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。     

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。     

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。     

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.     

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.     

Technetium-methylene diphosphonate bone imaging using low-intensity pulsed ultrasound: promotion of bone formation during mandibular distraction osteogenesis in dogs

Our objective was to assess the value of ^99mtechnetium-methylene diphosphonate (^99mTc-MDP) bone imaging in the use of low-intensity pulsed ultrasound to promote bony formation during mandibular distraction osteogenesis in dogs. The body of the mandibles in 7 dogs were cut between the first and the second premolar and were lengthened at the rate of 1 mm/day, twice a day, for 20 days. During the period of distraction one lateral distraction gap was irradiated with low-intensity pulsed ultrasound (LIPUS) for 10 min twice a day, and the other side was used as control. Serial radiographic inspections were made at different periods (0, 1, 2, 4, 6, 8, and 12 weeks) during the consolidation phase, followed by a plain radiograph and histological examination. The ^99mTc-MDP imaging showed that the ratio of bone formation on the LIPUS-treated side was significantly higher than that on the control side during the early period of consolidation (before the 4th week), but later this was reversed and there were no significant differences between the two sides by the 12th week. Plain radiographs and histological examination showed that the new bone on the experimental side had matured earlier than that on the control side. Radionuclide bone imaging is a good way to assess the formation of bone after distraction osteogenesis.     

Effect of icariin on bone formation during distraction osteogenesis in the rabbit mandible

The aim of this study was to evaluate the effect of icariin on bone formation during mandibular distraction. 40 Rabbits were randomly divided into experimental and control groups. Mandibular distraction was performed 5 days after unilateral mandibular osteotomy using a custom-made external distractor at a rate of 0.5 mm/12 h for 10 days. From the first day of distraction, icariin (2.5 mg/kg·day) was orally administered to the experimental group and placebo to the controls. 10 Rabbits were killed at the end of weeks 2 and 4 of the consolidation phase. The distracted hemimandible was harvested and newly formed bone was evaluated by soft radiography, histology and bone histomorphometry. Regenerated bone was evaluated for bone mineral density by dual-energy X-ray absorptiometry. The experimental group had fewer radiolucent areas on soft radiography. Bone mineral density of regenerated bone was higher in the experimental than in the control group at 2 and 4 weeks. At 4 weeks, the experimental group had greater volumes of new bone, higher trabecular number, and less trabecular separation than the controls. Oral administration of icariin could promote bone formation during mandibular distraction osteogenesis and might be a promising method for shortening the course of distraction osteogenesis.     

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.     

Effects of irradiation on bone remodelling around mandibular implants: an experimental study in dogs

This research focuses on the effects of radiotherapy on bone remodelling around mandibular implants in dogs. After bilateral extraction of the mandibular premolars and first 2 molars, each of 11 beagles received 8 mandibular implants. Four animals were irradiated 4 weeks after implantation and 4 others 8 weeks before implantation; the remaining 3 did not receive radiotherapy. Irradiation consisted of 10 daily fractions of 4.3Gy (60)Co. Fluorochromes were given at implantation and irradiation to allow the measurement of bone apposition. The dogs were killed 6 months after implantation. Each hemi-mandible was processed according to bone-specific histological techniques. New bone formation was visible around 85 of the 88 implants. Stimulated mandibular remodelling was attested in both irradiated groups by increased porosity and numerous labelled osteons. Resorption was more pronounced in the group irradiated after implantation, but osteon formation appeared unvarying. Osseointegration was thus shown to be compatible with bone irradiation as bone turnover activities were maintained throughout the experiment. As the apposition stage of the remodelling cycle appears crucial to achieve optimal osseointegration, its normal completion should be taken into account in clinical practice by respecting a 6-month period between irradiation and implantation.     

Comparing calvarial transport distraction with and without radiation and fat grafting

The purpose of this study is to: a) assess transport distraction to reconstruct cranial defects in radiated and non-radiated fields b) examine adipose grafting's effect on the bony regenerate and overlying wound, and c) elucidate sources of bone formation during transport distraction osteogenesis.Twenty-three male New Zealand white rabbits (3 months; 3.5 kg) were used, 10 non-irradiated and 13 irradiated (17 treatment, 6 control) with a one-time fraction of 35 Gy. A 16 × 16 mm defect was abutted by a 10 × 16 mm transport disc 5 weeks after irradiation, and 11 animals were fat grafted at the distraction site. Latency (1 day), distraction (1.5 mm/day), and consolidation (4 weeks) followed. Fluorochromes were injected subcutaneously and microCT, fluorescence, and histology assessed.In distracted animals without fat grafting, bone density measured 701.87 mgHA/ccm and 2271.95 mgHA/ccm in irradiated and non-irradiated animals. In distracted animals with fat grafting, bone density measured 703.23 mgHA/ccm and 2254.27 mgHA/ccm in irradiated and non-irradiated animals. Fluorescence revealed ossification emanating from the dura, periosteum, and transport segment with decreased formation in irradiated animals.Transport distraction is possible for cranial reconstruction in irradiated fields but short-term osseous fill is significantly diminished. Adipose grafting enhances wound healing in previously irradiated fields but does not enhance ossification.     

