输送盘牵张成骨重建下颌髁突的骨密度和力学性能变化

目的 探讨运用输送盘牵张成骨术重建髁突的骨密度和力学性能变化.方法 成年山羊16只.截除右侧髁突后运用输送盘牵张成骨术重建髁突,左侧作为正常对照组.牵张结束后24周处死所有动物.采用双能X线吸收法和压缩力学性能测试技术.定量分析并对比两侧髁突的骨密度和压缩力学性能变化.结果 手术侧髁突骨密度较正常侧显著升高;其轴向弹性模量和最大应力较正常侧显著升高,横向弹性模量和最大应力两侧无显著性差异,轴向和横向最大应变两侧均无显著性差异.髁突骨松质的力学性能具有明显的各向异性.结论 运用输送盘牵张成骨术重建的髁突的骨密度和生物力学性能明显升高;这种适应性改建与颞下颌关节的功能刺激直接相关.     

Reconstruction of mandibular condyle by transport distraction osteogenesis: Experimental study in rhesus monkey.

PURPOSE: This study investigated histomorphologic changes in the newly formed condyle reconstructed by transport distraction osteogenesis through a nonhuman primate model. MATERIALS AND METHODS: Six adult rhesus monkeys were used in this study. Bilateral condyles and articular discs were extirpated, and the technique of transport distraction osteogenesis was carried out to reconstruct the condyles. X-ray and 3-dimensional (3D) computed tomography (CT) scanning films were taken at various intervals. Two monkeys were killed respectively at 4, 12, and 24 weeks after completion of distraction; the transport segments and the distracted calluses were harvested and processed for histologic examination. The original condyles removed at surgery served as normal control. RESULTS: Open bite was seen in all animals postoperatively and diminished at the end of distraction. Bone regeneration was perfect in the distraction gap between the transport disc and the pre-existing mandible. The bony transport disc gradually remodeled to a neocondyle that was similar to the original condyle in the appearances and structures. The head of neocondyle was covered with a fibrous cap, which might play the role of an articular disc. CONCLUSION: A neocondyle with functional shape can be created by transport distraction osteogenesis. This suggests that this technique is an alternative method for reconstruction of the mandibular condyle.     

运用输送盘牵张成骨术重建猴下颌髁突的实验研究

目的研究在猴颞下颌关节（TMJ）缺损动物模型上运用输送盘牵张成骨术重建髁突的可行性及其整复效果。方法选取6只成年恒河猴,手术截除其双侧关节髁突与关节盘,在下颌升支部行“L”形骨切开术,形成骨输送盘,并安置自行研制的牵张器。按每次0.4 mm,每次间隔12 h的牵张速率向上牵引输送盘至关节窝。牵张结束后第4、12、24周各处死2只动物。通过影像学分析和组织学检查评价输送盘改建与牵张间隙内新骨生成情况。以术中切除的髁突作为正常对照组。结果术后所有动物都有不同程度的咬合错乱,牵张结束后咬合基本恢复正常。骨输送盘形态基本接近正常髁突,其下方可见大量软骨细胞;牵张间隙内新骨生成良好。结论输送盘牵张成骨术可以重建一个形态和功能都基本接近正常的髁突,这种技术可以作为一种整复TMJ缺损的新方法。     

自体喙突移植重建下颌髁突的实验研究

目的:研究运用自体喙突移植重建髁突的可行性及其整复效果。方法:选取12只成年雄性山羊,手术截除右侧髁突与关节盘,取同侧喙突以L型钛板固定在下颌升支。分别在术后第4、12、24周各处死4只动物。通过大体观察、三维CT分析和组织学检查等方法评价自体喙突移植后的形态学和组织学变化。结果:所有动物术后咬合基本正常。术后4周可见喙突再生,术后24周时自体喙突形态基本接近正常髁突。新生髁突表面有较厚的致密纤维结缔组织覆盖,其下方的组织结构类似正常髁突表面的关节软骨。结论:自体喙突移植可以重建一个形态和功能都基本接近正常的髁突,因此这种技术可以作为一种整复TMJ缺损的新方法。     

