A toothache after a filling is usually a painful tooth after a filling treatment for a cavity or after a root canal treatment. The pain after filling should be treated according to the nature of tooth pain and the specific examination in the oral cavity. 1.Pain after filling, if the tooth after filling has slight pain of hot and cold irritation, it may be related to the cavity is too big or the decay is close to the pulp. Pay attention not to eat too hot and cold food to avoid stimulating the pulp, and observe it first. If the pain is not relieved, but the pain is stimulated by hot, cold, sour or sweet, spontaneous pain, and the pain is aggravated at night, it often indicates that the caries is too deep and affects the tooth nerve, so root canal treatment is needed in time. In addition, if there is biting pain after filling, we have to exclude whether the filled resin is too much, and grind and polish in time, so that the long-term biting discomfort will cause damage to the teeth. Often there is pain in the tooth after filling for more than one year, in this case, we should consider that the tooth after filling has the inflammation of root tip or pulpitis. 2.If there is only slight discomfort after root canal treatment, you can observe for about two weeks and try not to eat hard food with the tooth after root canal treatment to avoid stimulating the tooth. If the pain has not been reduced, consider whether the root canal treatment is not perfect. A toothache after a filling can usually be relieved by proper treatment.