The Effect of Canine Mandible in Distraction Osteogenesis Relating to Distraction Rate

ABSTRACT

There have been great concerns about the application of distraction osteosynthesis to facial reconstruction, a technique which was proposed by Ilizarov in the early 20th century. Despite of many studies and trials since then, little research has been done concerning the specific response of facial bone to distracting stress. The purposes of this study are to investigate the maximal distraction rates and lengthening amounts which are safe from poor osteogenesis and possible adverse reaction. After corticotomy, eleven Korean mongrel dogs were distracted on their mandible for 28 days at different speeds A group-3 dogs, 1.0 mm/4 times/day; B group-3 dogs, 1.5 mm/4 times/day; C group-2 dogs, 1.75mm /4 times/day; D group-3 dogs, 2.0 mm/4 times/day respectively, which were then examined in gross architecture, radiologic and histologic changes after 7 weeks fixation. The following results were obtained dense osseous tissue was observed in new bone with the distraction rate of 2.0 mm/day. With maximum distraction rate and lengthening, most nerve fibers of the inferior alveolar nerve were well myelinated and had relatively normal axon structures in the region of the new bone except for rare findings of minimal disfiguration of axons and demyelination in some areas. There was not any evidence of arthrotic changes in temporomandibular joint under maximum distraction, but some adaptive changes were observed. In conclusion, relatively favorable bone formation was possible at the distraction rate of 2.0 mm per day. Because there was little damage of nerve and joint against maximum lengthening (43.4% of original bone length), this technique can be considered as a useful choice for reconstruction of larger defects on facial bone. However, a more systemized longitudinal analysis is needed to determine the regional effects of distraction and the detailed mechanism of ossification on the mandible.