Histologic and histometric study of the effect of fluoride on the rat mandibular condyle

Abstract. The effect of fluoride on the rat mandibular condyle was studied histologically and histometrically. The condyles of the rats that received 50 ppm fluoride in the drinking water for 17 weeks did not differ in structure from those of the control rats fed tap water containing 1 ppm fluoride. However, the condyles of the rats given 100 ppm fluoride in the drinking water for the same period showed a significant increase in both the thickness of the cartilage layer ( P < 0.02) and the density of cancellous bone ( P < 0.01) when compared to the controls. The thickening of the cartilage layer was due to an increase in the number of hypertrophied chondrocytes. The trabeculae of cancellous bone were thicker and consequently the bone marrow spaces were extremely reduced. The trabeculae contained more calcified cartilage in their cores.     

双侧下颌牵张成骨对转化生长因子β1在颞下颌关节髁突表达的影响

目的　研究狗的双侧下颌牵张成骨中颞下颌关节髁突的形态改变及转化生长因子β1(TGF-β1)在髁突的 表达。方法　16只狗随机分为4组,每组4只,分别为牵张6 d组、牵张后固定2周组、牵张后固定8周组及正常对 照组。各实验组的牵张频率均为1 mm/d,1次/天。对每组动物的髁突标本进行苏木精-伊红染色及TGF-β1的免 疫组化染色观察。结果　苏木精-伊红染色可见实验组动物的髁突纤维软骨早期有不同程度的损伤,增殖带、肥 大带细胞增生活跃,软骨钙化层及其深层软骨成骨活跃;TGF-β1阳性染色主要定位在肥大带细胞胞浆、周围基质和 成骨反应活跃处的成软骨细胞、成骨细胞及周围基质。牵张后固定2周时这种改建修复现象最明显,8周时逐渐恢 复至正常对照组的表现。结论　双侧下颌牵张成骨对颞下颌关节髁突影响主要表现为髁突纤维软骨组织形态学 的改变和软骨、骨的改建活动,但随着固定时间的延长这种改变逐渐修复。     

Histologic and histometric study of the effect of fluoride on the rat mandibular condyle

The effect of fluoride on the rat mandibular condyle was studied histologically and histometrically. The condyles of the rats that received 50 ppm fluoride in the drinking water for 17 weeks did not differ in structure from those of the control rats fed tap water containing 1 ppm fluoride. However, the condyles of the rats given 100 ppm fluoride in the drinking water for the same period showed a significant increase in both the thickness of the cartilage layer (P smaller than 0.02) and the density of cancellous bone (P smaller than 0.01) when compared to the controls. The thickening of the cartilage layer was due to an increase in the number of hypertrophied chondrocytes. The trabeculae of cancellous bone were thicker and consequently the bone marrow spaces were extremely reduced. The trabeculae contained more calcified cartilage in their cores.     

咬肌再附着界面的生物力学研究

目的：研究山羊咬肌与下颌骨皮质骨面和松质骨面再附着的生物力学特性变化。方法：9只成年山羊为研究对象,其中1只为正常对照,实验组山羊双侧下颌骨咬肌附着从骨面剥离,附着区骨面平均分为两部分,分别保留原骨面或去除皮质骨,暴露松质骨,咬肌原位缝合,术后2,4,8,12周采集标本,进行生物力学测试。结果：生物力学检测表明,2－12周肌－骨界面附着强度随时间延长有显著增强,而同一时间两种骨面的肌附着强度无显著差异。结论：咬肌再附着的形成与附着骨面结构无关。     

Prediction of mechanical properties of the cancellous bone of the mandibular condyle

