The aim of this study is to measure the labial alveolar bone thickness of the Angle Ⅱ, Division 2 patients and healthy adults with CBCT technique, in order to provide reference for clinical dental orthodontic design.

Sixty cases were consecutively selected from the Fourth Affiliated Hospital outpatients of Inner Mongolia Medical College. They were divided into the case group and control group. Each group contains 30 patients (15 men and 15 women). CBCT was used to scan maxillofacial region and 3D models were made on computer, software was used to measure labial alveolar bone thickness in three points of the teeth (the root, central and apical). Analyze the result finally.

There was no significant difference between contralateral teeth. There was significant difference between the Angle Ⅱ, Division 2 patients and control group in different gender. There was significant difference between the case and control group in the thickness of incisor L1, L3, lateral incisor of L1, L3 and canine of L1, L2, L3.

There is no difference in the thickness of labial alveolar bone wall of the same tooth in both groups. Maxillary anterior labial bone wall of male is thicker than female’ in both groups. The maxillary anterior region of labial bone of Angle Ⅱ, Division 2 patients is thinner than normal adults in thecontrol group.

By analyzing changes of dental arch width and length during the aligning and leveling period (non-extraction case) with two kinds of self-locking bracket, compare the difference between the active self-locking bracket with the passive bracket.

The data of dental arch perimeter change amount and dental arch width and length change amount (WU/L3, WU/L4, WU/L5, WU/L6, U/LL) were statistically analyzed using the correlation and regression method by comparing active and passive brackets for the correction of dental arch variations. Two different brackets for the correction of the measured values of the dental arch variations was analyzed by t-test.

There were statistical relationships between the amount of arch perimeter increase and the amount of width and length increase. The regression equation was statistically significant (P < 0.05), It was greater impacted arch width increase to arch perimeter in the self-locking. The t-test results showed WU3, WL3, WL6, LR 4 measured values (P < 0.05) statistically significant in the active self-locking group and passive group.

Active and passive self-locking bracket have good arch expansion effecting. The active self-locking bracket is slightly dominant than the passive bracket in the expansion of the canine width whereas the active self-locking bracket is better than the passive in the expansion of the mandibular first molar and arch perimeter which should be widely applied to the appropriate cases.