Smile: There are many options for whiter teeth

Teeth whitening dates back some 4,000 years.

The Romans used urine, which contains ammonia, as a bleaching agent for their teeth.

The Egyptians made a whitening paste with ground pumice stone mixed in wine vinegar.

Today, it can take just a whitening strip to remove that stubborn stain on your pearly whites.

There are a number of causes for yellow or stained teeth, said Dr Vivian Wong, a dental surgeon at the National Healthcare Group's Toa Payoh Polyclinic.

In extremely rare cases, yellow teeth are a result of genetic diseases that cause thin or defective enamel, which is the hard outer white surface of the tooth.

But in most cases, it is not a cause for worry unless aesthetics is a concern, Dr Wong told The New Paper.

Extrinsic causes of stained teeth are usually preventable. They include:

• Drinking coffee or tea
• Eating foods with tannins, such as berries and curry spices
• Smoking
• Poor oral hygiene

A thin tooth enamel may also cause teeth to look yellow, said Dr Wong. Beneath the enamel is the dentine layer - a soft and yellow-brown substance.

"With ageing, the enamel wears thin over time, causing the underlying dentine layer to show through, resulting in the yellow appearance of the tooth," she said.

Acidic food and drinks such as oranges, sour-flavour candies and juices may also wear off the outer layer of enamel and cause teeth to turn yellow.

While saliva helps wash away acids in the mouth, those who suffer from a dry mouth may lack enough saliva.

Dr Wong said accidents or physical trauma can also crack the enamel, exposing the underlying dentine, or even damage the interior of the tooth. This would require a dentist's attention.

Tooth grinding, often done unconsciously during sleep, is another type of physical wearing down of teeth that causes yellowing.

Other causes of yellow teeth include the use of antibiotics or excessive fluoride use in young children, which can cause the staining of their adult teeth.

Whitening toothpastes can help remove stained plaque on teeth through mechanical or chemical action.

"They contain abrasive substances such as silica or carbonates. Some may also contain chemical agents such as enzymes, which act on the proteins within the plaque that cause staining.

"Additionally, some whitening toothpastes contain a low concentration of peroxide compounds, which break down the stains and infiltrate the tooth surface and minimally removes intrinsic stains," said Dr Wong.

The whitening effect of such toothpastes alone, however, may not be significant.

METHODS

Other methods for teeth whitening include bleaching strips or procedures at a dental clinic.

The key to these options is the hydrogen peroxide content, a bleaching agent.

The downside? You may experience tooth sensitivity and irritation of the soft tissues, such as the gums surrounding the teeth.

Dr Wong said: "There is also a possibility of relapse. Some studies show that only 50 per cent of patients receiving dentist-prescribed home-whitening retained their whitened colour six months after bleaching.

"Hence, to maintain tooth colour, repeated rounds of tooth whitening may be necessary."

The best way is to get to the root of the cause of the stains, she said.

This means removing the extrinsic causes of teeth staining by changing your lifestyle.

"Good oral hygiene and removing the known root cause of the stains are probably the best options to prevent further staining.

"As with all aesthetic dental treatments, optimal dental health is a minimum requirement before the commencement of the aesthetic treatment.

"Regular check-ups should be scheduled to maintain health and cleanliness of the teeth," she said.