Osteoarthritis of the Temporomandibular Joint: A Narrative Overview

Do I-PRF adjuvant injections in TMJ arthrocentesis have a cumulative physiological effect? A retrospective cohort study

OBJECTIVE

The aim of this study was to compare the therapeutic outcomes of single versus multiple injectable platelet-rich fibrin (i-PRF) injections after arthrocentesis in patients with temporomandibular joint osteoarthritis (TMJ-OA). The objective was to evaluate and compare TMJ pain and mobility at the 1st, 6th, and 12th months postoperatively.

METHODS

This retrospective cohort study included 85 female patients (age: 31-73 years, mean ± sd: 54.9 ± 8.8) who underwent arthrocentesis with i-PRF injections from June 2018 to November 2021, diagnosed with osteoarthritis based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). Patients had no prior use of occlusal splint. During follow-up visits, pain was evaluated with a visual analog scale (pVAS) during function and maximum interincisal opening (MIO) was measured to assess jaw mobility. The study included patient follow-up records at four time points: preoperative (T0), 1 month postoperative (T1), 6 months postoperative (T2), and 12 months postoperative (T3). The primary outcome variable was pVAS at T3, secondary outcome variables were pVAS at T1 and T2, and MIO at T1, T2, and T3.

RESULTS

No significant differences were found in joint pain or mobility between groups at follow-ups (> 0.05).

CONCLUSIONS

Both groups showed similar outcomes in terms of pain and mobility over a 12-month period. Increasing the frequency of i-PRF injections does not appear to have an impact on therapeutic outcomes in patients with TMJOA. Given the retrospective design of this study, it is important to evaluate the results with caution.

The effect of Rsk2 on TNFα-mediated bone loss in the TMJ and craniofacial skeleton

OBJECTIVES

This study aims to investigate the impact of the pro-osteoblastogenic ERK-activated ribosomal S6 kinase (Rsk2) on Tumor necrosis factor (TNF)α-induced bone loss in the craniofacial system, focusing on its role in rheumatoid arthritis (RA). The objective is to understand whether Rsk2, previously shown to have protective effects in long bones against TNFα-induced bone resorption, exhibits similar effects in the craniofacial region.

MATERIALS

, and Methods. The study compares mice with TNFα overexpression, Rsk2 knockout mice, and a combination of TNFα, and Rsk2 knockout mice using detailed micro-computed tomography coupled with landmark based morphometric analysis, and classical histology. The overall skull morphology, mandible shape, and the temporomandibular joint were examined. Additionally, histological sections were utilized to examine the synovial membrane.

RESULTS

Combining TNFα, and Rsk2 deficiency does not further alter overall skull shape compared to TNFα alone. TNFα overexpression shortens the mandibular ramus, exacerbated by Rsk2 absence. Micro-computed tomography (µCT) reveals significant temporomandibular joint damage from TNFα, independent of Rsk2. However, histological sections show increased synovial membrane thickness with TNFα, heightened in the absence of Rsk2.

CONCLUSIONS

Rsk2 mitigates TNFα-induced effects on mandibular ramus length in the craniofacial system but has limited impact on the temporomandibular joint, except for synovial membrane thickness. Overall, Rsk2 demonstrates a weaker preventive effect on TNFα-induced craniofacial bone loss compared to its established role in the appendicular skeleton.

CLINICAL RELEVANCE

This study highlights regional differences in Rsk2's protective mechanisms, emphasizing the need for further exploration of the underlying mechanisms for these disparities. Understanding these regional differences can be crucial for the development of targeted therapeutic interventions.

Cyclic compression loading alters osteoarthritis-related gene expression in three-dimensionally cultured human articular chondrocytes via a different mechanism than interleukin-1β induction

OBJECTIVES

Mechanical and inflammatory stimuli are key factors in the pathophysiology of osteoarthritis (OA). However, the effects of mechanical stimulation on joint tissues and cells at the molecular level and the mechanisms of interaction after stimulation with inflammatory cytokines remains uninvestigated.

METHODS

Three-dimensional cyclic compression loading (CCL) was applied to human articular chondrocytes, and the expression of OA-related genes was analyzed using reverse transcription quantitative real-time polymerase chain reaction. Additionally, the effects of CCL after the chondrocytes were stimulated with interleukin (IL)-1β were evaluated. A DNA microarray assay was used to compare changes in gene expression after chondrocytes were stimulated with IL-1β and CCL was applied, and to search for pathways that are affected by CCL.

