White Fright: Burns & Multicoloured Teeth

Media item: article

Date published: 11 May 2014

Subject: harm from tooth whitening, and discolouration

This page records the media item. The original article is the property of its publisher and is not reproduced here. The service page is Professional Teeth Whitening.

The harm side

Whitening is a chemical oxidation reaction using hydrogen peroxide. At the concentrations used professionally, peroxide is a genuine chemical hazard to soft tissue. What should I know about teeth whitening? and Why should I go to a dentist for teeth whitening? cover the same ground.

Chemical burns

Peroxide in contact with gum, lip or cheek causes a chemical burn — a white, blanched patch that then becomes red, raw and painful, usually over the following hours.

Most are superficial and heal within days to a couple of weeks. More severe burns take longer and can scar.

How it happens:

A poorly fitting tray, which is the most common cause. Custom trays exist largely to prevent this, and it is the main clinical argument against one-size and boil-and-bite kits at higher concentrations — Difference between pharmacy whitening kits and dentist whitening?
Inadequate gingival isolation during in-chair whitening. The barrier placed over the gums before high-concentration gel is applied is not decoration — The difference between in-chair whitening and take-home whitening
Overfilling the tray, so gel extrudes onto the gum — The do's and don'ts of home teeth whitening
Leaving product on longer than instructed.
Products bought online from overseas at concentrations that cannot lawfully be sold to the public in Australia, with no examination, no custom tray and no supervision — Home teeth whitening vs having your teeth whitened at the dentist

If it happens: rinse thoroughly with water, stop using the product, take simple analgesia, and contact the practitioner who provided it. For anything more than a small area, or if it is not settling, be seen — Emergency Dentistry.

The other harms

Sensitivity — the most common side effect, usually short-lived, and worse with higher concentration and longer contact (What to do if you suffer from sensitive teeth)
Whitening over untreated decay, cracks or exposed dentine, where peroxide reaches the pulp far more readily — which is exactly why an examination before whitening is not a formality (The stages of dental decay, Chipped or Cracked Teeth)
Swallowing product from an ill-fitting tray
Damage to existing restorations' margins in some circumstances (Tooth Fillings)

The Australian regulatory position

Tooth whitening products in Australia are regulated on the basis of peroxide concentration. Products above the low-concentration threshold set for general retail sale are restricted to supply by, or under the supervision of, a registered practitioner — see Dentists & Registered Specialists.

The practical consequences:

A supermarket or pharmacy kit is a genuinely weaker formulation, not the same product cheaper.
Whitening offered by a non-registered operator — a kiosk, a salon, a mobile service — is subject to those retail limits, and the operator is not qualified to examine you beforehand or to manage a complication.
Overseas online products may exceed what can lawfully be sold to the public here — the same pattern as dental tourism.

The "multicoloured teeth" side

This is the more useful half, because whitening does not fix most of it, and knowing which you have determines what actually helps. How can I improve the whiteness of my teeth? is the general version.

Extrinsic staining

Surface pigment from coffee, tea, red wine, dark cola, curry, tobacco, plus stained calculus. Removed by a professional clean — Dental Cleans and Hygienists. Peroxide does not remove calculus.

Generalised intrinsic discolouration

Pigmented molecules within the tooth, accumulated over years. This is what whitening actually treats, and treats well — How long do teeth whitening effects last?

Tetracycline staining

From tetracycline antibiotic exposure while the teeth were forming — in childhood, or through the mother during pregnancy (Oral health care while pregnant). It produces grey, brown or blue-grey banding across the teeth, often in horizontal bands corresponding to the period of exposure.

It responds poorly to whitening, particularly the darker grey-blue forms. Prolonged home whitening improves some cases. Severe cases are managed restoratively (Porcelain Veneers, Composite bonding), or accepted.

Dental fluorosis

From swallowing too much fluoride while the teeth were forming — usually swallowed toothpaste in early childhood. White flecks and lines in mild cases; brown mottling and pitted enamel in severe cases. See What causes white spots on teeth? and The benefits of fluoride.

It is cosmetic, permanent, and entirely preventable: a smear of toothpaste under three, a pea from three to six, supervised, and taught to spit — Kids' teeth cleaning tips and Choosing the right toothpaste.

Mild fluorosis often responds well to microabrasion or resin infiltration — conservative techniques that remove almost nothing.

Molar incisor hypomineralisation (MIH)

Common and under-recognised. Creamy-white, yellow or brown patches with sharply demarcated edges, on the first permanent molars and often the incisors. The enamel is soft, porous, extremely sensitive, decays fast, and local anaesthetic works less reliably in it.

