Soft tissue cephalometric norms in Japanese adults.

Lateral soft tissue cephalometric standards of Japanese normal adults were developed with the use of Ricketts, Epker, Holdaway, and Legan cephalometric analyses. Cephalometric radiographs of 211 Japanese normal adults were analyzed, and the soft tissue measurements were compared with those of an esthetically pleasant Japanese subgroup and white adult sample. Statistically significant differences were found in the Japanese sample when compared with the white norms. On the other hand, the soft tissue mean values of the Japanese supernormal group were similar to the white norms, with the exception of the nasolabial angle and the lip prominence. Soft tissue cephalometric norms are specific for ethnic groups, but these values should not be interpreted as treatment goals. Normative data represent an aid for the diagnosis and planning of orthodontic treatment and orthognathic surgery.

Effect of occlusal appliances and clenching on the internally deranged TMJ space.

AIMS: Stabilization appliances and mandibular anterior repositioning appliances have been used to treat patients with internal derangement of the temporomandibular joint (TMJ) based on the assumption that these appliances work by decompressing the TMJ. The purpose of this study was to indirectly test this assumption. METHODS: Bilateral TMJ tomograms of 7 subjects with unilateral anterior disc displacement without reduction (ADDwor) were taken during comfortable closure and during maximum clenching in maximum intercuspation; tomograms were also taken with the 2 types of occlusal appliances in use. Outlines of the condyle and the temporal fossa were automatically determined by an edge-detection protocol, and the minimum joint space dimension of the joints with and without ADDwor was automatically measured for each experimental condition as the outcome variable. RESULTS: Upon comfortable closure and maximum clenching, the minimum joint space dimensions of the ipsilateral and contralateral joints with the use of stabilization appliances and mandibular anterior repositioning appliances were not significantly different from those seen in maximum intercuspation. CONCLUSION: These findings do not indicate that these appliances induce an increase in joint space during closing and clenching in joints with ADDwor.

Clinical predictability of temporomandibular joint disc displacement.

Single items from a typical clinical examination have proved disappointing in their predictive value for temporomandibular joint (TMJ) disc displacement. Only one criterion (the 12 o'clock) is used to diagnose normal disc position. According to this criterion, the posterior band of the disc should be located at the top of the condyle, at the 12 o'clock position. The purpose of this study was to determine which signs and symptoms provide a valid prediction of the condition of the joint based on 4 magnetic resonance imaging (MRI) criteria used to define normal disc position. Sagittal MRI and clinical findings of 137 temporomandibular disorder patients and 23 normal asymptomatic volunteers were used. Three calibrated and blinded observers interpreted the images. Disc position with the mouth closed was evaluated based on 4 MRI criteria: 12, 11, 10 o'clock, and the intermediate zone. Disc position with the mouth open was determined based on one criterion. It was considered normal if the intermediate zone of the disc was located between the condyle and the articular eminence. Joints were classified as normal or as having disc displacement with or without reduction. The sensitivity and specificity of multiple clinical parameters for predicting the condition of the joint established by each of these 4 gold-standard MRI criteria were then determined. Regarding disc displacement with reduction, significant differences were observed in the sensitivity and specificity of all of the clinical parameters used to predict the imaging diagnosis established by each of the criteria. Concerning disc displacement without reduction, no significant differences were observed. The intermediate zone criterion was the criterion that most accurately reflected the condition of the joint. The clinical predictability of the disorder diagnosed according to this criterion suggests that clinical findings alone are too often nonspecific as predictors of the imaging stage of disc displacement. However, we found that combining the most sensitive clinical items to predict the disorder and using an overall criterion for positivity to interpret the results led to an impressive increase in the specificity of the combination, enabling false-positive diagnoses to be excluded.

Diagnostic value of 4 criteria to interpret temporomandibular joint normal disk position on magnetic resonance images.

