放射照射后牵张下颌骨成骨犬实验动物模型的建立

目的：建立放射照射后牵张下颌骨成骨犬实验动物模型。方法：选取成年中国犬12只,实验组10只以60 Co 颊舌向照射下颌骨后部标定区域,照射方法为22．8 Gy、5．7 Gy／次,共4次（生物等效剂量为50 Gy／25次）。对照组2只不照射。照射完成后3个月,在动物下颌第五和第六臼齿间行骨皮质切开术,植入骨牵张器,经过1周的延迟期,2次／d,每次0．5 mm 的速率连续牵张下颌骨10 d,然后固定8周。处死动物,以放射学,组织学和 SPECT 方法对牵张区新骨进行检查,对下牙槽神经进行组织学检查。结果：除实验组1只动物因麻醉意外死亡,其他动物都完成了实验。实验组和对照组新骨形成无明显差异。SPECT 显示实验组成骨活跃。观察到下牙槽神经修复性组织学变化。结论：放射照射后牵张犬下颌骨可形成新骨。     

兔下颌骨放疗后牵张成骨动物模型的建立

目的探讨建立兔下颌骨放疗后牵张成骨动物模型的可行性。方法24只成年新西兰大白兔随机分为放疗组和未放疗组,每组12只。放疗组采用60Co放疗机照射兔下颌骨,5.4Gy/次,隔日1次,共5次。3个月后在2组兔下颌骨的双侧截骨处安装牵张器,经5d延迟期后开始牵张,速率为1mm/d,0.5mm/次,每日2次,连续7d,共延长下颌骨7mm。固定期的第0、4、6周摄下颌骨侧位X线片。固定期的第4、6周分别取出下颌骨行组织学观察。结果兔对放疗和牵张成骨术耐受良好,未见放疗引起的不良反应。X线片有新骨形成,未见死骨;组织学观察见放疗组较未放疗组有更多软骨形成。结论兔是一种用于建立放射损伤区牵张成骨模型的良好动物。     

放疗对兔下颌骨牵张成骨骨再生的影响

目的：探讨兔下颌骨放疗后牵张成骨（DO）的可行性及其骨再生的特点。方法：将12只成年新西兰大白兔随机分为放疗组和未放疗组，每组6只：放疗组用^60Co机照射大白兔下颌骨，5．4Gy／次，隔天1次，共5次，总剂量为27Gy。3个月后，在2组动物下颌骨的双侧截骨处安装牵张器，经5天延迟期开始牵张，速率为1mm／d，0．5mm／次，每天2次．连续7d，共延长下颌骨7mm．固定期的第4、6周拍摄下颌骨侧位X线片，取双侧新生骨痂行组织学和扫描电镜检查，观察其成骨特征。结果：X线片显示，2组动物同一固定时间牵张间隙内透射密度无明显差异；组织学观察显示，牵张区以膜内成骨为主，但放疗组有更多的软骨形成，放疗组较未放疗组新骨骨小梁细小、稀疏；扫描电镜示同定第6周时，放疗组新骨不如未放疗组致密、成熟。结论：在兔下颌骨放射损伤区行DO是可行的，但成骨质量较差，成骨方式以膜内成骨为主，放射线照射可促进软骨成骨。     

不同速率牵张下颌下齿槽神经的组织学和超微结构改变

目的 研究不同速率牵张延长下颌骨后下齿槽神经的组织学和超微结构改变，为临床上确立合理而安全的牵张速度提供实验依据。方法 8只山羊随机分为A、B、C三组，A、B组各3只。A组1mm/d，B组以2mm/d牵张，C组2只动物为对照。牵张延长下颌骨10mm，固定2w处死。取下齿槽神经行组织学，透射电镜观察。结果 牵张动物的下齿槽神经均发生了Wsaller变性，以2mm/d牵张神经退行性病变严重而广泛。超微结构病变主要发生于粗大的有髓神经纤维，而细小的有髓神经及无髓神经纤维未见异常。结论 2mm/d牵张会对下齿槽神经造成严重损伤，而1mm/d牵张速度为较适宜而安全的下颌牵张速率。     