The cause is not established, and it is not caused by poor brushing. Covered in more detail at Molar Power and Everything you need to know about chalky teeth.

A single dark tooth after trauma

Usually a non-vital tooth. The pulp has died and blood breakdown products have discoloured the dentine from the inside.

External whitening will not fix it. It needs assessment; internal (non-vital) bleaching after root canal treatment is often the answer, and it is a different procedure entirely. See Everything you need to know about root canal treatment and Children's Dental Emergencies for the trauma that starts it.

Developmental conditions

Amelogenesis imperfecta (abnormal enamel formation) and dentinogenesis imperfecta (abnormal dentine) produce discoloured, weak or translucent teeth. These are genetic, they affect the whole dentition, and they need proper restorative planning — frequently with a prosthodontist or paediatric dentist.

And the ones that are not the tooth at all

Mismatched or stained restorations, which peroxide does not touch
Thinning enamel letting yellow dentine show through — structural, not chemical, and whitening helps very little (If enamel is the hardest substance in the body, why do teeth break?, What is dental erosion and how is it addressed?)
Metal-ceramic crowns showing a dark line at the gum as it recedes

The practical summary

Before whitening anything: get examined. Which of the above you have determines whether whitening will do anything at all, and whether it is safe. Understanding Your Treatment and the price guide cover what that conversation should produce.

And the single most common cause of disappointment remains this one: whitening does not change the colour of any existing crown, veneer or filling. If you whiten around a front crown, the crown stays exactly as it was and then looks darker — I want to whiten my teeth but one of my front teeth has a porcelain crown. Replacing it afterwards can cost several times the whitening, and that belongs in the decision before, not after.

Common questions

What are the actual numbers? Which concentrations can be sold to me and which cannot?

The thresholds are specific, and knowing them turns a vague warning into something you can check on a box.

The Poisons Standard classification, as set out in the Australian Dental Association's policy on whitening by persons other than dental practitioners:

Concentration	Status
Hydrogen peroxide 3–6%, or carbamide peroxide 9–18%	Schedule 5, requiring “Caution” — may be “sold direct to consumers if they are labelled with stipulated safety warnings”
More than 6% hydrogen peroxide, or more than 18% carbamide peroxide	Schedule 10 — “may only be sold, supplied and used by registered dental practitioners as part of their dental practise”

The Dental Board of Australia states the same line from the practitioner's side: “Australian laws mean only registered dental practitioners can use or supply high-concentration teeth whitening products (over 18% carbamide peroxide or 6% hydrogen peroxide).” The ADA adds that these provisions “are formalised in all state and territory poisons legislation”.

Two things that make the labels readable:

The two chemicals are not interchangeable numbers. Carbamide peroxide is roughly a third as strong: “18% carbamide peroxide approximates 6% hydrogen peroxide”. So a 16% carbamide gel is a retail-strength product, not a professional one, whatever the packaging suggests.
The professional range goes much higher. The ADA describes effective concentrations ranging “from concentrations as low as 3-6% for some products supplied to patients for home use to 35% in some office-based bleaching products”. That is the gap a supermarket kit cannot close.

For context on why the line sits where it does: “WorkSafe Australia's current guidelines designate hydrogen peroxide at concentrations above 5% as a hazardous substance.” Regulation changes — check the current Poisons Standard rather than relying on a 2014 media page.

A salon does whitening for a fraction of the price. What is actually different?

Three things, and only one of them is the price.

The product must be weaker. A non-registered operator cannot lawfully use or supply anything above the Schedule 5 limits above. So a salon session is, by law, using a retail-strength gel. If it is not, something unlawful is happening.

Nobody has examined you. This is the substantive objection, and the ADA puts it directly: “Only Dental Practitioners who have been educated, trained, and attained competence in teeth whitening can assess whether it is safe for individual patients to undergo teeth whitening”, and “Appropriate examination to diagnose and treat any dental or oral health problems is required to minimise any potential discomfort or health risks associated with exposure to bleaching agents.” Its position is that whitening “should only be performed if the treatment can be justified, and after a comprehensive dental examination has been conducted by a Dental Practitioner”. Why that matters chemically: “Percolation of hydrogen peroxide into the nerve tissues - often accelerated by exposed dentine and enamel fractures - can lead to nerve inflammation.” An undetected crack or area of exposed dentine changes the risk, and nobody in a kiosk is looking for either.

Nobody can manage a complication. The ADA notes the growth of services “offered by unregulated, unqualified non dental practitioners in settings such as beauty and hair salons, shopping mall kiosks, dedicated teeth whitening salons, or via mobile services”, and that operators there may present themselves as trained to do it safely. Its answer is that only registered dental practitioners “have the expertise to assess whether bleaching is safe for individual patients, to recommend the most appropriate technique and materials, and to provide treatment that meets regulated safety and quality standards of care.” Read that as the profession's position, which it is — but the underlying legal point about Schedule 10 is not a matter of opinion.

