Does reading the headline “Man has been fined for illegal whitening”, sound familiar? It seems teeth whitening has been getting a lot of negative press of late, but we continue to assert that only dentists (or those who are working under a prescription from a dentist) may do tooth whitening.The run up to Christmas does seem a time when more patients are requesting teeth whitening, just ahead of the party season. Also with growing trend of the selfie, patients are becoming more aware of their appearance, and the quest for that ‘perfect’ smile.
Patients however, often seem unaware of the pitfalls of illegal whitening and this is really concerning. Here’s what you need to know and how to make sure you are doing the best for your patients.
The BDA’s advice sheet on teeth whitening is also available free for members and covers detailed information on the legal levels of whitening agents, advice on treating under 18s, and legal usage of whitening products.
What whitening agents can I use?
The main choices are between hydrogen peroxide (HP) or carbamide peroxide (CP).
The maximum concentration that may be used is 6% HP present or released. 10% CP content produces a maximum of 3.6% HP, therefore commonly used products containing 16% CP are permitted because they would normally be releasing less than 6% HP.
Data on 10% carbamide peroxide (CP) has confirmed the safety and effectiveness of this bleaching agent. Higher concentrations of carbamide peroxide can be prescribed (up to 16%) but there is little evidence for doing so.
Higher concentrations of products can produce a more rapid response in some patients but there is a greater chance of tooth or gingival sensitivity.
The concentration does not affect the outcome since the final colour is determined by the inherent lightness potential of the tooth.
What do I do about tooth sensitivity?
Tooth sensitivity is a common side effect of all peroxide-based whitening procedures.
The cause of tooth sensitivity is not completely understood, it has been demonstrated that peroxide penetrates through the tooth to the pulp in a matter of minutes and may cause a mild, reversible inflammatory response.
This can result in tooth sensitivity, but if the pulp is healthy the sensitivity is reversible. It has also been suggested that stain removal can open tubules and increase tooth sensitivity with the movement of fluid within the dentinal tubules causing pain.
There are many desensitising pastes available such as fluoride varnish (thought to act as a tubular blocker to control pulpal fluid flow), 26. 5% Potassium nitrate in toothpaste (e.g. Sensodyne, Colgate Sensitive Pro Relief) if used as part of a regular regimen or pre-brushing for two weeks could significantly reduce sensitivity during whitening.
Potassium nitrate penetrates the tooth and is thought to have a calming effect on the nerve by preventing it from repolarising after it has depolarised in the pain cycle.
Sugar-free chewing gum could help by causing dentinal tubular blockage associated with an increase in saliva flow.
Amorphous calcium phosphate (ACP, eg Tooth Moouse) works in a carbonate solution to crystallise and form hydroxyapaptite. These crystals fill in microscopic surface defects and repair weakened enamel.
ACP may also bond with enamel or dentine and decrease sensitivity by blocking open dentinal tubules.
Gingival irritation can be related to contact of bleaching gel to the soft tissue. 10% CP gel is unlikely to cause any irritation but higher strengths can cause reversible soft tissue burns.
What are the protocols for teeth whitening?
The protocol for bleaching is based on that originally developed by Haywood and Heymann:
- A detailed dental and medical history is taken, a comprehensive clinical examination carried out and a differential diagnosis of the discoloration is made.
- Any abnormalities of enamel and dentine, the extent and adequacy of any restorations and the presence or absence of any periodontal conditions are recorded.
- An air-water syringe is used to stimulate the teeth to be whitened and any sensitivity recorded. Any teeth that are sensitive at the time of initial examination are likely to get more sensitive during bleaching.
- The shade of the teeth is determined by referring to a value-oriented shade guide. A pre-operative photograph is taken using the shade guide tab as a reference.
- The patient’s main complaint and expectations must be assessed. Unrealistic high expectation of the patient is considered a major contraindication.
- Radiographs are taken and any findings investigated.