小型猪下颌骨放射性骨坏死动物模型的建立

目的 探讨利用小型猪建立下颌骨放射性骨坏死（ORN）动物模型的可行性。方法 应用三维适形放疗（3D-CRT）技术,采用电子直线加速器照射源对24只小型猪右侧下颌骨进行25 Gy和28 Gy一次性照射,于照射结束后2个月拔除双侧下颌第一磨牙,通过定期局部观察、X线、CT检查和组织病理学方法诊断下颌骨ORN的发生。结果 照射结束后3~4个月,拔牙后的小型猪先后全部发生了下颌骨ORN,28 Gy+拔牙组症状较重。结论 25 Gy单一剂量放射小型猪下颌骨+拔牙能建立有效的、可信的下颌骨ORN模型,可用于ORN病因学及治疗等方面的进一步研究。     

α2巨球蛋白对大鼠下颌骨放射性骨坏死的预防作用

目的: 观察和分析在X线照射前于大鼠下颌骨体局部注射α2巨球蛋白（alpha2-macroglobulin, α2M）是否对大鼠下颌骨放射性骨坏死（osteoradionecrosis,ORN）具有预防作用。 方法: 健康SD雄性大鼠18只,随机分为3组,每组6只。其中A组为空白对照组,B组为单纯X线照射组,C组为X线照射前左侧下颌骨局部注射α2M组。大鼠均经麻醉后使用3D打印装置固定,B、C组使用X线生物学辐照器对其左侧下颌骨进行精准照射,每天7 Gy,连续照射5 d;A组假照射;C组在第1次X线照射前30 min于大鼠左侧下颌骨体部骨膜下局部注射0.5 mL 2000 mg/L的α2M,A、B组在同样部位注射等量无菌生理盐水（normal saline,NS）。照射完成后第7天,拔除大鼠左侧下颌3颗磨牙。照射完成后第28天处死所有大鼠,从大体、影像学、病理学等方面系统评估各组大鼠的放射损伤。采用SPSS 13.0软件包对数据进行统计学分析。 结果: B组5只大鼠大体上体重明显减轻、照射区黏膜重度溃疡、受照侧颊部脱毛、咬合关系紊乱;影像学显示明显的骨质缺损;病理观察发现照射区皮质骨空白骨陷窝增多、死骨形成、纤维增生等骨坏死典型症状,证实发生下颌骨ORN,发生率为5/6;与B组相比,C组大鼠大体上仅表现为轻度体重下降及照射区脱毛,影像学上未见明显骨质缺损,病理观察仅见骨髓腔内轻微炎症,皮质骨无明显破坏,骨陷窝空虚率较B组显著降低（P<0.001）;C组大鼠下颌骨ORN发生率为零。 结论: X线照射前注射α2M对下颌骨ORN的发生具有较好的预防作用。     

引导组织再生膜促进兔下颌骨牵张成骨的实验研究

目的 探讨引导组织再生膜（GTRM）对兔下颌骨牵张成骨新骨形成的促进作用。方法 将20只新西兰大白兔随机分为2组,每组10只,建立兔下颌骨牵张成骨模型,A组单纯单侧下颌骨牵张成骨;B组将GTRM固定于牵张器内侧行单侧下颌骨牵张成骨。分别于固定期第2、6周时随机处死半数动物获取标本,通过X线、骨组织形态计量学比较2组牵张间隙内成骨效果。采用SPSS11.0软件包对数据进行两样本均数t检验。结果 通过X线及骨组织形态计量学检查并经过统计学分析发现,在固定期第2周和6周时,B组牵张区域内成骨质量显著好于A组（P<0.05）。结论 引导组织再生膜能有效促进兔下颌骨牵张成骨区域新骨的形成。     

下颌骨放射性骨坏死山羊动物模型的建立

目的建立下颌骨放射性骨坏死(osteoradionecrosis,ORN)山羊动物模型。方法6只成年山羊根据不同照射剂量随机分为3组(15、20、25Gy),照射前收集正常下颌骨影像学及病理学资料,资料收集完成后采用直线加速器按分组剂量对左侧下颌骨行单次照射。照射结束后45d在照射侧行拔牙术,拔牙后每周观察局部及全身情况,拔牙结束后3、6个月行影像学、病理学及骨代谢检查。结果在组织病理学检查上,3组均符合ORN,其严重程度与照射剂量正相关;其中20Gy和25Gy组有典型的临床症状出现;照射前后颌骨影像学检查无明显改变;骨代谢检查发现放疗侧颌骨代谢明显较对侧低。结论成功建立下颌骨ORN山羊动物模型。ORN组织细胞学及颌骨代谢变化先于影像学改变。     

