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Temporomandibular disorders are the most common cause of chronic orofacial pain, but, except where they occur subsequent to trauma, their cause remains unknown. This cross-sectional study assessed chewing function (habitual chewing side) and the differences of the chewing side and condylar path and lateral anterior guidance angles in participants with chronic unilateral temporomandibular disorder. This is the preliminary report of a randomized trial that aimed to test the effect of a new occlusal adjustment therapy. The masticatory function of 21 randomly selected completely dentate participants with chronic temporomandibular disorders (all but one with unilateral symptoms) was assessed by observing them eat almonds, inspecting the lateral horizontal movement of the jaw, with kinesiography, and by means of interview. The condylar path in the sagittal plane and the lateral anterior guidance angles with respect to the Frankfort horizontal plane in the frontal plane were measured on both sides in each individual. Sixteen of 20 participants with unilateral symptoms chewed on the affected side; the concordance (Fisher's exact test, P = .003) and the concordance-symmetry level (Kappa coefficient κ = 0.689; 95% confidence interval [CI], 0.38 to 0.99; P = .002) were significant. The mean condylar path angle was steeper (53.47(10.88) degrees versus 46.16(7.25) degrees; P = .001), and the mean lateral anterior guidance angle was flatter (41.63(13.35) degrees versus 48.32(9.53) degrees P = .036) on the symptomatic side. The results of this study support the use of a new term based on etiology, \"habitual chewing side syndrome\", instead of the nonspecific symptom-based \"temporomandibular joint disorders\"; this denomination is characterized in adults by a steeper condylar path, flatter lateral anterior guidance, and habitual chewing on the symptomatic side.

To reveal morphological changes in musculoskeletal apparatus after conservative treatment of condylar head fracture (CHF) by clinical examinations, condylar and masticatory muscle reconstruction, to guide the clinical therapeutic strategy. Patients with unilateral CHF and treated conservatively during November 2015 to January 2020 were enrolled and followed up for 2 years. Clinical assessments (mouth open, mandible deviation and occlusal relationship), and CT reconstruction (condyle, ramus height, masseter and lateral pterygoid) immediately and 2 years after fracture were compared with the unfractured side as control group. Mixed-effect analysis and two-way ANOVA were manipulated and P ≤ 0.05 was defined as significant. 26 patients were involved. The average of maximum mouth opening increased from 12.6 ± 5.40 mm to 27.8 ± 8.60 mm. Significant musculoskeletal resorption with an average condyle volume decrease of 241.86 mm3 (P = 0.0029), ramus height decrease of 1.87 mm (P = 0.0004), masseter volume decrease of 3,447.3 mm3 (P < 0.0001), and lateral pterygoid volume decrease of 1203.05 mm3 (P = 0.0049) occurred. No significant changes occurred to the unfractured sides. Conservative treatment of CHF displayed significant musculoskeletal resorption. Clinical assessments showed less optimal improvements. Surgeons should be aware of these trends and take full consideration before applying nonsurgical treatment.

Objective The objective of this study was to measure and analyze the joint space, condylar morphology, and thickness of the roof of the glenoid fossa (RGF) in patients with unilateral second molar scissor bite using cone beam CT (CBCT). Methods A total of 80 patients were included in this study. Forty patients with a normal posterior occlusal relationship, who attended the Department of Orthodontics at the First Hospital of Shanxi Medical University from December 2021 to August 2023, were selected as the control group. The experimental group consisted of 40 patients with unilateral second molar scissor bite during the same period. All patients underwent CBCT scanning, and the resulting images were analyzed using the NNT viewer software in multiplanar reconstruction (MPR). Axial, coronal, and sagittal adjustments were made for each patient. Results In the control group, the right and left joint spaces (PS, SS, AS), the height of the upper part of the condyle, and the depth of the glenoid fossa did not show statistically significant differences (P > 0.05). When comparing bilateral condylar morphology and joint space in the experimental group, it was found that the posterior joint space on the scissor bite side was greater than that on the normal occlusion side, while the anterior joint space on the scissor bite side was smaller than that on the normal occlusal side. Additionally, the height of the upper condyle and the depth of the glenoid fossa on the scissor bite side were greater than that on the normal occlusal side, with statistically significant differences (P < 0.05). However, there were no statistically significant differences in SS, internal and external joint diameter, as well as anterior and posterior diameters (P > 0.05). The comparison of the minimum thickness of the roof of the glenoid fossa in both the sagittal and coronal directions between the patients in the experimental group and the control group showed no statistically significant difference (P > 0.05). Furthermore, the asymmetry index of the supracondylar height in the control group was significantly smaller than that in the experimental group, displaying a statistically significant difference (P < 0.05). The differences in the asymmetry indices of the anterior and posterior diameters of the condyle, as well as the inner and outer diameters, were not statistically significant (P > 0.05). When analyzing the position of the condyle in the sagittal direction of the glenoid fossa in the patients of the control group, it was observed that the majority were in the anterior and medial positions, with only 10% and 5% being in the posterior position. However, the analysis of the condyle position in the sagittal direction of the glenoid fossa in the experimental group revealed statistically significant differences (P < 0.05), with the condyle position on the scissor bite side being more anterior. Conclusion Unilateral second molar scissor bite can result in anterior displacement of the condyle, greater height of the condyle superiorly as well as the depth of the glenoid fossa.

