Association of Condylar Bone Quality with TMJ Osteoarthritis

Bone Density of the Condyle of Children with Craniofacial Microsomia and its Correlation with Condylar Resorption After Mandible Distraction Osteogenesis

OBJECTIVE

To investigate condylar bone density (BD) in children with craniofacial microsomia (CFM) and identify factors that contribute to early stage condylar resorption (CR) after mandibular distraction osteogenesis (MDO).

DESIGN

Retrospective study.

SETTING

Craniofacial department of a plastic surgery hospital.

PATIENTS

Fifty-one children with CFM classified as Pruzansky IIa based on complete pre-(T0) and post-MDO (T1) computed tomography (CT) data.

INTERVENTION AND MAIN OUTCOME MEASUREMENTS

Mimic 21.0 (Materialise Inc., Belgium) was used to measure bilateral BD and condylar height (CH) and volume (CV) of affected side. Children were split into groups based on either affected side BD or the distraction length (DL,25 mm as cutoff) .Bilateral BD was compared using a paired t-test in each group. The CH and CV of affected side at T0 and T1 were compared. The relative values of the CH and CV (CH ratio) and the volume (CV ratio) of the affected side were compared across the groups.

RESULTS

The BD was lower on affected side than on unaffected side. Regarding BD, CH and CV decreased after MDO in group I, while the CH ratio and CV ratio of group I was lower than that of groups II and III. Regarding DL, the CV ratio was lower in Group L than Group S.

CONCLUSIONS

The condylar bone quality on affected side is compromised in type IIa CFM. A low BD in combination with a larger distraction distance may increase the risk of CR; therefore, MDO in patients with such characteristics should be postponed.

Long-term haplodeficency of DSPP causes temporomandibular joint osteoarthritis in mice

BACKGROUND

Extracellular matrix (ECM) protein malfunction or defect may lead to temporomandibular joint osteoarthritis (TMJ OA). Dentin sialophophoprotein (DSPP) is a mandibular condylar cartilage ECM protein, and its deletion impacted cell proliferation and other extracellular matrix alterations of postnatal condylar cartilage. However, it remains unclear if long-term loss of function of DSPP leads to TMJ OA. The study aimed to test the hypothesis that long-term haploinsufficiency of DSPP causes TMJ OA.

MATERIALS AND METHODS

To determine whether Dspp+/- mice exhibit TMJ OA but no severe tooth defects, mandibles of wild-type (WT), Dspp+/-, and Dspp homozygous (Dspp-/-) mice were analyzed by Micro-computed tomography (micro-CT). To characterize the progression and possible mechanisms of osteoarthritic degeneration over time in Dspp+/- mice over time, condyles of Dspp+/- and WT mice were analyzed radiologically, histologically, and immunohistochemically.

RESULTS

Micro-CT and histomorphometric analyses revealed that Dspp+/- and Dspp-/- mice had significantly lower subchondral bone mass, bone volume fraction, bone mineral density, and trabecular thickness compared to WT mice at 12 months. Interestingly, in contrast to Dspp-/- mice which exhibited tooth loss, Dspp+/- mice had minor tooth defects. RNA sequencing data showed that haplodeficency of DSPP affects the biological process of ossification and osteoclast differentiation. Additionally, histological analysis showed that Dspp+/- mice had condylar cartilage fissures, reduced cartilage thickness, decreased articular cell numbers and severe subchondral bone cavities, and with signs that were exaggerated with age. Radiographic data showed an increase in subchondral osteoporosis up to 18 months and osteophyte formation at 21 months. Moreover, Dspp+/- mice showed increased distribution of osteoclasts in the subchondral bone and increased expression of MMP2, IL-6, FN-1, and TLR4 in the mandibular condylar cartilage.

CONCLUSIONS

Dspp+/- mice exhibit TMJ OA in a time-dependent manner, with lesions in the mandibular condyle attributed to hypomineralization of subchondral bone and breakdown of the mandibular condylar cartilage, accompanied by upregulation of inflammatory markers.

A study on volumetric change of mandibular condyles with osteoarthritis using cone-beam computed tomography

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.

Evaluation of the mandibular condylar bone microarchitecture in people living with HIV

OBJECTIVES

People living with HIV (PLWH) have been shown to have lower bone density at the spine, hip, and radius. However, whether a similar bone phenotype is seen in craniofacial bones is not known. The goal of this study was to evaluate the bone microarchitecture of the mandibular condyle in PLWH.

