Dental caries (tooth decay) is a major oral health problem in most industrialised countries, affecting 60–90% of schoolchildren and the vast majority of adults.
The early manifestation of the caries process is a small patch of demineralised (softened) enamel at the tooth surface, often hidden from sight in the fissures (grooves) of teeth or in between the teeth. The destruction spreads into the softer, sensitive part of the tooth beneath the enamel (dentine). The weakened enamel then collapses to form a cavity and the tooth is progressively destroyed. Caries can also attack the roots of teeth should they become exposed by gum recession. This is more common in older adults.
Dental caries is caused by the action of acids on the enamel surface. The acid is produced when sugars (mainly sucrose) in foods or drinks react with bacteria present in the dental biofilm (plaque) on the tooth surface. The acid produced leads to a loss of calcium and phosphate from the enamel; this process is called demineralisation.
Saliva acts to dilute and neutralise the acid which causes demineralisation and is an important natural defence against caries. Aside from buffering plaque acids and halting the demineralisation of enamel, saliva provides a reservoir of minerals adjacent to the enamel from which it can remineralise and “heal” once the acids have been neutralised. The enamel demineralises and remineralises many times during the course of a day. It is when this balance is upset and demineralisation exceeds remineralisation that caries progresses. When demineralisation occurs frequently and exceeds remineralisation over many months, there is a breakdown of the enamel surface leading to a cavity. Cavities, even in children who do not yet have their permanent teeth, can have serious and lasting complications such as pain, tooth abscess, tooth loss, broken teeth, chewing problems and serious infection.
The main treatment option for a tooth cavity is to drill out the decay and put in a filling (restoration) made from various materials (e.g., composite resins, amalgam, porcelain).Extensive tooth decay may necessitate a crown, root canal treatment or even extraction of the tooth.