OBJECTIVE: This study was undertaken to evaluate different criteria to establish normal disk position on magnetic resonance images. STUDY DESIGN: Magnetic resonance image findings of 137 consecutive patients with temporomandibular disorders and 23 asymptomatic volunteers were used in this study. Three calibrated observers interpreted the images individually. Four closed-mouth and 1 open-mouth criteria were tested for their ability to define normal and abnormal temporomandibular joint disk positions on magnetic resonance images. RESULTS: For the 46 joints in the asymptomatic volunteers, the criterion that yielded the highest percentage of normal disk position diagnoses was the disk's intermediate zone (93.5%). Clock face criteria produced the following declining percentages of normal disk position diagnoses: 10 o'clock, 82.6%; 11 o'clock, 63.0%; and 12 o'clock, 39.1%. Similar results were obtained for the patients with temporomandibular disorders. In both groups, as the number of normal disk position diagnoses declined, the percentage of joints with a diagnosis of disk displacement with reduction increased. Conversely, the percentage of joints with a diagnosis of disk displacement without reduction (in the group of patients with temporomandibular disorders) did not appear to be substantially affected by the 4 closed-mouth disk position criteria. CONCLUSIONS: These results suggest that the intermediate zone criterion for disk displacement is the more stringent criterion and the one that would yield the lowest number of false positives when the disk position is being judged in the closed-mouth sagittal view.

The relationship between signs and symptoms of temporomandibular disorders and bilateral occlusal contact patterns during lateral excursions.

The relationship between signs and symptoms of temporomandibular disorders (TMD) and bilateral occlusal contact patterns was investigated in 143 TMD patients (mean age: 34.0 +/- 15.9 years; 38 male and 105 female). In addition to an interview regarding chief complaints and accompanying symptoms, various muscles and the temporomandibular joints were palpated bilaterally and occlusal analyses were made. Only 5 out of 108 paired variables were found to be significantly associated by using the chi-squared test. Medial pterygoid muscle pain on palpation showed significant associations with the occlusal contact pattern (P < 0.005), especially working side contacts (interocclusal tooth contacts on the working side) (P < 0.005), during contralateral excursions; sternocleidomastoid muscle pain on palpation showed a significant association with balancing side contacts (interocclusal tooth contacts on the balancing side) during ipsilateral excursions P < 0.05); shoulder stiffness and pain in the eye showed significant associations with balancing side contacts during contralateral excursions (P < 0.05). The results show only a weak relationship between some TMD symptomatology and bilateral occlusal contact patterns during lateral excursions. The findings suggesting the specific laterality of a few TMD signs and symptoms associated with particular occlusal contacts may deserve closer case-control study.

The validity of clinical examination for diagnosing anterior disk displacement with reduction.

OBJECTIVE: The objective of this study was to evaluate the diagnostic accuracy of a clinical examination for diagnosing anterior disk displacement with reduction. STUDY DESIGN: A series of 273 consecutive patients with temporomandibular disorders were clinically examined according to well-defined criteria. The patients were examined for clicking by digital palpation during maximal mouth opening and closing (the Clicking test). When clicking was identified, two additional tests were performed: one determined whether the clicking was eliminated at a protruded position, and the other determined whether the clicking became louder when the patient's mandible was manipulated toward the eminences. Bilateral magnetic resonance images were subsequently obtained from all patients; the clinical examination findings were then compared to the imaging-based diagnoses of the temporomandibular joint status to assess the diagnostic accuracy of the clinical findings. RESULTS: Although the predictability of identifying anterior disk displacement with reduction by clicking was relatively low, it increased to an acceptable level when the additional tests were used. The overall accuracy for the Clicking test combined with either of the other tests was about 90%. CONCLUSION: Our results suggest that anterior disk displacement with reduction can be diagnosed with considerable accuracy through the use of a clinical examination only.

Viscoelastic properties of the pig temporomandibular joint articular soft tissues of the condyle and disc.

