放射照射后牵张成骨下牙槽神经电生理变化的实验研究

目的:探讨放射照射后牵张成骨过程中下牙槽神经的电生理变化。方法:12只中国杂种犬随机分为A、B、C三组,A、B、C组为实验组,每组4只,单侧下颌A组接受总剂量22.8 Gy,5.7 Gy/4次/2周(相当于50 Gy/25次/5周),B组接受总剂量24.8 Gy,6.2 Gy/4次/2周(相当于60 Gy/30次/6周),C组接受总剂量27.2 Gy,6.8 Gy/4次/2周(相当于70 Gy/35次/7周)的⁶⁰Co放射照射。放射照射完成后3个月时,各组分别于照射区下颌骨切开,置入牵张器。经五天延迟期,以0.5 mm/次,2次/d的速度牵张下颌骨10 d,然后固定8周。分别于放疗前、放疗结束后、牵张前、牵张第6天、牵张完成即时、固定第2,4,8周8个时间点以神经电生理检诊仪测定神经电生理变化。结果:50 Gy和60 Gy组牵张过程中动作电位呈现适应性变化,70 Gy组不能完整导出动作电位。结论:低剂量放射照射不会单独对牵张过程中神经电生理变化造成影响,高剂量放射照射不能完成电生理检查。     

下颌骨牵张成骨对下牙槽神经影响的实验研究

目的　观察狗双侧下颌骨牵张成骨术中不同时间点的下牙槽神经的电生理功能及组织学结构的变化。方法　实验组 :12只狗行保留下牙槽神经的双侧下颌骨截断术 ,装上自制的口内牵张器 ,于术后第 8天开始牵张 ,1mm/d ,共 10d ,牵张长度约 10mm。分别在牵张中第 6天、牵张完毕后固定 2周及 8周时各处死 4只动物。分别在术前及术后的不同时期用电生理方法检测双侧下牙槽神经的传导功能 ,并于处死前取出双侧下牙槽神经进行组织病理学及超微结构组织学检查。对照组 :4只狗 ,其中 2只狗作为对照组 ,未行手术 ;另 2只狗为手术对照组 ,进行与实验组相同的骨切开截断术 ,上牵张器 ,但未行牵张和固定 ,于操作完毕时取出双侧下牙槽神经作为术后的组织学结构标本。结果　实验组动物的下牙槽神经在光镜下显示部分神经纤维稍肿胀变粗 ;电镜下显示部分神经纤维髓鞘的板层松解及脱髓鞘现象 ;电生理结果显示 ,神经传导的速度于截断术后的不同时期均低于术前 ,但仅术后第 8天 (即牵张前 )的传导速度与术前的传导速度差异有显著性 (P <0 .0 1)。结论　对狗的双侧下颌骨进行牵张成骨时 ,可一过性引起下牙槽神经损伤。其损伤的主要原因是手术过程所致。在适当的牵张速率、牵张长度和牢固的固定条件下 ,下颌骨的牵张成骨术对下牙槽 还原。     

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。     

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。     

丹参酮Ⅱa磺酸钠对兔下颌骨牵张成骨促进作用的研究

目的：探讨丹参酮Ⅱa磺酸钠注射液对兔下颌骨牵张成骨的作用。方法：将12只大耳白兔随机分为对照组和实验组,建立单侧兔下颌骨牵张成骨模型,实验组自牵张期开始每日注射丹参酮Ⅱa磺酸钠注射液3mL,并分别于固定期1周、4周、7周各处死2只对照兔和2只实验兔,对标本进行大体观察、X线观察、组织学观察和骨组织计量学观察。结果：实验组动物牵张间隙内新骨形成速度及质量均优于对照组,实验组成骨细胞活跃,骨小梁较成熟,单位面积内成骨细胞个数及骨小梁面积百分比均高于对照组。结论：丹参酮Ⅱa磺酸钠对兔下颌骨牵张成骨过程具有促进作用。     

下颌骨缺损牵张成骨动物模型的建立

目的建立兔下颌骨缺损牵张成骨动物模型,为进一步研究牵张成骨奠定实验基础。方法25只健康成年兔随机分成6组,实验组5组,每组4只,对照组1组共5只。25只兔均行一侧下颌骨切开截骨术,实验组安置自行设计的下颌骨牵张器,经6 d间歇期后,以每天2次,每次0.4 mm的速度牵张8 d进入固定期,于牵张中期(牵张第4天)、牵张末期(牵张第8天),固定期第2、4、6周分别处死4只动物;对照组术后仅保持缺隙而不牵张,与实验组对应的每个时间点处死1只动物,取下颌骨观察骨愈合情况。结果牵张器牵张效率好,固位稳定,实验组动物的下颌骨被成功牵张,牵张区可见新骨形成。实验对照组表现为不同程度的骨不连及骨缺损。结论本研究建立的兔下颌骨缺损牵张成骨模型是较理想的动物模型。     

