To diagnose dental defect, a comprehensive oral examination should be carried out first, as follows: 1, visual examination should observe whether there is any change in tooth shape, normal teeth are complete, defective teeth may have cavities, teeth with defects indicate that the crown is not complete, which is easy to diagnose; 2, there is abnormality in the color of the crown when the tooth is defective, the color of normal teeth is more uniform and consistent throughout the mouth, the crown with defects will be black or brown or chalky If there is color change, it can be considered to be diagnosed as dental defect; 3, abnormal crown texture also suggests dental defect, the normal crown is very hard, after decay and defect, there will be a lot of decayed tooth above the crown, i.e., soft texture, which is very soft when probed, this is one of the diagnosis methods of dental defect; 4, abnormal anatomical shape of the crown suggests dental defect, originally the crown contact between the two neighboring teeth is very normal, but if there is defect, the crown contact between the two neighboring teeth is very normal. However, if there is a defect, there will be food embedment, etc., and it will no longer be the same as the normal anatomical form, and this phenomenon can be considered for the diagnosis of dental defect.