METHODS

We recruited 212 participants, which included 88 HIV-negative participants and 124 PLWH on combination antiretroviral therapy with virological suppression from a single academic center. Each participant filled out a validated temporomandibular disorder (TMD) pain screening questionnaire and had cone beam computed tomography (CBCT) of their mandibular condyles. Qualitative radiographic evidence of temporomandibular joint disorders-osteoarthritis (TMJD-OA) assessment and quantitative microarchitecture analysis of their mandibular condylar bones were conducted.

RESULTS

There was no statistically significant difference in either self-reported TMD or in radiographic evidence of TMJD-OA in PLWH compared with HIV-negative controls. Linear regression analysis revealed that positive HIV status remained significantly associated with increased trabecular thickness, decreased cortical porosity, and increased cortical bone volume fraction after adjusting for race, diabetes, sex, and age.

CONCLUSION

PLWH have increased mandibular condylar trabecular bone thickness and cortical bone volume fraction compared with HIV-negative controls.

Systematic review of computed tomography parameters used for the assessment of subchondral bone in osteoarthritis

OBJECTIVE

To systematically review the published parameters for the assessment of subchondral bone in human osteoarthritis (OA) using computed tomography (CT) and gain an overview of current practices and standards.

DESIGN

A literature search of Medline, Embase and Cochrane Library databases was performed with search strategies tailored to each database (search from 2010 to January 2023). The search results were screened independently by two reviewers against pre-determined inclusion and exclusion criteria. Studies were deemed eligible if conducted in vivo/ex vivo in human adults (>18 years) using any type of CT to assess subchondral bone in OA. Extracted data from eligible studies were compiled in a qualitative summary and formal narrative synthesis.

RESULTS

This analysis included 202 studies. Four groups of CT modalities were identified to have been used for subchondral bone assessment in OA across nine anatomical locations. Subchondral bone parameters measuring similar features of OA were combined in six categories: (i) microstructure, (ii) bone adaptation, (iii) gross morphology (iv) mineralisation, (v) joint space, and (vi) mechanical properties.

CONCLUSIONS

Clinically meaningful parameter categories were identified as well as categories with the potential to become relevant in the clinical field. Furthermore, we stress the importance of quantification of parameters to improve their sensitivity and reliability for the evaluation of OA disease progression and the need for standardised measurement methods to improve their clinical value.

Relationship between condylar surface CT value in coronal plane and condylar morphology in jaw deformity patients

OBJECTIVES

This study aimed to examine the relationship between condylar surface computed tomography (CT) values in the coronal plane and condylar morphology in patients with jaw deformities classes II and III before and after orthognathic surgery.

MATERIALS AND METHODS

The maximum CT values (pixel values) at three points on the condylar surface, height, and joint space were measured on the coronal plane. The condylar width, thickness, and angle were measured on the horizontal plane preoperatively and at 1 year postoperatively.

RESULTS

A total of 112 temporomandibular joints of 56 female patients were divided into two groups according to skeletal class (56 joints each in class II and class III). The maximum CT values of class II were higher than those of class III at the medial, central, and lateral sites on the condylar surface, preoperatively and at 1 year postoperatively (P < 0.05). CT values of the condylar surface were significantly negatively correlated with the condylar heights at the center and lateral sites preoperatively and at 1 year postoperatively (P < 0.05).

CONCLUSIONS

Condylar surface CT values in the coronal plane are associated with condylar morphology, including condylar height.

Epigenetic PPARγ preservation attenuates temporomandibular joint osteoarthritis

OBJECTIVE

Previous studies have demonstrated that PPARγ deficiency is associated with osteoarthritis in the knee joint. However, whether epigenetic PPARγ dysregulation has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. This study aims to determine the role and mechanism of epigenetic PPARγ dysregulation in TMJOA.

METHODS

Partial TMJ discectomy was performed to induce TMJOA in rat. Primary condylar chondrocytes were isolated, and TNF-α-induced inflammatory condition was created in vitro. The expressions of PPARγ and DNA methyltransferase were investigated in vivo and in vitro. The association of PPARγ and DNA methylation was further studied by treating chondrocytes with DNA demethylation agent 5-Aza-2'-deoxycytidine (5Aza) and transfecting with siRNA of DNA methyltransferase (DNMT)1 and DNMT3a, and the methylation level of PPARγ promoter was evaluated by Bisulfite-sequencing PCR. The chondroprotective effects of 5Aza were explored in vitro and in vivo.