种植型骨牵张器的初步实验研究

目的：了解种植型骨牵张器的牵张成骨效果及骨结合情况。方法：杂种犬6只,拨除双侧下颌前磨牙,12周后随机选取一侧犬下颌牙槽嵴,矩形截骨,植入种植型骨牵张器,延迟1周后垂直牵引加高牙槽嵴,1次／d,1.05mm/次,共加力牵引4d,固定6周,并进行X线和组织学观察。结果：除一枚牙种植型牵引器因伤口感染发生松动而取出外,其余牵引器与周围组织均愈合良好,牙槽嵴平均加高4．00mm,X线显示牵引6间隙消失,牵引器的周围骨组织密合,组织学观察牵张间隙被成熟新生骨修复,牵张器－肌界面形成良好的骨性结合。结论：种植型骨牵张器可用于垂直牵张加牙槽嵴,并可发生骨结合。     

bFGF—in vivo基因治疗促进兔下颌牵张成骨的实验研究

目的：探讨碱性成纤维细胞生长因子（bFGF）基因促进兔下颌牵张成骨的可行性。方法：选用16只新西兰白兔,建立下颌牵张模型后随机分为实验组和对照组。在牵张结束的最后1d,对实验组的牵张间隙内注入转染重组腺病毒（Ad5一bFGF）,而对照组的牵张间隙内则注入生理盐水。并于牵张结束后4周处死所有实验动物,将取下的下颌骨标本分别进行影像学和组织学分析。结果：影像学、组织学以及三维CT重建结果证实：实验组牵张间隙内新骨形成的量明显高于对照组;双能X线（DXA）分析也显示实验组牵张间隙内新骨的骨密度（BMD）和骨矿物质含量（BMC）均明显高于对照组。结论：bFGF—invivo基因治疗可有效地促进DO过程中的新骨形成。     

变速牵引成骨对兔下牙槽神经的影响

目的　研究变速牵引兔下颌骨15mm对下牙槽神经的影响。方法　5只新西兰白兔单侧下颌骨截开。延迟5d ,以每天1 5mm ,每天2次牵引9mm ,然后继续以每天1mm ,每天2次牵引6mm ,完成牵引后固定15周,分别行肉眼及组织学观察和电生理学检查。结果　下颌骨延长15mm ,新骨生成良好。下牙槽神经牵长2 1. 99% ,牵引结束时神经变性明显,感觉神经动作电位波幅下降为术前的9. 70 % ,潜伏期较术前有所延长,随后出现恢复趋势,到固定15周时,波幅恢复到术前的33. 85 % ,潜伏期基本恢复正常。结论　下颌骨变速牵引15mm后,下牙槽神经受到明显的影响,到15周时,下牙槽神经的功能有恢复的趋势,但恢复尚不完全。     

下颌骨牵引成骨术对免下牙槽神经的影响

新西兰白兔16只，以不同的牵引速度和牵引距离组合，随机分成5组。通过肉眼观察、X线片及电生理检查、组织学观察等了解下颌骨成骨及下牙槽神经再生情况。结果：以2．0mm／d速度牵引下颌骨会产生骨不连接，以1．5mm／d速度牵引颌骨15mm，虽可获得良好的成骨，但可造成下牙槽神经不可逆性的损伤。     

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.     

Implant osseointegration in the irradiated mandible. A comparative study in dogs with a microradiographic and histologic assessment

This research focuses on the effects of radiotherapy on the osseointegration of dental implants placed before or after radiotherapy in 11 male beagles. After the extraction of all mandibular premolars 1st and 2nd molars, three dogs were implanted without radiotherapy (Control group), four dogs were irradiated 4 weeks after implantation (IrA group) and four dogs were irradiated 8 weeks before implantation (IrB group). Eight implants were placed in each dog, in an alternating pattern: four nonsubmerged ITI Bonefit titanium plasma spray-coated and four submerged Steri-Oss hydroxyapatite-coated. The irradiated dogs received 4.3 Gy daily for 10 days. Two different fluorescent markers were administered at the time of implantation and of irradiation. The dogs were sacrificed 6 months after implantation, i.e. 5 months after radiotherapy for the IrA group and 8 months for the IrB group. Each mandible was submitted to histological and microradiographic analysis. Bone formation occurred around 85 of the 88 implants and consisted mostly of the successive deposit of woven and lamellar bone. Both irradiated groups showed obvious bone remodeling in alveolar bone as well as in the basilar part of the mandible. Nevertheless, in the IrA group, the resorption phenomena predominated over osteogenesis. The balance between these two opposite processes seemed to be restored 8 months after the end of radiotherapy (IrB group). In spite of focal lesions of radiation-specific bone destruction emphasized in some irradiated dogs, we conclude from our results that osseointegration of dental implants is possible in irradiated bone tissue.     