RESULTS

CCL of 40 kPa significantly upregulated the expression of IL-8, cyclooxygenase (COX)-2, nerve growth factor, matrix metalloproteinase (MMP)-1, and MMP-3. Transcription of IL-8, COX-2, and MMP-3 was synergistically promoted by CCL and IL-1β. The top 10 pathways enriched in the Kyoto Encyclopedia of Genes and Genomes enrichment analysis of differentially expressed genes were not common in either group, except for the "cytokine-cytokine receptor interaction". The "tumor necrosis factor signaling pathway" and the "nuclear factor-kappa B signaling pathway" in the IL-1β group and "cell cycle" and the "Hippo signaling pathway" in the CCL group were included.

CONCLUSIONS

Comprehensive gene expression analysis revealed that CCL-induced changes in gene expression were different to those induced by stimulation with IL-1β. Our results provide new insights into the involvement of mechanical stimulation in the pathogenesis of OA.

Loss of SCRG1 in chondrocytes inhibits osteoarthritis by promoting autophagy activity in the temporomandibular joint through inhibition of neurokine receptors

BACKGROUND

To investigate in vitro how scrapie responsive gene 1 (SCRG1) contributes to the development of temporomandibular joint osteoarthritis (TMJOA).

METHODS

Western blotting was used to identify protein expression. Proinflammatory cytokine levels were assessed by means of an enzyme-linked immunosorbent test. In order to find out whether chondrocytes expressed protein light chain 3B (LC3B), immunofluorescence was utilized.

RESULTS

In the TMJOA in vitro model, hydrogen peroxide (H2O2) treatment increased the expression of SCRG1, stimulated chondrocyte catabolism and inflammatory response, and blocked autophagy. In chondrocytes, SCRG1 silencing reduces the inflammatory response, catabolism, and autophagy inhibition brought on by H2O2. Concurrently, H2O2 induction triggers the nuclear factor (NF)-κB pathway and nerve growth factor receptor (NGFR). When SCRG1 is downregulated, NGFR expression is inhibited and the NF-κB pathway is blocked.

CONCLUSIONS

By inhibiting NGFR and blocking the NF-κB pathway, knocking down SCRG1 can prevent H2O2-induced inflammatory response, metabolic breakdown and autophagy inhibition in chondrocytes.

Fostamatinib alleviates temporomandibular joint osteoarthritis by maintaining cartilage homeostasis through MAPK/NF-κB and AKT/mTOR pathways

Temporomandibular joint osteoarthritis (TMJ OA) is a common degenerative disease characterized by cartilage degeneration. However, the therapeutic strategies aimed to maintain cartilage homeostasis remain unclear. Fostamatinib (Fos) is a potential clinical drug for rheumatoid arthritis (RA) and predicted as target drug for many inflammatory diseases. In this study we investigated the therapeutic effects of Fos for TMJ OA and underlying mechanisms. Interleukin-1β (IL-1β) was used to construct a condylar chondrocyte injury model in vitro and rat TMJ OA models were induced by unilateral anterior crossbite (UAC) in vivo. Subsequently, a series of experiments were performed to assess the therapeutic effects and potential mechanisms of Fos in TMJ OA. Herein, we verified that Fos improved IL-1β-induced decrease in chondrocyte viability and proliferation, as well as inhibited cell apoptosis. Additionally, Fos could alleviate IL-1β-induced inflammation, ECM degradation, and chondrocyte phenotype change through blocking MAPK/NF-κB pathways, as well as promote chondrocyte autophagy by regulating AKT/mTOR pathways. The therapeutic effects of Fos on TMJ OA were further validated through rat UAC model in vivo. Overall, Fos could maintaining cartilage homeostasis through regulating chondrocyte inflammation, ECM degradation, and abnormal cell biological behaviors (apoptosis and autophagy), which made it a promising small molecule drug for TMJ OA early intervention.

Is Ultrasonography an Effective Method for Diagnosing Degenerative Changes in the Temporomandibular Joint?

BACKGROUND

The accurate diagnosis of degenerative joint diseases (DJDs) of the temporomandibular joint (TMJ) presents a significant clinical challenge due to their progressive nature and the complexity of associated structural changes. These conditions, characterized by cartilage degradation, subchondral bone remodeling, and eventual joint dysfunction, necessitate reliable and efficient imaging techniques for early detection and effective management. Cone-beam computed tomography (CBCT) is widely regarded as the gold standard for evaluating osseous changes in the TMJ, offering detailed visualization of bony structures. However, ultrasonography (US) has emerged as a promising alternative, offering a non-invasive and radiation-free option for assessing TMJ disorders. This study aims to evaluate the diagnostic accuracy of US in identifying degenerative changes in the TMJ, with CBCT serving as the definitive diagnostic reference. By analyzing the sensitivity, specificity, and predictive values of US in detecting key degenerative markers-such as subchondral erosion, osteophytes, and joint space narrowing-this investigation seeks to assess its utility as a screening tool and its potential integration into clinical workflows.

