RESUMO
<p><b>OBJECTIVE</b>To investigate the condensability of mandibular length.</p><p><b>METHODS</b>In six goats were used in the study. Corticotomy at right mandibular angles was performed via extral-oral accession. Special devices were applied to shorten the mandible by 0.5 mm per three days respectively.</p><p><b>RESULTS</b>1. Mandibular angles of the six goats were shorten by 0.8 cm to 1.3 cm respectively in 48 days to 78 days; 2. In spite of the lower ascending ramus moving forward and angles being blunt, the occlusion scarcely varied because of contralateral bite-lock; 3. X-ray demonstrated that, at first, bone density in contracted areas declined, and then increased gradually to almost normal density; 4. Under microscope there were three tissues layers from central to lateral within the bone gap: fiber layer, cartilage layer and bone layer, and fiber layer gradually transform into cartilage layer with the fixed time. At the end of fixation they all transform into bone tissue.</p><p><b>CONCLUSION</b>Contraction osteogenesis is actually a process of compression, absorption and rebuilding. It is feasible that using contraction osteogenesis to shorten the mandible via cortcotomy.</p>