髁状突表面解剖标志的成像位置研究

目的：研究髁状突表面解剖标志在普通X线片位上的成像位置。方法：以带下颌骨的成人颅骨标本作为摄片对象。以细铅丝标识定位髁状突表面解剖标志，拍摄标识侧颞下颌关节的薛氏位、髁状突的经咽侧位和曲面体层片。结果：薛氏位显示髁状突外极处于高位，邻近关节凹底部；内极处于低位，远离关节凹底部。经咽侧位和曲面体层显示髁状突外极处于低位，远离关节凹底部；内极处于高位，邻近关节凹底部。髁状突前斜面约占据髁状突影像的前半部分，前斜面下缘位于髁状突影像前部，呈纵行斜向走行。结论：在普通X线片上，髁状突的内外极影像位置，会随着投照角度的改变而变化。     

Associations between the articular eminence inclination and condylar bone changes, condylar movements, and condyle and fossa shapes

Objectives

The purpose of the present study was to determine the inclination and height of the articular eminence with respect to the condylar bone changes, condyle shape, fossa shape and condylar movements in patients with and without temporomandibular joint (TMJ) dysfunction using cone-beam computed tomography (CBCT).

Methods

The associations between the eminence inclination and the condylar bone changes, condylar movements, condylar shape and fossa shape were evaluated in patients with TMJ disorders and control patients without TMJ disorders. The measurements of the articular eminence inclination were established on central sagittal slices of the TMJ. The central coronal slices were used to determine the condyle and fossa shapes. The types of movements of the condyles were determined on open-mouth images, and mandibular hypermobility or hypomobility was noted for each joint.

Results

There were no significant differences in the eminence inclination and height with respect to the condylar bone changes and condylar movements in the TMJ disorder group. However, there was a significant association between the eminence inclination and the fossa shape in the TMJ disorder group and significant associations between the eminence inclination and both the condyle and fossa shapes in the control group. The articular eminence inclination was steeper in the control group than in the TMJ disorder group.

Conclusions

The eminence inclination was steeper in the control patients than in the patients with TMJ disorders, and was not correlated with the condylar bone changes or condylar movements.     

颅底结构螺旋CT影像的三维定量测量

目的　分析健康成人当下颌骨处在正常牙尖交错位时 ,髁突与颅底颈内动脉管外口、颈静脉窝、卵圆孔、棘孔、破裂孔等之间的空间位置关系 ,为术中对其他重要结构的位置评估提供依据。方法　选择健康成人 10 0名 ,在正常牙尖交错位时 ,用螺旋CT扫描、颅底三维影像重建 ,测量各结构间的最短距离和空间角度。 12个定点 ,测量 2 8项距离和空间角度以极坐标表示 ,髁突内缘点为中心点 ,髁突长轴为 0°轴作为参照系。结果　颌下入路能顺利显露髁突内缘点和髁突长轴的方向 ,以此为参照系 ,确定颈内动脉管外口外缘点为 12 0 1± 2 71mm ,5 14± 1 2 2° ,颈静脉窝外缘点为 15 11±2 72mm ,- 5 6 2 7± 14 0 5°。结论　以髁突内缘点为中心点 ,髁突长轴为 0°轴参照系有助于为颌下入路颅底手术的术中定位及颅底解剖教学提供参考。     

Three-dimensional cephalometry using helical computer tomography: measurement error caused by head inclination

We performed a study of three-dimensional (3-D) linear measurements in the maxillofacial region using helical computer tomography (CT). The high accuracy of the linear measurements showed errors of less than 5% from the actual measures. But, it is possible that the accuracy was influenced by inaccurate head positions. In this study, we evaluated the errors when the head positions were tilted using the 3-D measurement system. Helical CT was used to scan a dry skull, and the data were reconstructed into a 3-D image. A total of 18 points were plotted on the 3-D images, and the distance between two points was calculated when the points were expressed as coordinates. A dry skull was tilted by 10 degrees from the reference position in the horizontal, sagittal, and frontal planes and was then tilted in a combination of directions. Scanning was performed with slice thicknesses of 1 mm, 3 mm, 5 mm, and 7 mm. The length between two points measured by 3-D cephalometry was compared with the actual length determined using an antenna meter and a caliper and expressed as percentage errors of the actual length. In all head positions, errors in all linear measurements on the images and the actual length measured on the skull were less than 5% when a slice thickness of 1 mm or 3 mm was used. But, on using a slice thickness of 5 mm or 7 mm, some linear measurements showed larger measurement errors. Therefore, a thickness of less than 3 mm was thought to be clinically appropriate because the accuracy of the measurements was not influenced by head rotation.     

