Study of the tidemark in human mandibular condylar cartilage

Objectives

The tidemark is the junction of mature calcified and uncalcified articular cartilage. Metabolic activity in the tidemark area makes this structure important in articular remodelling and osteoarthrosis. However, detailed study of the tidemark on the mandibular condyle has been limited. This study investigated the functional significance of the tidemark in the mandibular condyle with respect to load-bearing.

Design

The study sample included 87 healthy human mandibular condyles from subjects aged 14–76 years. The morphology, number, and thickness of tidemarks were observed and measured in the anterior, superior, and posterior regions. Five additional mandibular condyles were evaluated by scanning electron microscopy.

Results

The tidemark appeared in 80 specimens as a dense wavy line at the interface between the calcified and hypertrophic layers of the condylar cartilage. Scanning electron microscopy showed a highly wavy tidemark surface in the load-bearing areas and a relatively flat and smooth surface in the non-load-bearing areas. The thickness of the tidemark in the load-bearing areas was significantly higher than that in the non-load-bearing areas (P = 0.003).

Conclusion

The results of this study demonstrated that the thickness of the tidemark was related to load-bearing on the articular surface.     

The influence of canine guidance and condylar guidance on mandibular lateral movement

summary This Study investigates the definite influence of the working-side canine and balancing-side condylar guidances on mandibular lateral movement. Lateral movements were measured on 40 young adults (22 males and 18 females), using the three-dimensional mandibular movement analysing system. The inclinations of the paths were calculated on the working-side canine, incisor, balancing-side first and second molars and balancing-side condylar points in the frontal plane. Multiple regression analysis enabled quantitative evaluation of the influence of the canine path and condylar path on the path of each tooth. The canine path showed greater influence than the condylar path even on the balancing-side second molar path. There was no difference between male and female subjects in the influential ratio of the canine guidance to the condylar guidance on any tooth path. It was concluded that the influence of the anterior and posterior guidance on the lateral movement varied according to the type of tooth, but not to the gender of the subject. This functional characteristic was confirmed by the morphological finding that the relative location of the molars in relation to canine and condyle does not differ between the sexes. The difference in the guiding system between the protrusive and lateral movement is also described in this paper.     

The influence of anterior guidance and condylar guidance on mandibular protrusive movement

summary This Study reveals the influence of the incisal and condylar guidance on mandibular protrusive movement. The protrusive movements were measured on 54 young adults (27 females, 27 males) using a three-dimensional mandibular movement analysing system. The inclinations of the sagittal paths on the incisor, canine, 1st molar, 2nd molar and condylar points were calculated, and multiple regression analysis was performed to evaluate the influence of the incisal and condylar paths on the path of each tooth quantitatively. The influence of the incisal path on any tooth path was consistently greater than that of the condylar path. The condylar path had a greater influence on the paths of posterior teeth than on the paths of anterior teeth, especially in the female subjects. The influence of the condylar path on the molar paths was twice as great in the female than that in the male subjects. It was concluded that the influence of the incisal and condylar guidance on the protrusive movement path varies according to the kind of tooth and the gender of the subject. These guiding system characteristics were confirmed by morphological analysis.     

人髁突软骨细胞培养及细胞库建立

目的　建立生物学性状稳定的髁突软骨细胞库 ,为颞下颌关节髁突软骨缺损及关节盘的生物性修复奠定基础。方法　髁突软骨取自因母体健康原因需终止妊娠的人胚胎 ,经机械分离及胰蛋白酶、胶原酶联合消化获得 ,应用微载体培养技术进行髁突软骨细胞的体外扩增 ,采用液氮深低温保存细胞 ,并定期 (2周、1个月 )对复苏软骨细胞生物学特性鉴定。结果　微载体培养技术可在短期内获得大量的、高成活率的髁突软骨细胞。经液氮冻存的软骨细胞在细胞增殖动力学、表型特征及细胞代谢方面无显著变化 ,基本上保持了原代培养软骨细胞的生物学特性。结论　成功的建立了髁突软骨细胞库 ,可为应用组织工程技术修复关节软骨缺损及重建关节盘的研究提供良好的供体细胞     