单一剂量单侧腮腺放射损伤对双侧腮腺结构和功能的影响

目的 研究单一大剂量射线照射单侧小型猪腮腺对双侧腮腺结构和功能影响。方法 14只小型猪一侧腮腺用直线加速分别给予15 Gy（7只）和20 Gy（7只）离子射线照射,4只做为空白对照。分别在放射前,放射后4周和16周观察腮腺唾液流率、腺体重量、腺泡面积和组织学变化。结果 4周时,15 Gy和20 Gy照射后放射侧腮腺重量下降达50%;15 Gy照射后放射侧腮腺唾液流率无明显下降,20 Gy照射后放射侧腮腺唾液流率减少约50％。16周时,15 Gy和20 Gy照射后放射侧腮腺重量下降达50%,组织学明显改变,照射后放射侧腮腺流率分别下降约60%及80%。非放射侧腮腺重量及形态均无明显变化,但20 Gy照射后16周时非放射侧腮腺唾液流率明显下降。结论 单一剂量照射后腮腺结构的改变相对唾液流率下降发生较早,唾液流率减少与腺泡面积的减少不完全成正相关。非照射侧腮腺形态变化不明显,但唾液流率明显下降。     

兔下颌骨牵张成骨过程中内源性硫化氢信号系统的表达

目的 探讨兔下颌骨牵张过程中内源性硫化氢(H2S)信号系统的表达.方法 34只雄性新西兰兔下颌骨牵张术后5天,被随机分为A组:牵张速率为1mm (2次/d,共5d);B组:牵张速率为0.5mm(2次/d,共10d).选取5个时间点抽取静脉血监测血浆H2S含量.牵张结束后4周及8周,利用CT及双能骨密度测量仪检测牵张间隙成骨效果,收集牵张间隙组织检测局部胱硫醚-γ-裂解酶(cystathionine-γ-lyase,CSE)水平.结果 H2S信号系统在整个牵张过程中有表达,而快速牵张速率条件下,全身及局部H2S信号明显减弱,同时牵张间隙成骨不良明显.牵张结束后4周及8周B组牵张间隙组织CSE相对含量和表达强度均强于A组.结论 内源性H2S信号系统在牵张过程中有一定的作用,补充外源性的H2S可能促进牵张.     

Character of distracted bone in irradiated canine mandibles and electrophysiological changes in the inferior alveolar nerve

Our aim was to explore the character of distracted bone in irradiated canine mandibles and the electrophysiological changes in the irradiated inferior alveolar nerve (IAN). Twelve Chinese dogs were studied, 10 of which were given unilateral irradiation of ⁶⁰Co in the mandible with a total dose of 22.8 Gy in four 5.7 Gy fractions (biologically equivalent to 50 Gy/25 fractions) (experimental group). The other two dogs were not irradiated and served as controls. All had a bilateral corticotomy 3 months after irradiation. After a 1-week latency period distraction of the mandible was activated at a rate of 0.5 mm twice daily for 10 days, followed by a consolidation phase of 8 weeks. New bone was assessed by radiographic, histological, and single-photon electron computed tomographic (SPECT) analysis. The IAN was analysed electrophysiologically. One dog in the experimental group was excluded from the study with anaesthetic problems. After 8 weeks of consolidation there was no difference between the percentage area of new bone in the two groups. New bone was more mature and organised in the control group than in the experimental group. SPECT analysis showed that there was active osteogenic activity in dogs in the experimental group. The action potential of the IAN showed corresponding changes during the irradiation and distraction processes.     

下颌骨牵引延长过程中器械的应用与拆除时机

目的：确定下颌骨骨牵引引延长过程中器械应用与拆除时机,为临床应用提供参数。方法：采用自制的ＭＳ－１型内置式下颌骨骨牵引延长器行犬下颌骨牵引引延长;取新成骨,制成标准骨生物力学测试件,进行轴向压缩及三点弯曲实验;测量新成骨的弯曲强度、抗压强度、弹性模量、泊松比等特征材料参数,并与对照组分别比较。结果：新成骨在牵引引完成后３周时分别达到对照组的３７％～６０％,５周时各参数值分别达到正常对照组的８９％～     

