What are the causes of tooth decay?
Tooth decay (dental caries) has two stages:
This is a slow, reversible process that usually takes several years to complete but can be faster in baby or milk teeth because they have thinner enamel. It is characterised by a back and forth battle between the acid from dental plaque and our own saliva. Within minutes of eating a sugary snack the germs (bacteria) in plaque will metabolise the sugars and excrete acid directly on to the tooth surface. The acid de-mineralises, or dissolves, mineral from the enamel layer for approximately 15 minutes before the saliva is able to neutralise the acid and begin repairing, or re-mineralising, the enamel surface.
This process of weakening and repairing enamel can continue indefinitely without ever progressing to the second stage. Some toothpastes and mouth washes contain minerals, such as fluoride, that can strengthen enamel and make it more resistant to plaque acids. Higher concentrations of fluoride may also be applied by your dentist, in the form of a varnish to vulnerable areas of your teeth.
Caries will progress to the second stage when more enamel de-mineralisation is taking place than re-mineralisation - that is, a net loss of enamel minerals. If this is the case then the enamel will eventually weaken and crumble enough for bacteria and toxins to pass through and invade the dentine. Dentine is softer than enamel and is composed of tiny tubes, so caries will spread at a faster rate and in a wider arc through dentine than it could through enamel. When a large area of dentine has been de-mineralised and softened, the enamel layer above may collapse inwards, or cavitate, to form a tooth cavity.
When the bacteria invade the dentine, the tooth has a limited ability to protect the vulnerable pulp by producing a new layer of dentine. This is why some teeth can recover from very large dental cavities if the caries is removed and a filling is placed promptly. This healing potential within the tooth illustrates the benefit of attending for dental treatment when you suspect you may have a dental problem rather than waiting for weeks or months to see if the problem goes away.
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