Panoramic radiography: effects of head alignment on the vertical dimension of the mandibular ramus and condyle region

The aim of this study was to assess whether it is possible to derive accurate vertical measurements of the mandibular ramus and condyle from panoramic radiographs. A human dry skull was positioned in a panoramic machine. The skull was displaced along the sagittal and transverse plane and rotated around the vertical and transverse axes. A set of 252 digital radiographs with defined positioning errors was compared with a set of 42 radiographs in the 'ideal' position. The distances between the metal markers that had been attached at the angle of the mandible at a distance of 60 mm in the condyle region to produce fixed reference points on the radiographs were measured. Statistical differences were investigated using Friedman repeated measures analysis of variance on ranks followed by the Dunnett's test for the comparison against the control group in the ideal position (α = 0.05). Vertical measurements were significantly affected when the skull was rotated around the vertical (P < 0.001) or shifted along the transverse axis (P < 0.001). Misalignment of the head affected the vertical measurement of the mandibular ramus and condyle. However, asymmetries of more than 6 per cent are probably not due to patient positioning in the panoramic machine.     

Effects of head positioning on cephalometric measurements

Objective

The goal of the present work was to evaluate different head positions for their effects on cephalometric analysis.

Materials and methods

Cephalograms were obtained from a skull phantom adjusted to various degrees of inclination (0°, 2°, 4°, 6°, 8°, 10°), lateral tilting (0°, 2°, 4°, 6°, 8°, 10°), and rotation (0°, 3°, 6°, 9°, 12°, 15°, and 21°). All these combinations resulted in a total of 210?digital cephalograms for assessment. On-screen analysis of these images by an orthodontist was completed within a few days.

Results

Lateral tilting and rotation revealed considerably stronger effects on the values measured than inclination. Starting at 2° of tilting or 3° of rotation, numerous parameters yielded deviations of ≥?2° or 2?mm from the baseline values. Increasing degrees of rotation showed more pronounced value changes than increasing degrees of lateral tilting. Skeletal and dental parameters whose landmarks are mainly located in the median plane were less susceptible than parameters whose reference points had to be averaged. Values of parameters located in the median plane were less affected by rotation when combined with higher degrees of initial lateral tilting (>?6°) than with lower ones.

Conclusion

The usefulness of cephalometric data becomes limited once the head is rotated by 3° or laterally tilted by 2°. Values obtained in the median plane are more stable than those obtained in peripheral locations. Various degrees of inclination applied to the skull phantom with its solid structures had no measurable effects. Accurate head positioning is an essential prerequisite for obtaining meaningful results from cephalograms based on reproducibly identifiable landmarks.     

Statistical study of the angle formed by the lateral part of the mandibular condyle and the horizontal plane

The angle between the LCA and frontal plane and the inclination of the lateral part of the mandibular condyle and the horizontal plane were measured in a sample of the skulls used in the study. Correlation between the two angles was found to be almost insignificant. Fifty-eight percent of the TMJs had an inclination of the lateral part of the condyle less than 15 degrees. The maximum value for this angle was found to be 45 degrees, and the minimum was -6 degrees.     

Comparison of the intercondylar distance and the interfacial width as used with the electronic pantograph.

The electronic pantograph (Pantronic) records mandibular movements and computes the articulator settings. The Pantronic pantograph does not determine the intercondylar distance but approximates it from the interfacial width at the condyles. An average distance of 12.5 mm is subtracted from each side to determine the intercondylar distance. This study recorded 45 patients' articulator intercondylar distances that had been set from a mechanical pantograph and they were compared with the Pantronic's approximation. The difference between the interfacial width and the actual intercondylar distance was 15.1 mm on the right side and 14.9 mm on the left side. A numerical value of 15.0 mm was statistically superior to the Pantronic's 12.5 mm in estimating the average distance between the intercondylar distance and the surface of the skin at the condyle. No statistically significant difference was found between the differences of interfacial width and intercondylar distance values for men and women (p greater than 0.05). The mean intercondylar distance was 56.5 mm on the right side and 56.7 mm on the left side. A statistically significant difference was found between the mean intercondylar distances of men and women (p less than 0.05).     

