Computed tomography of condylar and articular disk positions within the temporomandibular joint

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

OBJECTIVE

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

METHODOLOGY

In 51 subjects 102 joints were analyzed using Anatomage Invivo dental 5.4. The measurements include: joints' parameters, position, angulation, and inclination of the condyle and articular fossa as well as 3D volumetric of the joint-spaces. All measurements were statistically analyzed by paired Student's t test to find out the differences between the left- and right sides. Pearson correlation coefficient test was done to figure out the relationship of the TMJ parts in the normal situation.

RESULTS

The inter-condyle distances medially, geometrically, and laterally were 90.2 ± 5.2,107 ± 6.1, and 125 ± 5.5 mm, respectively. However, the 102 condyles were angulated on three planes 54.9º ± 11.2, 71.8º ± 7.3, and 12.5º ± 6.3 at vertical-, horizontal-, and midsagittal planes, respectively. The joint spaces measurements were 2.6 ± 0.7 mm, 2.5 ± 0.8 mm, 2.4 ± 0.7 mm, and 3.3 ± 0.7 mm for anterior-, medial-, posterior-, and superior joints, respectively. The total volume of the whole joint-space was 404.3 ± 71mm³. The left condyle position was on the centric position whereas the right condyle was eccentric (slightly anterior).

CONCLUSION

Chinese subjects are characterized by wide inter-fossa distance and inter-condyle distance; however, no significant correlations with joint spaces in normal occlusion were found. The asymmetries between right- and left mandibular condyle were distinguished in angular and linear-vertical measurements. Finally, this study could be considered as reference data for upcoming research in the Chinese population.

Developing a reference MRI database for temporomandibular joints in healthy children and adolescents

BACKGROUND

Recognition of normal temporomandibular joints (TMJs) is essential to assess arthropathic changes. Few, if any, prior studies have evaluated the morphological appearance of growing TMJs by magnetic resonance (MR) examinations in the pediatric population.

OBJECTIVE

This study aimed to determine normative osseous appearance of growing TMJs according to age and gender, both qualitatively and quantitatively, concerning structural and bone marrow changes.

MATERIALS AND METHODS

From 1,036 MR scans screened, one joint was included from each of 157 patients (76% female; 2-18 years) presenting with at least one normal-appearing TMJ was included. Quantitatively, mandibular condyle was characterized by measuring the following: (i) head-neck angle, (ii) anteversion angle, (iii) condylar dimensions (mediolateral, craniocaudal and anteroposterior [AP]) and (iv) condylar volume. Furthermore, qualitative categorization of condylar shape, into one of three types, and condylar bone marrow type was performed.

RESULTS

The head-neck angle significantly correlated with age (bivariable regression β =0.60, P<0.001), indicating an increase of 1.6 degrees per year. Except for AP diameter of condyles, all other mandibular dimensions and condylar volume increased with age (β =0.20-0.59, P≤0.001-0.004). Significant age difference was observed among the different condylar shapes (P<0.001), indicating a change from rounded head without anterior tilt to rectangular head with anterior tilt. Lastly, mandibular condylar size, measured by volume and by AP and mediolateral dimensions, appeared larger in males.

CONCLUSION

The morphology of the mandibular condyles changes with age. During development, the shape of the condyles changes from round to rectangular in contour with the development of the anterior condylar tilt, as measured by the head-neck angle.

Evaluation of condylar positions in patients with temporomandibular disorders: A cone-beam computed tomographic study

Purpose

This study was performed to compare the condylar position in patients with temporomandibular joint disorders (TMDs) and a normal group by using cone-beam computed tomography (CBCT).

Materials and Methods

In the TMD group, 25 patients (5 men and 20 women) were randomly selected among the ones suffering from TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The control group consisted of 25 patients (8 men and 17 women) with normal temporomandibular joints (TMJs) who were referred to the radiology department in order to undergo CBCT scanning for implant treatment in the posterior maxilla. Linear measurements from the superior, anterior, and posterior joint spaces between the condyle and glenoid fossa were made through defined landmarks in the sagittal view. The inclination of articular eminence was also determined.

