Tooth whitening refers to any process that lightens the colour of teeth. The desire for whiter teeth is partly due to electronic, print and social media influences portraying perfectly white smiles. We see charcoal toothpastes, whitening toothpastes, fancy UV lights, lasers and celebrities swearing by any and all these products. With all the different options out there, how can you tell what will work and what won’t? Basically, they all work to some extent – it just depends on your expectations and what colour you are starting with.

The figure above shows a traditional Vita shade guide from lightest (B1) to darkest (C4). This guide is used by most dentists and dental companies to determine tooth shades as well as shades for restorative materials like fillings and crowns. It is also used to determine a before and after colour for in-office whitening. Generally, the higher you are on the shade guide (more left), the harder it is to upgrade to the next colour. There are colours beyond B1 where you start to get into bleach shades, however those colours are not very natural and teeth are not made to look that white. The natural colour of teeth ranges from light greyish-yellow.

There are two types of staining – intrinsic and extrinsic. It is important to understand the difference because whitening can only improve extrinsic stains that occur on the surface layers of the tooth. Intrinsic stains involve the internal structure and development of the tooth and can be due to many factors such as genetics, early antibiotic use (tetracycline) during tooth development and the nerve of a tooth dying. Whitening unfortunately cannot undo any developmental changes of a tooth. Intrinsic stains will require restorative work to mask the staining or in the case of a root canalled tooth, will require internal bleaching.

Extrinsic stains (or surface stains) are superficial discolouration involving the outermost layer of a tooth, or the enamel. The outer surfaces of teeth have pores and these pores are susceptible to staining from pigments in dark coloured foods, wine, tea, coffee, smoking etc. What whitening does is open up and clear out these pores so that these stains are no longer contributing to the overall colour of the tooth. However, once those pores open, they can cause sensitivity since those pores lead directly into the tooth and anything cold, sweet or even room temperature air can be uncomfortable until those pores close up again. They can be closed with certain toothpastes so that the staining is less likely to happen again or as quickly.

If you are considering using any whitening product, always consult with your dentist first to devise a plan that works for you. Your dentist will also let you know if you have any conditions that will not respond well to whitening or which may be aggravated by it.