RESULTS

PPARγ suppression and upregulated DNMT1/DNMT3a expression exist in TMJOA cartilage in vivo and primary condylar chondrocytes under TNF-α-induced inflammatory conditions in vitro. DNMT1 and DNMT3a elevation contributes to PPARγ-promoter hypermethylation in TMJ chondrocytes under TNF-α-induced inflammation conditions. DNA demethylation intervention by 5Aza protects chondrocytes from inflammation response in vitro. Mechanistically, 5Aza reversed the hypermethylation of the PPARγ promoter and subsequently resulted in PPARγ restoration and decreased expression of cartilage-catabolic factors in chondrocytes. Rat TMJOA model revealed that 5Aza, by reversing PPARγ suppression, effectively attenuated cartilage degeneration and stabilized cartilage homeostasis by balancing anabolic factor and catabolic factor expression.

CONCLUSION

Epigenetic PPARγ suppression may play a causal role in TMJOA pathogenesis, which can be alleviated by DNA demethylation with 5Aza treatment. This study provides new insights into the pathogenic mechanism and therapeutic strategy of TMJOA.

Osteoarthritis Diagnosis Integrating Whole Joint Radiomics and Clinical Features for Robust Learning Models Using Biological Privileged Information

This paper proposes a machine learning model using privileged information (LUPI) and normalized mutual information feature selection method (NMIFS) to build a robust and accurate framework to diagnose patients with Temporomandibular Joint Osteoarthritis (TMJ OA). To build such a model, we employ clinical, quantitative imaging and additional biological markers as privileged information. We show that clinical features play a leading role in the TMJ OA diagnosis and quantitative imaging features, extracted from cone-beam computerized tomography (CBCT) scans, improve the model performance. As the proposed LUPI model employs biological data in the training phase (which boosted the model performance), this data is unnecessary for the testing stage, indicating the model can be widely used even when only clinical and imaging data are collected. The model was validated using 5-fold stratified cross-validation with hyperparameter tuning to avoid the bias of data splitting. Our method achieved an AUC, specificity and precision of 0.81, 0.79 and 0.77, respectively.

Effects of food hardness on temporomandibular joint osteoarthritis: Qualitative and quantitative micro-CT analysis of rats in vivo

BACKGROUND

Temporomandibular joint osteoarthritis (TMJ-OA) is a degenerative joint disease in which quantitative analysis based on magnetic resonance image (MRI) or cone-beam computed tomography (CBCT) remains limited. Moreover, the long-term effects of soft food on the adaptive condylar remodeling process in TMJ-OA remain unclear. This study aimed to assess the effects of food hardness on adaptive condylar remodeling in a healthy TMJ, TMJ-OA, and controlled TMJ-OA.

METHODS

Complete Freund's adjuvant (CFA) was used for TMJ-OA induction and Link-N (LN) for TMJ repair. Eighteen mature rats were randomly divided into six groups: (1) control/normal diet (Ctrl-N); (2) control/soft diet (Ctrl-S); (3) TMJ-OA/normal diet (CFA-N); (4) TMJ-OA/soft diet (CFA-S); (5) Link-N-controlled TMJ-OA/normal diet (LN-N); and (6) Link-N-controlled TMJ-OA/soft diet (LN-S). Micro-CT was performed 14, 21, and 28 days after CFA injection to analyze the bone volume, bone volume fraction (BVF), bone mineral density (BMD), and trabecular bone number and thickness (Tb.N, Tb.Th). MRI and histological imaging were performed to support the analysis.

RESULTS

Under CFA treatment, the BVF and BMD decreased significantly (p < 0.01) and later recovered to normal. However, more significant improvements occurred in normal-diet groups than soft-diet groups. Additionally, bone volume changes were more predictable in the normal-diet groups than in the soft-diet groups. The normal-diet groups presented a significant decrease and increase in the Tb.N and Tb.Th, respectively (p < 0.05), while the Tb.N and Tb.Th in the soft-diet groups remained largely unchanged. Furthermore, a significantly higher frequency of irregularities on the condylar articular surface was found in the soft-diet groups.

CONCLUSIONS

Compared with a soft diet, a normal diet may be beneficial for preserving condyle articular surface and directing bone remodeling in TMJ-OA rats.

