It is widely known that the masticatory system is related to changes in the temporomandibular bone surface. However, researches differover the diagnostic value of the horizontal condylar angle. The functional anatomy of horizontal condylar angle has received little attention. The purposes of this article are to study the anatomical features of the horizontal condylar angle, and to evaluate its diagnostic value. 48 Japanese dry skulls (15-49y) were investigated for their maxillofacial and masticatory morphology, and their horizontal condylar angle, using three dimensional measurements. The relation between these two features was examined.
The following results were obtained: there was a difference between the mean of the right and left horizontal condylar angle. The discrepancy between the absolute value of the right and left angle in an individual was 0.1 to 10.5 degrees. The horizontal condylar angle of Angle's class 2 was larger than other classes, and there was a significant difference in class 3 (p<0.05). The angle showed a significant positive correlation with the masseter inclination (CX: r=3969), and with inclination of the lateral fossa angulation (CX: r=0.4148), but a negative correlation with the inclination of the lateral fossa angulation (CY: r=-3623) in all classes. These results suggest that the less the articular tubercle height, the larger the angle. They also indicate that there might be limitations to the diagnostic value of the horizontal condylar angle in TMJ dysfunctin and osteoarthrosis. These limitaions are particulally evident in the normal and abnormal, or right and left, discrepancy in an individual.

View full abstract

Twenty-five female patients less than 15 years old with TMJ arthrosis were analysed. As a control group, twenty-five females of the same age with normal TMJ function were selected. using statistical methods (t-test etc.) The following features in both graups were evaluated: 1) median line, 2) over bite, over jet, 3) Spee curve, 4) crowding, 5) total tooth size, archsize, 6) arch length, arch width, 7) basal arch length, basal arch width, 8) discrepancy, 9) Angle's classification.
The results showed that there were differences in 2), 3), 7) between the patient group and the normal group.
We conclude that the disharmony of occlusion in juveniles causes muscle spasms, retroposition of the mandible and abnormal movement of the mandible.
These factors may bring about TMJ arthrosis in the patients' later life.

View full abstract

The development of the human mandibular condyle is one of the most important topics in dentistry and the subject of much current research. However, little has been published on th development of the mandibular condyle during the fetal period, and in particular studies based on radiographic examination are almost nonexistens. Under the circumstances the present study of the 5 to 10 months old fetus was undertaken clarify the development of the fetal mandibular condyle.
The study was undertaken on 33 Japanese fetuses of between 5 to 10 months that had been preserved in formalin in the 1st Department of Anatomy, Nihon University School of Dentistry.
The ages of the fetus were determined by applying of Haase's method from crown-heel length measurements. Image measurements were made from radiographs using the method described by Toriumi and Sawada. Mento-Vertical Cephalography films were placed on a film viewer to trace an outline of the condyle. Then the long axis, the short axis, the maximum distance between the lateral poles of the condyles, the area of the condyle and the angle formed by the corrected axial plane of the two condyles were measured by a digitizer connected to a computer.
The results were as follows
1. The long and short axes, the maximum distance between the lateral poles of the condyles and the area of condyle in the Mento-Vertical Cephalography view show an almost linear development with increased fetal ages during the period 5 to 9 months. This linear development makes a spurt from the 9th month, with no significant difference between the sides.
2. The angle formed by the corrected axial plane of the two condyles of 5 to 10 month old fetuses was about 120 degrese, showing almost no change with increased fetal age.

View full abstract

The results obtained were as follows:
1) The peak latencies of wave I. III and V for patients with craniomandibular disorder were longer than longer than those for normal subjects.
2) The patients with craniomandibular disorder had larger right-left differences in the latencies. These results indicate that craniomadibular disorder may influence not only the stomatognathic system but also the auditory system and the brainstem.

View full abstract

In the treatments for the patients of stomatognatic dysfunction, various types of bite planes have been used. These blite planes can be divided into two types-one for muscles, another for TMJ. Recently we hare frequently used a ‘disk repositioning typebite plane’ for consevative TMJ therapy, with success.
We report the effects of the ‘disk repositioning type bite plane’ on masticatory muscles both during border movement and during the open-close-clench cycle in subjects with stomatognatic dysfunction with ‘anterior displacement of disk with reduction’.

