Tooth whitening is the restoration of the tooth’s normal colour as opposed to teeth bleaching which is lifting the colour beyond its natural colour. Teeth become discoloured through staining from substances called Chromogens in strongly coloured food and drink; Tannins that form a kind of glue; and Acids that make the teeth more susceptible to staining. Restoration is achieved through removing stains and tartar. This can be done with a scale and polish by a dental hygienist.
To bleach teeth, substances such as carbamide peroxide or hydrogen peroxide are used. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15% solution of carbamide peroxide is the rough equivalent of a 5% solution of hydrogen peroxide.
WHAT TO EXPECT
The dentist may examine teeth and take a dental history and ask about desired colour change using a colour shade guide to measure tooth colour. Whitening can results in between 2 to 7 shades lighter teeth.
Techniques vary. There are two main kinds of tooth whitening:
(1) The mouth is clamped open and light technology is applied. Therapeutic light comes from Halogen LED or plasma arc. It should be noted that the use of these lights will increase tooth sensitivity and may not be more effective than the bleach alone. The process should take between half an hour and a full hour.
(2) Trays are made and can be used and re-used. Trays may be pre-moulded or moulded to fit each individual’s mouth. Specially fitted trays are made by taking moulds of a patient's upper and lower teeth. The trays are then prepared and will fit exactly to the shape of the individual. The actual bleaching, however, takes place at home. The dental staff will teach each patient how to use the trays and bleaching gel.. Patients purchase tubes of the bleaching gel which are gently squeezed into each tooth shape in the trays, then placed into the patient's mouth for about 30 minutes per session. The whitening process occurs over time and for effective results, some discipline is needed and ideally a person should practise the bleaching at least 3 times per week.
As white teeth are associated with youth and health, whitening teeth generally creates a younger, healthier-looking, more attractive smile.
Teeth sensitivity may cause pain during and after treatment. Furthermore, teeth may develop sensitivity to hot and cold foods, and the mucous membrane within the mouth may also be irritated by the process.
The process itself may be unsatisfactory if it produces uneven results, although these do tend to even out over time. When teeth are bleached they become drier and this makes them appear whiter. As the moisture returns the colour darkens. This is known as the rebound effect and generally happens within a week of treatment. It is advisable to avoid staining foods for a week after the teeth have been bleached (e.g. red wine, tea, coffee, curry).