Use of an internal bidirectional distractor to elongate goats' mandibles

We investigated the feasibility of using an internal bidirectional mandibular distractor to elongate the mandibular bodies and rami of 4 mature male goats. An osteotomy was made at the right mandibular angle and the distractor placed within the osteotomy and allowed to heal in place for 5 days. The mandibles were simultaneously distracted vertically and horizontally at a rate of 0.5mm/day for 30 days. After a 12-week consolidation period, all the goats were killed for gross, radiographic, and histological evaluation. Smooth new bone had been restored in the distracted area after 12 weeks' consolidation, and the gross, radiographic, and histological evaluations showed that the new bone was similar to the native bone. These results suggest that the internal bidirectional distractor could permit bidirectional distraction osteogenesis in a goat model.     

不同牵张速率对山羊下颌骨牵张成骨中新骨形成的影响

目的:探讨山羊下颌骨牵张成骨中不同牵张速率对术后新骨形成的影响。方法:12只山羊随机分为3组,每组各4只,在对动物右下颌骨行骨皮质切开术后进行牵张,第1组动物以0.8mm/d的牵张速率进行牵张,第2组动物以1.6mm/d的牵张速率进行牵张,第3组动物以2.0mm/d的牵张速率进行牵张,随机选取实验组4只动物未手术侧正常下颌骨作为对照组。将各组新骨组织和对照组下颌骨组织分别进行骨密度检测和三点弯曲测试,对采用不同速率进行骨牵张后动物下颌骨新骨的生物力学强度和骨密度进行了对比观察。结果:0.8mm/d牵张组新骨骨密度值显著高于其余各牵张组,0.8mm/d牵张组新生骨三点弯曲实验指标均大于另2牵张组。结论:采用0.8mm/d的牵张速率进行牵张能最快促进新骨形成,提高成骨质量。     

Effect of recombinant human bone morphogenetic protein-2 on mandibular distraction osteogenesis

The purpose of this investigation was to study the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone formation of mandibular distraction osteogenesis. Six skeletally mature sheep underwent 10 mm of bilateral mandibular distraction osteogenesis via a custom-made distractor. Three micrograms of rhBMP-2 with a collagen carrier was implanted in the osteotomy site of one side of the mandible during the osteotomy phase. The contralateral side was used as the control group, and no material was implanted into the distracted area. At 10 days after the end of distraction, all animals were killed, and the distracted calluses were harvested for radiologic and histologic analysis. New bone was generated in the distracted zone in all groups. Histologic and radiologic examination showed that the new bone formation was greater in the rhBMP-2 group than in the control group. Quantitative computed tomography evaluation, however, did not demonstrate a significantly different mean bone density of the regenerates between the 2 groups. The results indicate that application of a rhBMP-2/collagen implant during the osteotomy phase of distraction osteogenesis increased bone formation but did not have a significant effect on bone density of the regenerates.     

核素骨显像在局部应用rh-BMP/bFGF加速山羊下颌骨牵张成骨实验研究中的应用价值

目的:应用核素骨显像观察局部应用rh-BMP/bFGF加速山羊下颌骨牵张成骨的效果.方法:利用外置式牵张器进行山羊下颌骨牵张成骨.将10只实验用山羊随机分为5组,每组2只,在下颌第2和第3前磨牙之间行骨皮质切开,将含有rh-BMP15mg及bFGF 2000 UI的载体胶原膜置入左侧牵张骨折间隙,即刻牵开1 mm以利容纳置入的载体胶原膜.对照侧不加生长因子,牵引速度同实验侧.术后5 d开始牵引,3 mm/d,0.5 mm/次×6次/d,分别于牵张完成当日及第2、4、6、12周时将动物进行放射性核素骨扫描检查.结果:随着时间的延长,在不同周期,实验侧牵张间隙中央出现核素浓聚,强度明显较对照侧强.牵张完成12周:实验侧和对照侧核素浓聚变弱,基本上回复到周围正常骨组织密度水平,两者差异明显减少.结论:局部应用rh-BMP/bFGF后实验侧下颌牵张后新骨生成速度和数量优于对照侧,说明外源性生长因子能够加速下颌骨牵张延长区的骨愈合,核素骨扫描检查在观察牵张成骨的效果中具有较高的应用价值.     

