register of Controlled Trails databases by 3 reviewers independently. Randomised controlled trials (RCTs) and clinical trials (CTs) were published in English were considered. Two reviewers independently extracted data and assessed study quality using the Cochrane risk of bias tool.

Colour change was the main outcome measure either measured digitally (ΔE [pooled measure of variation in colour] ΔL [variation of lightening] and Δb [variation of yellowing])or using a shade guide. Tooth sensitivity, reported gingival sensitivity, and observed gingival irritation were considered as safety indicators.

Results

• 9 studies were included.
• None of the studies were considered to be at low risk of bias and the overall quality of evidence based on GRADE criteria was considered to be very low.
• Six studies with a high level of heterogeneity (94%) expressed colour change through the mean ΔE. Meta-analysis revealed no significant difference between the intervention groups (MD −0.53; 95 % CI [−1.72 to 0.66]; Z = 0.88; p = 0.38).
• Meta-analysis of 2 studies also showed no significant difference in ΔL (MD-0.22; 95 % CI [-0.81 to 0.36]; z = 0.75; p = 0.45) but a reduction Δb that just reached significance (MD-0.47; 95 % CI [-0.89 to -0.06]; Z = 2.25; p = 0.02).
• Tooth sensitivity (risk ratio [RR] 1.17; 95 % CI [0.81 to 1.69]; Z = 0.81; p = 0.42) and gingival sensitivity (RR 0.76; 95 % CI [0.53 to 1.10]; Z = 1.44; p = 0.15) were similar, regardless of the whitening method used.
• The observed gingival irritation was higher when the 10 % CP gel was applied on tray (RR 0.43; 95 % CI [0.20-0.93]; Z = 2.14; p = 0.03).

Conclusions

The authors concluded:

There is no sound evidence in dental literature to suggest that the ADA-recommended whitening technique based on 10% carbamide peroxide gel could be substituted by the whitening strips. Well-designed studies are required to attest the efficacy and safety of this over-the-counter technique, especially due to the odds of improper use of these products without further professional monitoring. These studies should also consider the patient acceptance to the whitening treatment as a relevant outcome.

Comments

The included studies demonstrated a high degree of heterogeneity and the authors considered that the two most likely sources were the concentration of the whitening strips and the total contact time for the whitening agents. 7 out of the 9 studies included in this review were funding by the manufactures and the author’s assessment of the overall quality of the available evidence using the GRADE criteria was very low.

A 2006 Cochrane review by Hasson et al included 25 trials and concluded;-

There is evidence that whitening products work when compared with placebo/no treatment. There are differences in efficacy between the products, mainly due to the levels of active ingredients, hydrogen peroxide and carbamide peroxide. All trials were however short term and the majority of the studies were judged to be at high risk of bias and were either sponsored or conducted by the manufacturers. There is a need for pragmatic long-term and independent clinical studies that include participants representing diverse populations. There is also a need to evaluate long-term harms. Several studies reported (where measured) the common side effects of tooth sensitivity and gingival irritation, and people should be informed of this.

Links

Serraglio CR, Zanella L, Dalla-Vecchia KB, Rodrigues-Junior SA. Efficacy and safety of over-the-counter whitening strips as compared to home-whitening with 10 % carbamide peroxide gel-systematic review of RCTs and metanalysis. Clin Oral Investig. 2015 Aug 7. [Epub ahead of print] PubMed PMID: 26245272.

Hasson H, Ismail A, Neiva G. Home-based chemically-induced whitening of teeth in adults. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD006202. DOI: 10.1002/14651858.CD006202.