单侧后牙反(牙合)髁突前伸运动轨迹的研究

目的:探讨单侧后牙反牙合髁突前伸运动轨迹的特征并比较与正常牙合之间的差异。方法:正常牙合5人,单侧后牙反牙合7人,采用计算机化的髁突运动轨迹Ⅰ型描记仪及分析软件,记录下颌最大前伸运动时髁突在水平面及矢状面上的运动轨迹。结果:单侧后牙反牙合者前伸后退运动轨迹多不重合,反牙合侧前伸髁道斜度明显大于对侧。结论:单侧后牙反牙合者存在前伸牙合干扰,其两侧颞下颌关节不对称。     

Surgery in mandibular condylar hyperplasia

The experience with 35 patients with unilateral condylar hyperplasia is described. Possibilities of distinction between active and non-active cases are discussed as well as the histological findings. Different surgical procedures were used for treatment. Pain in the joint area is a prominent feature in this group. The treatment was effective in this regard in all patients.     

髁突骨软骨瘤与髁突增生患者的CT表现特点分析

目的:比较下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生的CT表现特点。方法:对2005—2010年上海交通大学医学院附属第九人民医院口腔颌面外科收治的下颌骨髁突骨软骨瘤11例和单侧下颌骨髁突增生8例患者的CT影像学资料进行评价,评价指标包括病变髁突大小、病变范围以及病变周围软硬组织改变。结果:11例下颌骨髁突骨软骨瘤病例CT显示肿瘤与病变髁突无明显分界(8/11)或与患侧髁突有蒂相连(3/11);肿瘤骨皮质及骨髓腔均与患侧髁突相续,瘤体表面均有特征性薄层软骨帽覆盖,瘤体外周密度通常高于中心;瘤体周围均有薄层软组织包绕。患侧颞骨关节面表面均有明显矿化,且因受瘤体压迫改建而较对侧平坦,患侧关节上、下腔间隙较对侧明显变窄;肿瘤生长方向不尽相同。8例单侧下颌骨髁突增生病例CT显示髁突颈部和(或)下颌支延长,髁突形状改变;增生的髁突外周骨皮质均有不同程度的骨化,硬化层厚度较对侧大;骨髓腔密度较不均匀。结论:CT检查能有效提供病变髁突及其周围软硬组织情况,为鉴别诊断下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生提供良好的依据。     

Influence of choice of reference point on the condylar movement paths during mandibular movements

summary Series of four open-close, protrusive and lateral movements were recorded by the six degrees of freedom jaw movement recording system OKAS- 3D in 20 healthy subjects. Consequently the movement paths of nine condylar points, the palpated lateral pole and eight points located on a square parallel to the sagittal plane with an edge of 10 mm and centred around the lateral pole were calculated. For all movements except the protrusive movements, the 3-D excursions of the condylar points strongly depended upon the choice condylar reference point (ANOVA, P < 0 001). During laterotrusive movements the Bennett angle and the Bennett shift also varied significantly according the position of the reference point (ANOVA, P < 0 001). The results of this study underline that comparison of condylar movements between different studies only possible when the same condylar reference point is used. General consensus on the choice condylar reference point is thus needed.     

Management of malunited mandibular condylar fractures

The non-surgical treatment of mandibular condylar fractures, may occasionally result in articular imbalance and temporomandibular joint dysfunction. This may be attributed to condylar head displacement and resorption, resulting in a shortened vertical ramus and lost posterior vertical facial height. Restoring the vertical ramus height is essential in the treatment of such dysfunction, and may be accomplished by unilateral, or bilateral ramus osteotomies. Four examples of patients treated with mandibular ramus osteotomies to restore vertical ramus height, with subsequent improvement in occlusal balance and function are presented. The use of the sagittal split mandibular osteotomy and the external vertical ramus osteotomy, stabilized with small osseous plates, and monocortical screws, is discussed.     