Comparison of the efficacy of intra-articular injections of hyaluronic acid and lactoferrin in mono-iodoacetate-induced temporomandibular joint osteoarthritis: A histomorphometric, immunohistochemistry, and micro-computed tomography analysis

OBJECTIVES

This study aims to evaluate the efficacy of high-molecular-weight hyaluronic acid (HMWHA) and lactoferrin (LF) injections on temporomandibular joint (TMJ) cartilage and subchondral bone in mono-iodoacetate (MIA)-induced temporomandibular joint osteoarthritis model in rats.

MATERIALS AND METHODS

In this in vivo study, a total of 24 rats were divided into three groups as follows: saline group (Group 1), HMWHA group (Group 2), and LF group (Group 3) including eight rats in each group. The intra-articular injections were administered once a week for three weeks after osteoarthritis was induced. All animals were euthanized 28 days after induction of osteoarthritis, and TMJs were harvested for histomorphometric, immunohistochemical, and micro-computed tomography (CT) analysis.

RESULTS

There was no significant difference between the HMWHA and LF groups in terms of the histomorphometric and immunohistochemical analysis results (p>0.05). According to the micro-CT analysis, the LF group had the highest mean bone volume fraction (74.9±0.5) and trabecular thickness (0.122±0.002), while the saline group had the lowest mean values (55.0±0.3 and 0.071±0.002, respectively) (p<0.001). There was no significant difference between the HMWHA and LF groups according to the micro-CT analysis (p>0.05). Both groups had better healing effects than the saline group in all analyses.

CONCLUSION

Lactoferrin has a healing effect at least as much as HMWHA in MIA-induced TMJ osteoarthritis. We suggest that LF may be evaluated in future clinical studies as a promising agent in the treatment of osteoarthritis.

Temporomandibular Disorders and Vitamin D Deficiency: What Is the Linkage between These Conditions? A Systematic Review

Although a growing body of literature has been emphasizing the role of vitamin D in oral health, there is still a gap of knowledge regarding the correlation between temporomandibular disorders (TMDs) and vitamin D. Therefore, the aim of this systematic review was to assess the linkage between hypovitaminosis D and TMDs to map the current literature in this field. On 10 September 2022, PubMed, Scopus, and Web of Science databases were systematically searched from the date of their inception to identify the studies that had assessed patients with TMDs. The primary outcome assessed in this review was the relationship between hypovitaminosis D and TMDs. Out of the 329 studies identified, 13 studies met the eligibility criteria and were included in the present work. Seven studies assessed the relationship between vitamin D and TMDs, reporting that vitamin D serum levels are lower in patients with TMDs. Our results suggested that vitamin D receptor (VDR) polymorphisms might have a role in TMDs’ development. However, the quality assessed underlined that only one study did not present a serious risk of bias. Further good-quality studies are needed to clarify the linkage between vitamin D deficiency and TMDs, but the evidence currently available has suggested potential correlations.

Antisense Oligonucleotide-Based Therapy on miR-181a-5p Alleviates Cartilage Degradation of Temporomandibular Joint Osteoarthritis via Promoting SIRT1

Temporomandibular joint osteoarthritis (TMJOA) condylar cartilage degeneration and abnormal subchondral bone pathological remodeling induce pain and joint dysfunction, and cartilage degeneration is considered irreversible. Very few therapeutic approaches are administrated in practice. Nucleotides have demonstrated considerable potential as a next-generation medication, and they have been applied in several models of osteoarthritis. There is a need to establish an effective protocol for TMJOA gene therapy. In the current study unilateral anterior crossbite (UAC) surgery was used to simulate mechanical stress-induced TMJOA in mice. Degeneration of condylar cartilage and destruction of subchondral bone were observed in damaged joints, and miR-181a-5p was elevated in chondrocytes. Intra-articular injection of miR-181a-5p antisense oligonucleotide (ASO) could reduce the cartilage damage and alleviate UAC-induced TMJOA progression, but it did not restore injured subchondral bone. Mechanically, miR-181a-5p evidently targeted the 3’ untranslated region of Sirt1 directly, resulting in inhibition of silent information regulator 1 expression and promoting apoptosis by elevating p53-dependent signaling, indicating that miR181a-5p ASO promoted chondrocyte survival. The present study suggests that ASO-based gene therapy may be an effective TMJOA treatment.

