Toothache occurs when the innermost layer of the tooth (dental pulp) becomes inflamed. The pulp is made up of sensitive nerves and blood vessels.
Dental pulp can become inflamed as a result of:
There are a number of other conditions that can cause pain similar to toothache, even though the pulp isn’t affected. These include:
Babies can also experience discomfort when their teeth start to develop. This is known as Teething.
SOURCE: NHS UK