There are a variety of reasons why your Pearlie whites aren’t as white as Jessica Simpson’s smile.

Extrinsic Staining

Extrinsic is just a fancy word for external i.e. stains ON the tooth surface. The most common of these include dental calculus (tartar), tobacco smoking, wine, coffee and tea. This is the reason why the very first step to any dental whitening process is a good scaling and polishing to expose the base colour of the tooth (see below for more on base colour). Keep in mind that the long term use of tobacco over many years can cause the stains to seep into the tooth, making it an intrinsic stain.

Intrinsic Staining

Intrinsic or internal stains refer to a deeper level of discolouration INSIDE the structure of the tooth. These may be caused by genetic malformations or the incorporation of substances during tooth formation. These include excessive fluoride and tetracycline.

Base Colour

Stains aside, the base colour of the tooth is revealed after a thorough dental cleanup or prophylaxis. This is the dominant or main colour of the tooth and is a combination of the dentine on the inside and enamel on the outside. The myth that enamel is an opaque, milky white substance couldn’t be further from the truth.

Consider this analogy. Press the palm of your hand behind a pane of frosted glass. Your hand would be the dentine and the glass would be enamel. The final shade that you see from outside the glass is the result of the colour of your palm SHOWING THROUGH the frosted glass.

While the base colours or shades of teeth vary over a wide spectrum, they are most popularly categorized into yellow, grey, reddish yellow and brown- grey.  In general, the yellow shades whiten the easiest, followed by reddish-yellow while grey and brown-grey teeth have been known to be more resistant.

Ageing of Teeth

As we age, dentine (the layer on the inside of our teeth) gets darker and more intense while the enamel gets thinner due to daily wear and tear (unlike skin and bone, human teeth stop growing once they are fully formed! What you were given is all you got so take care of it!). Returning to our earlier analogy of frosted glass, imagine what you would see if you had a thinner pane of glass i.e. thinner enamel. To compound the effect, imagine you were looking at the back of your hand instead of your palm. The result is simple. You would see a darker shade. Similarly, teeth appear darker with age.

Skin Tone and Lip Colour

The smile is often described as a portrait made up of the picture (the teeth) and the lips that frame it. While simple, the concept of skin tone and lip colour is an important aspect of how bright our smile is. People with darker complexion tend to appear to have brighter teeth, while those blessed with fairer skin often complain of not having white teeth.

For ladies, the choice of lipstick colour can greatly affect the perception of tooth shade. This is the why your cosmetic dentist would always ask you to wipe off any traces of that bright red lipstick before taking the shade of your teeth.