- The patient is provided with detailed informed consent that outlines procedures and alternatives. Patients must be warned that their restorations will not change colour and may possibly need replacing following the tooth whitening treatment.
- The patient is requested to return for a recall appointment to evaluate results and identify any problems associated with the procedure. All changes in colour should be recorded in the patient’s clinical records. Written maintenance care instructions should also be given to the patient, together with before and after photos.
Know the options
Nightguard Vital bleaching
Average treatment time for Nightguard Vital bleaching is approximately two weeks for upper teeth and three weeks for lower teeth, although lighter teeth may bleach in a few days but heavier staining can take up to six weeks.
Nicotine stains are more difficult to remove and generally require one to three months of nightly treatment. Mild to moderate tetracycline staining may respond to extended bleaching regimes of up to six months.
However, severe tetracycline staining is difficult to remove and combined treatments such as bleaching and veneers may be necessary
Mild fluorosis with white spots do not tend to bleach but will become less obvious as a result of the lightening of the surrounding tooth area
Most congenital conditions (such as dentinogenesis imperfecta or porphyria) are not amenable to bleaching and correction by restorative methods is preferred.
The most predictable results are seen if the trays are worn overnight as it keeps the gel in contact with teeth for a prolonged period (10% CP active for four to 10 hours).
Some patients may not want to sleep with the trays overnight, in which a minimum of two to four hours is the second best option. Less than two hours wastes material and will extend treatment time.
An alternative of day bleaching with HP can be an option in cases when they want to wear the trays less than two hours. HP is very unstable and is only active for 30-60 minutes, with most activity in the first 30 minutes.
It is advised to bleach the teeth until they have reached their maximum whiteness or the patient is satisfied with the result.
Once the whitening treatment is completed, it is important to wait at least a week before any restorative procedure. This allows the shade to stabilize and the bond strengths to return to normal.
There can be a significant decrease in sheer bond strengths if composite is applied immediately after bleaching. The residual oxygen in the tooth surface inhibits the polymerisation of the composite and disrupts the surface.
There is also a small relapse in shade shortly after tooth whitening (rebound) and related to a change in the optical qualities of the teeth that occurs as a result of the loss of oxygen from teeth and rehydration.
After teeth are whitened, the lighter shades will not last indefinitely but the modern gels produce results that are relatively long-lasting.
It has been suggested that top-up bleaching might be necessary at two-to three-yearly intervals. Topping up takes one night for each week taken to complete the initial bleaching. A good approach is to ask the patient to return for a shade evaluation if they feel re-treatment is necessary.
It has been debated to use reservoirs or not in the bleaching trays. There is no difference in the rate of bleaching if reservoirs are present or not but they do allow for the gel to be in contact with the teeth in optimum position for maximum time.
In-office or power bleaching (Zoom. Brightsmile)
These products can be popular because they can accelerate the bleaching process, gives the dental professional control and provides immediate results if the patient lacks patience for home whitening.
They use HP solutions activated by heat or light. The greater the concentration the quicker oxidation occurs and increased temperature accelerates the bleaching process (increase of 10 °c can double the rate of HP dissociation). Again in the UK the amount of HP cannot exceed 6%.
High concentrations of HP can cause burns to lips, cheeks, gingivae, eye or the rest of face so good isolation technique is essential. The high intensity light can generate excessive heat to dental pulp, but most lamps produce temperature changes less than 5.5°c.
The general consensus is that power bleaching is less effective and has greater degree of relapse compared with home bleaching. For challenging cases it is a good boost prior to home bleaching to shorten treatment time, and most companies now offer the trays as part of the power bleaching.
However there are situations where it is appropriate to combine tooth whitening with other procedures, including microabrasion, macroabrasion, bonded composite restorations, veneers and all-ceramic or porcelain-fused-to-metal crowns.
Surgical and orthodontic procedures should also be considered in some cases. This is beyond the remit of this article but readers are advised to research these techniques. In the long term if this article is popular we can provide some revision on these procedures.
Help us be the voice of young dentists
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