Wisdom teeth (or third permanent molars as they are known) usually start coming through in late teens. Sometimes there isn't enough room for them to erupt properly and they get stuck (impacted), often against the tooth in front. Sometimes the tooth in front can become damaged, or the gums around the wisdom tooth can become infected and quite painful. That is the time to see the dentist and decide on the appropriate treatment.
The picture shows an xray of an impacted wisdom tooth (the tooth on the right) growing in the direction of the second permanent molar (tooth on the left). To find out more about wisdom teeth, visit our Smile website.