The onset of dental lock (dentition) is primarily due to problems with the position of the teeth. Normal teeth, including the back teeth, are the same, with the upper and lower teeth clenched tightly together. If the entire upper jaw is locked, the upper jaw teeth move completely outside of the lower jaw teeth, while the lower jaw teeth move completely inside of the teeth, creating a state where the upper and lower teeth cannot bite together directly, it is called locking (dentition). Locked teeth are difficult to treat because the two teeth are completely uncrossed, like a pair of scissors, and there is no bite at all, so it takes longer to treat. It is due to the abnormal position of the teeth, and it is not only the teeth that are somewhat abnormal in this case, after the abnormal position, it is also a little abnormal in the corresponding jaw bone, so the treatment time is also longer. In particular, the treatment time for the last tooth of the adult is longer because of the anatomical position of the tooth. Therefore, the treatment of locking (dentition), although only one tooth is incorrectly occluded, it usually takes 4-5 months, or even half a year, to solve the locking (dentition) of the back teeth of adults.