Is Teeth Whitening Safe? What the Evidence Says

Teeth whitening has become one of the most commonly requested cosmetic dental treatments, and with that popularity has come a great deal of information - and misinformation - about its safety. For patients considering whitening, the fundamental question is a reasonable one: does whitening damage your teeth?

The short answer, based on the available evidence, is that teeth whitening performed correctly with appropriate products is safe. But the full picture is worth understanding.

How Whitening Works

Whitening works by using a peroxide-based agent - hydrogen peroxide or carbamide peroxide - to penetrate the enamel and break down the chromogenic compounds responsible for tooth discolouration. This is a chemical process that works within the tooth structure itself, which is why peroxide-based whitening can address intrinsic discolouration (staining within the tooth) whereas abrasive polishing (as in whitening toothpastes) can only address surface staining.

Does Whitening Damage Enamel?

This is the concern most commonly raised about whitening, and the research addresses it fairly clearly. Studies examining the effects of professional whitening on enamel have generally found no clinically significant damage to enamel structure when whitening is performed at appropriate concentrations for appropriate durations. The mineral content of enamel shows some temporary reduction during whitening, but this is reversed through remineralisation - the natural process by which minerals from saliva are redeposited into the enamel - within days to weeks after treatment.

Concerns about enamel damage are more relevant for very high concentrations used excessively or without professional supervision. This is one reason why the supervised approach through a dental practice is recommended over unsupervised use of high-concentration products purchased online.

Sensitivity

The most common side effect of whitening is temporary tooth sensitivity. Peroxide penetrates the enamel and can irritate the nerve inside the tooth, causing heightened sensitivity to temperature and pressure during and shortly after treatment. This is temporary and typically resolves within a few days of completing treatment.

Sensitivity is more likely in patients who already have some degree of tooth sensitivity, thin enamel, or exposed root surfaces. A dentist can identify these risk factors before whitening and adjust the protocol accordingly - using lower concentrations, shorter application times, or recommending a desensitising treatment before and during the whitening process.

Gum Safety

Professional whitening involves measures to protect the gum tissue from contact with the peroxide gel. In-chair treatments use a gum barrier applied before the gel. Custom-fitted trays for take-home whitening minimise gel overflow onto the gums. When gums are adequately protected, the risk of gum irritation is low. Over-the-counter products with ill-fitting trays or strips that contact the gum tissue are more likely to cause temporary gum irritation.

Who Should Not Whiten?

Whitening is not appropriate for everyone. Patients with active tooth decay or untreated gum disease should have these conditions addressed before whitening. Whitening will not change the colour of dental restorations such as crowns, veneers, or composite bonding, which can create a mismatch if the surrounding natural teeth are whitened. Pregnant and breastfeeding women are generally advised to wait. Children and adolescents under 18 are not candidates for whitening.

A professional assessment before whitening - checking the health of the teeth and gums, discussing the existing restorations, and reviewing the patient's history of sensitivity - ensures that whitening is safe and appropriate for the individual.