Three-dimensional computed tomographic analysis of frontal sinus in Asians

Although there are many reports on the measurement of the paranasal sinuses, few studies examined the development of frontal sinus with three-dimensional computed tomography (CT), especially in children. In this study, we evaluated the normal development of frontal sinus in Asian children, and we also analyzed the height, length, and width of the frontal sinus in Korean adults with three-dimensional CT imaging. We retrospectively reviewed three-dimensional facial bone CT of a total of 352 patients younger than 23 years. The occurrence of the frontal sinus was evaluated by their age. The maximal length, height, and width were measured with a computer device. The volume of the frontal sinus was also evaluated. In those older than 4 years, the pneumatization of frontal sinus was detected. Frontal sinus developed continuously and was observed in almost every child older than 17 years. The length, height, width, and volume of the frontal sinus continuously increased until the age of 20. The maximal growth of the frontal sinus was observed at puberty. The width and volume of the frontal sinus showed a high correlation coefficient (r=0.8) relative to the height or length. In adults, the mean height, width, depth, and volume of the frontal sinus were 27.2±7.0 mm, 52.5±17.1 mm, 22.0±6.3 mm, 8.39±3.78 cm, respectively. The results of this study may be helpful in understanding the normal development of frontal sinuses in children. It could be also helpful for further research and surgical approaches for frontal sinuses.     

Three-dimensional analysis of temporomandibular joint in Chinese adults with normal occlusion and harmonious skeleton

Oral Radiology - This study aimed to analyze the detailed three-dimensional measurements of temporomandibular joint (TMJ) in Chinese adults with normal occlusion and harmonious skeleton. In 51...     

Computed tomography of the normal temporomandibular joint

A study was made in two parts, retrospective (I) and prospective (II), on two samples of 36 and 17 individuals, respectively, who had temporal bone CT studies for reasons unrelated to TMJ pain and dysfunction. Groups I and II had no radiographic signs of TMJ disease and Group II had neither radiographic nor clinical signs of TMJ disease. Both groups were considered to have normal joints. Joint morphometrics for the two groups (I/II) were as follows; transverse condylar dimensions were 18.5/18.1 mm. Condylar angulation averaged 24 degrees/25 degrees and intercondylar distance averaged 83/83 mm while extra condylar distance averaged 118/118 mm. The condyle in the sagittal plane showed a smooth and rounded form with anterior-superior joint space averaging 1.9/1.7 mm while the central-superior joint space averaged 2.3/2.2 mm. The medial-horizontal joint space averaged 3.9/3.7 mm. The slope of the central portion of the articular eminence averaged 60 degrees/60 degrees in the sagittal plane.     

Computed tomography of the normal temporomandibular joint

Abstract – A study was made in two parts, retrospective (I) and prospective (II), on two samples of 36 and 17 individuals, respectively, who had temporal bone CT studies for reasons unrelated to TMJ pain and dysfunction. Groups I and II had no radiographic signs of TMJ disease and Group II had neither radiographic nor clinical signs of TMJ disease. Both groups were considered to have normal joints. Joint morphometrics for the two groups (I/II) were as follows; transverse condylar dimensions were 18.5/18.1 mm. Condylar angulation averaged 24°/25° and intercondylar distance averaged 83/83 mm while extra condylar distance averaged 118/118 mm. The condyle in the sagittal plane showed a smooth and rounded form with anterior-superior joint space averaging 1.9/1.7 mm while the central-superior joint space averaged 2.3/2.2 mm. The medial-horizontal joint space averaged 3.9/3.7 mm. The slope of the central portion of the articular eminence averaged 60°/60° in the sagittal plane.     

Computed tomographic evaluation of the density of the temporomandibular joint meniscus

Pathologic alteration of the articular disk, including moderate calcification within the meniscus proper, has been reported to occur in many cases of TMJ dysfunction with chronic anterior meniscal displacement. The purpose of this investigation was to measure, by means of direct sagittal computed tomographic scanning technology, the density (x-ray attenuation) of the meniscus. Fifty-two joints, shown to have meniscus displacement with or without reduction (MD/MDR), and 24 symptomatic joints with normal tomograms were evaluated with the use of a GE 8800 CT scanner. Mean attenuation values were extrapolated with the use of a symmetrical (1 to 9 pixels) region-of-interest (ROI) cursor. Density gradients of the masseter muscle, lateral pterygoid fat pad, and lateral pterygoid muscle were also obtained. The results of this study showed that the mean meniscal density values were 116.7 +/- 4.2 Hounsfield units (HU) for MD subjects, 111.3 +/- 4.6 HU for MDR subjects, and 82.4 +/- 2.9 HU for subjects with symptoms. The MD and MDR density group means were significantly different (p less than 0.001) from the normal group means. A relative comparison of the meniscus density with that of the lateral pterygoid muscle, its fat pad, and the masseter muscle showed a consistent mean difference when the paired t test was used. Meniscal displacement was found to be associated with an increase in density gradient, which suggests histologic alteration.     

