Changes in temporomandibular joint anatomy, changes in condylar translation, and their relationship with disc displacement: magnetic resonance imaging study

Comprehensive 3-dimensional Positional and Morphological Analyses of Condyle and Glenoid Fossa in Patients with Skeletal Class II Malocclusion following Bimaxillary Orthognathic Surgery

This study aimed to comprehensively and quantitatively characterize 3-dimensional (3D) positional and morphological changes of the condyle and glenoid fossa in patients with skeletal Class II malocclusion treated with bimaxillary orthognathic surgery. Twenty eligible patients treated at our institution from January 2016 to December 2021 with more than 12 months of postoperative follow-up were retrospectively enrolled. Radiographic data of cone-beam computed tomography (CBCT) for each patient were collected at 3 stages: 1 week preoperatively (T0), immediately after surgery (T1), and at least 12 months postoperatively (T2). Positional changes, surface and volumetric alterations of condyle, and bone remodeling in glenoid fossa were measured and compared based on voxel- and surface registrations in visual 3D methods. Most patients exhibited a tendency for condyles to shift posteriorly, laterally, superiorly, and rotated outward, downward, and forward immediately after surgery. Posterior, medial, superior movement and outward, upward, and backward rotation of condyles were observed during follow-up (T1-T2). Bone resorption frequently occurred in the posterior area of condylar surfaces, while bone remodeling was more common in the anterior region of the glenoid fossa. Reduced volume of the condyle was found in most cases, which was not associated with the amount of mandibular advancement. Overall, the condyle and its corresponding glenoid fossa remained relatively stable during the follow-up. Our results reveal positional and morphological alterations in the condyle and the glenoid fossa after bimaxillary orthognathic surgery in patients with skeletal class II malocclusion. These changes predominantly fall within the spectrum of physical adaption.

Three-dimensional bone remodelling of glenoid fossa in patients with skeletal Class III malocclusion after bimaxillary orthognathic surgery

This study aimed to characterize three-dimensional quantitative morphological changes of glenoid fossa in patients with skeletal Class III malocclusion treated with bimaxillary orthognathic surgery. Ninety-five eligible patients (50 male, 45 female; mean age 22.09 years) were enrolled retrospectively. Cone beam computed tomography obtained at 1 week preoperatively (T0), immediately after surgery (T1), and at ≥ 12 months postoperatively (T2) were registered based on cranial base using voxel-based registration in 3D Slicer. Glenoid fossa surface was divided spatially into four regions, and bone modelling in these regions was visualized with color maps. Our data revealed that the mean surface variations of glenoid fossa were small, with modest bone formation as a whole. No significant associations between anteroposterior or vertical mandibular displacement and overall glenoid fossa remodeling were found (P > 0.05). Moreover, bone deposition was frequently observed in the anterior-lateral region of glenoid fossa in patients with a larger mandibular movement during T0-T1 (P < 0.001). Paired bone formation in the anterior-lateral region of glenoid fossa and bone resorption in the anterior-lateral region of condylar head was frequently observed. Collectively, our results revealed that glenoid fossa underwent complex but modest bone remodeling after bimaxillary surgery in skeletal Class III patients.

Association between chewing side preference and MRI characteristics in patients with anterior disc displacement of the temporomandibular joint

OBJECTIVE

To compare the magnetic resonance imaging (MRI) characteristics in the anterior disc displacement (ADD) patients with and without chewing side preference (CSP).

METHODS

The MRI characteristics of the bilateral temporomandibular joint (TMJ) in 111 patients with ADD were retrospectively analysed. Based on the presence of CSP, all subjects were divided into the non-CSP group (NC group, N = 40) and CSP group (C group, N = 71). Based on the preferred chewing side in the C group, the patients were divided into ipsilateral and contralateral sides. The morphology, length, disc-condyle angle, and coordinate position of the disc and condyle of the bilateral TMJ were compared.

RESULTS

MRI examination showed a significant difference between ipsilateral and contralateral joint displacement in patients with CSP (P<0.05). In CSP patients, the disc length of the same side in the ipsilateral side was significantly shorter than the contralateral side (P<0.05). A significant difference in the Y-axis coordinates of the ipsilateral and contralateral discs was also found in patients with CSP (P<0.05). The disc displacement grade, morphology of the articular disc, ipsilateral disc length, and ipsilateral disc-condyle Y-axis distance were positively correlated with CSP (P<0.05).