METHODS

Forty adult patients presenting temporomandibular joint disorders were included in our cross-sectional study. Each patient underwent a clinical examination and was subjected to cone-beam computed tomography (CBCT) and ultrasonography (US). A statistical analysis was performed to compare the imaging results from CBCT and US.

RESULTS

The results are summarized in three tables. The first table presents a comparative analysis of radiological outcomes in patients with temporomandibular joint disorders using different imaging techniques. CBCT demonstrated higher sensitivity in detecting osteophytes in the right mandibular head (27.50% vs. 7.50%, p = 0.027) and higher detection rates for erosions, though without a significant advantage over US. The second table analyzes the consistency of diagnostic results between CBCT and US. A moderate agreement was observed for detecting normal bone structures, with AC1 values of 0.58 for the right and 0.68 for the left mandibular head (p < 0.001). The third table evaluates the diagnostic accuracy of US compared to CBCT. US demonstrated a positive predictive value (PPV) of 90% for detecting normal conditions, indicating its high reliability as a screening tool for normal findings. US demonstrates higher effectiveness in ruling out certain issues due to its high specificity and negative predictive value. However, its lower sensitivity in detecting abnormalities may lead to both false-positive and false-negative results.

CONCLUSIONS

US holds significant promise as a screening modality for detecting normal anatomical features of the temporomandibular joint, its limitations in identifying more complex degenerative changes necessitate a cautious and integrated approach to TMJ diagnostics.

Sulfur-species in Zinc-specific Condylar Zones of a Rat Temporomandibular Joint

In this study, we performed synchrotron-based micro-X-ray fluorescence (μ-XRF) imaging of elements Zn and S, and X-ray absorption near edge spectroscopy (XANES) coupled with μ-XRF for identification of Zn and S species in the condylar zones of a rat temporomandibular joint (TMJ). Histologic localization of Zn and hypoxia-inducible factor-1α (HIF-1α) were mapped using an optical microscope. These data were visually correlated with μ-XRF and XANES data to provide insights into plausible biological S-species in Z-enriched condylar zones of a rat TMJ. Furthermore, μ-XRF coupled with micro-X-ray diffraction (μ-XRD) was used to underline Z-incorporated biological apatite in the subchondral bone and bone of the rat TMJ. Results illustrated the potential dependence between biometal Zn and nonmetal S and their collective governance of cell and tissue functions in a zone-specific manner. Elemental Zn with organic and inorganic S-species at the cartilage-bone interface and transformation of plausible Zn-enriched mineralization kinetics of biological apatite from subchondral bone to condylar bone were ascertained using μ-XRF-XANES and μ-XRD. The coupled μ-XRF-XANES complementing with μ-XRD and immunohistology provided an informative view of S and Zn and their association with zone-specific biological pathways in situ. Understanding the spatial distributions of the main S-species with redox-inert Zn in regions of cartilage, bone, and the interface is essential for further unlocking questions surrounding formation and resorption-related biomineralization pathways as related to osteoarthritis or genetically inherited diseases. Using these complementary techniques with microspectroscopic spatial information provided insights into the associations between biometal Zn and nonmetal S and a window into detecting the plausible early-stage diagnostic biomarkers for humans with TMJ osteoarthritis.

β-catenin Orchestrates Gli1+ Cell Fate in Condylar Development and TMJOA

The fibrocartilage stem cells (FCSCs) on the surface of the condyle play an essential role in cartilage homeostasis and regeneration. However, few well-defined stem cell markers have been identified for the analysis of FCSCs' cell fate and regulation mechanism. In this study, we first mapped the transcriptional landscape of the condylar cartilage and identified a Gli1+ subset. Label-retaining cells and our lineage-tracing study showed that Gli1 labeled a group of FCSCs. Conditional knockout β-catenin inhibited Gli1+ cells differentiating into hypertrophic chondrocytes. In discectomy-induced temporomandibular joint osteoarthritis (TMJOA), Gli1+ cells were further activated, and their differentiation into hypertrophic chondrocytes was accelerated, which induced stem cell pool depletion. The deletion of β-catenin in Gli1+ cells preserved the FCSC pool and alleviated TMJOA cartilage degeneration. Collectively, we uncovered that a Gli1+ FCSC subpopulation and Wnt/β-catenin signaling orchestrate the Gli1+ cell fate in condyle postnatal development and TMJOA.

