الفهرس 
Maxillary and Cranial DistractionOnly 14 pages are availabe for public view
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Abstract
Distraction osteogenesis is a technique of new bone formation induced by gradual separation of bone fragments. This method was initially developed in orthopedic surgery, and it is now an established method for long bone lengthening. It has been recently applied in treatment of craniofacial deformities, showing considerable advantages over the previous methods. Donor site morbidity is avoided, the investing soft tissue envelop is concurrently expanded, and the magnitude of surgery is less. Because of these advantages, the technique started to develop an enlarging world-wide acceptance in the recent years. However, it is still in its growing phase and further investigations are still required for establishing it as a current treatment modality, with a better defined role in craniofacial surgery. the present thesis was conducted for the purpose of evaluation of this technique. Experimental and clinical studies were done. The experimental pat evaluated mechanically the bone quality after distraction compared to bone graft. Fifty two New Zealand white rabbits were used. four animals were devoted to preliminary experiments Then, the animals were divided into two groups according to time of sacrifice. Each group contained distraction and bone graft subgroups. The animals of distraction subgroups underwent a distraction protocol to achieve about 7 mm unilateral lengthening of the mandible. The animals were allowed to live either for 6 weeks postoperatively (1st group: n=29), or for 12 weeks (2nd group n=19). Then, specimens were prepared from both the operated sides of the mandibles and the non-operated sides that acted saw control. Some specimens were processed for histological examination and the others for mechanical evaluation by testing its tolerance to gradually increasing compression force. This was done by a special apparatus in the laboratory of materiology, at faculty of engineering, Ain Shams University. The results of histological examination showed that a new bone was formed through the process of endochondral ossification. The results of mechanical evaluation showed that destruction samples could tolerate stress much more than their non-operated controls. The differences were highly statistically significant in 1st group (at 6 weeks) and significant in the 2nd group (at 12 week). The cartilage content of the samples playing a role in making it more resistant to fracture. This is in contrast to bone graft samples which were less resistant to stress than their controls at any postoperative time. However, the differences at 12 weeks were statistically insignificant.