The effect of irradiation and hyperbaric oxygenation (HBO) on extracellular matrix of the condylar cartilage after mandibular distraction osteogenesis in the rabbit

The effects of irradiation and hyperbaric oxygenation (HBO) on the extracellular matrix of condylar cartilage after mandibular distraction were evaluated. Unilateral distraction was performed on 19 rabbits. Five study groups were included: control, low- and high-dose irradiation, and low- and high-dose irradiation groups with HBO. Additionally, four temporomandibular joints (TMJ) were used as control material. The high-dose irradiated animals were given in the TMJ 22.4 Gy/4 fractions irradiation (equivalent to 50 Gy/25 fractions). Low-dose irradiation group received a 2.2 Gy dosage. Two groups were also given preoperatively HBO 18 x 2.5ATA x 90 min. After a two-week distraction period (14 mm lengthening) and four-week consolidation period the TMJs were removed. Proteoglycan (PG) distribution of the extracellular matrix was evaluated using safranin O staining and collagen I and II using immunohistochemistry. The organization of fibrillar network was studied by polarized light microscopy. On the operated side of the control group and on the unoperated side in all, except for high-dose irradiated group, PG distribution and fibrillar network were normal appearing. In the irradiated groups, with or without HBO, the cartilaginous layer was partially or totally devoid of PG and the network structure was severely damaged. In conclusion, irradiation in conjunction with the pressure applied by distraction causes severe damage to extracellular matrix of condylar cartilage.     

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.     

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.     

The role of hyaluronic acid,chitosan, and calcium sulfate and their combined effect on early bony consolidation in distraction osteogenesis of a canine model

The purpose of this project was to study the effect of hyaluronic acid, calcium sulfate, and chitosan on early bony consolidation in distraction osteogenesis of a canine model. Sixteen dogs were used for this study. The lateral surface of the mandibular body was exposed in the subperiosteal plane, and the vertical osteotomy on the mandibular body was extended downward. An external distraction device was applied to the mandibular body, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was then divided into a control group, chitosan group, hyaluronic acid group, calcium sulfate combined with hyaluronic acid group, and calcium sulfate combined with chitosan group, depending on the type of implantation material in the distracted area. After completing the distraction, implantation material was injected into the distracted area, although no material was implanted into the distracted area of the control group. After implanting the materials, the distraction device was left in place for 6 weeks to allow for bony consolidation. Four dogs were allocated to each group. Two dogs in each group (total of 8 dogs) were killed 3 weeks after implantation of the material, and the other 8 dogs were killed after 6 weeks. New bone was generated in the distracted zone of all groups. In the calcium sulfate combined with chitosan group and calcium sulfate combined with hyaluronic acid group, the formation of active woven bone was observed throughout the distracted zone. Moreover, the new bone seemed to be nearly normal cortical bone at 6 weeks after implantation. In the chitosan group and hyaluronic acid group, the development of new bone was observed in the distracted zone at 6 weeks. The amount was less than that in the calcium sulfate combined with hyaluronic acid group and calcium sulfate combined with chitosan group. These findings suggest that calcium sulfate and its combined materials seem to be quite effective in early bony consolidation in distraction osteogenesis.     

BMP-2 and bFGF in an irradiated bone model.

INTRODUCTION: Basic fibroblast growth factor (bFGF) is considered to enhance angiogenesis and to support bone formation in the presence of vital bone cells. Bone morphogenetic protein-2 (rhBMP-2) is known to induce bone formation. The aim of this study was to analyze the effect of bFGF and rhBMP-2 in the irradiated mandible. MATERIAL AND METHODS: The right mandibles of 24 rats were irradiated with a single dose of 20 Gy at a high-dose-rate (HDR) after loading machine (bio effective equivalent dose to ca. 45 x 2 Gy). After 12 weeks 100 microg rhBMP-2 (n=6 animals, group 1), 100 microg bFGF (n=6 animals, group 2) and 100 microg rhBMP-2 plus 100 microg bFGF (n=6 animals, group 3) were injected along the right mandible (left mandible: no irradiation, no growth factor). Another 6 animals (group 4) remained untreated after the irradiation. After another 7 weeks the specimens were examined by non-decalcified histology. RESULTS: Bone apposition of the experimental versus control sides was not statistically significantly different when one of the growth factors was applied alone (rhBMP-2: p=0.917; bFGF: p=0.345). Average bone apposition was significantly decreased on the experimental sides of group 3 (rhBMP-2+bFGF: p=0.046) and group 4 (p=0.008). Average bone densities were unaffected in all settings (for all p>0.1). CONCLUSIONS: The application of bFGF and the application of rhBMP-2 alone did result in predictable bone generation in the irradiated mandible with the bone apposition being equal to that of the non-irradiated side. The application of both growth factors together or none at all after irradiation results in significantly reduced bone apposition.     