Condylar Remodeling and Skeletal Changes Following Occlusal Splint and Manual Therapy: A Cone Beam Computed Tomography Study in Temporomandibular Disorders

Background: Temporomandibular disorders (TMD) may be associated with degenerative disease of temporomandibular joint (TMJ), such as condyle erosion and subchondral cysts. Occlusal splint and cranio-mandibular manual therapy, or combined therapy, is recommended as a conservative treatment to alleviate pain-related signs and symptoms in TMD. This study aimed to assess osseous condylar changes and skeletal changes following occlusal splint and cranio-mandibular manual therapy in TMD using cone beam computed tomography (CBCT). Methods: A retrospective cohort study included 24 patients diagnosed with TMD. Combined therapy was performed until pain-related signs and symptoms disappeared. CBCT scans were performed before and after therapy. Osseous structure of condyles and their subsequent modifications were analyzed on CBCT images: flattening, erosion, and subchondral cyst. Sella-Nasion-A point (SNA), Sella-Nasion-B point (SNB), A point-Nasion-B point (ANB), Sella-Articulare-Gonion (Condylar angle), and anterior and posterior facial height (AFH, PFH) were measured on CBCT-generated lateral cephalograms. A paired t-test, Wilcoxon rank-sum test, McNemar test, and Stuart-Maxwell test were used for the statistical analyses. Results: The treatment period with combined therapy was 7.42 ± 3.27 months, and 21 out of 33 TMJ presenting degenerative disease (63.6%) had significant complete remodeling (p < 0.05). Following therapy, SNB significantly decreased from 75.61 ±3.47° to 74.82 ± 3.41° (p = 0.02), ANB significantly increased from 4.05° (3.35-4.9°) to 4.8° (3.3-6.12°) (p < 0.001), AFH significantly increased from 112.85 mm (109.28-118.72) to 115.3 mm (112.58-118.88) (p < 0.001), PFH/AFH significantly decreased from 64.17 (61.39-66.1) to 63 (59.68-64.51) (p = 0.012), and condylar angle significantly increased from 140.84 ± 8.18° to 144.42 ± 8.87° (p = 0.007). Conclusion: Combined therapy promoted significant condylar remodeling in TMJ degenerative disease, along with skeletal changes (mandibular retrusion and increase in facial height). Therapeutic strategies should consider condylar remodeling in TMD. Skeletal and dental parameters should be evaluated prior to occlusal splint therapy.

Hyaluronic Acid-Based Microparticles with Lubrication and Anti-Inflammation for Alleviating Temporomandibular Joint Osteoarthritis

The pathogenesis of temporomandibular joint osteoarthritis (TMJOA) is closely associated with mechanical friction, which leads to the up-regulation of inflammatory mediators and the degradation of articular cartilage. Injectable drug-loaded microparticles have attracted widespread interest in intra-articular treatment of TMJOA by providing lubrication and facilitating localized drug delivery. Herein, a hyaluronic acid-based microparticle is developed with excellent lubrication properties, drug loading capacity, antioxidant activity, and anti-inflammatory effect for the treatment of TMJOA. The microparticles are facilely prepared by the self-assembly of 3-aminophenylboronic acid-modified hyaluronic acid (HP) through hydrophobic interaction in an aqueous solution, which can further encapsulate diol-containing drugs through dynamic boronate ester bonds. The resulting microparticles demonstrate excellent injectability, lubrication properties, radical scavenging efficiency, and antibacterial activity. Additionally, the drug-loaded microparticles exhibit a favorable cytoprotective effect on chondrocyte cells in vitro under an oxidative stress microenvironment. In vivo experiments validate that intra-articular injection of drug-loaded microparticles effectively alleviates osteoporosis-like damage, suppresses inflammatory response, and facilitates matrix regeneration in the treatment of TMJOA. The HP microparticles demonstrate excellent injectability and encapsulation capacity for diol-containing drugs, highlighting its potential as a versatile drug delivery vehicle in the intra-articular treatment of TMJOA.

