Home-based chemical bleaching of teeth in adults

Review question
What evidence is available regarding the different home-based chemically-induced bleaching agents in whitening teeth?

Background
There has been an increasing demand for whiter teeth. Home-based whitening products with a bleaching action have become popular and are prescribed to people by the dentist or purchased over-the-counter. A variety of whitening products are available which include hydrogen peroxide, carbamide peroxide, sodium percarbonate, sodium hexametaphosphate, sodium tripolyphosphate, and calcium peroxide. These agents are supplied in different concentrations and are used with different methods of application (gel in tray, strips, paint-on gel, chewing gum, and mouthwash), which have varying application times and duration of treatment.

Study characteristics
Authors from Cochrane Oral Health carried out this review of existing studies and the evidence is current up to 12 June 2018. We included 71 trials that involved 3780 adults who underwent tooth whitening procedures with various bleaching agents using different methods of application, length of application and duration of treatment. 26 studies compared a bleaching agent to placebo and 51 studies compared one bleaching agent to another bleaching agent.

Key results

The bleaching agents whitened teeth compared to placebo over a short time period (from 2 weeks to 6 months), however the certainty of the evidence is low to very low.

The evidence currently available is insufficient to draw reliable conclusions regarding the superiority of home-based bleaching compositions or any particular method of application or concentration or application time or duration of use.

The most common adverse events were tooth sensitivity and oral irritation, which were reported with higher concentrations of active agents, although the effects were mild and transient.

Well-planned randomised controlled trials need to be conducted by standardising methods of application, concentrations, application times and duration of treatment.

Certainty of evidence
The overall certainty of the evidence was low to very low for all comparisons. This was because most of the comparisons were reported in single trials with small sample sizes and event rates. There was an unclear risk of bias in most of the trials.

Authors' conclusions: 

We found low to very low-certainty evidence over short time periods to support the effectiveness of home-based chemically-induced bleaching methods compared to placebo for all the outcomes tested.

We were unable to draw any conclusions regarding the superiority of home-based bleaching compositions or any particular method of application or concentration or application time or duration of use, as the overall evidence generated was of very low certainty. Well-planned RCTs need to be conducted by standardising methods of application, concentrations, application times, and duration of treatment.

Read the full abstract...
Background: 

With the increased demand for whiter teeth, home-based bleaching products, either dentist-prescribed or over-the-counter products have been exponentially increasing in the past few decades. This is an update of a Cochrane Review first published in 2006.

Objectives: 

To evaluate the effects of home-based tooth whitening products with chemical bleaching action, dispensed by a dentist or over-the-counter.

Search strategy: 

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 12 June 2018), the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 6) in the Cochrane Library (searched 12 June 2018), MEDLINE Ovid (1946 to 12 June 2018), and Embase Ovid (1980 to 12 June 2018). The US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (12 June 2018) and the World Health Organization International Clinical Trials Registry Platform (12 June 2018) were searched for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.

Selection criteria: 

We included in our review randomised controlled trials (RCTs) which involved adults who were 18 years and above, and compared dentist-dispensed or over-the-counter tooth whitening (bleaching) products with placebo or other comparable products.

Quasi-randomised trials, combination of in-office and home-based treatments, and home-based products having physical removal of stains were excluded.

Data collection and analysis: 

Two review authors independently selected trials. Two pairs of review authors independently extracted data and assessed risk of bias. We estimated risk ratios (RRs) for dichotomous data, and mean differences (MDs) or standardised mean difference (SMD) for continuous data, with 95% confidence intervals (CIs). We assessed the certainty of the evidence using the GRADE approach.

Main results: 

We included 71 trials in the review with 26 studies (1398 participants) comparing a bleaching agent to placebo and 51 studies (2382 participants) comparing a bleaching agent to another bleaching agent. Two studies were at low overall risk of bias; two at high overall risk of bias; and the remaining 67 at unclear overall risk of bias.

The bleaching agents (carbamide peroxide (CP) gel in tray, hydrogen peroxide (HP) gel in tray, HP strips, CP paint-on gel, HP paint-on gel, sodium hexametaphosphate (SHMP) chewing gum, sodium tripolyphosphate (STPP) chewing gum, and HP mouthwash) at different concentrations with varying application times whitened teeth compared to placebo over a short time period (from 2 weeks to 6 months), however the certainty of the evidence is low to very low.

In trials comparing one bleaching agent to another, concentrations, application method and application times, and duration of use varied widely. Most of the comparisons were reported in single trials with small sample sizes and event rates and certainty of the evidence was assessed as low to very low. Therefore the evidence currently available is insufficient to draw reliable conclusions regarding the superiority of home-based bleaching compositions or any particular method of application or concentration or application time or duration of use.

Tooth sensitivity and oral irritation were the most common side effects which were more prevalent with higher concentrations of active agents though the effects were mild and transient. Tooth whitening did not have any effect on oral health-related quality of life.

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