Teeth can not bite hard objects, may be the teeth have hidden cracks, periodontitis, apical periodontitis and so on. The cause of the disease should be clarified in a timely manner. 1. Cracked teeth: Excessive biting force and physiological biting force act directly on the teeth, resulting in damage to the tooth structure, which can cause cracked teeth. If you have a cracked tooth, when you bite something hard, it is especially easy to have pain, so that the tooth is afraid to bite hard objects. 2. Periodontitis: when the teeth plaque, tartar, traumatic bite, food impaction and genetic factors, etc., will trigger inflammatory destruction of periodontal tissues, resulting in inflammation of the gums, bleeding, the formation of periodontal pockets, the teeth do not dare to bite hard objects and other manifestations. 3. Apical periodontitis: generally refers to inflammatory diseases occurring in the apical part of the tooth and the surrounding tissues, which can be manifested as inflammatory reaction of the periodontal membrane, alveolar bone, and osteoid, resulting in loose teeth, loss, and the teeth can’t bite hard objects with a sense of touch. Teeth can not bite hard objects may also exist other reasons, should be timely consultation, please ask the doctor to clarify the specific causes, if necessary, the appropriate treatment.