If you have a concern about a whitening product or service, the ADA's own policy directs consumers to report it to the appropriate authorities, and it asks the ACCC to monitor the advertising and supply of these products, including under mandatory labelling standards and the product safety provisions of the Competition and Consumer Act 2010.

Does the light or the laser do anything, and is it a risk?

Its stated purpose is speed rather than a better end result. The ADA describes professional whitening as “sometimes with the aid of a light or heat source that may shorten the application time required” — that is the claim, and note what it is not claiming.

The risk side is more specific than most people expect, and it is worth asking about. The ADA warns that “The incorrect application of heat and other forms of energy during teeth whitening procedures, such as light from a plasma arc lamp or high-power (Class 4) laser may cause nerve damage to the tooth and burns to adjacent soft tissues”, and that “failure to ensure use of the appropriate protective eyewear may also cause irreversible injury.” There is an Australian standard for this: AS/NZS 4173:2018, Safe use of lasers and intense light sources in health care, which the ADA notes “specifies requirements for dental practices and the cosmetics industry, including required standards of training.”

So two fair questions before an in-chair appointment: what light or energy source is used and at what setting, and what eye protection will you be given. Both have documented answers in a properly run practice.

How often can I top up a home kit?

Less often than the marketing implies, and the honest answer is that nobody knows the safe long-term frequency.

The ADA is pointed about this. It observes that “The marketing of some teeth whitening products directly available to Australian consumers encourages unrealistic expectations about whitening results and promotes regular ongoing use to maintain desired effects”, and then names the gap: “This is a concern given the lack of clinical data supporting frequent home use of such products over long periods”. There is no evidence base for indefinite monthly topping-up, in either direction.

It also flags where the higher-risk products come from: “From time to time, some products containing concentrations of bleaching agents that exceed legal limits in Australia have been found to be available online to Australian consumers.” A gel ordered from overseas may sit above the Schedule 10 line, in a stock tray, with nobody having looked in your mouth.

The practical position: follow the directions that came with the product your practitioner supplied, report sensitivity rather than pushing through it, and treat a plan for maintenance as part of the original conversation — including what it will cost over a few years. Longevity is covered at How long do teeth whitening effects last?.

Taking all that together — how risky is whitening when a dentist does it?

The evidence the ADA cites is reassuring and carefully bounded, and both halves of the sentence matter: “Peer reviewed studies indicate that peroxide-containing teeth bleaching products are safe and effective when used by or under the supervision of a dentist and according to the professional directions for use. The most common side-effects are transient tooth sensitivity and soft tissue irritation during or immediately following treatment”.

Note what that does and does not say. The conditions — by or under the supervision of a dentist, and according to the professional directions — are load-bearing; they are exactly what is missing from an unsupervised kit or a salon. And it describes the common side effects as expected rather than as rare misfortunes: sensitivity and irritated soft tissue happen, usually settle, and are the ordinary cost of the procedure rather than a sign something went wrong.

What raises the risk above that baseline is the list already on this page — untreated decay, cracks, exposed dentine, a badly fitting tray, too long a contact time, a concentration above what the situation warrants. The ADA's own framing of the chemical is that weak solutions under 3% have been used in the mouth for many years with few problems, but “the potential for adverse effects on the oral tissues is increased when higher concentrations are used”, so “it is necessary to take great care when handling and using hydrogen peroxide bleaching agents, especially the higher concentrations.”

No whitening result can be promised in advance, and how much change is achievable depends entirely on which cause of discolouration you have — which is the whole argument of the section above for being examined first.

Practical details

Smile Solutions, Level 1, 220 Collins Street, Manchester Unity Building, Melbourne VIC 3000. Phone 13 13 96, or theteam@smilesolutions.com.au. Monday–Friday 8.00am–6.00pm, Saturday 8.30am–1.30pm, Sunday by appointment. Directions are on Location; enquiries go through Contact Us.

Every practitioner's registration and any specialist entry can be verified free on the AHPRA public register at ahpra.gov.au.

This page records a published article and its date, with general information. It is not a diagnosis, a treatment plan or a promise of any particular result. Whitening carries risks including sensitivity and soft-tissue burns, and results vary with the cause of the discolouration. Product regulation changes; confirm current requirements with the TGA. Concentration thresholds and quoted positions are those of the Poisons Standard as described by the Australian Dental Association, and of the Dental Board of Australia, and may be revised. Third-party published content is not reproduced.

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