Abstract: HE Sheng，HU Jing，SONG Jian,YE Bin.(State Key Laboratory of Oral Diseases,Sichuan University,Chengdu 610041,China) Abstract：Objective To assess the effect of parathyroid hormone(PTH) intermittent administration on bone regeneration after rapid mandibular distraction osteogenesis(DO) in rabbits. Methods Unilateral mandibular rapid DO was performed on 24 adult New Zealand white rabbits and they were randomly divided into two groups.At the beginning of the distraction,the experimental group was subcutaneously administered PTH daily for 30 days while the control group was injected with physiological saline.Rabbits sacrificed 6 weeks after the completion of DO.The distracted mandibular bones were collected and the calluses were processed with microCT,histology and biomechanical testing.Bone mineral density (BMD) in surrounding segments of the distraction gap was evaluated by dual energy xray absorptiometry (DEXA). Results The figures of microCT showed better growth and remodeling of regeneration of the experimental group than the control group.The result of the micro CT analysis showed greater parameters of the experimental group in bone volume fraction((48.30±3.46)%),bone connectivity density（(9.77±1.81）mm-3）,trabecular thickness（(0.25±0.01)mm） and number（(2.25±0.26)mm-1）than the control group(which were respectively （37.55±3.72）%,（7.89±1.73）mm-3,（0.12±0.03）mm，（1.27±0.27）mm-1）（P<0.01),yet the trabecular spacing of the experimental group((0.26±0.03)mm)was less than that of the control group ((0.30±0.04)mm)(P<0.01).Histological Examination showed a more mature newly formed bone in experimental group.PTH treated animals showed greater mechanical properties((378.30±29.10)N) and higher BMD（0.26±0.01）g/cm2) than the control group(which respectively were(196.60±14.50)N，(0.17±0.01)g/cm2)(P<0.01). Conclusions PTH enhances new bone formation and meanwhile prevents disuse osteopenia of surrounding segments of distraction gap in a rapid mandibular DO model.