patients were enrolled by the inclusion criteria and were undergo lefort 1 maxillary osteotomy. after the latency phase the distraction was done in anterior- posterior vector. patients were divided by randomized allocation in 2 groups. in group 1 the distractor was removed after consolation phase, and in group 2 fixation devices were placed immediately after removal of distractors. data regarding relapse were analyzed by lateral cephalogram X-ray taken in 3 different phases of the trial. change of occlusal plane and the "A point" of the cephalometric analysis were determined as reference point of the study.

All patients were undergo maxillary Lefort 1 osteotomy with intra oral distractors bilaterally. The latency phase was considered 5 days for all of them. Distraction was done in the anterior- posterior vector with 1 mm/day rate. In group 1 distraction devices were removed after finishing distraction and a 3 months consolation, in group 2 fixation devices (4 L shaped miniplates with 16 screws) were placed immediately after removing distractors.

The amount of horizontal and vertical relapse were determined in the "A point" 2 years after finishing distraction.

By using lateral cephalogram X-ray as a raw data base, taken in 3 occasions: preoperatively, immediately after finishing consolation phase and removing distractor with placing fixation devices or without them and 2 years postoperatively in every subject. Relevant skeletal points were determined and digitized to evaluate 2-dimensional skeletal changes during and after surgery and to subsequently determine the amount of relapse. The same X-ray machine and settings were used for all cephalograms.Patients were stabilized in the lateral Cephalogram unit (Planmeca, ProMax, Helsinki-Finland) using Cephalostat. With the position of the patients with their head oriented at 90 degree angle to the X-Ray beam at a distance of 5ft from the tube. The jaws were in maximum intercuspation, tip of the tongue behind the upper incisor teeth and lips in relaxed position. The receptor (CR, Konica Minolta medical imaging, USA) was placed 15 inches from the head. This is a standard under which all cephalometric radiographs are taken. It ensures that radiographs, taken in different times, are directly comparable.

Radiographic exposures were 60-80 Kvp, 10-15 mA, and 16-32 sec, and repeated for each case in three occasions.

The radiographs were processed in laser readout processor special for mentioned CR system. PACS. A DICOM system used for saving and transferring the images.

All Lateral cephalograms were traced by hand and digitized, superimposed and evaluated by the same examiner. The tracings were rechecked by another examiner.

Inclusion Criteria:

patients need lefort 1 maxillary advancement more than 8 mm and have presurgical orthodontic preparation

Exclusion Criteria:

patients with cleft lip and alveolar cleft ,traumatic patients ,patients with previous orthognathic surgery in the maxilla and edentulous patients