View full abstract

Strain measurements were taken on the cerebral surface of the Squamous part of the monkey temporal bone during mandibular movements, in order to elucidate the dynamic responses of the upper wall of mandibular fossa. The total strains in the bone of the upper walls of the mandibular fossa and articular eminence markedly increased in the protrusive movement of the mandible, and increased to a lesser extent in the lateral movements. But, this strain did not increase in the intercuspal position. The tensile strain was observed on the medial side of the upper wall of the mandibular fossa. In addition, the compressive strain was measured on the lateral side of the mandibular fossa for most of the mandibular movements and position. On the other hand the compressive strain was observed on the medial side and the tensile strain on the lateral side during posterior border movement of the madible. The largest principal strain was recorded during the protrusive movement of the mandible. The direction of the principal strain (tensile strain) was from anterolateral to posteromesial. It is suggested that the bone of the upper wall of mandibular fossa controls the quantities, quality and direction of the principal stran during mandibular movement. Moreover, during mandibular movements a buffer effect on the forces is produced not only by the articular disc but also by the bone of the upper wall of the mandibular fossa.

View full abstract

It is widely accepted that loading is an important factor in temporomandibular joint (TMJ) growth, stability, and function. Disk displacement, disk perforation and remodeling of TMJ bony components have been considered likewise to be a result of excessive or misdirected joint loading. Nevertheless, human TMJ loadings during chewing have not been estimated either directly or indirectly.
In this study, TMJ loading during the power stroke of mastication was investigated electromyographically and biomechanically.
The Electromyographic activities of the medial pterygoid muscles, masseter muscles and anterior temporal muscles during gum and beef jerkey chewing were first measured bilaterally. Then, the position and the angulation of the resultant muscle force vector were biomechanically calculated by using those muscle activities and 3-dimensional cephalometric data. The resultant muscle force vector calculated was used to estimate TMJ loading during the power stroke of mastication and it was compared with the loading during unilateral clenching obtained previously.
The following results were obtained:
1. At the beginning of unilatertal chewing, TMJ loading during the power stroke seemed to be distributed more to the balancing side condyle. However, when the subsequent rythmical chewing began, ‘working-side shift’ of the resultant muscle force vector was observed.
2. At the beginning of unilateral chewing, the resultant muscle force vector was approximately perpendicular to the occlusal plane on the frontal view. However, when the subsequent rythmical chewing began, the vector tilted slightly to the balancing side.
These results indicate that masticatory muscle activities during chewing are controlled so as to achieve two effects: to transmit muscle forces to biting force effectively, and to distribute muscle forces to the bilateral condyles equally.

View full abstract

A 38-year-old man was referred to our department because of a severe trismus and a toothache. He had taken the treatments of a osteoarthrotomy at the left TMJ and a mandibular shaping with iliac bone grafting at age 20 in another university hospital.
However, complete bony ankylosis has recurred. Therefore, a low positional arthroplasty of the left ramus using the casted titanium plate was perfomed and mouth opening exercise with original mouth gag has been continued.
The progress after these treatments is very satisfactory.

View full abstract

Two cases of bilateral coronoid hyperplasia are presented. One is a 17-year-old man who noticed a restriction of mouth opening at 14 years old. The other is a 13-year-old boy who noticed the symptom at 10 years old. Each of them was diagnosed as having a temporomandibular joint disorder and were placed on physical therapy and splint therapy for a few years before they were diagnosed correctly. They were treated successfully by intra-oral coronoidectomy.
A review of the literature revealed only forty-nine repored cases of bilateral coronoidhyperplasia. The majority of the cases were men and their symptoms occurred under 19 years old. It also showed that diagnosis of the disease was often difficult. In order not to overlook the condition, it is important that should beexamined if a patient has a difficulty in opening the mouth, not only the joints but also the coronoid processes.

View full abstract

A comparison between double-contrast arthrotomographic findings and arthroscopic findings of superior joint compartment of the TMJ is reported. Fibrous adhesion in this compartment was suggested by the double-contrast arthrotomographic findings: 1. incomplete expansion of the superior joint compartment can be seen when a contrast medium is injected. Also, the position of this stenosis hardly changes from the open to the closed mouth. 2. A narrow fibrous band-like structure is observed in the superior joint compartment.
The fibrous adhesions of double-contrast arthrotomographic findings are classified as follows
1) Wide area adhesion: Expansion of the superior compartment can not be seen.
2) Small area adhesion: Type A; a stenosis is observed in the superior joint compartment.
3) Small area adhesion: Type B; a narrow fibrous band-like structure is observed.
Double-contrast and single-contrast arthrotomography were applied to 175 patients (181 joint). Two patients were arthrotomographically normal with the superior disk position. Anterior displacement of the disk was found in 154 joints. Thirty-eight joints showed anterior disk displacement with reduction, 76 joints showed anterior disk displacement without reduction, and 40 joints showed anterior disk displacement associated with perforation of the posterior attachment of the disk.
In the joints having anterior disk displacement without reduction, capsular adhesion was seen more frequently in 53 joints-70% than in those having anterior disk displacement with reduction in 8 joints-21%. Nine patients (9 joints) were found to have capsular adhesion without disk displacenent. Three out of these 9 joints had wide area adhesion.
The detection of fibrous adhesion by double-and single-contrast arthrotomography was compared. In 64 out of the 75 joints with fibrous adhesion, double-contrast was rated as superior to singlecontrast. In 11 joints, the information about adhesion was equal by both methods. It is concluded that single-contrast arthrotomography alone cannot establish the diagnosis of capsular adhesion.