下颌骨牵引成骨过程中VEGF及其受体的表达

目的:通过建立兔下颌骨牵引成骨实验动物模型,研究下颌骨牵引成骨过程中血管内皮生长因子(vascular endothelial growth factor,VEGF)及其受体的表达及意义。方法:选用新西兰白兔30只,随机选取6只动物作空白对照组,24只动物右侧下颌骨植入外置式颌骨牵引器。经7d延迟期后,按1mm/d速率延长下颌骨7d,固定期8周。在延迟期第7d,牵引期第2、4、7d,固定期第1、3、6、8周分别处死3只动物,采用免疫组化方法,检测VEGF及其受体FLT-1(fms-like tyrosine kinase-1)、FLK-1(fetal liver kinese-1)的表达变化。结果:VEGF及其受体FLT-1、FLK-1的表达贯穿下颌骨牵引成骨全过程。下颌骨牵引成骨过程中不同时相多种组织细胞参与表达VEGF及其受体FLT-1、FLK-1,但在表达的变化上存在一定的差异。结论:VEGF通过与其受体特异性结合,在下颌骨牵引成骨血运重建及新骨生成过程中发挥重要作用。     

BMP-2、bFGF在牵引成骨中的表达及意义

目的 :通过两种不同术式的比较 ,研究骨形态发生蛋白 - 2 (BMP - 2 )、碱性成纤维细胞生长因子 (bFGF)的表达水平和成骨的关系 ,探讨牵引成骨的成骨机制。方法 :2 8只狗随机分为牵引成骨组和直接延长组各 12只及正常对照组 4只 ,用免疫组化染色方法观察比较BMP - 2、bFGF在两组牵引第 6天、固定 2周、固定 8周时的表达情况。结果 :两组在牵引第 6天骨断端附近的新生编织骨边缘基质及周缘的活跃的成骨细胞、骨膜下及牵开区增生活跃的间充质细胞、成纤维细胞、胶原纤维基质均可见BMP - 2、bFGF强阳性的染色 ,染色平均灰度比较均无统计学差异 (P >0 .0 5 ) ;牵引后固定 2周 ,牵引组新生编织骨边缘的成骨细胞、软骨细胞、牵开区纤维结缔组织仍可见BMP - 2、bFGF阳性染色 ,而直接延长组的BMP - 2、bFGF在牵开区的染色强度明显降低 (P <0 .0 5 ) ;牵引后固定8周 ,BMP - 2、bFGF在牵引组和直接延长组的组织中的染色强度均明显减弱 ,染色灰度比较均无统计学差异 (P >0 .0 5 )。结论 :在下颌骨牵引成骨过程中 ,在机械的牵引力和微创伤等多种因素刺激下 ,局部牵开区BMP - 2和bFGF持续高表达。两种生长因子可能共同参与促进了牵开区大量新骨的形成。     

Evaluation of alveolar nerve function after surgical lengthening of the mandible by a bilateral sagittal split osteotomy or distraction osteogenesis

This study compares the effects of bilateral sagittal split osteotomy (BSSO) and distraction osteogenesis (DO) for lengthening the mandible regarding loss of function of the inferior alveolar nerve (IAN). In a retrospective cohort study design, the function of the IAN was tested with a Weinstein monofilament 3.22, 1 year after the surgical procedure in 65 patients (35 BSSO; 30 DO). This was defined as the upper limit for normal function. Of 130 IAN studied (70 BSSO, 54%; 60 DO, 46%), nerve function was disturbed in 23 (18%). In this group, 14 cases (61%) had undergone BSSO and 9 (39%) DO. One-hundred and seven nerves had no neurosensory IAN changes; of these BSSO had been performed in 56 cases (52%) and DO in 51 cases (48%). After eliminating confounding factors, there was no significant difference in the occurrence of neurosensory changes between the treatment options (DO versus BSSO, odds ratio: 1.254 with 95% CI: 0.366–4.300). In conclusion, there was no difference in IAN function between patients treated with BSSO or DO for lengthening the mandible.     

The effects of irradiation and hyperbaric oxygen on bone formation during rabbit mandibular distraction

[18F-]fluoride positron-emission tomography (PET) was used to assess bone formation during mandibular distraction osteogenesis. There were three study groups: irradiation, irradiation+hyperbaric oxygen and control. The two experimental groups received a tumoricidal dose of irradiation to the mandible, and one group was also given hyperbaric oxygen (2.5 ATA (atmospheres absolute) for 90 min) 18 times preoperatively. Control animals received neither irradiation nor oxygen. A unilateral osteotomy was made and, after a period of latency, bone distraction was started, continued for 2 weeks, and the distraction generated was then allowed to consolidate for 4 weeks. The first PET study was performed at the end of distraction and the second at the end of consolidation. At the end of distraction, the metabolic activity of bone in the distracted area was significantly higher in the controls than in either experimental group; differences between the experimental groups were not statistically significant. By the end of consolidation, activity in the control group had diminished to the same as in the two experimental groups, in which no significant change had occurred. Radioactivity was still significantly higher at second imaging on the distracted than non-distracted side in the control and irradiation+hyperbaric oxygen groups, but not in the group that was only irradiated. The results indicate that previous irradiation disturbs bone formation during mandibular distraction osteogenesis. Hyperbaric oxygen was not able to prevent the suppression of osteogenesis caused by radiotherapy but it might improve bone formation by prolonging high osteogenic activity.     