Results

The mean anterior joint space was 2.3 mm in the normal group and 2.8 mm in the TMD group, respectively. The results showed that there was a significant correlation between the superior and posterior joint spaces in both the normal and TMD groups, but it was only in the TMD group that the correlation coefficient among the dimensions of anterior and superior spaces was significant. There was a significant correlation between the inclination of articular eminence and the size of the superior and posterior spaces in the normal group.

Conclusion

The average dimension of the anterior joint space was different between the two groups. CBCT could be considered a useful diagnostic imaging modality for TMD patients.

Treating temporomandibular disorders with permanent mandibular repositioning: is it medically necessary?

In this paper, the authors review the rationale and history of mandibular repositioning procedures in relation to temporomandibular disorders (TMDs) as these procedures have evolved over time. A large body of clinical research evidence shows that most TMDs can and should be managed with conservative treatment protocols that do not include any mandibular repositioning procedures. Although this provides a strong clinical argument for avoiding such procedures, very few reports have discussed the biologic reasons for either accepting or rejecting them. This scientific information could provide a basis for determining whether mandibular repositioning procedures can be defended as being medically necessary. This position paper introduces the biologic concept of homeostasis as it applies to this topic. The continuing adaptability of teeth, muscles, and temporomandibular joints throughout life is described in terms of homeostasis, which leads to the conclusion that each person's current temporomandibular joint position is biologically "correct." Therefore, that position does not need to be changed as part of a TMD treatment protocol. This means that irreversible TMD treatment procedures, such as equilibration, orthodontics, full-mouth reconstruction, and orthognathic surgery, cannot be defended as being medically necessary.

Assessment of optimal condylar position with limited cone-beam computed tomography

INTRODUCTION

There are no quantitative standards for the optimal position of the mandibular condyle in the glenoid fossa. Recently developed limited cone-beam computed tomography (LCBCT) allows measurement of this position with high accuracy.

METHODS

LCBCT was used to assess 24 joints in 22 symptom-free subjects (10 male, 12 female; mean age, 18 years) who had no disc displacement as verified by magnetic resonance imaging. Their joints had optimum function with the starting and end points of all functional jaw movements coincident with maximum intercuspation. Linear measurements of anterior space (AS), superior space (SS), and posterior space (PS) were made to determine the position of the condyle for each joint.

RESULTS

The mean AS, SS, and PS values were 1.3 mm (SD +/- 0.2 mm), 2.5 mm (SD +/- 0.5 mm), and 2.1 mm (SD +/- 0.3 mm), respectively. The ratio of AS to SS to PS was 1.0 to 1.9 to 1.6. No significant sex difference was noted in joint space distances. The results showed less variability of condylar position in the fossa than previously reported in normal subjects.

CONCLUSIONS

These data from optimal joints might serve as norms for the clinical assessment of condylar position obtained by LCBCT.

Horizontal condylar angulation and condyle position associated with adolescent TMJ disk status

The purpose of this research was to examine the relationship between horizontal condylar angulation and position and joint status in an adolescent population. Submentovertex (SMV) radiographs and MRI (magnetic resonance images) of 95 subjects (56 females and 39 males) between the ages of 10-17 years (mean age 13.3 years) were used for this study. Horizontal condylar angulation as well as A-P and transverse condyle position were determined in relation to a cranial base reference (a line formed between the two foramina spinosa) from SMV images. Joint status variables consisted of disk length and disk displacement measurements taken from medial, central and lateral sagittal MRI slices of each joint. Additional joint status variables were derived through a principal component analysis which was used to calculate a single disk length, disk displacement, and internal derangement variable for each joint. The results were: 1. No significant correlations (p = .05) were found between any of the joint status variables and horizontal condylar angulation; 2. Statistically significant correlations (r = .14 to .22, p = .05) were observed between certain joint status variables (anterior disk displacement in medial and central joint slices, disk displacement variable, and TMJ internal derangement variable) and transverse condyle position; and, 3. Statistically significant correlations (r = -.22 to .25; p = .05) were observed between condylar angulation and both A-P and transverse condyle position.

