Tooth pain is caused by a reaction of the nerves inside a tooth’s pulp chamber with the severity dependent upon the type and degree of the stimulus. The pulp contains nerve endings that are very sensitive to pain. Inflammation to the pulp may be caused by dental infection, gum disease, plaque, dental decay, injury, cracked teeth, poorly placed fillings or crowns, failing or leaking fillings or crowns, or loss of a tooth, repetitive motions such as chewing gum or grinding teeth.