CONCLUSION

CSP is related to the shape of the articular disc and disc-condyle position in patients with ADD. CSP may aggravate the development of ADD.

A Bibliometric Analysis of Research on Temporomandibular Joint Disc Displacement from 1992 to 2022

The temporomandibular joint (TMJ) disc displacement is the most common temporomandibular disorders (TMD) condition. It causes clicking, pain, limited mandibular movements, and even masticatory difficulties in many people. The aim of this study is showcasing hotspots and frontiers in the field and providing a reference for the future research by a bibliometric analysis. Studies published from 1992 to 2022 were retrieved from Web of Science Core Collection on 23 April 2023. A total of 1882 studies (1739 articles and 143 reviews) were included in the bibliometric analysis. From 1992 to 2022, the annual number of publications and citations greatly increased. The United States of America (USA) contributed the most publications about TMJ disc displacement. Shanghai Jiao Tong University was the most productive institution; meanwhile, Yang, C. from this institution was the most prolific author. The University of Washington was the most influential institution, and Brooks, S. was the most influential author. Diagnostic criteria and management of TMJ disc displacement, as well as TMJ disc displacement-associated conditions, might be a hotspot for current global research. We provided an objective and valuable reference for future research on TMJ disc displacement.

A Semi-Automatic Approach for Holistic 3D Assessment of Temporomandibular Joint Changes

The literature lacks a reliable holistic approach for the three-dimensional (3D) assessment of the temporomandibular joint (TMJ) including all three adaptive processes, which are believed to contribute to the position of the mandible: (1) adaptive condylar changes, (2) glenoid fossa changes, and (3) condylar positional changes within the fossa. Hence, the purpose of the present study was to propose and assess the reliability of a semi-automatic approach for a 3D assessment of the TMJ from cone-beam computed tomography (CBCT) following orthognathic surgery. The TMJs were 3D reconstructed from a pair of superimposed pre- and postoperative (two years) CBCT scans, and spatially divided into sub-regions. The changes in the TMJ were calculated and quantified by morphovolumetrical measurements. To evaluate the reliability, intra-class correlation coefficients (ICC) were calculated at a 95% confidence interval on the measurements of two observers. The approach was deemed reliable if the ICC was good (>0.60). Pre- and postoperative CBCT scans of ten subjects (nine female; one male; mean age 25.6 years) with class II malocclusion and maxillomandibular retrognathia, who underwent bimaxillary surgery, were assessed. The inter-observer reliability of the measurements on the sample of the twenty TMJs was good to excellent, ICC range (0.71-1.00). The range of the mean absolute difference of the repeated inter-observer condylar volumetric and distance measurements, glenoid fossa surface distance measurements, and change in minimum joint space distance measurements were (1.68% (1.58)-5.01% (3.85)), (0.09 mm (0.12)-0.25 mm (0.46)), (0.05 mm (0.05)-0.08 mm (0.06)) and (0.12 mm (0.09)-0.19 mm (0.18)), respectively. The proposed semi-automatic approach demonstrated good to excellent reliability for the holistic 3D assessment of the TMJ including all three adaptive processes.

Evaluation of the lateral pterygoid muscle area, attachment type, signal intensity and presence of arthrosis, effusion in the TMJ according to the position of the articular disc

PURPOSE

The aim of this study was to evaluate the lateral pterygoid muscle (LPM) area, attachment type, signal intensity and presence of arthrosis, effusion in the temporomandibular joint (TMJ) by magnetic resonance imaging (MRI) according to the position of the articular disc.

METHODS

The study included a total of 126 TMJs belonging to 69 patients over the age of 18 years who had MRI due to TMJ complaints. The position of the articular disc, the area, attachment type, and signal intensity of the LPM, the presence of arthrosis on the condyle surface, and the presence of effusion in the joint space were evaluated.

