The main reasons for tongue biting are upper and lower back teeth are shallow overlay, shallow cover or opposite edge jaw, as well as long-term missing multiple back teeth, impaired blood circulation of tongue, movable or fixed prosthesis is not adapted or occlusal relationship is not good, etc., the details are as follows:1. Upper and lower back teeth are shallow overlay, shallow cover or opposite edge jaw: at this time, the tip of tongue side can not protect the tongue body, and it may bite the lateral edge of the tongue body in mastication and eating.2. Long-term missing Multiple back teeth: the soft tissues of the tongue will expand to the gap, and sometimes the tongue can be bitten, forming traumatic ulcers.3. Obstruction of blood circulation of the tongue: at this time, it can cause local bruising or edema, which can lead to obvious hypertrophy of the tongue, and it is easy to be bitten.4. Inadaptation of movable or fixed prosthesis, and poor occlusal relationship: the movable or fixed prosthesis which has just been made can not be adapted to the situation, or the occlusal relationship which has just been formed is not good, and it is easy to bite when chewing muscles are not formed to coordinate movement. It is easy to bite the tongue tissue when no coordinated movement is formed, and it will be reduced gradually after 1-2 months.