Reconsideration of the TMJ condylar position during internal derangement: comparison between condylar position on tomogram and degree of disk displacement on MRI

The objective of this study was to investigate condylar position during different degrees of disk displacement. The degree of disk displacement was evaluated on 1.5 Tesla high-field sagittal MR images of 76 joints (48 patients; mean age 19.4 years) and was classified into three grades (1 to 3). To establish condylar position, the anterior, superior and posterior joint spaces were measured on corrected tomograms. The possible relationship between condylar position, indicated by the width of joint space and successive degree of disk displacement, was compared by a one-way factorial ANOVA (p < 0.05). The anterior joint space was significantly larger in grades 1, 2, and 3 disk displacements than in grade 0 pointing to a dorsal condylar position. The posterior joint space was significantly smaller in grades 1 and 2 compared with grade 0. When the degree of the disk displacement becomes severe (i.e., grade 3 disk displacement), the posterior joint space tends to increase to a similar distance as in a normal healthy joint pointing to a more normal condylar position.

Tuned-aperture computed tomography (TACT). Theory and application for three-dimensional dento-alveolar imaging

OBJECTIVES

To introduce a new method for creating three-dimensional (3-D) radiographic displays based on optical aperture theory known as tuned-aperture computed tomography (TACT). With a number of advantages over conventional plain film and tomographic imaging.

METHODS

The TACT algorithm and some of its capabilities are explained and published with results of in vitro simulations produced from a well-tested multi-tube tomosynthetic x-ray system. Examples of TACT reconstructions of a tooth with naturally occurring caries which were produced from multiple projections and generated with a new servo-controlled single-tube prototype are illustrated. Current imaging strategies in dentistry and their shortcomings in the detection of dento-alveolar disease are reviewed. Pertinent theoretical aspects of the TACT reconstruction algorithm are described and dental applications discussed in light of these limitations.

RESULTS

Results of several published in vitro investigations derived from a prototype TACT system are referenced. Sample images of a tooth with naturally occurring caries derived from an even newer system are displayed. All data are consistent with the hypothesis that TACT imaging yields diagnostic performance either comparable, or superior, to that obtainable from conventional control modalities depending on the diagnostic task. Moreover, all investigations cited demonstrated conclusively the obvious theoretical benefits associated with the acquisition of multiple projections in three dimensions.

CONCLUSIONS

TACT shows promise as a supplement to film-based dental radiography and as a digital alternative to conventional tomographic systems used in dento-alveolar applications.

Condyle position in the temporomandibular joint. Comparison between asymptomatic volunteers with normal disk position and patients with disk displacement

Though the significance of condyle-fossa relationship in the temporomandibular joint has not yet been clarified and normal condyle position not yet defined, efforts have been made to guide the mandibular condyle into a centric position in the glenoid fossa with the aim of relieving the symptoms in patients with orofacial pain and temporomandibular joint internal derangement. The present study investigated the mandibular condyle position in 34 joints in asymptomatic volunteers with normal disk position as verified by arthrography and compared it with the mandibular condyle position in 85 joints in patients with different stages of internal derangement. The results showed that in the volunteers with normal joints including normal superior disk position, the condyles were almost randomly distributed in anterior, centric, and posterior positions in the glenoid fossa. Of the joints with anterior disk displacement approximately half of the number of joints with reducing disks and two thirds of the joints with nonreducing disks appeared to have posterior condyle position. Posterior condyle position cannot, however, be used to diagnose internal derangement because the condyle was found to be either in anterior or centric position in many joints with a displaced disk. The variety in condyle position in the healthy joints ought to be taken into consideration if treatment is chosen to normalize the mandibular condyle position by bringing it into a centric position in the glenoid fossa.

Histologic evaluation of computed tomographic TMJ articular disk visualization

The reliability of computed tomography (CT) for visualization of the temporomandibular joint (TMJ) articular disk has often been the subject of discussion. The success or failure of CT may be determined by different factors. This study was designed to evaluate the effect of these factors, such as type of equipment used, patient motion and artifacts on articular disk visualization, and also to assess the validity of the articular disk image in comparison with histological pictures. Ten TMJ autopsy specimens were collected after the teeth were placed in intercuspal position. The TMJ was deep frozen, dissected and kept frozen during subsequent CT scanning and histological processing. To study the influence of the specifications of the CT equipment on the visualization of the TMJ articular disk, two different CT units were used. The CT images were evaluated for interpretability and interpretation of articular disk position. The validity of the CT appearance of articular disk position and form was assessed by superposition of CT and histological pictures. The interpretability of the articular disk visualization in the CT images was very low. However, for CT images judged to be interpretable, there was a good degree of matching between the diagnosed articular disk position and form and the findings in the corresponding histological pictures. No significant differences between the two different CT units were noted. It is concluded that CT is inappropriate for TMJ articular disk visualization. Nevertheless, if the disk is visible on the CT image, its appearance represents the true position and form within the joint.

