The muscles around the old teeth hurt when biting, which may be related to temporomandibular joint disorder, periapical inflammation, muscle strain and other reasons. 1. Temporomandibular joint disorder: mainly manifested as pain in the joint area or muscles around the joint when opening or biting. 2. Periapical inflammation: If a tooth has periapical inflammation, the tooth will have a floating sensation, and due to the stimulation of inflammation, pain will occur when biting. 3. Muscle strain: If the occlusal muscles are overactive or the intensity of activity is too high, localized soreness may occur when biting. It is recommended that people whose muscles around the old teeth hurt a lot when biting should go to the hospital in time to clarify the cause of the disease and standardize the treatment under the guidance of the doctor.