الفهرس 
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Abstract
Craniofacial distraction osteogenesis (DO) also called callus distraction, callotasis, osteodistraction, which is the gradual lengthening of bone by applying controlled mechanical force in order to separate osteomatised bone segments.
The aim of this study was to evaluate the effect of β-tricalcium phosphate on mandibular distraction osteogenesis at different rates in rabbits.
The present study was carried out on eight healthy adult male white New Zealand rabbits, weighed from 3-3.5 kg, their ages ranged from 7 to 9 months old.
The surgical operation was performed where each rabbit anaesthetized using intramuscular Ketamine (50mg/Kg) and Xylazine (10mg/Kg). After shaving the submandibular hair and the area was scrubbed with povidone iodine solution, two bilateral extraoral submandibular incisions were done then vertical corticotomy was made on both sides right and left at the premolars area just anterior to the mental foramen. This was followed by fixation of custom made distraction device, and then the osteotomy was continued on both sides.
Each rabbit served as its own control, as the distraction procedure was done bilaterally; the right side of the mandible represented the study side, where β-TCP was injected at the osteotomy site, while the left side unfilled in order to serve as the control side where only DO was done. After 5 days latency period, the rabbits were divided into two groups according to the rate of distraction; group I (0.5mm/day for 10 days) and group II (1mm/day for 5days). Then the animals were left for 14 days consolidation period before scarification.
Clinically, the steps of distraction procedure were carried out with no significant problems.
At sacrifice, the mandible of each animal was removed and blocks of bone were taken, containing the osteotomy site in both study and control sides. And then blocks were prepared for histological examination by the light microscope.
Our histological finding in the control side (group II) revealed well marked woven and new bone bridged the distraction gap with osteoblastic activity.
The study side of the same group showed intense invasion of β-TCP particles were observed within the host bone and the newly formed bone. β-TCP particles were illustrated with dilated blood vessels. Also osteoclastic activity was detected.