RESULTS

The attachment type of the LPM did not show a statistically significant difference according to the position of the articular disc. The groups were not statistically different in terms of LPM intensity. Although the distribution of the LPM area was found to be low in the anterior disc displacement with reduction (R+DD) group and high in the anterior disc displacement without reduction (R-DD) group. It was determined that the rate of arthrosis at the condyle head was significantly higher in the R-DD group compared to the normal disc position group. The incidence of effusion was found significantly higher in the R-DD and R+DD groups than joints with normal disc position.

CONCLUSIONS

Pathological changes in LPM and TMJ can be detected by MRI. In the group with R-DD, the rate of arthrosis at the condyle head, effusion, LPM area, and intensity of the Sup. LPM were higher.

Action of Hyaluronic Acid as a Damage-Associated Molecular Pattern Molecule and Its Function on the Treatment of Temporomandibular Disorders

The temporomandibular joint is responsible for fundamental functions. However, mechanical overload or microtraumas can cause temporomandibular disorders (TMD). In addition to external factors, it is known that these conditions are involved in complex biological mechanisms, such as activation of the immune system, activation of the inflammatory process, and degradation of extracellular matrix (ECM) components. The ECM is a non-cellular three-dimensional macromolecular network; its most studied components is hyaluronic acid (HA). HA is naturally found in many tissues, and most of it has a high molecular weight. HA has attributed an essential role in the viscoelastic properties of the synovial fluid and other tissues. Additionally, it has been shown that HA molecules can contribute to other mechanisms in the processes of injury and healing. It has been speculated that the degradation product of high molecular weight HA in healthy tissues during injury, a low molecular weight HA, may act as damage-associated molecular patterns (DAMPs). DAMPs are multifunctional and structurally diverse molecules that play critical intracellular roles in the absence of injury or infection. However, after cellular damage or stress, these molecules promote the activation of the immune response. Fragments from the degradation of HA can also act as immune response activators. Low molecular weight HA would have the ability to act as a pro-inflammatory marker, promoting the activation and maturation of dendritic cells, the release of pro-inflammatory cytokines such as interleukin 1 beta (IL-1β), and tumor necrosis factor α (TNF-α). It also increases the expression of chemokines and cell proliferation. Many of the pro-inflammatory effects of low molecular weight HA are attributed to its interactions with the activation of toll-like receptors (TLRs 2 and 4). In contrast, the high molecular weight HA found in healthy tissues would act as an anti-inflammatory, inhibiting cell growth and differentiation, decreasing the production of inflammatory cytokines, and reducing phagocytosis by macrophages. These anti-inflammatory effects are mainly attributed to the interaction of high-weight HA with the CD44 receptor. In this study, we review the action of the HA as a DAMP and its functions on pain control, more specifically in orofacial origin (e.g., TMD).

Upregulation of FosB/ΔFosB in limbic circuits after tooth exodontia-induced occlusal instability in an experimental model of unpredictable chronic stress

Psychological stress and occlusal alterations are contributing etiologic factors for temporomandibular and muscular disorders in the orofacial area. The neural modulation recruited for this relationship, however, is not elucidated. The aim of this study was to investigate potential central mechanisms involved in the exodontia-induced occlusal instability associated with unpredictable chronic stress (UCS). Male adult Wistar rats were submitted to occlusal instability (unilateral molar teeth extraction) and/or to a UCS protocol and treated with diazepam or vehicle. The anxiety-like behavior was evaluated by elevated plus maze (EPM) and open field (OF) tests. Limbic structures such as the central nucleus of the amygdala (CeA), paraventricular nucleus of the hypothalamus (PVN), dorsal periaqueductal gray matter (dPAG) and nucleus accumbens core (NAc) were analyzed for expression of FosB/ΔFosB (immediate early genes) by immunohistochemistry. Exodontia and/or UCS decreased the time spent in the open arms at the EPM and the distance travelled at the OF, and increased the immobility time at the OF, suggesting anxiety-like behavior. In addition, exodontia induction resulted in an upregulation of FosB/ΔFosB in the CeA, PVN and dPAG, while UCS and exodontia + UCS upregulate FosB/ΔFosB immunoreactivity in the CeA, PVN, dPAG and NAc. Treatment with diazepam decreased the expression of FosB/ΔFosB in all analyzed structures of animals subject to UCS and exodontia + UCS, while promoted a reduction in the FosB/ΔFosB expression in the CeA, PVN and dPAG in animals subject to exodontia. Our findings showed an anxiogenic effect of exodontia and UCS, which is correlated with intranuclear neuron activation of limbic structures in a spatially dependent manner and that is prevented by the administration of diazepam.