Morphologic and histologic characterization of sheep and porcine TMJ as large animal models for tissue engineering applications

Objective

The aim of this study was to compare and characterize the structural and ultrastructural organization of the temporomandibular joint (TMJ) between two large animal models for use in the development of tissue engineering strategies.

Materials and methods

Whole TMJs from sheep and pigs were evaluated with micro-computed tomography (μCT) for morphology and quantitative analyses of bone parameters. Histological examination was performed on the TMJ disc and its attachments to investigate regional distribution of collagen, elastin, and glycosaminoglycans (GAGs).

Results

μCT analyses demonstrate higher bone mineral density (BMD) in the temporal fossa compared to the mandibular condyle in both species, with this variable being significantly higher in sheep than pig. Quantitative morphometry of the trabecular condyle reveals no statistical differences between the species. Histology demonstrates similar structural organization of collagen and elastin between species. Elastin staining was nearly twofold greater in sheep than in the pig disc. Finally, Safranin-O staining for GAGs in the TMJ disc was localized to the intermediate zone in the sheep but was absent from the porcine disc.

Conclusions

Our findings show some important differences in the pig and sheep TMJ μCT variables and histology and composition of the disc and discal attachment. These disparities likely reflect differences in masticatory and TMJ functional loading patterns between the two species and provide insights into large animal models towards human applications.

Clinical relevance

As with the established pig model, the sheep is a suitable large animal model for TMJ research such as regenerative strategies, with specific considerations for design parameters appropriate for human-analog applications.

Overloading stress-induced progressive degeneration and self-repair in condylar cartilage

Overloading stress-induced condylar cartilage degeneration acts as the main pathologic change in temporomandibular joint osteoarthritis (TMJ-OA). However, the progression of degeneration and the ability for self-repair remain poorly understood. Here, we explored the progression of cartilage degeneration by dividing pathological stages using a steady mouth-opening mouse model. Then, we observed changes of cartilage by removing the loading at different stages to test the potential self-repair after degeneration induced. Three-dimensional confocal microscopy combined with histology and micro-CT scanning was applied to examine TMJ at different stages of degeneration before and after self-repair. We found the cartilage underwent progressive and thorough degeneration as the overloading stress developed. During the initial adaptation stage, robust proliferation of posteromedial cartilage began at the area of direct loading. Subsequently, widespread chondrocyte apoptosis was found, followed by new chondrocyte proliferation in aggregates with matrix degradation and subchondral bone catabolism. Finally, with cartilage surface damage, the degeneration reached a point where the lesion could not be reversed by self-repair. While the cartilage nearly returned to normal when the interference was removed within 5 days. These results suggested overloading force induces a pathological process of successive degeneration in TMJ cartilage, which can be reversed by self-repair at early stages.

Pathological mechanism of chondrocytes and the surrounding environment during osteoarthritis of temporomandibular joint

Temporomandibular joint (TMJ) osteoarthritis is a common chronic degenerative disease of the TMJ. In order to explore its aetiology and pathological mechanism, many animal models and cell models have been constructed to simulate the pathological process of TMJ osteoarthritis. The main pathological features of TMJ osteoarthritis include chondrocyte death, extracellular matrix (ECM) degradation and subchondral bone remodelling. Chondrocyte apoptosis accelerates the destruction of cartilage. However, autophagy has a protective effect on condylar chondrocytes. Degradation of ECM not only changes the properties of cartilage but also affects the phenotype of chondrocytes. The loss of subchondral bone in the early stages of TMJ osteoarthritis plays an aetiological role in the onset of osteoarthritis. In recent years, increasing evidence has suggested that chondrocyte hypertrophy and endochondral angiogenesis promote TMJ osteoarthritis. Hypertrophic chondrocytes secrete many factors that promote cartilage degeneration. These chondrocytes can further differentiate into osteoblasts and osteocytes and accelerate cartilage ossification. Intrachondral angiogenesis and neoneurogenesis are considered to be important triggers of arthralgia in TMJ osteoarthritis. Many molecular signalling pathways in endochondral osteogenesis are responsible for TMJ osteoarthritis. These latest discoveries in TMJ osteoarthritis have further enhanced the understanding of this disease and contributed to the development of molecular therapies. This paper summarizes recent cognition on the pathogenesis of TMJ osteoarthritis, focusing on the role of chondrocyte hypertrophy degeneration and cartilage angiogenesis.

