During recent years media coverage has generated widespread interest in tooth whitening procedures.
What causes tooth discolouration?
There are many different causes of tooth discolouration. They can be extrinsic (on the surface), caused by, for example, poor oral hygiene, smoking, chewing tobacco or betel nuts, tea, coffee or red wine. They can also be intrinsic, due to various causes such as discolouration of internal structures, hairline cracks, inherited dark coloured teeth, long term treatment with tetracycline while teeth are developing, old and discoloured fillings, dark coloured metal fillings, dead teeth and tooth decay.
How is whitening achieved?
All the various whitening methods involve the application of toothpastes, gels or liquids which release highly reactive single atoms (rather than molecules) of oxygen onto the tooth surface. These atoms penetrate the crystal structure of tooth enamel and dentine and react with stains or discolorations to produce colourless oxides.
These are widely advertised and available in High Street chemists. People who have used them tend to be disappointed with the result because the concentration of oxidising agent is low enough not to cause gum irritation but not sufficiently high to be an effective whitening agent.
Whitening dead teeth
A tooth that has died because of injury, infection or decay will discolour and eventually require root canal treatment. Root filled teeth can be whitened by removing part of the root filling and packing a few crystals of Sodium Perborate into the nerve canal. The dead tooth will slowly lighten during the following 3 or 4 weeks. Whitening of dead teeth may have to be repeated every few years.
Whitening discoloured vital teeth by using oxygen producing gels
A patient who wishes to have tooth whitening must first consult a dentist to be assessed for suitability. For whitening to be effective, sufficient concentration of oxygen releasing agent must be used. This may occasionally be irritating to the gums. If all is well, impressions will be taken from which closely fitting, vacuum moulded whitening trays are constructed in the dental laboratory. The trays are similar to very thin sports mouth guards and are generally easily tolerated.
At a second visit the patient’s teeth are thoroughly scaled and polished and oral hygiene instruction is given. Dietary advice about avoidance of foods containing stains and dyes will also be given.
The patient is then instructed in the correct placement and quantity of whitening gel into the trays and advised about fitting and wearing times. The longer the tray is worn the faster the whitening will be achieved. Many patients prefer to wear the trays whilst asleep and achieve a satisfactory result in three weeks of night-time wear.
Some patients prefer to whiten the upper teeth first whilst comparing the change in shade with the untreated lowers. When a satisfactory appearance has been achieved they wear the tray in the lower jaw and whiten those teeth until they match the uppers.
Are there any side effects?
Some patients using whitening trays experience increased sensitivity to cold during treatment and this may persist for a few days. Using ‘Duraphat’ fluoride containing dentifrice, ‘Sensodyne’ toothpaste or calcium phosphate rich Tooth Mousse alternately with the whitening gel will greatly reduce the sensitivity. We recommend 10 % concentration.
Avoidance of coloured foods
During the period of treatment with whitening trays and gels patients may wish to reduce their consumption of beetroot, curry, saffron, turmeric, red wine, black coffee, or any highly coloured foods as these may extend the period of treatment.
Does it always work?
NO – Metal fillings, discoloured white fillings, tooth decay and crowns will not change colour. Grey teeth caused by Tetracycline staining may become a lighter shade of grey rather than a creamy white colour. Smokers and curry eaters may soon notice discolouration returning. Regular repeat whitening is easy and not expensive once the plastic trays have been made.
Patients considering whitening should be prepared to have any decay removed. Metal or old discoloured composite resin fillings should ideally be replaced. The patient’s oral hygiene methods should be checked for effectiveness.
How long does it last?
This will vary from patient to patient and depend on the starting colour, dietary habits, smoking habits and age. The follow up gel can be used at any time to ‘top up’ the whitening.