Objective The aim of this study is to investigate the changes of hard tissue profile in anterior-posterior and vertical direction in bimaxillary protrusion patients after orthodontic treatment. Methods A total of 24 bimaxillary protrusion patients (male 8, female 16)，aged from II. 2 to 29.0 (average 16. 9 years old)， were selected to be treated with standard edgewise tech- nique consisted of 4 first premolars extraction. Cephalometrics were taken before and after treatment. The changes of hard tissue profile were studied using the computer-aid X-ray cephalometric analysis. Results 1.The length of the maxillary and the mandi- ble increased significantly, but the anterior-posterior relationship of the maxillary and the mandible did not change significantly. 2. The anterior and posterior facial height increased significantly, but the ratio of anterior and posterior facial height and the angle of MP-FH which reflected the inclination of the mandible plane did not change significantly. 3. The height of the upper and lower first molar increased significantly along with the increase of the anterior and posterior facial height. 4. The height of the upper inci- ~increased significantly, but the height of the lower incisors decreased significantly. Conclusion The anchorage in anterior- posterior and vertical direction were controlled preferably, the patients did not manifest disadvantageous vertical growth trend.
