Tooth decay is caused by acid produced by bacteria in the mouth dissolving the hard enamel outer covering of the tooth. This can lead to a cavity extending into the sensitive dentine layer of the tooth (dental caries). If not treated tooth decay can cause pain, infection, and even tooth loss.
Inadequate brushing and flossing of your teeth allows the bacteria that form plaque to multiply and potentially cause a cavity. Regular visits to your dentist and hygienist can identify and treat potential problems early.
It can also be caused by eating foods that are high in sugar and other carbohydrates, which feed the bacteria in your mouth or by not using a fluoride toothpaste. Fluoride helps prevent tooth decay by making the enamel more resistant to acids produced by plaque.
Saliva washes away food and harmful sugars, so it helps protect your teeth from decay. A dry mouth can lead to caries and may be caused by a condition such as xerostomia or by taking certain medicines, or by breathing through your mouth. Older adults are more likely to have a dry mouth.
Other systemic diseases (ie not confined to the mouth) such as diabetes can also lead to decay by reducing the your body’s natural ability to fight bacteria.