The enamel layer of the tooth does not have a nerve supply, but the underlying dentine does.
When the dentine is exposed it will react to hot, cold and sweet foods and drinks. The pain may be mild, and will disappear immediately the cause is removed.
The dentine layer is exposed in the early stages of the decay process.
Dentine can also be exposed by any of the following:
Abrasion. This is the wearing away of the enamel at the gum margin by brushing too vigorously. The dentine in the root is also exposed in this way. The thin covering of cementum on the root is easily worn away.
Erosion. This is caused by conditions in which stomach acids are regurgitated into the mouth, and erode the enamel and dentine.
Attrition. This is the wearing down of teeth by grinding. It is normal for teeth to show some signs of attrition as we age. Bruxism is the abnormal grinding of teeth.
The problem of sensitivity in the early stages can be controlled by using a desensitising toothpaste, and having a desensitising treatment at the dentist.
The sensitivity caused by decay will be treated by repairing the tooth with a filling.