The mechanical properties of cancellous bone depend on the bone structure. The present study examined the extent to which the apparent stiffness of the cancellous bone of the human mandibular condyle can be predicted from its structure. Two models were compared. The first, a structure model, used structural parameters such as bone volume fraction and anisotropy to estimate the apparent stiffness. The second was a finite element model (FEM) of the cancellous bone. The bone structure was characterized by micro-computed tomography. The calculated stiffnesses of 24 bone samples were compared with measured stiffnesses. Both models could predict 89% of the variation in the measured stiffnesses. From the stiffness approximated by FEM in combination with the measured stiffness, the stiffness of the bone tissue was estimated to be 11.1 +/- 3.2 GPa. It was concluded that both models could predict the stiffness of cancellous bone with adequate accuracy.     

Changed morphology and mechanical properties of cancellous bone in the mandibular condyles of edentate people

Since edentate subjects have a reduced masticatory function, it can be expected that the morphology of the cancellous bone of their mandibular condyles has changed according to the altered mechanical environment. In the present study, the morphology of cylindrical cancellous bone specimens of the mandibular condyles of edentate subjects (n = 25) was compared with that of dentate subjects (n = 24) by means of micro-computed tomography and by the application of Archimedes' principle. Stiffness and strength were determined by destructive mechanical testing. Compared with dentate subjects, it appeared that, in edentate subjects, the bone was less dense and the trabecular structure was less plate-like. The regression models of stiffness and strength built from bone volume fraction and the trabecular orientation relative to the axis of the specimen were similar for both dentate and edentate subjects. This indicates that, under reduced mechanical load, the fundamental relationship between bone morphology and mechanical properties does not change.     

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat

Authors– Nakano H, Watahiki J, Kubota M, Maki K, Shibasaki Y, Hatcher D, Miller AJ Objectives – To investigate the influence of forced lateral bite on mandibular growth, micro X‐ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). Settings and sample population – The rats were divided into two groups – experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right–left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three‐dimensional (3‐D) finite element analysis were assessed using 3‐D images reconstructed from micro X‐ray CT scans when the mice had reached 21 weeks. Measurements and Results – Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X‐ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle. Conclusions – These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.     

Evaluation of Fractured Condylar Head Along the Sagittal Plane: Report of Three Cases

There are case reports of sagittal fractures of the condylar head leading to bifid condyle. However bifid condyles maybe found in patients with no history of trauma. A split in the saggital plane of the condyle is not visible with a lateral, oblique or panaromic radiographs but only with anteriorposterior, transorbital projections or CT scan of the temperomandibular joint. The chances of condyle being split in the sagittal plane may be due to the medial pole extending beyond the condylar neck, moreover the condyle is composed of cancellous bone covered by a thin layer of cortical bone. Here we are presenting three case reports of Saggital split condyles and stress the need for inclusion of these type of fractures in the classification of condylar fractures.     

Local administration of IGF-I stimulates the growth of mandibular condyle in mature rats

AIM: To evaluate the effects of local injection of insulin-like growth factor I (IGF-I) on the growth of mandibular condyle in mature rats. MATERIALS AND METHODS: Sixteen 15 week-old male rats were used in this study. In the experimental group, IGF-I at a concentration of 50 microg/ml was injected into articular capsules of the condyle, while rats in the control group were injected with equal volume of physiological saline. These injections were performed three times at 7 day intervals, and all of the rats were killed on the 7th day after the last injection. Tetracycline and calcein were used for vital staining. After death, the condyles were extracted and undecalcified ground sections were prepared for histological and histomorphometric observations. The thickness of the cartilaginous layer of the condyle, the percentage of bone area in the subchondral cancellous bone layer and the amount of endochondral bone growth in the condyle were measured. The significance of the difference in these measurements between IGF-I and control group was evaluated. RESULTS: An increase in the thickness of the cartilaginous layer, and a decrease in the percentage of bone area in the subchondral cancellous bone layer was recognized in IGF-I treated condyle. The amount of endochondral bone growth in the experimental group was greater than that in the control group. CONCLUSION: The local injection of IGF-I into mature condyle seemed to reactivate the process of endochondral bone formation and induced actual bone growth in mature condyle.     

