When the tooth sends out pain signals, it is letting you know the problem is serious. Aim to visit a dentist ASAP to get the pain under control. Early attention can result in the dentist filling the tooth. Sometimes the dentist will use medicine under the filling to disinfect the tooth first. However sometimes the tooth is too far gone. With a toothache or swelling, instead of a filling the dentist may advise to have root canal treatment, or have the tooth removed.