不同速率牵张山羊下颌后下齿槽血管变化与血管生成的实验研究

目的:研究不同速率牵张延长山羊下颌骨后下齿槽动静脉的变化和新骨组织内血管生成情况。方法:8只成年山羊随机分为3组,A组(3只)以110 mm/d牵张,B组(3只)以210 mm/d牵张,C组(2只)为对照。A、B两组均牵张延长下颌10 mm,于牵张结束固定后第2周时处死动物,取牵张区下齿槽动静脉及新骨组织行组织学和定量组织学研究,观察下齿槽血管的管壁厚度和管径大小变化,以及新骨中微血管数量变化。结果:两种速率牵张后均未见下齿槽血管壁有病理性改变,但210 mm/d组的血管管径变小,管壁变薄,与对照组相比有显著差异(P<0105)。110 mm/d牵张后微血管密度较210 mm/d牵张后微血管密度高,且新生骨小梁更为成熟,其差异具有统计学意义(P< 0105)。结论:下颌骨牵张后下齿槽血管无明显变化,但快速牵张可能对牵张间隙内血管生成有不良影响。     

山羊下颌牵张成骨的超微结构观察及新骨钙磷元素测定

目的为进一步探索DO的成骨方式和新骨改建过程提供实验依据。方法标本取自6只山羊双侧下颌骨牵张成骨形成的新生骨组织及其邻近原骨组织,用扫描电镜观察骨组织断面的超微结构,同时用X线能谱仪测定新骨Ca/P原子个数比及其动态变化。结果牵张间隙超微结构观察显示大量新骨组织生成,其骨质密度和钙、磷元素含量随牵张后固定时间的延长而趋于正常骨组织。结论山羊下颌牵张成骨形成的新生骨段可逐渐改建为具有正常结构的骨组织。     

不同牵张速率对下颌骨延长后新骨生成的影响

目的 :研究不同牵张速率延长下颌骨时对新骨生成的影响。方法 :将 12只山羊随机分为三组 ,行双侧下颌体骨皮质切开术后以三种不同牵张速率 (0 .5mm/d ,1mm/d ,2mm/d)向前延长下颌 10mm。牵张完成后第 2、4周各处死 2只山羊 ,取双侧牵张间隙内新骨组织作X光片、组织学、扫描电镜和能谱仪分析。结果 :以 0 .5mm/d和1mm/d牵张下颌骨后形成的新骨质量要好于 2mm/d。结论 :在牵张延长下颌骨时 ,1mm/d可能是最适宜的速率     

Mandibular distraction osteogenesis: a rabbit model using a novel experimental design.

PURPOSE: Distraction osteogenesis (DO) is a surgical procedure that targets bone regeneration and elongation, currently used in the treatment of many craniofacial deformities. The quest for optimization of DO clinical parameters has led to the development of a variety of animal models. Our study aims to establish a rabbit animal model of mandibular DO, in which the control osteotomy and distraction device are placed on the opposite hemimandible from the one being distracted, within the same animal host. Furthermore, we propose to histologically characterize the different stages or distraction and consolidation in the same animal model. MATERIALS AND METHODS: Twenty-five rabbits underwent mandibular osteotomies and bilateral placement of distraction devices. After a latency of 3 days, the distraction device was activated on one side of each animal at a rate of 0.5 mm/12 hours for 7 days, while the other side remained inactive (control). This was followed by a consolidation period of 14 days. Five animals per time-point were killed on days 3, 7, 10, 17, and 24. RESULTS: Gross tissue analysis showed a 7-mm callus formation at the distracted side and a well-healed osteotomy in the non-distracted side. Clinically, a unilateral Class III malocclusion occurred in the distracted side. Histology at each time-point shows new bone formation and orientation of the bony spicules along the axis of the mechanical strain. CONCLUSIONS: We have established and characterized an animal model of mandibular DO that outlines valid biologic controls and provides thorough monitoring of the DO process.     

