Cold tooth acid after filling may be related to the filling material, filling operation, or it may be caused by the complication of pulpitis. 1. Filling material: If the cavity before filling is deep, the material used is too thin, which can not block the hot and cold stimulation conducted by amalgam, and then there will be symptoms of cold soreness and pain. 2. Stimulation of filling operation: Secondly, it may also be caused by the stimulation of the dental pulp by the hot and cold of the dental drill used in the process of filling, so that the patients will have the situation of acidity in the cold teeth in a short time after filling. 3. Pulpitis: This disease is mainly caused by bacterial infection, followed by excessive wear and tear of teeth, weak teeth and so on. If the patient does not pay attention to oral hygiene after filling, it may be complicated by pulpitis, which will cause pain and acidity when the teeth are cold. To summarize, there are many reasons for the acidity of teeth in the cold after filling, patients need to go to the hospital to clarify the specific causes, and may need to cooperate with the doctor for active treatment if necessary.