Osteoarthritis is a degenerative joint disease that disrupts the cellular homeostasis within cartilage tissues, promoting further disease progression that can lead to debilitating pain. Cartilage of the temporomandibular joint (TMJ) is unique among diarthrodial joints because they are of neural crest origin, rather than the mesoderm germ layer. TMJ cartilage also has different cellular architecture, where it is composed of a superficial fibrous layer, a proliferative layer, and a fibrocartilage layer overlying subchondral bone. Understanding of the cytopathological changes that occur during TMJ osteoarthritis (TMJOA) could potentiate therapies to mitigate disease progression and repair diseased tissues. Here, we analyzed the unique cell populations present in healthy and OA-induced condylar cartilage of adult rats through single-cell RNA-sequencing. TMJOA was established via our previous rat model to study the changes in the cellular composition of the condyle in response to OA. Several cell types could be uniquely identified, and the prominent matrix producing cells were fibroblasts and chondrocyte subsets. Our trajectory and pseudotime analysis revealed three cell fates stemming from a fibrochondrocyte-like population and two chondrocyte cell fates that stem from a shared progenitor population. We also found that Pleiotrophin is uniquely expressed in the proliferative zone by cells with a chondrocyte progenitor phenotype. In OA cartilage, differential gene expression in the fibroblast group revealed responses to inflammation, possibly through activation of chondrocyte differentiation. The chondrocyte group was highly metabolically active, indicative of rapid repair or remodeling. Cell-cell signaling analysis revealed that chondrocyte and chondrocyte progenitor communication became highly activated. Additionally, intracellular pathways that may contribute to cellular dysfunction and tissue remodeling were highly active, while pathways related to tissue catabolism appeared less active.

Condylar resorption is a feared complication of orthognathic surgery. This study investigated condylar resorption in a cohort of 200 patients This allowed for a powerful update on incidence and risk factors. 9.5% of patients developed resorption. These patients had on average, 17% volume loss with 3.9 mm ramal height loss and 3.1 mm posterior mandibular displacement. 2% of patients had bilateral resorption. Univariable analysis identified a younger age, a bimaxillary + genioplasty procedure, larger mandibular advancements, upward movements of the distal segment, a higher counterclockwise pitch of the distal segment, smaller preoperative condylar volumes and a higher anterior/posterior lower facial height ratio as risk factors on a patient level. Univariable analysis on a condylar level also identified compressive movements of the ramus and a higher mandibular plane angle as risk factors. Using machine learning for the multivariable analysis, the amount of mandibular advancement was the most important predictor for condylar resorption. There were no differences in preoperative mandibular, ramal or condylar shape between patients with or without resorption. These findings suggest condylar resorption may be more common than thought. Identifying risk factors allows surgical plans to be adjusted to reduce the likelihood of resorption, and patients can be more selectively screened postoperatively.

