Nowadays most people take good teeth for granted. This happy state of affairs can be attributed to water fluoridation, oral hygiene and advances in dentistry.
As with most things we take for granted, their value is appreciated only after we lose them. In ages past people were keenly aware of the value of teeth because many lost most or all of them as young adults.
The primary function of our teeth is mastication, t they also serve other important functions. They are directly involved in speech, allowing the tongue to form certain sounds. Teeth also affect the dimensions and appearance of the face, clearly illustrated when a person removes his/her dentures.
A tooth consists of an external part, the crown, and a root embedded in the jaw. The outside layer of the crown is the hardest substance in the body, known as enamel, and is composed of calcified tissue. The enamel covers the dentine, a substance like bone that extends throughout the crown and root.
The dentine of the crown encloses the pulp chamber which continues down into the root as the root canal. Blood vessels, nerves and connective tissue enter the root through an opening at the end of the canal and fill the root canal and pulp chamber.
In humans, a set of 20 teeth is produced during early jaw development. These are the deciduous teeth, popularly called the baby teeth. As the jaw matures, a second set of 32 permanent teeth replaces these baby teeth. The crowns of the permanent teeth come in four general types; incisors, canines, premolars and molars.
The front teeth, the incisors, are flattened like chisels to help the cutting of food. Canine teeth have the function of gripping prey for many mammals, and in humans they are consequently much reduced in prominence. Behind the canines are the two premolars and three molars, which have a broad chewing surface and perform a grinding action on food. Food is cut with the incisor teeth, and is ground to a digestible size by the premolars and molars.
Scientists predict that the third molars, the wisdom teeth, may disappear because the recent trend in the evolution of the human face has included a reduction in the size of the jaws. Teeth are very susceptible to decay (dental caries). Oral bacteria react with carbohydrates in food to form acids capable of dissolving the enamel. This allows other bacteria to penetrate the dentine. This process eventually produces a cavity in the structure.
Extension of the decay causes infection within the pulp chamber, usually accompanied by pain. The tooth can usually be treated by removing infected material from the root canal. If the infection is very advanced, the tooth may have to be extracted.
Unlike most organs, teeth have little capacity to repair themselves, and so, when damage occurs, early dental treatment is necessary to prevent serious consequences. A very common practice is to remove decayed material and replace it with an inert filling which restores the tooth. Fillings commonly used are silver amalgam, gold, synthetic cement or plastic.
Good oral hygiene and regular dental examinations help greatly to prevent dental disease. Brushing the teeth after meals to remove food particles is very helpful. A well-balanced diet also helps to minimise dental infections.
Research in the 1940s showed that applying sodium fluoride to teeth greatly reduced dental decay. Experiments showed that adding fluoride to drinking water at a concentration of one part per million can reduce dental decay by over 65 per cent. Public drinking water in Ireland has been fluoridated since 1964.
In previous centuries a typical dental history went as follows. You had teeth for a while, they decayed, you endured the pain as long as possible, and then you had the teeth extracted. When you finally reached the toothless condition you could have a set of false teeth made from ivory, mother of pearl, polished stones, or even human teeth.
These ill-fitting dentures carried the in-built expense of having to be replaced annually when they turned black. Presumably you could avoid this expense if you weren't too fussy about your appearance. Only well-off people could afford false teeth. This left the ordinary toothless punter with a serious problem; how to chew food. This could be solved in either of two ways. You could revert to eating infant gruel, or you could resort to a mechanical grinder that would reduce your meat and two veg to a gummable consistency.
It was widely thought in centuries past that tooth decay was caused by tiny worms that bored through the tooth enamel. Roman doctors advised smoking out the tooth worms with acrid narcotic vapours from burning seeds.
Another preventive measure was to use an efficient vermicide (worm-killer) as a mouthwash. The "daddy of all" solutions was an Egyptian prescription for rinsing the teeth in "water in which the phallus has been washed". (Don't knock it if you haven't tried it).
Not until the microbiological theory of decay towards the end of the 19th century was there any rational basis for dental hygiene. Indeed, it is only in recent decades that investigators have identified specific strains of bacteria that are responsible for dental caries.
Up to this century the only practical intervention available was to extract decaying teeth. This was usually carried out by a quack practitioner, without the benefit of anaesthesia, using pincers. The best that one could hope for was an experienced tooth-puller and a speedy extraction.
Scientific dentistry this century produced the treatments that we now take for granted: fillings, comfortable dentures, electric drills and effective painkillers. Even in my lifetime things have improved enormously in dentistry, e.g. any significant pain in the dentist's chair is now a thing of the past. The history of dentistry is recounted in humorous detail in The Excruciating History of Dentistry, by J. Wybrandt (St Martin's Press, 1998).
William Reville is a senior lecturer in biochemistry and director of microscopy at UCC