Cone-beam computed tomographic assessment of the inclination of the articular eminence in patients with temporomandibular disorders and chewing side preference

Background

Chewing side preference (CSP) has been proposed as one etiology of temporomandibular disorders (TMDs) as it can induce the structural changes of the temporomandibular joint. But its association with the inclination of the articular eminence (IAE) is unknown. This study aimed to compare IAE between patients with CSP and without CSP.

Methods

Cone-beam computed tomography images of 90 patients with TMD (mean age of 45.6 years, 69 with CSP, 21 without CSP) and 20 participants without TMD and CSP (mean age of 41.3 years) were measured to compare IAE and depth of the glenoid fossa (DGF)

Results

IAE and DGF showed a positive correlation among all the participants. Compared with the participants without TMD and CSP, the TMD patients without CSP presented a similar IAE but with a significantly higher value of DGF (p < 0.05); in contrast, the TMD patients with CSP presented a significantly greater IAE and DGF (p < 0.05). No bilateral differences in IAE and DGF were observed in all the participants. Except the male patients with CSP had a deeper fossa than did the female, no differences in IAE and DGF according to gender were observed.

Conclusions

TMD patients with CSP seem to have a deep glenoid fossa with steep eminence which might be considered one characteristic imaging feature.

Automated cortical thickness measurement of the mandibular condyle head on CBCT images using a deep learning method

This study proposes a deep learning model for cortical bone segmentation in the mandibular condyle head using cone-beam computed tomography (CBCT) and an automated method for measuring cortical thickness with a color display based on the segmentation results. In total, 12,800 CBCT images from 25 normal subjects, manually labeled by an oral radiologist, served as the gold-standard. The segmentation model combined a modified U-Net and a convolutional neural network for target region classification. Model performance was evaluated using intersection over union (IoU) and the Hausdorff distance in comparison with the gold standard. The second automated model measured the cortical thickness based on a three-dimensional (3D) model rendered from the segmentation results and presented a color visualization of the measurements. The IoU and Hausdorff distance showed high accuracy (0.870 and 0.928 for marrow bone and 0.734 and 1.247 for cortical bone, respectively). A visual comparison of the 3D color maps showed a similar trend to the gold standard. This algorithm for automatic segmentation of the mandibular condyle head and visualization of the measured cortical thickness as a 3D-rendered model with a color map may contribute to the automated quantification of bone thickness changes of the temporomandibular joint complex on CBCT.

Temporomandibular Joints' Morphology and Osteoarthritic Changes in Cone-Beam Computed Tomography Images in Patients with and without Reciprocal Clicking-A Case Control Study

Background: Patients referred for orthodontic treatment often present symptoms of temporomandibular joints’ disorders (TMD), predominantly clicking. The objective was to analyze the morphology of the temporomandibular joints in cone-beam computed tomography (CBCT) images based on the presence of reciprocal clicking before orthodontic treatment. Methods: 105 participants took part in the study. 210 temporomandibular joints (TMJs) were allocated into one of two groups regarding the presence of reciprocal clicking. Morphology of condyle’s head, glenoid fossa, and articular eminence as well as condylar head position in the glenoid fossa and osteoarthritic changes in the area of the condylar head were examined for each TMJ in the CBCT images. Statistical analysis was performed with STATISTICA version 12.0. The following tests were performed: U-Mann Whitney, Kruskal-Wallis, t-Student, and chi-square. The statistical significance level was p = 0.05 for all the measurements included. Results: Significantly smaller condylar A-P dimension (p = 0.040) characterized temporomandibular joints with reciprocal clicking. Condyles were substantially more often positioned posteriorly (p = 0.043) and were significantly more often accompanied by subcortical cysts and pathologic osteoarthritic bone changes (p < 0.001). Conclusions: The early stages of internal derangements stay with alterations in morphology and position of TMJs as well as with the presence of osteoarthritic changes.