Magnetic resonance imaging on TMJ disc thickness in TMD patients: A pilot study

Nonlinear Relationship between Temporomandibular Joint Disc Displacement Distance and Disc Length: A Magnetic Resonance Imaging Analysis

Objective: to explore the association between the distance of disc displacement and disc morphology in patients with temporomandibular disorders (TMDs). Methods: a total of 717 joints in 473 subjects were enrolled in this cross-sectional study. The magnetic resonance imaging (MRI) of each patient was evaluated for temporomandibular joint (TMJ) disc morphology classification and position. The distance of the disc displacement and disc length were measured for smoothing spline prediction. A stratified analysis was performed based on the types of disc positions. The disc width and length-width ratio (L/W) were also measured. Descriptive statistics, one-way analysis of variance, smoothing spline analysis, threshold analysis, and two piecewise linear regression were performed to investigate the association between the displacement distance and length of discs. Results: the differences in displacement distance among morphological categories and among different disc positions were statistically significant. Nonlinear relationships were found between distance and length in all subjects. Two turning points of distance (−1.8 mm and 1.7 mm) were found, dividing the curve into three segments. Disc width and L/W were significantly different among discs in the three segments of the curve. The correlation coefficient (β) for the three segments were as follows: −0.6 [95% confidence interval (CI) = −0.9 to −0.3, p < 0.001], 0.0 (95% CI = −0.1 to 0.0, p = 0.027), and −0.7 (95% CI = −0.8 to −0.7, p < 0.001). Nonlinear relationships were also found between the distance and length in cases with anterior disc displacement (ADD), anterior disc displacement with reduction (ADDWR), and without reduction (ADDWoR). Conclusion: the turning points of the disc displacement distance may be considered as a potential reference value for high-risk disc deformation and ADD. Disc length decreases sharply with anterior disc displacement when the disc displacement distance is over 1.7 mm. Prospective and long-term studies are required to clarify the natural course of the disc at different stages of the regression curve.

MRI-based observation of the size and morphology of temporomandibular joint articular disc and condyle in young asymptomatic adults

OBJECTIVE

To investigate the size and morphology of the temporomandibular joint (TMJ) articular disc and condyle in young asymptomatic adults by using magnetic resonance imaging (MRI) and to provide a reference for clinical diagnosis and scientific study of temporomandibular disorders (TMD).

METHODS

Overall, 93 undergraduate volunteers without TMD were enrolled from the freshmen pool at the Qingdao University. All participants underwent MRI of the oblique sagittal and oblique coronal TMJ planes. The articular disc and condyle were subsequently measured, and their morphology was evaluated. The obtained data were then grouped and analyzed statistically. Finally, intragroup correlation coefficient (ICC) was used to evaluate the interobserver measurement reliability.

RESULTS

We totally received 186 TMJ imaging samples. Based on our analysis, disc's anterior band in young asymptomatic adult females were thicker than males of the same age (p = 0.024). Moreover, the media-lateral dimensions of the condylar head of adult females were shorter than males of equal age (P＜0.001). The bilateral articular disc morphology was the same in 72.4% of subjects while the condylar morphology was the same in 63.4% of participants. Finally, using measurement reliability assessment, we demonstrated that our conclusions are reliable (ICC ≥0.7).

CONCLUSION

The thickness of the anterior band of the disc and the media-lateral dimensions of the condylar head were gender-related. Additionally, the morphology of the bilateral articular disc and condyle was different among the subset of young asymptomatic adults.

Accuracy of patient-specific temporal implants using PEKK

The main aim of this study was to evaluate the accuracy of immediate CAD/CAM reconstruction of the temporal hollowing following temporalis muscle surgery, using a patient-specific implant (PSI) PEKK model. This case series included ten patients who underwent maxillofacial reconstruction using temporalis muscle flap (TMF). The study involved the preoperative planning and fabrication of the temporal implant using virtual surgical planning software. The planning was based on multislice CT scans, from which DICOM files were used to fabricate a 3D model of the temporalis muscle using polyetherketoneketone (PEKK). The patients were followed up for 12 months, to check for any signs of infection or mobilization, and to assess accuracy. At the end of the follow-up period, all the patients showed acceptance of the external appearance, with no signs of infection or rejection. These customized implants were measured and compared with their original 3D preoperative planning using a point-based analysis. This revealed a mean difference (±SD) of 0.0373 (±0.3036) mm and a median difference (Q1 to Q3) of 0.0809 (-0.2108 to 0.2769) mm. The study demonstrated that a highly accurate duplication of PSIs can be achieved using this template-molding workflow. The use of PEKK PSIs resulted in uneventful healing and esthetic acceptance by the patients and, therefore, is a relevant treatment option when temporal hollowing has to be corrected.