Evaluation of the consolidation period during osteodistraction using computed tomography.

The use of distraction osteogenesis offers an alternative approach to the correction of craniofacial deformities. However, little is known with respect to the appropriate length of the consolidation period for the newly formed bone. The objective of this study was to evaluate, by quantitative computed tomography, the regenerate bone produced during osteodistraction of the dog mandible at three different consolidation times. Twelve skeletally mature male beagle dogs were equally separated into three experimental groups. Each dog underwent 10 mm of bilateral distraction osteogenesis to lengthen the mandible. After the distraction period, the bone was allowed to consolidate for 4, 6, or 8 weeks, at which time the animals were sacrificed and the mandibles harvested for computed tomographic imaging. The results demonstrate a significantly lower mean bone density of the regenerate in the 4 week group when compared with either the 6 or 8 week groups (P < .01). There was no significant difference, however, in mean bone density between the 6 and 8 week groups.     

Osteodistraction of a previously irradiated mandible with or without adjunctive hyperbaric oxygenation: an experimental study in rabbits

The purpose of this study was to analyse the effects of irradiation and hyperbaric oxygenation (HBO) on mandibular osteodistraction (OD). Eighteen rabbits were divided into three groups: 1. Irradiation (R), 2. Irradiation+HBO (R-HO), and 3. Control group (C). Animals of groups R and R-HO received in the mandible irradiation 22.4 Gy in four 5.6 Gy fractions (equivalent to 50 Gy/25 fractions). In addition, group R-HO was given HBO at 2.5 ATA for 90 min per day 18 times preoperatively. Unilateral osteotomy was made 1 month after completion of radiotherapy. After a 1 week latency period bone distraction was started at rate of 1 mm per day, continued for 2 weeks, and left to consolidate for 4 weeks. Amount of new bone was measured histomorphometrically from midsagittal sections. Area of new bone was equal in all groups. Bone was more mature and bone spicules better organized in group C than in groups R and R-HO. Cartilaginous cells were found in distracted bone in all groups but larger chondroid islands were evident only in group R. It seems that despite delayed bone formation, OD can be performed after radiotherapy. HBO had a beneficial effect on bone quality of a previously irradiated mandible.     

Distraction osteogenesis after membranous bone onlay grafting in a dog model.

PURPOSE: The purpose of this experiment was to study the possibility of distraction osteogenesis in a membranous bone onlay graft to the mandible and to clarify the histology of the bone repair. MATERIALS AND METHODS: Four dogs, 5 months of age at the beginning of the experiment, were used for this study. The zygomatic arch was exposed in the subperiosteal plane, and a 3-cm long, full-thickness portion of the arch was harvested. The lateral surface of the mandibular body was exposed in the subperiosteal plane, and the bone was fixed to the lateral surface as a membranous onlay graft using screws. A vertical osteotomy through the graft and underlying mandibular body was done postoperatively at week 1 in dog 1, week 2 in dog 2, week 3 in dog 3, and week 4 in dog 4. An external distraction device was applied to the mandibular body, and distraction was started 7 days after the operation at a rate of 1 mm/d for 10 days. After completion of distraction, the device was left in place for 6 weeks to allow for bony consolidation. Radiographs were carried out at 2, 4, and 6 weeks postdistraction. All dogs were killed 6 weeks after distraction. RESULTS: New bone between the native underlying mandibular segments was generated in the distraction zone in all dogs. New bone was not generated between the segments of the membranous bone onlay graft in dog 1, but was generated in dog 2, dog 3, and dog 4. However, in dogs 2 and 3, the new bone between the segments was less firm, with more fibrous tissue, than the bone between the native underlying mandibular segments. Histologically, the distraction gap between the segments of the membranous bone onlay graft in dogs 2 and 3 was composed of considerable fibrous tissue in the central zone and activated osteoblastic cells forming new bone in the margins. In dog 4, there was much more osteoblastic activity in the distraction gap, and the new bone had the appearance of almost normal cortical bone. CONCLUSION: These findings show that distraction osteogenesis is possible in a membranous bone onlay graft and suggest that the distraction should be performed at least 4 weeks after the onlay grafting.     