The bone regenerative effect of chitosan microsphere-encapsulated growth hormone on bony consolidation in mandibular distraction osteogenesis in a dog model

The purpose of this project was to study the effect of chitosan microsphere-encapsulated human growth hormone, which causes sustained release of chitosan and human growth hormone after implantation on early bony consolidation in distraction osteogenesis of a canine model. Forty-eight dogs were used for this study. An external distraction device was applied to the mandibular body after a vertical osteotomy, and the mandibular distraction was started 5 days after the operation at a rate of 1 mm/d up to a 10-mm distraction. The experimental group was divided into a control group (I), hyaluronic acid group (II), chitosan microsphere group (III), and chitosan microsphere-encapsulated human growth hormone group (IV). Normal saline was injected in group I. In group II, a 1-ml volume of hyaluronic acid solution was injected into the distracted area. In the group III, powder of chitosan microspheres and hGH were mixed with a 1-ml volume of hyaluronic acid to make an injectable form, and it was implanted into the distracted area. In group IV, powder of chitosan microsphere-encapsulated hGH was mixed with a 1-ml volume of hyaluronic acid. A total of 1-ml volume of the solution mix was implanted into the distracted area. Five dogs in each group (total of 20 dogs) were killed 3 weeks after completion of distraction. Twenty-eight dogs were killed at 6 weeks. Bone mineral density was 13.1% of the contralateral normal mandible at 3 weeks and 29.6% at 6 weeks in group I, 16.4% at 3 weeks and 40.4% at 6 weeks in group II, 16.6% at 3 weeks and 45.95% at 6 weeks in group III, and 29.6% at 3 weeks and 66.7% at 6 weeks in group IV. The mean three-point failure load was 16.1% in the control group, 34.7% in group II, 41.5% in group III, and 52.1% in group IV compared with the intact contralateral mandible, with statistical significance. In the histological findings, new bone was generated in all groups. In group IV, the formation of active woven bone was observed throughout the distracted area at 6 weeks. The amount of new bone formation in the distracted zone was in the order of group IV, group III, group II, and the control group. In conclusion, these findings suggest that chitosan microsphere-encapsulated hGH seems to be quite effective in early bone consolidation in distraction osteogenesis.     

Soft tissue changes during distraction osteogenesis

This study aimed to investigate soft tissue changes in distraction osteogenesis depending on various distraction and consolidation periods. Fifteen male rabbits were divided into three groups and evaluated for five parameters. An external custom-made device was placed on the right side of the mandible. The postoperative latent period was 4 days. The groups were distracted for different periods (6 days, 3 mm; 11 days, 5.5 mm, 16 days, 8 mm). For histomorphometric analyses, specimens were retrieved from both study and control sides of the mandible and were examined with light microscopy. The number of muscle fibres and nuclei on the study side increase proportionally with the distraction period. Regeneration in the first group continued in its natural pattern; in the second group, there seemed to be degeneration rather than regeneration; and in the third group there seemed to be a balance between regeneration and degeneration processes. In conclusion, when a massive amount of bone is to be obtained, instead of distracting the bone at once, it is thought to give better results if the total amount of distraction is divided into several time periods.     

Einfluss von bFGF auf die Regeneration von distrahierten Unterkiefern nach Radiatio

The potential of distraction osteogenesis in mandibular reconstruction has been limited by its questionable efficacy in previously irradiated bone. The possible osteogenetic effect of recombinant human basic fibroblast growth factor (bFGF) on lengthening of irradiated mandibles was investigated in beagle dogs. We studied nine adult dogs which underwent a full course of external beam radiation therapy (60 Gy/30 fractions). Six months after completion of radiotherapy, the molars were extracted bilaterally followed by bone lengthening of the mandible using an intraoral device. On postoperative day 3 and 7 we injected 10 μg bFGF into the osteotomy site of each right hemimandible. The left sides were used as controls. The time course in ossification of the distracted area was evaluated at 2, 4, and 6 weeks after completion of bone lengthening. The radiographs of the newly formed bone tissue were measured by digital image analysis. Corresponding to the radiographic findings, the histological examination of the removed jaws showed an earlier and more intensive bone formation in the treated side after 2, 4, and 6 weeks compared to the control side. We conclude that bFGF promotes the ossification of distracted mandibles after radiation therapy in dogs.     

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。     

Experimental study of mechanical analysis in mandibular lengthening. Application of strain gauge measurement

In distraction osteogenesis, the assessment of new bone formation and the decision of when to remove the distraction device are very important from clinical viewpoint. The purpose of this study was to measure bone stiffness using a strain gauge during and after mandibular lengthening, and to compare the results with those from radiographic and histological examinations. Twelve adult mongrel dogs served as the experimental subjects. An external distraction device was connected to the mandible, and distraction was started 7 days after operation and continued for 10 consecutive days. The animals underwent strain gauge measurement and radiographic examination of the mandible at the completion of distraction and every 2 weeks until the end of the consolidation period. The animals were then sacrificed at 2, 4, 6, 8, 10, and 12 weeks after completion of the distraction for histologic examinations. There was correlation between the amount of decrease in strain, increase in ratio of radiopacity, and newly formed bone in the distracted area.