Initiation and progression of dental-stimulated temporomandibular joints osteoarthritis

Temporomandibular joint (TMJ), a site that is often impacted by osteoarthritis (OA), is biomechanically linked with dental occlusion. Tissue responses in TMJ condyle to biomechanical stimulation could be investigated by intervention of the dental occlusion in animals. Unilateral anterior crossbite, an experimental malocclusion, has been demonstrated to induce TMJ-OA lesions, showing primarily as enhanced cartilage calcification and subchondral cortical bone formation at the osteochondral interface, causing the osteochondral interface thickening and stiffening. The changed interface would worsen the local biomechanical environment. At the cartilage side, the matrix degenerates. In the case of insufficient restoration of the matrix, the cells in the deep zone flow into the ones undergoing autophagy, apoptosis, and terminal differentiation while the cells in the superficial zone are promoted to differentiate to supply the loss of the deep zone cells. At the meantime, the bone marrow stromal cells are stimulated to bone formation in the subchondral cortical region which is uncoupled with the sites of the osteoclast-mediated resorption process that is predominantly observed at the subchondral trabecular bone region. Overall, the thickening and stiffening osteochondral interface, due greatly to the enhanced endochondral ossification in deep zone cartilage, should be a central pathological process that links with cartilage decay and subchondral bone remodelling in OA joints. The residual chondrocytes locating in the cartilage superficial zone have the progenitor-like qualities that can proliferate, and also differentiate into the deep zone chondrocytes, thus should be critical in progression and rehabilitation of TMJ-OA.

Bone mineral density, bone microstructure, and bone turnover markers in females with temporomandibular joint osteoarthritis

OBJECTIVE

The pathogenesis of the temporomandibular joint osteoarthritis (TMJ OA) has not been clearly revealed. This study aimed to investigate the pathogenesis of TMJ OA based on bone metabolism.

METHODS

Fifty-nine young (mean age 23.4 ± 3.4 years) and 41 post-menopausal females (mean age 57.2 ± 4.6 years) were enrolled. Areal bone mineral density (aBMD) was measured via dual-energy X-ray absorptiometry of the lumbar spine, femoral neck, total hip, and ultradistal radius. Levels of four bone resorption markers, serum ionized calcium and C-telopeptide of type I collagen (CTx) and urinary N-telopeptide of type I collagen and deoxypyridinoline, two bone formation markers, serum bone alkaline phosphatase and osteocalcin, and serum 25-dihydroxyvitamin D were analyzed at baseline and after 12 months. Condylar bone quality was assessed by 3D reconstructed CT images.

RESULTS

Significant differences in condylar bone quality and aBMDs of the lumbar spine in accordance with TMJ OA stages were observed in young and post-menopausal females. The level of CTx was significantly associated with the development and progression of TMJ OA only in young females, whereas 25-dihydroxyvitamine D demonstrated significant associations in young and post-menopausal females. Progression of TMJ OA was accompanied by reduced condylar bone quality and concomitant with lower lumbar spine aBMDs in young and post-menopausal females.

CONCLUSION

Bone metabolism and condylar quality might be involved in the development and progression of TMJ OA.

CLINICAL RELEVANCE

CTx could be considered as a potential diagnostic and monitoring marker in young females, and vitamin D showed a therapeutic potential for TMJ OA.

Evaluation of condylar surface CT values related to condylar height reduction after orthognathic surgery

This study was performed to evaluate the relationship between condylar height reduction and changes in condylar surface computed tomography (CT) values in jaw deformity patients following orthognathic surgery. Mandibular advancement by sagittal split ramus osteotomy (SSRO) with Le Fort I osteotomy was performed in class II patients, and mandibular setback by SSRO with Le Fort I osteotomy was performed in class III patients. The maximum CT values (pixel values) at five points on the condylar surface and the condylar height, ramus height, condylar square, ramus angle, and gonial angle in the sagittal plane were measured preoperatively and 1 year postoperatively. Disc position was classified as anterior disc displacement (ADD) or other types by using magnetic resonance imaging (MRI). Ninety-two condyles of 46 female patients were prepared for this study. Their temporomandibular joints (TMJs) were divided into two groups based on class (46 joints in class II and 46 joints in class III) and two groups based on the findings (25 joints with ADD and 67 joints with other findings). ADD with and without reduction was observed in two joints in the class III group and in 23 joints in the class II group. The distribution of ADD incidence had not changed 1 year after surgery. Condylar height decreased 1 year after surgery in both class II patients (mandibular advancement) (p < 0.0001) and class III patients (mandibular setback) (p = 0.0306). Similarly, condylar height decreased 1 year after surgery both in patients who showed ADD (p = 0.0087) and those with other types (p = 0.0023). Significant postoperative increases at all angle sites on the condylar surface were found in the class II (p < 0.05) and ADD (p < 0.05) groups. This study showed that an enhanced condylar surface CT value might be one sign of condylar height reduction related to sequential condylar resorption, in combination with ADD.