View full abstract

Nine joints of arthroscopic surgery patients were studied postoperatively by dual-space, double-contrast arthrotomography. The postoperative clinical conditions of patients were estimated by Sanders' standard. 5 cases were excellent, 2 cases were good and 2 were poor. Three out of 5 excellent cases showed resorptive bone change of the condyle and eminence in their postoperative condition. Two good and two poor cases did not have resorptive bone change. Four out of the 5 excellent cases had altered disk configuration. In all of the 5 excellent cases, fibrous adhesions in superior joint compartment were absent. Five excellent, two good and one poor cases showed a decrease of the size of the superior joint compartment.

View full abstract

MR imaging of 138 patients (276 TMJs) was performed at 0.2 T with a surface coil from January 1990 to December 1990. 190 of the 276 TMJs appeared with signs and symptoms suggestive of internal derangements of the TMJ. The MR imaging protocol was as follows: (a) an axial localizer with a TR of 100 msec., TE of 20 msec., fiele of view of 26cm, 5-mm slice thickness, 256×128 matrix and two excitations (26-second imaging time); (b) 5-mm -thick sagittal slices with the jaw closed, with no interslice gap, and with TR of 500 msec., TE of 38 msec., field of view of 20cm, 256×192 matrix and five excitations (imaging time, 8 minutes) (c) 5-mm-thick coronal slices with the jaw closed, TR of 300-500 msec., TE field of view, matrix and excitations were equal to the sagittal imagings. When anterior disk displacement of the TMJ was not revealed by sagittal images, coronal imaging was added. Clinical MR imaging of the 138 patients showed sideways disk displacement in six patients (6 TMJs: 4%). These six patients had intermediate opening clicking (2 TMJs), late opening clicking (3 TMJs) and clicking at side shift (1 TMJs).

View full abstract

We studied the findings of the initial visit to our clinic in 71 patients (9 males and 62 females) with unilateral closed lock which hadn't been treated. All of the patients were diagnosed by either MRI or arthrography. The average age of the patients was 33.4 years with a range of 13 to 81 years. The incidence of closed lock was high between the ages of 15 to 29 years. The average maximal opening was 29.1mm with a range of 14 to 55mm. The duration from the onset of closed lock to the initial visit was mainly within 30 days, although the average was 106 days. The degree of pain during chewing and during opening and closing, and the disturbance to daily life were moderate according to visual analog scales. The average maximal opening was significantly smaller in patients with a short closed lock period (1 to 30 days) than in those with a long one (more than 30 days). The average maximal opening was larger in patients under 20 years than in those 20 years old or more. The fact that 7 patients were able to open the mouth more than 40mm, that 19 patients hadn't had any history of clicking, and that 4 patients had clicking at the time of initial examination indicates that MRI or arthrography is important for the confirmation of closed lock, as clinical diagnosis in itself may not identify this condition.

View full abstract

A report is presented on a case of severe deformity of both mandibular condyles in renal osteodystrophy.
The patient was a 44-years-old female who visited our department with a chief complaint of right temporomandibular joint pain. Her past history showed that she has been under hemodialysis therapy for about 4 years and 5 months at this hospital for chronic renal failure. As for her present illness, for about the past three years she had habitually bitten on ice cubes to relieve her dry throat. Physically, she had pain of the right chest, right lumbar region, and right knee joint with a slight gait disturbance. In the oral cavity, the lower jaw was receded, and open bite of the anterior teeth was observed at the time of occlusion. Radiographically, remarkable bilateral absorption of th mandibular condyle was seen. The results of the clinical laboratory tests were characterized by the findings of renal failure and secondary hyperparathyroidism.
As for therapy, efforts were made to relieve burden on the temporomandibular joint by suspending her habit of biting on ice cubes and prohibiting her to chew hard foodstuffs. The results of this therapy brought about disappearance of right temporomandibular joint pain within about 2 weeks.
The cause of severe deformity of both mandibular condyles in this case was considered to be the burden placed on the temporomandibular joint from her habit of biting on ice cubes.

View full abstract

A rare cace of posterior disc displacement without reduction of the temporomandibular joint is described. The double-contrast arthrotomography of temporomandibular joint proved valuable in establishing a definitive diagnosis. Repositioning of the disc is succeeded in this case by the pumping manipulation technique.

View full abstract