Temporomandibular joint: computed tomographic three-dimensional reconstruction

Computed tomography represents an effective and highly automated method to display biomedical data from many sources. It has a number of advantages over previous reconstruction methods, particularly the ability to automatically locate object-boundary outlines and produce shaded three-dimensional images of reconstructed data. A three-dimensional reconstruction of the temporomandibular joint was performed successfully on five cadaver heads using the Phillips Tomoscan and IP5000 image processor. The program used in this study of the temporomandibular joint is divided into five distinct steps: data gathering, rotation and projection, filtering, smoothing, and shading. Comparison of this type of data is important in the study of the normal and abnormal anatomy of the temporomandibular joint. Similarly, quantitative data obtained from reconstructed computed tomograms can be used to study normal anatomy in vivo and to examine the effects of various treatment modalities on the size and morphologic characteristics of tumors and other pathologic entities.     

Three-dimensional finite element analysis of the cartilaginous structures in the human temporomandibular joint.

While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30 degrees variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers on the articular surfaces.     

Computed tomographic analysis of the position of the mandibular canal in unilateral temporomandibular joint ankylosis patients

The aim of this study was to investigate the position of the mandibular canal through the region of the mandibular angle and body using computed tomographic (CT) imaging, and to relate the findings to those in the molar region on the ankylosed temporomandibular joint (TMJ) and the normal side. The mandibles of 25 patients with unilateral ankylosis of the TMJ (14 women and 11 men) were recorded on coronal CT slices 2 mm thick. All patients included in the study had had ankylosis diagnosed before they were 16 years old. The position of the mandibular canal was studied from the region of the third molar to that of the first molar on ankylosed and normal mandibles. The following variables were measured: the distance between the external surface of the buccal cortical plate and the outer surface of the mandibular canal (B); the distance between the external surface of the lingual cortical plate and the outer surface of the mandibular canal (L), and the distance between the external surface of the inferior border of the mandible and the outer surface of the mandibular canal (I). Our results suggest that changes are more pronounced in the regions of the second and third molars. The mandibular canal is closest to the inferior border of the mandible in the region of the second molar and farthest in that of the third molar. The greatest distance between the outer surface of the mandibular canal to the external surface of the buccal cortex on the ankylosed and normal sides was found in the first and second molars, and it was greater on the normal side. To minimise the risk of injury to the inferior alveolar nerve, the measurements of B, L, and I should be considered separately on the ankylosed and normal sides when planning mandibular osteotomies for distraction osteogenesis and orthognathic surgery, and when using monocortical screws.     

A clinical and tomographic study on temporomandibular joint osteoarthritis

One hundred and twenty two patients with temporomandibular joint (TMJ) disorders were examined by lateral and frontal tomograms. A comparison between clinical and radiographic findings was performed to confirm the clinical characteristics of TMJ osteoarthritis. The patients with radiographic abnormal or suspicious findings showed a significantly higher frequency of TMJ pain and limitation of mouth opening less than 29mm than the patients with normal findings. The TMJs with surface erosion also showed a significantly higher frequency of TMJ pain than the TMJs with normal findings. Therefore, these findings were thought to be one of the distinctive feature of TMJ osteoarthritis. However, 22 patients with unilateral clinically primary symptoms presented bilateral abnormal or suspicious findings and 7 patients with unilateral clinically primary symptoms presented abnormal or suspicious findings only in the TMJ opposite to the clinically primary symptomatic site. Therefore, the necessity of radiographic examination of the clinically unaffected TMJ was concurrently indicated for the treatment planning and for the further research. Dr. Yamada was the Professor of the Department of Oral Radiology April 1982–March 1991     

