Abstract: [Abstract]Objective: The purpose of this retrospective cephalometric study was to compare skeletal and soft tissue point B changes in Class I malocclusion patients by difference extraction model. Method: The pretreatment and posttreatment records of 50 patients were used in the study. 25 patients involved extraction of first premolars and 25 patients involved extraction of second premolars. The lateral cephalometric radiographs taken before and after treatment were traced and measured 14 typical values were measured in Winceph 7.0 software and statistical analysis was carried by Spss17.0 software with t test. Result: (1) The horizontal and vertical lines were not significant different in the two extraction group before the treatment. But after the treatment the vertical changes of skeletal and soft tissue point B were more apparent in the first premolar extraction group. And the horizontal change of soft tissue point B was apparent in the second premolar extraction group. (2) In the hard tissue measurements, all the values were not significant different in the two extraction group before the treatment. After the treatment all the patients had a significant decrease in incisal inclination and length of L1-NB. But the changes were not significant difference between the two premolar extraction groups. (3) In the soft tissue measurements, the values of

Key words: Premolar extraction, ClassⅠ, Point B, Cephalometric analysis