Objective To compare skeletal and soft tissue point B changes in Class I malocclusion patients by difference extraction models.Methods 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 out by Spss17.0 software with t test.Results (1 )The horizontal and vertical lines were not significantly different between the two extrac-tion groups before the treatment.But the vertical changes of skeletal and soft tissue point B were more apparent in the first premolar ex-traction group after the treatment.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 significantly different between the two extraction groups before the treat-ment.After the treatment all the patients had a significant decrease in incisal inclination and length of L1 -NB.significantly different be-tween the two premolar extraction groups.(3)In the soft tissue measurements,the values of 展开▼