Applications of hydrogels in tissue-engineered repairing of temporomandibular joint diseases

Epidemiological studies reveal that symptoms of temporomandibular joint disorders (TMDs) occur in 60-70% of adults. The inflammatory damage caused by TMDs can easily lead to defects in the articular disc, condylar cartilage, subchondral bone and muscle of the temporomandibular joint (TMJ) and cause pain. Despite the availability of various methods for treating TMDs, few existing treatment schemes can achieve permanent recovery. This necessity drives the search for new approaches. Hydrogels, polymers with high water content, have found widespread use in tissue engineering and regeneration due to their excellent biocompatibility and mechanical properties, which resemble those of human tissues. In the context of TMD therapy, numerous experiments have demonstrated that hydrogels show favorable effects in aspects such as articular disc repair, cartilage regeneration, muscle repair, pain relief, and drug delivery. This review aims to summarize the application of hydrogels in the therapy of TMDs based on recent research findings. It also highlights deficiencies in current hydrogel research related to TMD therapy and outlines the broad potential of hydrogel applications in treating TMJ diseases in the future.

Conditioned Medium From Stem Cells of Human Exfoliated Deciduous Teeth Alleviates Mouse Osteoarthritis by Inducing sFRP1-Expressing M2 Macrophages

Intravenous administration of conditioned medium from stem cells of human exfoliated deciduous teeth (SHED-CM) regenerates mechanically injured osteochondral tissues in mouse temporomandibular joint osteoarthritis (TMJOA). However, the underlying therapeutic mechanisms remain unclear. Here, we showed that SHED-CM alleviated injured TMJ by inducing anti-inflammatory M2 macrophages in the synovium. Depletion of M2 by Mannosylated Clodrosome abolished the osteochondral repair activities of SHED-CM. Administration of CM from M2-induced by SHED-CM (M2-CM) effectively ameliorated mouse TMJOA by inhibiting chondrocyte inflammation and matrix degradation while enhancing chondrocyte proliferation and matrix formation. Notably, in vitro, M2-CM directly suppressed the catabolic activities while enhancing the anabolic activities of interleukin-1β-stimulated mouse primary chondrocytes. M2-CM also inhibited receptor activator of nuclear factor NF-κB ligand-induced osteoclastogenesis in RAW264.7 cells. Secretome analysis of M2-CM and M0-CM revealed that 5 proteins related to anti-inflammation and/or osteochondrogenesis were enriched in M2-CM. Of these proteins, the Wnt signal antagonist, secreted frizzled-related protein 1 (sFRP1), was the most abundant and played an essential role in the shift to anabolic chondrocytes, suggesting that M2 ameliorated TMJOA partly through sFRP1. This study suggests that secretome from SHED exerted remarkable osteochondral regeneration activities in TMJOA through the induction of sFRP1-expressing tissue-repair M2 macrophages.

Short term effects of a novel combined approach compared with physical therapy alone among older patients with temporomandibular degenerative joint disease: a prospective cohort study

BACKGROUND

There is a lack of consensus regarding the best treatment option, including physical exercise, available for temporomandibular degenerative joint disease (DJD) that affect the older patients. Herein, we aimed to study and compare the efficacy of a combined approach using injection and home physical exercise with physical therapy alone as well as explored an optimal treatment strategy for older patients with DJD.

METHODS

We included 213 older patients with DJD treated at our medical centre from June 2020 to June 2021, 64 of whom were selected for analysis. Of these 64 patients, 32 received injections combined with home physical exercise, and the other 32 received physical therapy alone. Propensity score matching was used to ensure that the two groups did not differ significantly in categorical and continuous variables. Measurements included pain intensity, maximum mouth opening, joint crepitus, jaw functional limitation scale (JFLS) scores, treatment times, and treatment durations. Improvement in each measurement was compared between the two groups 2, 4, and 12 weeks after the treatment commenced, as were the final treatment times and durations.

RESULTS

Pain intensity, maximum mouth opening, and JFLS scores in the two groups improved 2, 4, and 12 weeks after treatment (all p < 0.05). The crepitus ratio improved significantly only in the combined treatment group after 12 weeks. Compared with the physical therapy group, pain while opening the mouth improved after 2, 4, and 12 weeks in the combined treatment group. Furthermore, 2 weeks after treatment, the physical therapy group showed significant improvement in maximal mouth opening compared with the combined treatment group. No significant between-group differences were observed regarding improvement in joint crepitus and JFLS scores at each observation point. The combined treatment group had a significantly lower number of visits than the physical therapy group; however, the treatment duration was longer.

CONCLUSION

Compared with physical therapy, pain while opening the mouth is significantly improved by the combined treatment within 12 weeks, and the number of required visits is fewer. Physical therapy improves the patients' mouth-opening capabilities in a short time (2 weeks), and the treatment cycle is short.