Because they are common dental problems, teeth may crack and become painful. Some causes of cracked or fractured teeth are grinding or clenching of the teeth, biting on hard objects or trauma, to name a few.
While there may be no discomfort when no pressure is exerted on the crack, the crack will widen when the cracked tooth performs a biting action, exposing the pulp and inner workings of the tooth and causing pain. Afterwards, the two parts of the crack fuse back together, and pain subsides as pressure is released again. However, the pulp can become irreversibly damaged and constantly painful if left untreated and the resulting pulp infection can affect the bone and soft tissue surrounding the tooth, possibly leading to a root canal.