Effect of latency period and direction of distraction on the new bone formation during distraction osteogenesis

Jang, Gun Taek; Oh, Jung Hwan; Kim, Yeo Gab

Abstract

This study was designed to investigate the effect of latency period and direction of applied forces on the new bone formation during distraction osteogenesis. For this study 7 beagle dogs weighing 9-11 kg (mean 10 kg) were used. The vertical osteotomy on the left side of mandible, the step osteotomy on the right side were performed and the segments were fixated with 4 screws (2.0-mm diameter and 18.0-mm length) and. prefabricated distractors made with orthodontic palatal expansion screws. Distraction was initiated after a 3-day latency period or 7-day latency. Lengthening was achieved by distraction at a rate of 1.0 mm/day (0.5 mm every 12 hours) for 6 days, followed by a 3-week or 5-week consolidation period. After consolidation, histologic technique-Goldner's modified Masson trichrome method- was used to estimate the new bone formation between the groups. The 7-day latency groups showed clinically more stable, less infection rate, and more new bone formation than the 3-day latency groups. So it was recommended that 7-day latency is favorable in maxillofacial distraction and Histologic findings also revealed that the distracted site were filled with fibrous callus showing fibro-osseous metaplasia. Many osteoblasts were observed around new bone deposition. Intramembraneous and endochondral bone formation could be observed in the gap distraction groups. The stability and initial callus formation in the 7-day latency groups are better than that in the 3-day latency groups. Lateral force as well as tensile force could also accelerate the new bone formation and bone formation occurred parallel to the direction of distraction.