The use of computed tomography to define zygomatic complex position.

PURPOSE: The purpose of this study was to analyze the use of midline references and landmarks to assess the position of the zygomatic complex relative to the cranial base, and to test the reliability of these measurements in assessing facial symmetry. METHODS: Direct skull measurements were compared with measurements made on computed tomography (CT) images. The effect of CT scanner error, technologist error, gantry angle error, error of skull inclination, and error due to the presence of titanium rigid fixation hardware were assessed. To test observer variation and the effect of each level of error, 4 blinded bilateral measurements were repeated 3 times by 5 observers on both dry skull and CT scans. A mixed effect analysis of variance model then assessed for effect of method of measurement (dry skull vs CT), observer, CT scanner, technologist, gantry angle, skull inclination, and rigid fixation. RESULTS: A total of 2,040 measurements were made. Measurements for zygomatic complex posterior and anterior width and height were reliable and had an interobserver variations of 0.02 +/- 0.03 mm, 0.5 +/- 0.4 mm, and 0.37 +/- 0.3 mm, respectively. The difference between dry skull and CT assessment for the 3 reliable measurements was 1.2 +/- 0.3 mm, 0.44 +/- 0.4 mm, and 1.1 +/- 0.5 mm, respectively. The errors produced by the CT scanner, technologist, and rigid internal fixation hardware were not clinically significant. The measurements were not sensitive to gantry angle and skull inclination changes of 10 degrees or less. A fourth measurement assessing zygomatic complex projection was found not to be accurate or reliable. CONCLUSIONS: These findings suggest that the 3 CT scan measurements describing the position of the zygomatic complex relative to the cranial base are clinically useful.     

The role of posterior guidances under the altered anterior guidance

In five subjects, bilateral condylar movement was assessed during lateral excursions with different tooth guidance angles without changing the intercuspal position. Statistical analysis of anova (P < 0.01) revealed that when the incisal path angle became steeper than the natural tooth guidance, distances of the non-working side condyle paths (centre of condyle) decreased significantly, while distances of the working side condyle paths (centre of condyle) remained unchanged. Directions of the working side condyle paths were random, while directions of the non-working side condyle paths remained stable. By analysing six points around the centre of the condyle, it was not possible to confirm any affect on the working side condyle movement by changing the tooth guidance angle. It was revealed that the non-working side condyle had an 'active' role during lateral excursions, and that the working side condyle moved as a result of mandibular movement that was changed because of a steepening of the incisal path angle during lateral excursions. This suggests the possibility that the working side condyle movements were affected 'passively' by altering the tooth guidance.     

Frequency domain analysis of cross-sectional images of the posterior mandible

The Siemens Orthophos (Siemens, Mu¨nchen, Germany) is a panoramic machine that uses a microchip to control the movements of the radiation source and film. Several programs are available for different views of the facial skeleton and associated structures. Program 16 is dedicated to cross-sectional imaging of the posterior mandible. Three millimeter cross-sections were cut from 12 cadaver specimens of the mandible. These sections were imaged separately by contact radiography, 48° hypocycloidal tomography of Philips Polytome (Philips-Massiot, Paris, France), and program 16 of the Orthophos panoramic machine. Program 16 of the Orthophos was also used to image the cross-sections after they were glued back together with the surrounding parts of the specimens. Four different images of the cross-sections were thus obtained. The contact radiographs were used as gold standards. Frequency domain analysis, which was used to compare the images resulting from each imaging modality, demonstrated that useful diagnostic information was in the range of 0.12 to 0.60 cycles/mm for the contact radiographs. In spite of differing tomographic angles for the Orthophos program 16 and the hypocycloidal tomography, the images of the 3 mm cross-sections showed similar frequency distribution. However, the Orthophos Program 16 did not produce diagnostically useful images when the cross-sections were imaged with the surrounding parts of the specimens probably because of the narrow tomographic angle used for this program. These images had strong low to medium frequency components compared with the gold standard images. These results suggest that diagnostically more useful images with the Orthophos might be obtained by increasing the tomographic angle.     

