Filled tooth is sore when biting hard may be due to the high point of occlusion, loosening of filling materials, caused by secondary caries or apical inflammation, etc. It is recommended to go to the stomatology department for timely examination and diagnosis and treatment. 1. If you have just finished filling the tooth, the biting pain may be caused by too much filling material, there is a high point when biting, and the point of force is concentrated, which will cause the tooth to be sore. 2. If the filling is not firmly bonded or the material is loose due to the influence of saliva, blood, etc., the material or food presses against the cavity when biting and produces stimulation to the dental pulp, then there will be pain. 3. A tooth that has been filled for a long period of time may also become sore when biting if secondary caries occurs. 4. Root canal inflammation, cracked teeth, fractured teeth, etc. may also cause pain when biting.