There's something to smile about if your goal is sparkling teeth. But when it comes to whitening and bleaching, be sure to listen to the professionals

PUBLISHED : Friday, 31 October, 2003, 12:00am
UPDATED : Friday, 31 October, 2003, 12:00am

IN A TECHNOLOGICALLY-ADVANCED, consumer-oriented world, buying beauty gets easier by the day. A Botox jab can sort out laughter lines, laser surgery can smooth over skin.

And discoloured teeth can be fixed with a splash of peroxide solution. Not literally, of course. The safety of teeth whitening procedures has been the subject of much controversy.

The main ingredient in teeth whitening products is either hydrogen peroxide or carbamide peroxide, the same chemicals used to bleach hair. The efficacy of whitening is directly related to the concentration of the peroxide, and the extent of the peroxide's exposure to teeth.

Bleaching has been practised here for about 10 years, says Hong Kong Dental Association spokesman, Dr William Cheung. The demand for treatment appears to be following an international trend. Exact figures are not available, but Dr Cheung believes a significant number of people are seeking professional help.

There are a number of ways to attain pearly whites, either through home remedies or with professional guidance.

Whitening toothpaste tends to have a minimal effect, because of the low peroxide concentration and the nominal contact with teeth.

Paint-on kits are just that. A solution is painted on the teeth with a small brush. This can be a fiddly, time-consuming procedure. The mouth must be kept dry for the time the solution is left on the teeth, usually up to one hour twice a day, for 14 days.

The third method is to use a standard tooth mould, commonly called the tray method, which is filled with gel and fitted over the teeth for one hour. A problem with the tray method is that the one size available is supposed to fit all - except that each jaw is different. Dr Cheung says that if the tray is too small, it can rub gums and cause irritation, and if it is too big the gel may flow over the sides and be swallowed.

The alternative to home-use kits is professional whitening. Under professional guidance, the concentration of peroxide is higher and the effects likely to last longer.

Custom trays work in the same way as the standard tray, except that they are fabricated to fit the patient's mouth. During a two-week regimen, the patients applies a gel to the trays and fits them over the jaw, for between one and two hours a day.

Professional whitening strips can be used at home, but these require a fair amount of patience. Strips are placed on teeth for 30 minutes, twice a day, for 14 days. The method is good only for straight teeth, as a strip on crooked teeth will not reach all areas, and the final effect will be patchy.

The quickest (and most expensive) teeth-whitening method is with the use of whitening gel, which is activated by a light source. A high concentration of peroxide is used, and the treatment is usually completed in 60 or 90 minutes. The results are immediate, and patients do not have to take follow-up treatment.

Prices vary from practice to practice, but a patient can expect to pay between $6,000 and $10,000. The results usually last between one and three years.

Custom-fit trays are the most common choice in Hong Kong, and cost anything from $1,000 to $4,000. The results usually last one to two years. Whitening strips cost between $300 and $600.

The over-the-counter solutions tend to have short-term results. The paint-on method can last between three and six months, the standard tray technique six to 12 months. Home-use methods are cheaper, costing from about $80 for paint to $300 for the tray.

The Hong Kong Dental Association says it has not noticed any adverse effects from the use of whitening kits. Dr Cheung says there are no irreversible side-effects, 'provided they are used properly, preferably with professional guidance'.

Australia and America allow the sale of over-the-counter kits with a hydrogen peroxide percentage of six, while European Union law dictates that any teeth bleaching kit with a peroxide concentration of above 0.1 per cent may be purchased and administered only by a qualified dentist. The association says there is no conclusive evidence that bleaching teeth can be harmful, nor is there evidence to conclude that it is safe to bleach regularly over a long period.

A common downside in all teeth whitening procedures is a degree of tooth sensitivity during and shortly after administration. The sensitivity is caused by irritation of the nerve inside teeth from peroxide.

A higher peroxide concentration (in Hong Kong it is usually between 12 and 15 per cent) does mean a greater sensitivity in the course of a professional treatment. This can be eased by prescribing medication or through pre-treatment action.

In some cases, bleaching is not effective. Tooth restoration work, such as fillings and crowns, do not respond to whitening. And it is difficult to whiten grey discoloration caused by too much fluoride during the developmental stage of teeth.

Dr Cheung says professional consultation and monitoring is recommended for anyone seeking whiter teeth. That way suitability, uneven whitening and gum irritations can be monitored.