A tooth with a cavity and nighttime pain requires a timely visit to the dentist for root canal treatment, which is a sign of pulpitis. Under normal circumstances, a cavity in a tooth does not have any sensation and can be filled with a routine filling. As the cavity gradually develops, it gets closer and closer to the nerve, and eventually bacteria will invade the nerve and pulpitis will occur. At this point, the regular filling treatment is no longer effective and root canal treatment is required. Root canal therapy involves the complete cleaning of the infected pulp from the pulp chamber, followed by a tight filling, and the upper portion of the tooth is finally restored with a crown. Developing a toothache is already one of the more complex treatments for teeth and requires 2-3 visits, each of which should basically take around 30-60 minutes.