Background Temporomandibular joint osteoarthritis (TMJOA) has a high incidence rate, but its pathogenesis remains unclear. Circadian rhythm is an important oscillation in the human body and influences various biological activities. However, it is still unclear whether circadian rhythm affects the onset and development of TMJOA. Methods We disrupted the normal rhythm of rats and examined the expression of core clock genes in the mandibular condylar cartilage of the jaw and histological changes in condyles. After isolating rat mandibular condylar chondrocytes, we upregulated or downregulated the clock gene Per1 , examined the expression of cartilage matrix-degrading enzymes, tested the activation of the GSK3β/β-CATENIN pathway and verified it using agonists and inhibitors. Finally, after downregulating the expression of Per1 in the mandibular condylar cartilage of rats with jet lag, we examined the expression of cartilage matrix-degrading enzymes and histological changes in condyles. Results Jet lag led to TMJOA-like lesions in the rat mandibular condyles, and the expression of the clock gene Per1 and cartilage matrix-degrading enzymes increased in the condylar cartilage of rats. When Per1 was downregulated or upregulated in mandibular condylar chondrocytes, the GSK3β/β-CATENIN pathway was inhibited or activated, and the expression of cartilage matrix-degrading enzymes decreased or increased, which can be rescued by activator and inhibitor of the GSK3β/β-CATENIN pathway. Moreover, after down-regulation of Per1 in mandibular condylar cartilage in vivo, significant alleviation of cartilage degradation, cartilage loss, subchondral bone loss induced by jet lag, and inhibition of the GSK3β/β-CATENIN signaling pathway were observed. Circadian rhythm disruption can lead to TMJOA. The clock gene Per1 can promote the occurrence of TMJOA by activating the GSK3β/β-CATENIN pathway and promoting the expression of cartilage matrix-degrading enzymes. The clock gene Per1 is a target for the prevention and treatment of TMJOA.

The correlation between the lateral pterygoid muscle attachment type to the disc-condyle complex and temporomandibular joint (TMJ) dysfunction has rarely been discussed and remains unclear. The study aimed to assess the correlation between the number and pattern of LPM attachment and the pathologic findings of the temporomandibular joint based on MR imaging findings. The study population comprised consecutive TMD patients. They were included if they had TMD requiring MRI examination for evaluation of internal derangement. Patients with either TMJ clicking, TMJ locking, restricted movement of the jaw, or pain in the TMJ region were included in the study. Patients with rheumatoid arthritis, condylar hyperplasia, and congenital craniofacial syndrome, and those who had undergone previous TMJ surgery were excluded from this study. Variations of the number of heads and the attachment pattern of the LPM to DCC was evaluated using MRI in the oblique sagittal and coronal images. The variation of the LPM heads and attachment patterns was correlated with pathologic changes of the TMJ. The sample size calculation was performed using G*Power version 3.1.9.2. The significance level was set at 0.05. The data were analysed using Instat statistical software (GraphPad Software, Inc., La Jolla, CA). A total of 255 patients (510 joints) were enrolled in the study. Of these, 52 (104 joints) were male and 203 (406 joints) were female, with ages ranging from 18 to 67 (mean age 32.05). Patients with internal derangement of TMJ were included. According to the data obtained from MRI examinations, LPM attachments to the disc condyle complex were categorized into four different types. The most common variation (type II-B) was shown to be two heads with the upper head attached to the disc and condyle, and the lower to the condyle. There was a statistical correlation between the type of LPM attachment and the pathological changes within the joint regarding disc displacement, osteoarthritis, joint effusion, disc degeneration, and condylar translation ( P  = 0.0003, r = -0.87, P  < 0.0001& r  = 0.29, P  = 0.0002 & r = -0.93, P  = 0.0061 & r = -0.98, and P  = 0.0004, r = -0.54 respectively). The current study shows a statistically significant direct correlation between LPM attachment and TMJ osteoarthritis, while the disc-condyle relationship, joint effusion, disc degeneration, and condylar translation shown significant inverse correlations with LPM attachment patterns.