The three-dimensional cancellous bone architecture of the human mandibular condyle

In the present study, we tested the hypothesis that the cancellous bone of the mandibular condyle is inhomogeneous and anisotropic. For this purpose, 11 mandibular condyles from embalmed human cadavers were scanned in a micro-CT system. Within each condyle, 9 volumes of interest were selected from different mediolateral and supero-inferior regions. Several bone parameters were calculated to describe the morphology. It appeared that the cancellous bone of the condyle could be approximated by parallel plates. These plates were almost vertically oriented at an angle of 17 degrees relative to the sagittal plane, i.e., perpendicular to the condylar axis. In the superior regions of the condyle, the cancellous bone had the largest bone volume fraction (0.19), associated with the thickest trabeculae (0.11 mm), and the highest trabecular number (1.72 mm(-1)). The lowest bone volume fraction (0.15) was found more inferiorly. The degree of anisotropy increased from superior to inferior across the condyle. No mediolateral differences in bone morphology were found, but superiorly central regions contained more bone than peripheral regions. The plate-like trabeculae could indicate that the condyle is optimally adapted to sustain loads from all directions in a plane perpendicular to the condylar axis. The high bone mass and lower anisotropy in the superior regions could enable the condyle to sustain multiple load directions. Toward the collum, the trabeculae are more aligned. This could point to stresses acting predominantly in one direction.     

Local administration of IGF-I stimulates the growth of mandibular condyle in mature rats

Abstract

Aim: To evaluate the effects of local injection of insulin-like growth factor I (IGF-I) on the growth of mandibular condyle in mature rats.

Materials and methods: Sixteen 15 week-old male rats were used in this study. In the experimental group, IGF-I at a concentration of 50 μg/ml was injected into articular capsules of the condyle, while rats in the control group were injected with equal volume of physiological saline. These injections were performed three times at 7 day intervals, and all of the rats were killed on the 7th day after the last injection. Tetracycline and calcein were used for vital staining. After death, the condyles were extracted and undecalcified ground sections were prepared for histological and histomorphometric observations. The thickness of the cartilaginous layer of the condyle, the percentage of bone area in the subchondral cancellous bone layer and the amount of endochondral bone growth in the condyle were measured. The significance of the difference in these measurements between IGF-I and control group was evaluated.

Results: An increase in the thickness of the cartilaginous layer, and a decrease in the percentage of bone area in the subchondral cancellous bone layer was recognized in IGF-I treated condyle. The amount of endochondral bone growth in the experimental group was greater than that in the control group.

Conclusion: The local injection of IGF-I into mature condyle seemed to reactivate the process of endochondral bone formation and induced actual bone growth in mature condyle.     

下颌骨髁突骨密度的相关性研究

目的 利用锥形束CT(cone beam computed tomography,CBCT)测量下颌骨髁突骨密度,研究下颌骨髁突骨密度与性别、年龄、垂直及矢状骨面型的相关性.方法 收集700例患者正畸治疗前的CBCT数据,将患者按照性别、年龄、垂直骨面型和矢状骨面型进行分组,测量双侧水平面下颌骨髁突最大径处的髁突骨皮质...     

Transport distraction osteogenesis as a method of reconstruction of the temporomandibular joint following gap arthroplasty for post-traumatic ankylosis in children: a clinical and radiological prospective assessment of outcome

