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

ABSTRACT

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 callusshowing 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.