It has been suggested that a sustained loading condition such as clenching could compress the temporomandibular joint (TMJ) articular soft tissues. However, there is still no clear understanding of how the TM joint articular tissues respond under compression. To answer this question, we performed in vitro indentation tests on fresh articular discs and cartilage-bone systems of the condyles of 10 Yorkshire pigs (aged 7 months) using a self-developed indentation tester. The indenter was 5 mm in diameter and was controlled by means of a computer-aided feedback mechanism. Bilateral condyles from the same mandible were uniformly prepared; one was used for measurements under sustained compression (SC) and the other for measurements under intermittent compression (IC). The displacements of the indenter induced by a SC of 10, 20, and 30 Newtons (N, units of force) for 10 min and by an IC, also of 10, 20, and 30 N, with one-second duration and two-second intervals for 10 min were measured by means of a displacement sensor with a resolution of 0.001 mm. From these data, the indentation curves of the articular discs and the cartilage-bone systems were calculated. Both the disc and the articular cartilage showed characteristic displacement vs. time curves-namely, an instantaneous deformation upon load application, followed by a time-dependent creep phase of asymptotically increasing deformation under constant load. However, the indentation curves of the two tissues were not identical: The deformation of the articular cartilage was dose-dependent, but that of the disc was not. Moreover, the articular cartilage deformed significantly less under IC than under SC. This difference was not found in the disc. It can be concluded that both the disc and the articular cartilage of the pig temporomandibular joint have viscoelastic properties against compression; however, the disc is stiffer than the articular cartilage.

The influence of observer calibration in temporomandibular joint magnetic resonance imaging diagnosis.

OBJECTIVE: This study was undertaken to investigate the potential of reducing observer variation through a calibration program. STUDY DESIGN: The study was based on three sets of randomly selected temporomandibular joint magnetic resonance images. Each set consisted of bilateral images from 20 consecutive patients with temporomandibular disorders. As a baseline, three well-experienced noncalibrated investigators interpreted the images individually for disk position and disk configuration. After the initial interpretation, interobserver agreement was calculated as a kappa index and presented to the examiners. On the same occasion, the investigators analyzed agreement between them on the criteria to be used. RESULTS: Overall data in this study showed an increase in the frequency of interobserver agreement with regard to disk position after the calibration trials were instituted. With regard to disk configuration, substantial interindividual variations were observed even after the observers reached consensus as to the criteria to be used. CONCLUSIONS: These data suggest that after calibration trials, it is possible for three examiners to obtain reliable and reproducible results in reporting temporomandibular joint disk position on magnetic resonance images.

The effect of occlusal appliances and clenching on the temporomandibular joint space.

It has been suggested that stabilization appliances and mandibular anterior repositioning appliances work by decompressing the temporomandibular joint. To indirectly test this assumption, tomograms of right temporomandibular joints of seven subjects were taken during comfortable closure and maximum clenching in maximum intercuspation and on the two types of occlusal appliances. Outlines of the condyle and the temporal fossa were automatically determined by an edge detection protocol. Upon comfortable closure, the anterior joint space dimension was reduced with stabilization appliances and mandibular anterior repositioning appliances. Upon maximum clenching, the minimum joint space dimension on stabilization appliances was equivalent to that seen in maximum intercuspation, while that on mandibular anterior repositioning appliances was substantially less (P < .05). Findings do not indicate that these appliances induce an increase in joint space during clenching.

Effects of sustained unilateral molar clenching on the temporomandibular joint space.

OBJECTIVE: To measure the effect of unilateral sustained clenching on the temporomandibular joints, changes in the minimum joint space dimension were assessed. STUDY DESIGN: Ten healthy subjects performed a sustained clench on a bite force transducer in the first molar region for 5 minutes with a constant force of 170 N. Three separate sagittal tomograms were bilaterally obtained with the transducer in place before clenching and during the beginning and at the end of the contraction. Changes were quantified with a computerized image analysis system. RESULTS: The minimum joint space of the contralateral temporomandibular joint was significantly reduced both at the beginning and at the end of the contraction task. Further the minimum joint space was also significantly less at the end than at the beginning of the contraction even though bite force level was identical. The ipsilateral condyle images showed no significant shift in the minimum joint space. CONCLUSIONS: These data suggest that unilateral molar clenching induces a significant reduction of the minimum joint space in the contralateral temporomandibular joint and a sustained condition remarkably increases this change.