A Gleaming Smile

You may be looking good, thanks to your hair, and seeing better, thanks to contact lenses, but when you smile at the boy or girl of your dreams, are you spoiling your chances by having discoloured teeth If you suspect that this may be so, then chemistry can help. 

Dentists did little more than pull out rotten and painful teeth, of which there were many, but they eventually started to make false ones to fill the gaps. Some even used human teeth for this purpose and in 1781 a practitioner of Gerard Street, London, was offering to buy real teeth for 2 each, equivalent to something like /400 (approximately 600 or 700) in today s money, provided they were in good condition. (Such teeth were extracted from newly buried corpses by resur-rectionsts who dug up bodies to sell to surgeons for their anatomy lec- 

26 Better Looking (I) Hair, Eyes, Teeth, Nails 

The aim of regular brushing is to keep teeth germ-free and looking good. Discolouration, however, comes slowly and cannot be removed by brushing alone. 

Teeth have a transparent outer layer of enamel which is about 2 mm thick, and an inner layer of white dentine which surrounds the innermost pulp cavity where the nerves are located. Both the enamel and the dentine are calcium phosphate, a mineral that can exist in various forms, that of the enamel layer being hydroxyapatite, which is one of the hardest naturally occurring minerals. When this is exposed to fluoride it forms an even harder mineral fluoroapatite. Unfortunately both this and hydroxyapatite are slightly porous and this is why teeth become stained by chemicals such as polyphenols and other dark coloured substances that are present in coffee, tea, red wine, bilberries, blueberries, and cigarette smoke. (Staining can also be caused by tetracycline antibiotics, especially when taken by children whose teeth are developing. This type of discoloration is permanent, which is why such antibiotics are now only prescribed for adults.) 

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