不同速率牵张下颌后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率提供实验依据。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Ｗａｌｌｅｒ变性,以２ ｍｍ／ｄ牵张组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牵张速率为较适宜而安全的下颌牵张速率。     

羊颧骨缝三维牵张成骨的组织学观察

目的探索不截骨的骨缝牵张成骨组织学变化。方法采用10～13个月龄普通山羊为实验对象，每只动物左颧骨行三维牵张成骨，固定1、3、5、8周后取材，和对侧空白对照标本比较，观察缝区组织变化、新骨形成情况。结果骨缝被牵开后1周，成纤维细胞、成骨细胞、毛细血管增生，大量纤维软组织排列有序并连接骨缝两侧，骨缝两侧组织面不整齐，牵张侧成骨活跃，大量类骨质形成；3周时形成较成熟的骨小梁；5周时编织骨形成；8周时结构成熟完整。结论不截骨的骨缝三维牵张成骨，骨缝牵张侧新骨快速形成；     

Gonial angle changes after bilateral unidirectional mandibular distraction in sheep

It was the aim of this study to investigate radiologically the distraction site in the gonial angle area after three different protocols of unidirectional mandibular distraction in sheep. Bilateral mandibular distraction was performed in nine sheep, and one other sheep served as a sham-operated control. In the nine experimental sheep, three different distraction protocols were used. In three sheep, an oblique corticotomy line was applied and the distractors were positioned perpendicular to the corticotomy line. In three other sheep, a horizontal corticotomy line was applied and the distractors were also positioned perpendicular to this corticotomy line. In the remaining three sheep, again, a horizontal corticotomy was performed, but with an angular positioning of the distractors relative to this corticotomy line. Distraction of 20 mm was performed over 20 days at a rate of 1 mm per day. After 3 weeks of retention the sheep were sacrificed, the mandibles were dissected and hemisectioned, and standardized hemimandibular contact radiographs were made of the specimens. The distracted gaps were traced from the radiograph and the gonial angle was measured. The displacements of the distracted parts were measured, the gonial angles were determined, and the values were compared with four additional control non-distracted sheep mandibles. The results show that there was a very large variability in the distracted gaps as well as in the gonial angle changes after distraction, and it was not possible to recognize any of the three different distraction protocols radiographically after distraction. Although performed under standardized conditions it is difficult to reproduce intended mandibular corticotomy lines in sheep.     

Alterations of morphology and microdensity in the condyle after mandibular osteodistraction in the rat.

PURPOSE: In this study, we examined the effects of mandibular distraction osteogenesis on the morphology and the microdensity of the rat condyle. Materials and Methods: One hundred twenty-nine rats were allocated to 4 experimental groups (n = 32 or 33). Each received unilateral mandibular ramus osteotomy and distraction device placement. After a 3-day latency, these were distracted once a day for 5 days. The slow distraction group was distracted a total of 1 mm (0.2 mm/d); the moderate group, 2 mm (0.4 mm/d); the rapid group, 3 mm (0.6 mm/d); and the sham group, no distraction (0.0 mm/d). Eight to 9 rats in each group were sacrificed at each of 4 time points after device placement (6, 10, 24, and 38 days). Baseline data were obtained 3 days after osteotomy and device placement without distraction from an additional 10 rats. Radiographs of the hemimandibles were scanned and measured to evaluate changes in condylar size (height, width, and area), angulation, and bone microdensity converted to equivalent bone thickness using a stepwedge. The wet weights of masseter muscle were measured at the time of harvest. RESULTS: 1) Muscle weight gains over time were significantly lower in the treated than the untreated sides throughout the consolidation period (P <.001). 2) Condylar size and angulation on the untreated side increased postoperatively, whereas there was a significant reduction of these parameters (P <.01 to.001) on the treated side at 24 and/or 38 days. 3) Condylar microdensity significantly increased on the untreated side at 24 and 38 days (P <.05 to.01) but not on the treated side. 4) Faster or larger distraction caused more severe size reduction and more upright condylar angulation, prevented an increase in bone microdensity on the treated side, especially during the consolidation periods (P <.05 to.01), and retarded increase in muscle weight, whereas a slower distraction rate showed few negative, and even some positive effects. 5) Correlations in size, angulation, and microdensity between right and left condyles became less significant over time. 6) There were positive correlations between muscle weight and condylar size, angulation, and microdensity. CONCLUSION: An increased rate of mandibular distraction has significant negative effects on condylar morphology and microdensity.     

