Objective The purpose of this studywas to studythe changes of available spaces of posterior arch segments inman- dible dentitions (ASPAS) from ages of 11 to 20 years, whichwould provide information on normal growth and development of the dental arches in teenagers in Chengdu area.Methods The data were derived from systematically collected preorthodontic lateral cephalograms of 526 patients, including 232 males and 294 females from the Orthodontic Department of West China College of Stomatology, Sichuan University during the period of 1999~2000 (aged 11~20 years). The values of ANB angle, FH-MP, ASPAS were obtained using the cephalometric analysis. Afterwards, the growth changes of ASPAS from the subjects and their correlations with age, gender, angle mal- occlusion types and vertical skeletal patterns were analyzed.Results ASPAS was related to age and classⅡangle malocclusion. Though gender was not associated with ASPAS, significant differences in curves of ASPAS were found between males and females. The growth changes of ASPAS in the patients with skeletal ClassⅢmalocclusion were more obvious than in patients with ClassⅠandⅡ malocclusion.Conclusion Our results reveal that significant differences were demonstrated in growth change values in posterior avail- able spaces of patients with different races and angle malocclusion types.