骨性Ⅲ类偏颌患者下颌骨髁突位置三维评估研究

目的    利用Mimics软件对成人骨性Ⅲ类错牙合伴下颌偏斜患者下颌骨髁突的位置特征进行三维测量。方法    对50例骨性Ⅲ类错牙合畸形患者（18～34岁）的颅面部进行螺旋CT扫描（偏斜组28例,非偏斜组22例）, 采集DICOM数据,利用Mimics17.0软件对骨组织进行三维重建并建立三维坐标系,分离上下颌骨,显露完整的髁突形态,确定标志点及测量相关参考平面,对结果进行统计学分析。结果    非偏斜组两侧测量值差异无统计学意义。偏斜组中,偏斜侧髁突的冠状面和水平面与颅骨冠状面交角均大于对侧,髁突水平面与眼耳平面交角小于对侧,髁突矢状面与眼耳平面交角大于对侧,乙状切迹到眼耳平面和冠状面距离均小于对侧,到正中矢状面距离大于对侧。其余结果差异无统计学意义。结论    骨性Ⅲ类错牙合伴下颌偏斜患者的髁突位置不对称。偏斜侧髁突位置相对关节窝向后、内旋转,乙状切迹向后、上、外旋转。偏斜对侧髁突位置相对关节窝向前、外旋转,乙状切迹向前、下、内旋转。左右侧关节间隙无明显差异。     

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??Objective The location features of adult skeletal class ?? malocclusion mandibular deviation patients with mandibular condyle using Mimics software for 3D measurement. Methods    Fifty patients with skeletal class ?? malocclusion and mandibular deviation??deviation group??28 patients??nondeviation group??22 patients??received spiral computed tomography??DICOM data were collected. Maxillary and mandibular three-dimensional reconstruction was performed using Mimics 17.0. The upper and lower jaws were separated and the condylar morphology was revealed completely. To make sure measurements and analyze statistically. Results    There was no statistical difference in nondeviation group. In deviation group??the angle of coronal and horizontal plane in deviated condyle with coronal plane in skull was larger than the other side??the angle of horizontal plane in condyle with FH plane was smaller than the other side. The distance of sigmoid notch to FH plane and coronal plane was smaller than the other side. The distance of sigmoid notch to midsagittal plane is larger than the other side. The other measurements had no satistical difference. Conclusion    Mandibular condyle position of adults with skeletal class ?? malocclusion and mandibular deviation is asymmetric. The lateral condyle is more laterally and inferiorly positioned on the contralateral side than on the deviated side. The sigmoid notch is more laterally??superiorly??and posteriorly positioned on the deviated side. There is no obvious change in the TMJ space.     

单侧后牙反者髁突侧向运动轨迹的研究

目的通过记录单侧后牙反者与正常者下颌侧向运动时髁突在三雏方向上的运动轨迹。探讨单侧后牙反者髁交侧向运动轨迹的特征。揭示其与正常之间的差异。方法正常15例,单侧后牙反7例．应用计算机化的髁突运动轨迹描记仅(computer-Aide,Axiography,CADlAX)Ⅰ型以及分析软件(Gamma Dental Sofrware for Windows 2．3．2．22。GDSW)记录下颌做左右侧向运动时髁突在水平面及矢状面上的运动轨迹。结果实验组侧向运动中非工作侧矢状向最大位移量王著小于正常对照组。工作侧髁突向后运动的幅度大于正常对照组。结论单侧后牙反者髁突侧向运动轨迹形态与正常有明显差异。其两侧关节囊、韧带松驰。     

A study of the movements of the human temporomandibular joint complex in the cadaver

The objective of this study was to define the movements in the sagittal plane of the articular disk relative to the temporal bone and the mandibular condyle respectively, on jaw-opening in the absence of loads. Four temporomandibular joints from two human cadavers were used as materials in the study. Ten steel needles were placed in the lateral plane. Lateral photographs were taken of the articular area in different mandibular positions. OXY reference systems were adapted to the temporal and condylar points. The movements of the disk relative to the temporal bone are statistically different from those relative to the condyle. These findings are consistent with the new concept that the mandible joins the skull through two Temporomandibular Joint Complexes (TMJCs), one on each side and each one made up of a reciprocally fitting temporodiskal joint and a disko-condyle of the condylar type.     

