Toothache or tooth pain is caused when the nerve root of a tooth is irritated. Dental (tooth) infection, decay, injury, or loss of a tooth are the most common causes of dental pain. Pain may also occur after an extraction (tooth is pulled out). Pain sometimes originates from other areas and radiates to the jaw, thus appearing to be tooth pain. The most common areas include the jaw joint (temporomandibular joint or TMJ), ear pain, and even occasional heart problems.