Background Mandibular condylar hyperplasia (MCH) is a rare developmental disorder characterized by excessive growth of the mandibular condyle, leading to facial asymmetry, functional impairment, and dental malocclusion. Early radiological identification is essential for timely intervention, particularly when parotid gland involvement masks the underlying skeletal pathology. Case presentation A 15-year-old male presented with an 8–9 month history of painless left parotid swelling. MRI revealed a unique triad comprising a bulky left parotid gland measuring 4.3 × 3.2 cm compared to 3.1 × 2.4 cm on the right, left masseter hypertrophy with a volume of 28.3 cm³ versus 18.7 cm³ on the right representing a 51% increase, and left medial pterygoid hypertrophy measuring 15.2 cm³ versus 10.1 cm³ on the right showing a 50% increase. Quantitative analysis demonstrated significant left condylar enlargement with 31% height asymmetry, measuring 24.3 mm on the left versus 18.5 mm on the right, and increased anteroposterior diameter of 11.2 mm versus 8.3 mm. SPECT imaging was performed to assess growth activity, guiding subsequent management decisions between immediate surgical intervention versus conservative monitoring. Conclusion This case demonstrates how unilateral condylar hyperplasia can present primarily as parotid swelling, potentially misdirecting clinical attention. Quantitative volumetric analysis proved essential for diagnosis. The documented 31% condylar asymmetry with preserved function illustrates effective neuromuscular compensation, providing a 6–12 month window for intervention before symptom development. Early multidisciplinary collaboration is crucial for optimal outcomes.

Objective Unilateral posterior scissors-bite (uPSB) malocclusion is common clinically. This study aimed to investigate the condylar morphological alterations and condyle-fossa relationship in patients with uPSB, through cone beam computed tomography (CBCT) and three-dimensional reconstructive imaging technique. Methods A retrospective study was designed to comparatively analyze 95 patients with uPSB between July 2016 and December 2021. They were divided into three subgroups: 12 to 20, 21 to 30, and ≥ 31 years, according the age distribution. The morphological parameters regarding condyle, fossa, and joint space after three-dimensional reconstruction were measured and analyzed by a series of digital software. SPSS 26.0 software package was performed for statistical analysis on data sets, using paired t –test, one–way analysis of variance, Wilcoxon signed–rank sun test, Kruskal–Wallis H test, and Bonferroni correction. Results The condylar volume (CV) of scissors-bite side was greater than that of the non-scissors-bite side ( CV A  = 1740.68 ± 559.80 mm 3  >  CV N  = 1662.25 ± 524.88 mm 3 , P  = 0.027). So was the condylar superficial area (CSA) ( CSA A  = 818.71 ± 186.82 mm 2  >  CSA N  = 792.63 ± 173.44 mm 2 , P  = 0.030), and the superior joint space (SJS) [ SJS A  = 2.46 (1.61, 3.68) mm) >  SJS N  = 2.01 (1.55, 2.87) mm), P  = 0.018], and the anterior joint space (AJS) ( AJS A  = 3.94 ± 1.46 mm >  AJS N  = 3.57 ± 1.30 mm, P  = 0.017). The constituent ratios of the different parts of the bilateral condyles were 23% on the posterior slope, 21% on the top, 20% on the anterior slope, 19% on the lateral slope and 17% on the medial slope, respectively. Conclusion Due to long-term abnormal occlusion of uPSB, the pathological bite force in temporomandibular joint would cause changes in the shape of the condyle. Among them, CV, CSA, SJS and AJS had significant changes in the scissors-bite status, which has the greatest damage to the posterior slope of the condyloid process.

This study aimed to quantitatively assess three-dimensional changes in the mandibular condyle with osteoarthritis using cone-beam computed tomography (CBCT). Pre- and post-treatment CBCT images of temporomandibular joints (TMJs) from 66 patients were used to assess longitudinal changes in condylar volume within individual patients using 3D slicer software. Total volume difference (dV), net increase (dV + , bone deposition), and net decrease (dV− , bone resorption) after treatment were analyzed based on clinical and radiological factors. Condyles with surface erosion at their first visit showed significantly decreased volume after treatment compared to condyles without erosion ( p  < 0.05). Amounts of bone resorption and deposition were higher in condyles with surface erosion (both p  < 0.01). In patients with condylar erosion, the presence of joint pain was associated with a decrease in condylar volume and an increase in net resorption (both p  < 0.01). When both joint pain and condylar erosion were present, patients with parafunctional habits showed reduced condylar volume after treatment ( p  < 0.05). Condylar volume change after treatment was negatively correlated with the duration of pain relief (R = − 0.501, p  < 0.05). These results indicate that condylar erosion and TMJ pain could be significant variables affecting TMJ volume changes after treatment. Establishing appropriate treatment strategies is crucial for managing condylar erosion and TMJ pain.