健康人最大开口运动的研究

目的 探讨开口运动中髁突的运动及其与切点运动的关系。方法采用三维下颌运动轨迹描记仪ＭＴ－１６０２,记录３８名健康人髁突、切点标志点的运动数据,分析水平面髁突的运动曲线与速度。结果 研究结果表明：①髁突水平轨迹为直线、流畅曲线共存;②运动速度曲线似三角形,波峰前后的加速度恒定;③双侧髁突滑动速度不等者较常见;④开口初期速度与水平轨迹形态有一定关系,轨迹矢量偏向运动较快的一侧;⑤开口形受髁突水平轨迹和     

Relation of the glenoid fossa to craniofacial morphology, studied on dry human skulls

The purpose of this work was to compare glenoid fossa dimensions and craniofacial morphology on the basis of standard lateral roentgenograms. To overcome the difficulties encountered in making exact measurements on living subjects, 59 dry skulls were used. Eight angular measurements were taken to describe the form of the skull base, mandible, and articulating surface of the glenoid fossa, four linear measurements to describe the position of the fossa, and one to describe the size of the whole skull. A close relationship was observed between the morphology of the articulating surface of the glenoid fossa and the mandibular morphology. The skull base angulation was associated with the position of glenoid fossa in two ways. Basically, the position of the fossa is related to skull base characteristics, but the location of the articular eminence in relation to the clival plane suggests that the mandibular condyle may cause a remodeling of the eminence anteriorly when the glenoid fossa otherwise is translocated posteriorly in association with the flat skull base.     

骨性Ⅲ类偏颌患者髁突与(牙合)平面特征的CBCT研究

目的 利用锥形束CT(CBCT)测量分析骨性Ⅲ类偏颌患者髁突及(牙合)平面特征。方法 选取符合纳入标准的骨性Ⅲ类成年患者40例,所有个体按照颏下点偏离正中矢状面距离进行分组,分别测量各组左右两侧(牙合)平面角、髁突位置及形态,并对数据进行统计学分析。结果 骨性Ⅲ类偏颌患者的偏侧与对侧相比,(牙合)平面角、关节前间隙、关节上间隙、关节外间隙及髁突内外径差异有统计学意义(P<0.05),偏侧关节后位所占比例较大,下颌骨偏移量与偏侧髁突前间隙及对侧(牙合)平面角均呈正相关(P<0.01)。骨性Ⅲ类非偏颌患者的左右两侧(牙合)平面角、髁突位置及形态指标之间差异均无统计学意义(P>0.05),关节以前位、中位为主。结论 骨性Ⅲ类偏颌患者左右两侧(牙合)平面角、髁突位置及形态不对称,偏侧(牙合)平面角及髁突内外径较小,髁突向后下内方移位,且偏颌程度与(牙合)平面角及髁突位置之间存在相关性。     

反瞰髁状突头部100侧形态的X线分析

目的 :建立国人反瞰髁状突头部形态类型数据。方法 :使用颅底位X线片 ,对反瞰髁状突头部形态分型。结果 :男 3 3例 65侧 ,女 18例 3 5侧 ,共 51例 10 0侧反瞰髁状突头部形态分出A、B、C、D、E、F 6个型 ,E .E1、E .E2、F .F1、F .F2 4个亚型。其中 :A型最多 ,占 41.0 %。F .F1亚型最少 ,占 1.0 %。各类型所占的百分数左与右侧接近。 2 6例双侧类型同型 ,占总例数的 51.0 %。 2 3例双侧不同型中 ,男性占 3 9.1% ,女性占 60 .9%。结论 :反瞰方法是较为实用方法 ,可将颗状突形态分为 6型 4亚型     

单侧后牙长期缺失后髁突形态的锥形束CT研究

目的采用锥形束CT（CBCT）研究单侧后牙长期游离缺失对双侧髁突形态的影响。方法收集30例单侧后牙长期游离缺失患者和30例正常对照者的CBCT图像,应用Mimics 15.0软件测量双侧髁突体积、面积、线距及骨密度,对测量结果进行统计学分析。结果缺牙侧的髁突体积、髁顶体积及其骨密度明显小于非缺牙侧（P<0.05）;髁突横截平面的面积及其骨密度大于非缺牙侧（P<0.05）。结论单侧后牙长期游离缺失后,双侧髁突均发生适应性改建,缺牙侧髁突小于非缺牙侧。