Effect of Measurement Technique on TMJ Mandibular Condyle and Articular Disc Morphometry: CBCT, MRI, and Physical Measurements

PURPOSE

Accurate description of the temporomandibular size and shape (morphometry) is critical for clinical diagnosis and surgical planning and the design and development of regenerative scaffolds and prosthetic devices and to model the temporomandibular loading environment. The study objective was to determine the 3-dimensional morphometry of the temporomandibular joint (TMJ) condyle and articular disc using cone-beam computed tomography (CBCT), magnetic resonance imaging (MRI), and physical measurements of the same joints using a repeated measures design and to determine the effect of the measurement technique on temporomandibular size and shape.

MATERIALS AND METHODS

Human cadaveric heads underwent a multistep protocol to acquire physiologically meaningful measurements of the condyle and disc. The heads first underwent CBCT scanning, and solid models were automatically generated. The superficial soft tissues were dissected, and intact TMJs were excised and underwent MRI scanning, with solid models generated after manual segmentation. After MRI, the intact joints were dissected, and physical measurements of the condyle and articular disc were performed. The CBCT-based model measurements, MRI-based model measurements, and physical measurements were standardized, and a repeated measures study design was used to determine the effect of the measurement technique on the morphometric parameters.

RESULTS

Multivariate general linear mixed effects models showed significant effects for measurement technique for condylar morphometric outcomes (P < .001) and articular disc morphometric outcomes (P < .001). The physical measurements after dissection were larger than either the CBCT-based or MRI-based measurements. Differences in imaging-based morphometric parameters followed a complex relationship between imaging modality resolution and contrast between tissue types.

CONCLUSIONS

Physical measurements after dissection are still considered the reference standard. However, owing to their inaccessibility in vivo, understanding how the imaging technique affects the temporomandibular size and shape is critical toward the development of high-fidelity solid models to be used in the design and development of regenerative scaffolds, surgical planning, prosthetic devices, and anatomic investigations.

Tensile biomechanical properties of human temporomandibular joint disc: Effects of direction, region and sex

Approximately 30% of temporomandibular joint (TMJ) disorders include degenerative changes to the articular disc, with sex-specific differences in prevalence and severity. Limited tensile biomechanical properties of human TMJ discs have been reported. Stress relaxation tests were conducted on TMJ disc specimens harvested bilaterally from six males and six females (68.9±7.9 years), with step-strain increments of 5%, 10%, 15%, 20% and 30%, at 1% strain-per-second. Stress versus strain plots were constructed, and Young׳s Modulus, Instantaneous Modulus and Relaxed Modulus were determined. The effects of direction, region, and sex were examined. Regional effects were significant (p<0.01) for Young׳s Modulus and Instantaneous Modulus. Anteroposteriorly, the central region was significantly stiffer than medial and lateral regions. Mediolaterally, the posterior region was significantly stiffer than central and anterior regions. In the central region, anteroposteriorly directed specimens were significantly stiffer compared to mediolateral specimens (p<0.04). TMJ disc stiffness, indicated by Young׳s Modulus and Instantaneous Modulus, was higher in directions corresponding to high fiber alignment. Additionally, human TMJ discs were stiffer for females compared to males, with higher Young׳s Modulus and Instantaneous Modulus, and female TMJ discs relaxed less. However, sex effects were not statistically significant. Using second-harmonic generation microscopy, regional collagen fiber organization was identified as a potentially significant factor in determining the biomechanical properties for any combination of direction and region. These findings establish structure-function relationships between collagen fiber direction and organization with biomechanical response to tensile loading, and may provide insights into the prevalence of TMJ disorders among women.

Disk and joint morphology variations on coronal and sagittal MRI in temporomandibular joint disorders

OBJECTIVES

This study aims to assess the disk morphology and the condyle position in subjects with temporomandibular (TMJ) disk displacements on sagittal and coronal magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Seventy-four TMJs (from 37 patients) with positive clinical TMD symptoms according to the RDC/TMD axis I protocol were evaluated by 1.5 T MRI. Disk position, disk morphology, sagittal and coronal condyle position, joint effusion, joint space, and coronal condyle angulation were evaluated. Multivariate logistic regression was used to explore the relationship between disk displacement and MRI variables.

RESULTS

Disk displacement with reduction (DDR) was found in 36.48 % and without reduction (DDwR), in 21.62 % of the joints. Disk displacement was anterior in 35.1 %, anterior-medial in 13.5 %, and anterior-lateral in 9.45 % of cases. The thickened posterior band (94.48 OR, p = 0.001) and the posterior condyle position (4.57 OR, p = 0.03) were more likely found on sagittal MRI in disk displacements. On coronal slices, the disk displacement was significantly associated with the distance from the most medial condyle point to the midplane (p < 0.05).

CONCLUSIONS

Disk displacement is associated with changes of disk shape, disk dimension, and condyle position on sagittal MRI. A significant variation of the distance from the most medial condyle point to the midplane in disk displacement was found on coronal MRI.

CLINICAL RELEVANCE

Our study highlights the existence of changes on coronal MRI in TMD patients which should be assessed for better understanding of the clinical evolution of temporomandibular disorders.