What’s the Colour of your Smile?

As a young Dental student, I was in the habit of looking at peoples mouth, and one thing I discovered is that different people have different colours of teeth. Some were really white, others greyish,  yellowish, brownish and varying colours. This leads to the big question, what is the normal colour of the human teeth? At what point can a tooth be said to be discoloured?

NORMAL TOOTH COLOUR

The normal tooth colour is not WHITE!  There are in fact a variety of natural teeth colour, and this is determined by a variety of factors which include, whether the teeth are baby teeth or adult teeth, age, the position of the tooth in the mouth, skin colour etc.

The shade of teeth also depends on the hard substances of the teeth, the enamel and Dentin.  Enamel is usually lighter in colour compared to Dentin which actually is yellow in colour. The thicker the layer of enamel, the whither the teeth appears, and the reverse is also true.

Generally, baby teeth are whiter than their permanent counterpart. Also in the same mouth, front teeth are whither than back teeth, as the back teeth contain a thicker layer of dentin making them more yellowish. As one grows older the teeth become darker as the enamel layer begins to wear out and there is deposition of more dentin. Teeth in darker skinned people appear whither probably because of a greater contrast between their gums and the teeth colour.

WHEN IS THE TOOTH SAID TO BE DISCOLOURED?

Although we now know that teeth colour varies, teeth can become discoloured from a variety of causes. A tooth is said to be discoloured when it has deviated from an acceptable colour and has become a source of aesthetic worry to the individual.

Discolourations in teeth can be said to be extrinsic or intrinsic.

EXTRINSIC STAINS  are those stains located on the outer surface of the tooth structure and are caused by topical or extrinsic substances. Causes of extrinsic stains include the following;

1.Poor oral health.  This is the commonest cause, and stains range from yellowish to grey to even brown stains. This usually results from the action of chromogenic bacteria present in plaque and calculus.

2. Deposition of tannins found in tea, coffee and other beverages. This causes brown stains on the lingual and palatal surfaces(inner surfaces) of teeth.

3. In the western Pacific and South Asian region, Pan a combination of betel nut, Betel leaf and lime is commonly chewed, and it causes a red-black stain on teeth, gums and oral mucosa.

4. Metallic compounds. This is usually from industrial exposure. The metals interact with a dental plaque to produce a surface stain. Exposure to iron, manganese and silver leaves a black stain, mercury and lead dust cause a blue-green stain, copper and nickel causes a green stain and iodine solution causes a brown stain.

5. Mouthwashes and medications. Studies have shown that continuous use of chlorhexidine mouthwashes, as well as other mouthwashes and oral solutions containing cetyl pyridinium (eg Cepacol, Scope), iron, potassium permanganate, silver nitrate and stannous fluoride, cause some form of discolourations.

Systemic medications such as minocycline and doxycycline have also been shown to cause extrinsic discolourations

INTRINSIC DISCOLOURATIONS;  These are discolourations which are internalized within the tooth structure. They vary in appearance and location. They can affect a single tooth, a group of teeth or the whole dentition, they can be localized to the baby teeth or adult teeth alone or could affect both. They also vary in colour based on the causes. Common causes of intrinsic discolourations include;

1. Dental materials. Materials used in restoring decayed teeth can over time cause discolouration of teeth. Examples include dental amalgam, eugenol,  formocresol and root canal sealants.
2. Dental conditions. These include tooth decay, which leaves a dark stain on the tooth over time, tooth wear.
3. Trauma. injury to developing teeth can result in areas of hypoplasia which may appear as whitish areas on the tooth when they erupt.

Trauma to erupted teeth usually leads to a pinkish discolouration at first due to internal bleeding within the tooth.  Over time, this becomes brownish in colour. This type of discolouration is usually localized to single teeth.

4. Medications. Drugs of the tetracycline family have been implicated in causing tooth discolouration. Tetracycline is absorbed into d bloodstream on consumption and is incorporated into developing teeth affecting primary or secondary dentition after maternal or childhood ingestion respectively.

Minocycline causes a green-grey or blue-grey discolouration of teeth when taken even after a full eruption of teeth.

Fluoride is a compound commonly found in drinking water and an additive to toothpaste. Inappropriate doses it helps protect the teeth from decay but in excess amounts, it causes various degrees of discolouration ranging from mottling to severe discolourations and chipping

       5. Genetic defects and hereditary conditions.

Defects in the formation of tooth structures like enamel and dentin usually result in discolourations, these defects include; amelogenesis imperfect, dentinogenesis imperfecta and dentin dysplasia. These leaves stains ranging from yellow to grey to brown on teeth.

Can discoloured teeth be salvaged? Can its occurrence be prevented, can it be treated, find out in our next article!