This clinical and radiographic study investigated the use of transport distraction osteogenesis in unilateral temporomandibular joint (TMJ) ankylosis patients. Six patients aged between 4 and 8 years were selected for the study; the mean preoperative maximal inter-incisal opening (MIO) was 3.5 mm without lateral and protrusive mandibular movements. The ankylotic mass along with the posterior border of the ascending ramus was exposed via ‘lazy-S’ incision. A gap arthroplasty was performed, followed by a ‘reverse L’ osteotomy on the posterior border of the ramus. In-house manufactured extraoral distraction devices were used for this prospective study. Follow-up clinical and radiographic evaluation was carried out for 13–27 months after completion of the activation period. After a mean follow-up of 19 months, the mean MIO was 29.1 mm and the lateral and protrusive movements changed from none to slight. Cone beam computed tomography images of all patients showed remodelled neocondyle created by transport distraction osteogenesis with no statistically significant differences observed for average cancellous bone density, trabecular number, and trabecular spacing between the neocondyle of the operated side (test) and the condyle of the non-operated side (control). Neocondyle formation by transport distraction osteogenesis using the in-house distraction device is a promising treatment option for TMJ reconstruction in ankylosis patients.     

翼外肌在髁突矢状骨折愈合过程中对髁突形态改建影响的动物实验研究

目的 观察翼外肌在髁突矢状骨折愈合过程中对髁突形态的改建是否有影响以及是否会进一步导致关节强直的发生。方法 将12只健康成年绵羊随机分为2组,均以右侧颞下颌关节作为手术实验侧,人为手术造成髁突矢状骨折。一组保留翼外肌在髁突内极的附丽,行使其功能,另一组切断翼外肌在髁突内极的附丽,阻断其功能,术后即刻行MRI检查,确定翼外肌是否离断。术后1周对动物模型行CT三维检查,测量髁突骨折块的移位距离及髁突内外径的改变,术后4周、12周及24周时处死动物,再次行CT检查,多平面重建后对髁突形态相关参数测量,以观察髁突的形态变化。结果 通过CT三维测量,两组髁突内外径的改变有明显的差异（P＜0.05）,证实翼外肌对髁突游离骨折端有牵拉作用,保留翼外肌功能组,对髁突矢状骨折后髁突形态的影响更明显。结论 此动物模型的建立,证实翼外肌对髁突矢状骨折后髁突形态改建的确有影响,为进一步研究“翼外肌牵张成骨在创伤性颞下颌关节强直发生中的作用研究”提供研究平台。     

髁突——升支后份骨游离再植颞颌关节重建的实验研究

本文报告用犬做髁突-升支后份骨游离再植重建颞颌关节后关节形态、结构和组织学的研究情况。实验犬8只,做升支后份全层纵行切骨,整体摘下踝突-升支后份骨块,切除髁突内外极,修整后原位植回,分期观察。6周后的7侧髁突有5侧再生明显,2侧形态恢复较差;24周时髁突形态与对照侧无明显差别,关节面为软骨修复,关节盘、关节腔及滑膜等组织结构得以保存:翼外肌能够原位附着,附着处肌纤维间纤维组织增生。本文就影响髁突再生的因素进行了讨论。     

牵引成骨结合组织工程化软骨重建山羊髁突缺损的实验研究

目的：利用牵引成骨结合组织工程化软骨重建山羊髁突缺损。方法：12只山羊随机分为两组：实验组在下颌切迹下方作截骨线,切除一侧髁突及其颈部,左右随机。再于下颌支后缘形成转移盘,在转移盘的远中植入软骨细胞支架复合物。对照组在转移盘的远中仅植入支架。分别于牵引结束4、8、12周大体及组织学观察山羊髁突的形成情况。结果：牵引结束后4周,实验组山羊髁突已具备良好的外形,髁突表面覆盖软骨组织：对照组山羊新形成之髁突外形虽与正常髁突相似但表面无软骨层。12周时,实验组山羊髁突外形与正常髁突相似,表面仍有软骨层覆盖：而对照组山羊新形成的髁突外形虽与正常髁突相似,但表面仍无软骨层覆盖。结论：利用牵引成骨结合组织工程化软骨的方法不仅可以从外形上重建山羊髁突,而且在解剖结构上与正常髁突相似,为髁突正常功能的行使提供了良好的解剖学基础。