A study on reliability of the tomographic image of the temporomandibular joint

Summary For this study, seven different types of phantom were made simulating the condyle. The phantoms attached to a human dry skull were tomographed using the Polytome-U, under identical conditions to those of tomography for patients. There was no significant difference of the images between tube side and film side of the mandible. The images of the medial part of the TMJ were clearer than that of the lateral part. A discrepancy of contours on the focal plane between the phantom and the tomographic image occurred when the inclination of the phantom surface was larger than the maximum exposure angle. Concerning the influence of focal movements to image quality, the images obtained from hypocycloidal movements were superior with minimum superimposition, although the contrast of the image varied when the phase of the hypocycloidal movements were altered. Any sectional images were not manifested with the phantoms when the inclination of the phantom surface was larger than 23 degrees. Furthermore, 106 condyles from human dry skull were examined on the area of which the inclination of the condylar surface was less than 23 degrees. The mean latero-medial distance of the area was 14.1mm, which corresponded to 75% of whole latero-medial distance of the condyle.     

The acoustical characteristics of the normal temporomandibular joint

Both clinical and empirical evidence suggests that the "normal" temporomandibular joint produces noise during function. The purpose of this study was to determine the conditions under which these noises might arise. Joint sounds and mandibular movements were recorded simultaneously from 200 adults who had no previous history or present symptoms of TMJ pain or dysfunction. The joint sounds were recorded bilaterally by means of two separate miniature vibration transducers mounted on a common headband, and incisal point mandibular movements were measured by a magnetometer tracking system. Recordings were made while each subject opened and closed the mouth, first in a natural and comfortable manner, and then to maximum displacement. Two types of measurements were made: the appearance, onset, and duration of joint-propagated sounds in relation to relative mandibular position; and the spectral properties of the detected sounds. The results of this study showed that for natural opening and closing movements of the mandible, the "normal" TMJ was silent for all age groups. However, for the maximum displacement condition, detectable sounds appeared at the points of maximum displacement in both the opening and closing phases of the cycle in over 80 percent of the subjects. However, these sounds were, as a class, substantially longer than, and spectrally distinct from, abnormal joint sounds, suggesting that they arise from a distinct physical substrate.     

牵张力作用下颞下颌关节受力的三维有限元研究

目的 研究不同方向牵张力作用下颞下颌关节的受力状况,探讨下颌骨牵张成骨过程中牵张力合理的方向.方法 通过建立颞下颌关节及下颌骨的三维有限元模型,在模型上模拟牵张力的作用,得到下颌骨牵张成骨过程中,颞下颌关节的受力状况.牵张力的方向为平行于下颌骨下缘或平行于正中矢状面.分别观察牵张延长1 mm、3 mm、5 mm的应力分布状况.结果 不同方向牵张力作用下颞下颌关节的受力情况是不同的.当牵张力平行正中矢状面时,颞下颌关节的受力较大.结论 在下颌骨牵张成骨过程中,牵张力的方向具有重要的生物力学效果.     

Three-dimensional observation of the temporomandibular joint disk in the rhesus monkey

The three-dimensional ultrastructure of the TMJ disk of two normal rhesus monkeys was investigated using the SEM. The upper and under surface of the TMJ disk consists of a close network of delicate collagen fibrils. On the undersurface, they have an undulating configuration, with the elevations running in one direction. On the upper surface, irregular and gentle waves can be observed. The matrix of the TMJ disk is composed of two main parts: one is the collagen fibrils that run in a sagittal direction making up the central fibrous core, and the other consists of the collagen fibrils that enclose the fibrous core. The collagen fibrils running in a sagittal direction show a wavy, winding appearance, and these structures are more numerous on the side of the TMJ disk facing the condyle. It is concluded that the wavy, winding structure and undulated configuration of the collagen fibers results in an elastic quality, opposes stress, and functions to absorb shock.     

Diagnosis by computed tomography of temporomandibular joint meniscus displacement

CT may be a practical alternative to arthrography for diagnosing displacement of the meniscus in the TMJ. In a study of 75 patients, 69 were diagnosed by CT to have meniscal displacement. Thirty-four diagnoses were subsequently confirmed by surgery or arthrography.Disadvantages of CT are cost (almost twice as much as an arthrogram), inability to diagnose perforations, and inability to judge meniscus dynamics, which can be done by fluoroscopy. Advantages are patient comfort, safety, and decreased total radiation dose.Continued research and clinical correlation will be needed to determine the role of CT in the diagnosis of meniscus displacement of the TMJ. However, initial results are promising, and CT may quickly replace arthrography as the diagnostic procedure of choice.     