Accuracy of measures of temporomandibular joint space and condylar position with three tomographic imaging techniques

Fourteen temporomandibular joints in seven dry skulls, representing the distribution of horizontal and vertical condylar axis inclinations of a larger population, were imaged with three tomographic projection techniques. Closest anterior and posterior joint spaces were measured on radiographs, and sectioned plaster casts were made from impressions of actual joint space, Individualized horizontal and vertical correction of the condylar axis produced significantly more accurate (p less than 0.005) measures of condylar space than either standard 20-degree horizontal correction (SHC) or individualized horizontal correction (IHC) of the axis. Representations of joint space by SHC and IHC were not significantly different from each other. Numbers of uninterpretable images displayed a similar pattern of 9.5% for individualized horizontal and vertical correction, 14% for IHC, and 17% for SHC. This study supports the use of fully individualized condylar axis correction with temporomandibular joint tomography for increased accuracy of visualization of the osseous anatomy of the joint.

Increased horizontal angle of the mandibular condyle in abnormal temporomandibular joints. A magnetic resonance imaging study

The horizontal condylar angle was measured in axial magnetic resonance images of normal and abnormal temporomandibular joints (TMJs). The average condylar angle in the normal joints was 21.2 degrees. In joints with disk displacement with reduction it was 29.7 degrees; joints with disk displacement without reduction, 33.5 degrees; and in joints with degenerative joint disease, 36.5 degrees. There were statistically significant differences between all four groups. Thus the condylar angle seemed to be increasingly larger with more advanced pathologic changes related to internal derangement and degenerative disease in the joint. The reason for the larger condylar angle in the abnormal joint was unclear. Joints with a larger condylar angle might have a greater tendency for internal derangement and degenerative joint disease to develop. Another possible explanation could be that remodeling associated with internal derangement and degenerative joint disease might result in a larger condylar angle. Further studies with longitudinal observations are needed to determine whether a causal relationship exists between the changes of the joint and a large condylar angle.

The effects of positioning variations in transcranial radiographs of the temporomandibular joint: a laboratory study

The relationship of the mandibular condyle to the articular fossa and eminence as seen on transcranial oblique lateral (TOL) radiographs of the temporomandibular joint is used by some clinicians as an important diagnostic sign and indicator of treatment. The literature is divided on the validity of this. The aim of this study was to consider the effects of variations in both the position of the joint and the X-ray beam orientation on the image seen on TOL radiographs. TOL radiography of a mounted block specimen of a human temporomandibular joint and associated tissues was carried out using a range of specimen rotations (+20 degrees to -20 degrees with respect to the sagittal plane) and X-ray beam angulations (20 degrees, 25 degrees, 30 degrees). Analysis of tracings of the joint images showed that most of the parameters measured varied by statistically significant amounts with changes in either specimen rotation or beam angulation. It is concluded that any convention which purports to evaluate the position of the mandibular condyle in relation to the articular fossa from TOL radiographs is invalid when the orientation of the condyle to coronal and horizontal planes is unknown.

Computed tomography versus single-contrast arthrotomography in evaluation of the temporomandibular joint disc. A study of autopsy specimens

The lateral, central and medial parts of 15 right temporomandibular joint autopsy specimens were studied to compare the ability of computed tomography (CT) and single-contrast arthrotomography in diagnosing the disc position and configuration. The radiologic findings were compared with macroscopic findings in a blinded fashion. In the CT examination, the diagnostic accuracy was 40% in determining the disc position and 26.7% in determining the disc configuration. However, in many areas of the joints the disc was not possible to evaluate by CT. With arthrotomography the diagnostic accuracy in determining the disc position was 75.6% and the disc configuration 60%. The sensitivity of CT was 0.45 and of arthrotomography 0.95 for the diagnosis of the disc position. The specificity was 0.87 for CT and 0.76 for arthrotomography. From these results, we conclude that arthrotomography is a reliable aid to diagnosis of TMJ disc changes and that CT cannot replace it.