Co-expression of nerve growth factor and p75NGFR in the inferior alveolar nerve after mandibular distraction osteogenesis

During mandibular distraction osteogenesis (DO), the inferior alveolar nerve (IAN) is damaged during distractor activation, but spontaneously recovers during consolidation. Although many neurotrophic factors are known to play critical roles, there have been few studies on the mechanism of peripheral nerve recovery after DO. The aim of this study was to observe the expression pattern of p75NGFR (low-affinity receptor of NGF) and to detect autocrine growth activity in IANs following mandibular DO. Unilateral mandibular distractions (0.5mm each, twice per day for 10 days) were conducted on eight mongrel dogs. Two each were killed at 7, 14, 28 and 56 days after completing distraction. The distracted IAN and contralateral control nerve were harvested. Immunohistochemical staining was performed to determine p75NGFR expression, and double immunofluorescent staining to detect NGF and p75NGFR co-expression. Levels of p75NGFR expression were found to be significantly elevated at 7 and 14 days in Schwann cells located in the outer layer of axon, but were almost undetectable at 28 and 56 days. In double immunofluorescent images, the co-expression of NGF and p75NGFR was also detected at 7 and 14 days. p75NGFR plays an important role in remyelination due to its abundant expression in Schwann cells of damaged nerves, and NGF is an autocrine growth factor present in distracted IANs during the early consolidation period after mandibular DO.     

The BMP signaling and its Smads in mandibular distraction osteogenesis

Aim:  The aim of the present study was to clarify the mechanism of signal transduction of bone morphogenetic proteins (BMPs) through their specific down signaling molecules Smads inducing bone formation in response to mechanical stimulus during distraction osteogenesis (DO) in the rat mandible.
Materials and methods:  Osteotomy of the left mandible was performed in 45 rats. Thirty rats underwent mandibular distraction (protocol; 5 days latency, 8 days distraction, and 2 weeks consolidation) while 15 rats served as non-distracted (fracture healing) group. The expression of BMPs-2,-4 and Smads 1, 5, and 8 were evaluated in the new regenerate area using immunohistochemistry.
Results:  Expressions of BMPs-2,-4 and Smads 1, 5, and 8 were moderate during latency, significantly increased during distraction and decreased towards consolidation period.
Conclusions:  The enhanced expression of BMPs and its Smads during distraction compared to the non-distracted group suggests the possible role of BMP signaling pathway in translation of mechanical forces into biological results during DO.     

Evaluation of inferior alveolar nerve function during distraction osteogenesis in the dog

Purpose: A series of electrophysiologic studies were performed in a canine model to evaluate inferior alveolar nerve (IAN) function during distraction osteogenesis of the mandible.Materials and Methods: Fourteen dogs, including two controls, were used in the study. Twelve dogs underwent a 10-mm bilateral mandibular lengthening with an intraoral bone-borne appliance and midbody osteotomy. By using sensory nerve action potentials, IAN function was assessed before and immediately after surgery, before and at the completion of distraction, and before necropsy after 4, 6, or 8 weeks of fixation.Results: Twelve of the 24 nerves showed a complete loss of evoked potential after surgery without recovery at any point throughout the study. Acute nerve injury caused by either the osteotomy or screw encroachment was identified at necropsy. The other 12 nerves showed reproducible responses after surgery. Eight of these nerves had significant amplitude attenuation of the evoked potentials, which was identified at necropsy as a result of acute injury. The remaining four nerves did not show significant evoked potential abnormalities and appeared to be grossly normal at necropsy. During distraction, the amplitude of evoked potentials in all 12 nerves remained at the postoperative level, whereas latency showed a significant delay. In 7 of these 12 nerves, various degrees of evoked potential recovery were identified at the completion of the study.Conclusions: The high incidence of acute IAN injury in the current study was primarily related to device construction and osteotomy technique. If acute nerve injury is avoided at surgery, distraction osteogenesis with 10 mm mandibular lengthening appears to produce minimal deleterious effect on IAN function.