All crowns in the process of use may fall off, fall off for a number of reasons: 1, the patient’s abutment teeth, that is, natural teeth, some people are too short crowns, after the preparation has been very short or not more than 3 mm of clinical height. Like this all-ceramic crown after bonding, may fall off; 2, all-ceramic crown bonding, the larger the contact area, the stronger the bonding effect, and vice versa, the smaller the contact area, the poorer the bonding effect, may lead to a large lateral force in the use of the process, the bite force is likely to fall off; 3, too small teeth, the crown is short, the possibility of falling off in the process of clinical use; 4, the front teeth deep over jaw, the bite force is relatively Large; 5, the patient night grinding, in this case may lead to all-ceramic crown off. Of course, there are ways to fall off, fall off after the different reasons for the loss, and then can be re-made or bonded.