张应力诱导生长期山羊颅骨缝改建的实验研究

目的：研究处于生长发育期山羊颅骨冠状缝受张应力作用后的变化规律，探讨牙面矫形治疗的生物学原理。方法：选用处于生长期山羊12只，在颅骨冠状缝两侧安放自行研制的牵张器以每天0．4mm的速率进行骨缝牵张，连续加力8d后停止。在牵张结束后第0，2，4和8周分别处死3只动物，取骨缝标本进行X线检查和组织学观察。另选2只同龄山羊作为正常对照。结果：所有实验动物的冠状缝均被成功分离。在实验早期(0，2周)，扩大骨缝中可见大量胶原纤维沿牵张力方向有序排列，骨缝边缘有大量的成骨细胞并出现幼稚骨小梁。在实验后期(4，8周)，牵张骨缝新生骨组织改建活跃，骨缝组织结构最终基本恢复到正常状态。结论：骨缝组织受牵张力作用后将发生活跃的膜内成骨反应，主要集中于骨缝边缘，扩大的骨缝可以通过适应性改建恢复其正常结构。     

重组人骨形成蛋白-2促进兔下颌牵张成骨的研究

目的　研究局部应用基因重组人骨形成蛋白-2(rhBMP-2)对兔下颌牵张成骨的影响。方法　在12只成年大耳白兔的双侧下颌骨前部行骨切开术,将rhBMP-2与胶原复合植入一侧下颌骨切开处,另一侧单纯植入胶原作对照。用自行研制牵张器延长双侧下颌骨6 mm,在牵张结束后第4周处死动物,取双侧牵张区新生骨痂行组织学、扫描电镜及Ca/P元素测定。结果　下颌延长后两侧牵张间隙均有新骨形成,应用rhBMP-2的一侧牵张骨痂中的新骨组织比对照侧多而成熟,钙化程度较高。结论　基因重组人骨形成蛋白-2可能有促进兔下颌牵张成骨的作用。     

Preliminary investigation into the effects of electrical stimulation on mandibular distraction osteogenesis in goats

Craniofacial distraction osteogenesis (DO) was found to be a procedure with low preoperative and postoperative morbidity. Direct current electrical stimulation is used clinically to treat different orthopaedic problems. It provided a significant increase in new-bone formation, and a higher mechanical strength of healing.The purpose of this study was to test the effect of electric current on distraction osteogenesis and to establish the best period to apply an electric current during the different distraction phases.Twelve healthy adult goats were subjected to a vertical osteotomy in the symphyseal area. A distraction device was fixed to the bone. Animals were divided into two groups, Group I (three goats) and group II (nine goats). In group I, the device was activated 1mm per day for 10 days; while in group II, the device was activated 1mm per day for 10 days with the application of direct electric current stimulation of 10 microA either during the first 3 days of latency in a continuous mode (ESL group), or during the first 3 days of the activation period in a continuous mode (ESA group); or during the first 3 days of the consolidation period in a continuous mode (ESC group). After the activation period was completed, the distraction device left in place for additional 15 days for bone consolidation in all animals. Animals were then sacrificed, the mandible was harvested, and the distracted areas were removed and processed for mechanical and histological studies. The results of this study suggested that direct current electrical stimulation display synergism on mandibular distraction when this stimulation applied to the distraction zone during activation or consolidation periods.     

Three-dimensional sutural expansion osteogenesis to expand zygomatic bone: an experimental study

Sutural expansion osteogenesis was used to extend zygomatic bone three-dimensionally by the formation of new bone in eight goats. A 3 cm incision without osteomy was made in the infraorbital part of the zygomatic bone. The external expansion appliance was then placed on the zygomatic bone. The expansion appliance was activated 10 days after the operation at a rate of 0.9 mm/day for 10 days. The direction could be changed through turning the nuts and moving the brace boards. All the zygomatic bones were expanded anterosuperolaterally and inferolaterally by a mean of 9 mm (range 7.8-11.5mm). The regenerating bone tissues in the distracted sutures were recorded radiographically, clinically, and histologically. The experiment succeeded in expanding the zygoma quickly. The three-dimensional external expansion appliance was simple to operate. The result of sutural expansion osteogenesis is stable and credible, and the method is feasible.     

