The effect of distraction rate on bone histological and histomorphometrical properties in an ovine mandible model

Lengthening the mandible by distraction osteogenesis (DO) is nowadays a well-recognized technique in maxillofacial surgery. This study compared two different distraction rates and evaluated histological and histomorphometrical properties of the distracted bone in an experimental ovine mandible model with the goal of elaborating a universally accepted distraction protocol. Tissue blocks of regenerated bone were harvested from twelve young adult sheep. DO was performed on the mandibular midline after five days of latency period. The sheep were divided into two groups. The first group underwent activation of 0.8 mm÷day during 12 days resulting in 9.6 mm of new bone while the second group followed a geometric rate pattern of 0.2 mm - three days, 0.4 mm - three days, 0.8 mm - three days and 1.6 mm - three days resulting in 9 mm of new bone. The regenerated bone was histologically and histomorphometrically analyzed after 30, 45 and 60 days of consolidation. The relative osteoid volume (OV÷TTV) was significantly increased in the geometric rate distraction group (p=0.015) comparing with linear distraction group while the relative bone volume (BV÷TTV) was significantly increased in the linear distraction group (p=0.019) compared to the geometric distraction group.