Most commonly, the problem begins when the gums recede.

Like a protective blanket, the gums cover the roots of teeth as gums recede, the underlying tooth roots are exposed. Gums commonly recede for the following reasons:

• Improper heavy handed brushing of the teeth. It is estimated that 50-90% of people brush with too much pressure. Over weeks, months and years of brushing they remove significant gum tissue exposing the tooth roots.
• Tooth pain or sensitivity – because the tooth enamel is worn away with teeth grinding this can expose the inner more sensitive areas of your teeth, which can cause sharp pain and sensitivity to cold drinks and certain foods.
• Poor oral hygiene can lead to plaque build-up around teeth and gums. Over time this plaque hardens into tartar. Bacteria in this tartar are responsible for the gingivitis and periodontal disease that cause gum recession.
• Diet can be a major reason teeth become sensitive. If you are prone to acid reflux and drink a lot of soda you can become prone to teeth sensitivity.