山羊下颌骨牵张成骨的生物力学研究

目的：探讨下颌骨牵张成骨进程中骨段间张力强度的变化特征。方法：8只山羊右下颌骨行骨皮质切开术并牵张后,对牵张期的每个工作日内的牵张前骨段间张力值、牵张时张力值和牵张后张力值进行测量分析,同时对固定期内的骨段间张力也进行了测量分析。结果：牵张期内骨段间张力值逐日显著增高,牵张期结束时达到峰值;固定期内张力值逐周显著下降,至骨皮质切开术9周后与施加牵张力前正常状态时骨段间张力值无显著性差异。结论：下颌骨牵张成骨进程中骨段间延长区组织所承受的张力值表现为先上升后下降的走势,这可能与骨周组织的适应性增长和新骨强度的逐渐增高有关。     

Reconstruction of curved mandibular angle defects using a new internal transport distraction device: an experiment in goats

A new internal distraction device, comprising a square-bodied bow, a transport plate, a traction mechanism, and two stabilisers, was developed to allow transportation of bone around an arc. Eight adult goats were studied. A curved mandibulectomy 3cm long was made on the mandibular angle. The distractor was implanted to restore the defect. The bone was distracted at a rate of 1mm per day after a 5-day latent period. Distraction lasted 25 to 32 days. Curvilinear distraction was successful in six of the eight goats. After consolidation periods of four or eight weeks, smooth curved bone masses were restored in the distracted areas. Radiographically, there was considerable bone density in the distraction area and opaque columns streamed in the direction of distraction. Histological examination showed membranous bony regeneration in the restored bone. These results suggest that restoration of curved bone defects using the new internal transport distraction device was feasible in goats.     

骨髓间充质干细胞移植对山羊颅骨骨缝牵张成骨的影响

目的研究自体骨髓间充质干细胞（MSCs）移植对生长期山羊颅骨冠状缝牵张后组织改建的影响。方法选用处于发育期山羊10只,随机分为实验组与对照组,各5只。在颅骨冠状缝两侧安放自行研制的牵张器,以每天0．4mm的速率进行骨缝牵张,连续加力8d。实验组动物骨缝牵张区给予注射自体骨髓间充质干细胞,对照组同期注射生理盐水。在牵张结束后第4周处死动物,取骨缝标本进行组织学和扫描电镜观察。结果所有实验动物的冠状缝均被成功牵开,骨缝边缘均可见新骨组织生成与改建。同对照组相比,实验组骨缝成骨与矿化较快,骨小梁分布密度及成熟程度也较高,骨缝形状已开始恢复正常。结论自体骨髓间充质干细胞移植对山羊颅骨缝牵张成骨可能有明显的促进作用。     

Changes in the inferior alveolar nerve after mandibular lengthening with different rates of distraction.

PURPOSE: This study investigated the changes in the inferior alveolar nerve after mandibular lengthening with different rates of distraction. MATERIALS AND METHODS: Bilateral mandibular corticotomies were performed in 8 goats. The mandibles in 6 goats were lengthened 10 mm using a custom-made distractor with 2 different rates of distraction (1 mm/d [n = 3] and 2 mm/d [n = 3]); the other 2 nondistracted mandibles served as a control. The goats with distracted mandibles were killed at 2 weeks after completion of distraction. The inferior alveolar nerve specimens from all animals were harvested and processed for histologic and ultrastructural evaluation. RESULTS: The mandibles were lengthened successfully in the distracted animals. Morphologic changes in the inferior alveolar nerves were observed when compared with the nondistracted controls. Moreover, signs of nerve degeneration, such as demyelination, axonal swelling, axoplasmic darking, and decrease in the number of axons, were more extensive and prominent in those nerves distracted at a rate of 2 mm/d. CONCLUSIONS: Degenerative changes in the inferior alveolar nerve occur after mandibular lengthening by distraction osteogenesis. The distraction rate of 1 mm/d appears to be tolerable and safe for the inferior alveolar nerve, but rapid distraction may cause serious degeneration.