Consolidation period in alveolar distraction: a pilot histomorphometric study in the mandible of the beagle dog

PURPOSE: Osteogenic alveolar distraction remains in an experimental stage. The present study aimed to compare histologic and histomorphometric results with 2 different consolidation periods (4 and 8 weeks) to determine which period obtained better bone quality after distraction with a prototype alveolar distractor. MATERIALS AND METHODS: Five beagle dogs were used. Four underwent alveolar distraction in an edentulous segment of the right mandible. After a 7-day latency period, distraction was carried out at a rate of 1 mm/d for 5 days; the consolidation period was 4 weeks in 2 dogs (group 1), and 8 weeks in the other 2 (group 2). The fifth dog was used as control (group 3); it underwent removal of its right premolars but not distraction. Histologic and histomorphometric studies were conducted. RESULTS: One animal from each distraction group was withdrawn from the study because of wound dehiscence that allowed invasion of mucosa into the distraction chamber, which was incompatible with bone regeneration. In the group 1 animal, a predominance of immature woven bone was observed in the distraction chamber, whereas the group 2 animal showed a predominance of immature parallel-fibered bone. The group 1 and 2 animals that remained in the study differed in bone area density in the distraction chamber (36.61% +/- 9.79% versus 58.72% +/- 8.30%), bone perimeter in the distraction chamber (262.89 +/- 10.46 mm versus 201.44 +/- 22.64 mm), total height attained (21.31 +/- 0.32 mm versus 18.37 +/- 0.50 mm), lingual trabecular width (134.00 +/- 15.56 versus 229.50 +/- 29.24), buccal trabecular width (90.00 +/- 4.24 mm versus 154.50 +/- 21.64 mm), lingual osteoid area density (4.08% +/- 0.46% versus 1.61% +/- 0.33%), and buccal osteoid area density (3.75% +/- 1.28% versus 2.09% +/- 0.79%). CONCLUSION: Quantitative and qualitative differences in newly formed bone were observed after 4 and 8 weeks of consolidation. These preliminary results serve as a basis for further experimental research with larger samples and for clinical studies.     

牵张成骨区牙移动动物模型的建立

目的:建立双侧下颌骨牵张成骨区快速正畸牙移动的实验动物模型,为其后的系列研究建立可靠的实验平台。方法:选择8只牙列完整的Beagle犬,其中4只犬建立双侧下颌骨牵张成骨动物模型,牵张完成后即刻以150g力远中移动下颌第三前磨牙进入牵张成骨区;另外4只犬拔除双侧下颌第四前磨牙后3个月,以150g力远中移动下颌第三前磨牙。实验中,每周加力1次,拍摄X线片并记录牙移动速率。牙移动8周后,观察实验牙及其牙周组织特点。结果:接受牵张成骨手术的4只犬,双侧下颌骨均被成功延长1cm,前牙出现反合,无实验犬死亡。实验牙借助自制的持续加力装置移动进入牵张成骨区。实验组牙移动显著快于对照组,X线观察实验组牙移动进入牵张成骨区,牙根未见明显吸收。组织学观察压力侧牙槽骨和牙周膜未出现不可逆性损伤。结论:以Beagle犬为实验对象,用成品牵张成骨器借助种植支抗钉和自制的牙移动装置远中移动下颌第三前磨牙,可建立可靠的动物模型。     

Distraction osteogenesis after irradiation in rabbit mandibles

The aim of this study was to investigate the influence of irradiation on the formation of bone after distraction osteogenesis in rabbit mandibles. Sixteen rabbits were randomly divided into 3 groups: one was given 50Gy (n=6), one was given 60Gy (n=6), and one acted as a control group (n=4). One month after irradiation, the distractors were inserted. The control group was not irradiated. After a latency period of 8 days, distraction was activated at a rate of 0.4mm twice a day. The mandibles were harvested 6 weeks after consolidation. The specimens and histological examination showed good formation of bone. Histological slides stained with haematoxylin and eosin confirmed that the regeneration was bone. The bony trabeculae of the control group were much better than those of the irradiated groups. However, the nuclei of osteocytes were round and the osteoblasts around the trabeculae were columnar or cubic in shape in the irradiated groups. Osteoid was present in the dense fibrous connective tissue. There were significant differences in the surface:volume ratio of areas of bony trabeculae between the control and both experimental groups (p=0.010 and p=0.001), but there was no significant difference between the 50Gy and 60Gy groups. The results suggested that preoperative radiation prevented optimal regeneration of bone. However, the microscopic appearance of osteocytes and osteoblasts and the osteoid in the dense fibrous connective tissue in both irradiated groups showed that osteogenesis was still active and in progress. These findings may indicate that bone formation had only been delayed. The evidence was similar for both 50Gy and 60Gy.