Surgical complications of mandibular condylar fractures

The purpose of this study was to retrospectively evaluate the complications of 58 patients who underwent surgery for mandibular condylar process fractures. Data were collected from patients during a 10-year period (1999-2009). The data recorded included demographic data, etiology, diagnosis, type of condylar fracture, surgical approaches, and postoperative complications. A total of 58 underwent surgery for reduction of the condylar fractures. There were 22 patients with bilateral condyle fractures and 36 patients with unilateral condyle fractures, accounting for 65 surgeries. In 8 fractures, a preauricular approach was performed to access the fractures condyle, whereas the retromandibular approach was performed in 57 fractures. There were 2 temporary facial palsies, 1 permanent facial palsy, and 1 sialocele. There were no cases of hypertrophic scar, Frey syndrome, or salivary fistula. In conclusion, permanent deformities after surgical complications were unusual, and the results are acceptably safe.     

bFGF、IGF-Ⅰ及TGF-β1对人髁突软骨细胞增殖的影响

目的 研究胰岛素样生长因子（ｉｎｓｕｌｉｎ－ｌｉｋｅ ｇｒｏｗｔｈ ｆａｃｔｏｒ Ⅰ,ＩＧＦ－Ⅰ）,碱性成纤维细胞生长因子（ｂａｓｉｃ ｆｉｂｒｏｂｌａｓｔ ｇｒｏｗｔｈ ｂＦＧＦ）,转化生长因子β１（ｔｒａｎｓｆｏｒｍｉｎｇ ｇｒｏｗｔｈ ｆａｃｔｏｒ β１,ＴＧＦ－β１）单独及联合应用,对人髁突软骨细胞增殖的剂量－效应及时间－效应。方法 采用体外细胞培养技术及噻唑蓝比色法,对３种生长因子对软骨     

Roles of notch signalling in mandibular condylar cartilage

Importance

Notch proteins are cell surface transmembrane spanning receptors which mediate critically important cellular functions through direct cell–cell contact. Interactions between Notch receptors and their ligands regulate cell fate decisions such differentiation, proliferation and apoptosis in numerous tissues. We have previously shown using immunohistochemistry that Notch1 is localized primarily to the prechondroblastic (chondroprogenitor) layer of the mandibular condylar cartilage (MCC).

Objective

To test if Notch signalling changes patterns of proliferation and differentiation in the MCC and to investigate if Notch signalling acts downstream of Fibroblast Growth Factor 2 (FGF-2).

Methods

Condylar cartilage explants were cultured over serum-free DMEM containing either 0 or 50 nM DAPT, a Notch signal inhibitor. Explants were used for RNA extraction and immunohistochemistry.

Results

Analysis of gene array data demonstrated that the perichondrial layer of the MCC is rich in Notch receptors (Notch 3 and 4) and Notch ligands (Jagged and Delta) as well as various downstream facilitators of Notch signalling. Disruption of Notch signalling in MCC explants decreased proliferation (Cyclin B1 expression) and increased chondrocyte differentiation (Sox9 expression). Moreover, we found that the actions of FGF-2 in MCC are mediated in part by Notch signalling.

Conclusion

These data suggest that Notch signalling contributes to the regulation of proliferation and differentiation in the MCC.     

Progressive condylar resorption after mandibular advancement

Progressive condylar resorption is an irreversible complication and a factor in the development of late skeletal relapse after orthognathic surgery. We have evaluated cephalometric characteristics, signs and symptoms in the temporomandibular joint (TMJ), and surgical factors in six patients (one man and five women) who developed it after orthognathic surgery. The findings in preoperative cephalograms indicated that the patients had clockwise rotation of the mandible and retrognathism because of a small SNB angle, a wide mandibular plane angle, and a "minus" value for inclination of the ramus. There were erosions or deformities of the condyles, or both, on three-dimensional computed tomography (CT) taken before treatment. The mean (SD) anterior movement of the mandible at operation was 12.1 (3.9)mm and the mean relapse was -6.4 (2.5)mm. The mean change in posterior facial height was 4.5 (2.1)mm at operation and the mean relapse was -5.3 (1.8)mm. Two patients had click, or pain, or both, preoperatively. The click disappeared in one patient postoperatively, but one of the patients who had been symptom-free developed crepitus postoperatively. In the classified resorption pattern, posterior-superior bone loss was seen in three cases, anterior-superior bone loss in two, and superior bone loss in one. Progressive condylar resorption after orthognathic surgery is multifactorial, and some of the risk factors are inter-related. Patients with clockwise rotation of the mandible and retrognathism in preoperative cephalograms; erosion, or deformity of the condyle, or both, on preoperative CT; and wide mandibular advancement and counterclockwise rotation of the mandibular proximal segment at operation, seemed to be at risk. The mandible should therefore be advanced only when the condyles are stable on radiographs, and careful attention should be paid to postoperative mechanical loading on the TMJ in high-risk patients.