Three-dimensional finite element analysis of cartilaginous tissues in human temporomandibular joint during prolonged clenching

Objective

Bruxism, the parafunctional habit of nocturnal grinding of the teeth and clenching, is associated with the onset of joint degeneration. Especially prolonged clenching is suggested to cause functional overloading in the temporomandibular joint (TMJ). In this study, the distributions of stresses in the cartilaginous TMJ disc and articular cartilage, were analysed during prolonged clenching. The purpose of this study was to examine if joint degradation due to prolonged clenching can be attributed to changes in stress concentration in the cartilaginous tissues.

Design

Finite element model was developed on the basis of magnetic resonance images from a healthy volunteer. Condylar movements recorded during prolonged clenching were used as the loading condition for stress analysis.

Results

At the onset of clenching (time = 0 s), the highest von Mises stresses were located in the middle and posterior areas (6.18 MPa) of the inferior disc surface facing the condylar cartilage. The largest magnitude of the minimum principal stress (−6.72 MPa) was found in the condylar cartilage. The stress concentrations were relieved towards the superior disc surface facing the temporal cartilage. On the surfaces of the temporal cartilage, relatively lower stresses were found. After 5-min clenching, both stress values induced in the TMJ components were reduced to 50-80% of the stress values at the onset of clenching, although the concomitant strains increased slightly during this period.

Conclusions

It is suggested that both the condylar and temporal cartilage layers along with the TMJ disc, play an important role in stress distribution and transmission during prolonged clenching due to tissue expansion. Furthermore, our study suggests that a development of stress concentrations in the TMJ during prolonged clenching and risk factors for the initiation of TMJ degeneration could not be confirmed.     

Bony ankylosis of the temporomandibular joint: a computed tomography study

Bony ankylosis of the temporomandibular joint is a disabling disease that almost invariably manifests itself in the first two decades of life. CT of the temporomandibular joints was performed in 50 patients--axial CT in 2 and coronal CT in 48--of whom 43 (86%) had received trauma to the joints. New bone of variable form and thickness was observed in 64 joints (the involvement was bilateral in 14 patients). These joints were classified into one of two categories: type I, medially angulated condyle with deformed articular fossa and a mild-to-moderate amount of new bone formation; and type II, no recognizable condyle or fossa but instead a large mass of new bone. Type I was etiology-specific and seen only when trauma was the antecedent, whereas type II was a sequelae of either insult. A pseudofracture in the new bone was seen in 49 (77%) joints. Six joints showed subtle deformities but no new bone. Since coronal CT fully characterizes the lesion at acceptable radiation exposure levels, it appears to be valuable in the preoperative workup of these patients.     

应用锥形束CT诊断颞下颌关节骨关节病的探讨

目的探讨锥形束CT（cone beam CT，CBCT）在颞下颌关节骨关节病诊断中的应用前景。方法临床诊断为颞下颌关节骨关节病（炎）、不可复（可复）性盘前移位伴骨关节病患者共48例（96侧关节）。48例同时拍摄经咽侧位x线平片和CBCT，比较两种x线检查方法的病变检出率、医师判断的重复性和一致性。结果颞下颌关节骨关节病x线表现分为6型：髁突表面皮质骨模糊消失型（I型）、表面缺损破坏型（Ⅱ型）、髁突磨平型（Ⅲ型）、骨质硬化型（IV型）、骨质增生型（V型）、囊样变型（Ⅵ型）。CBCT的检出率分别为65．63％、37．50％、27．08％、31．25％、28．13％、1．04％；经咽侧位x线平片的检出率分别为52．08％、19．79％、32．29％、23．96％、12．50％、2．08％。对每一型病变的程度和范围，同一医师两次判断或不同医师之间，对I、Ⅱ型病变的评判，经咽侧位x线平片和CBCT均有高度的一致性，Kappa值大于0．60。结论除Ⅲ型外，CBCT对每一类型的病变均有很高的检出率，所显示的病变及其部位清晰、明确。CBCT清晰的病变影像、明确的病变部位和显示多层面病变的优势，使其有望成为颞下颌关节骨关节病判定病变程度、预后以及药物治疗后效果的定量评价手段。