Experimental study of mechanical analysis in mandibular lengthening. Application of strain gauge measurement.

In distraction osteogenesis, the assessment of new bone formation and the decision of when to remove the distraction device are very important from clinical viewpoint. The purpose of this study was to measure bone stiffness using a strain gauge during and after mandibular lengthening, and to compare the results with those from radiographic and histological examinations. Twelve adult mongrel dogs served as the experimental subjects. An external distraction device was connected to the mandible, and distraction was started 7 days after operation and continued for 10 consecutive days. The animals underwent strain gauge measurement and radiographic examination of the mandible at the completion of distraction and every 2 weeks until the end of the consolidation period. The animals were then sacrificed at 2, 4, 6, 8, 10, and 12 weeks after completion of the distraction for histologic examinations. There was correlation between the amount of decrease in strain, increase in ratio of radiopacity, and newly formed bone in the distracted area.