Obstructed teeth that do not erupt normally, decay themselves or cause decay or resorption of adjacent teeth, or frequently induce pericoronal inflammation, or press on the nerve and become painful, should be extracted. For those who have not yet developed clinical symptoms, but the growth direction of the blocked tooth is tilted, which may cause damage to soft and hard tissues, they can also be prophylactically extracted. However, some of the following cases can be considered for retention: 1. If the anteriorly inclined third molar of the mandible does not exceed 45°, and the adjacent teeth are loose or decayed and cannot be retained for a long time, the orthodontic treatment should be carried out to make the blocked tooth perform the function instead of the adjacent teeth, or become a bridge abutment tooth, which can be considered for retention. 2.If the blocked teeth buried in the jaw bone are likely to damage the neighboring teeth when extracted, they can be retained temporarily and should be observed regularly. 3, mandibular vertical obstructive teeth, has erupted up to the jaw plane of the adjacent teeth and normal jaw relationship, only a small gingival flap cover in the far middle, after removal can reveal the far middle crown surface, can cut gingival surgery and should not be extracted. 4, mandibular anteriorly inclined obstructed third molars with a small anterior inclination angle and the root has not yet been fully formed, after reset, there is a normal jaw relationship, available tooth jerk up to reset, do not have to be extracted.