Evaluation of the relationship between the degenerative changes and bone quality of mandibular condyle and articular eminence in temporomandibular disorders by cone beam computed tomography

Objective: To evaluate whether there was a relationship between the degenerative bone changes and bone quality of the mandibular condyle and articular eminence in patients with temporomandibular disorder (TMD).Methods: The study group consisted of 100 patients with TMD. "Diagnostic Criteria/TMD" was used to identify the pathologies. Degenerative bone changes and bone qualities were detected by cone beam computed tomography; the bone qualities were classified using the Bone Quality Index (BQI) scale.Results: No statistically significant difference was found between degenerative bone changes and bone quality of the temporomandibular joint (TMJ) according to gender (p > 0.05). However, degenerative bone changes were more frequent than articular eminence in the mandibular condyle. BQI Type III was the most common bone quality among all types of degenerative bone changes.Discussion: Although no causality relationship was found between the bone quality and degenerative bone changes, low bone quality was found in TMD patients.

Low-intensity pulsed ultrasound protects subchondral bone in rabbit temporomandibular joint osteoarthritis by suppressing TGF-β1/Smad3 pathway

Transforming growth factor β1(TGF-β1)/Smad3 pathway promotes the pathological progression of subchondral bone in osteoarthritis. The aim of this study is to determine the effect of low-intensity pulsed ultrasound (LIPUS) on the pathological progression and TGF-β1/Smad3 pathway of subchondral bone in temporomandibular joint osteoarthritis (TMJOA). Rabbit TMJOA model was established by type II collagenase induction. The left joint in this model was continuously stimulated with LIPUS for 3 and 6 weeks (1 MHz; 30 mW/cm² ) for 20 min/day. The morphological and histological features of subchondral bone were respectively examined by microcomputed tomography and Safranin-O staining. The number of osteoclasts was quantitatively assessed by tartrate-resistant acid phosphatase staining. Immunohistochemistry and Western blot analysis were conducted to evaluate the protein expression of Cathepsin K and TGF-β1/Smad3 pathway. The results indicated that LIPUS could improve the trabecular microstructure and histological characteristics of subchondral bone in rabbit TMJOA. It also suppressed abnormal subchondral bone resorption and activation of TGF-β1/Smad3 pathway, characterized by the number of osteoclasts, protein expression levels of Cathepsin K, TGF-β1, type II TGFβ receptor, and phosphorylated Smad3 (pSmad3) were decreased. In conclusion, LIPUS promoted the quality of subchondral bone by suppressing osteoclast activity and TGF-β1/Smad3 pathway in rabbit TMJOA.

Skeletal Stem Cells-A Paradigm Shift in the Field of Craniofacial Bone Tissue Engineering

Defects of the craniofacial skeleton arise as a direct result of trauma, diseases, oncological resection, or congenital anomalies. Current treatment options are limited, highlighting the importance for developing new strategies to restore form, function, and aesthetics of missing or damaged bone in the face and the cranium. For optimal reconstruction, the goal is to replace "like with like." With the inherent challenges of existing options, there is a clear need to develop alternative strategies to reconstruct the craniofacial skeleton. The success of mesenchymal stem cell-based approaches has been hampered by high heterogeneity of transplanted cell populations with inconsistent preclinical and clinical trial outcomes. Here, we discuss the novel characterization and isolation of mouse skeletal stem cell (SSC) populations and their response to injury, systemic disease, and how their re-activation in vivo can contribute to tissue regeneration. These studies led to the characterization of human SSCs which are able to self-renew, give rise to increasingly fate restricted progenitors, and differentiate into bone, cartilage, and bone marrow stroma, all on the clonal level in vivo without prior in vitro culture. SSCs hold great potential for implementation in craniofacial bone tissue engineering and regenerative medicine. As we begin to better understand the diversity and the nature of skeletal stem and progenitor cells, there is a tangible future whereby a subset of human adult SSCs can be readily purified from bone or activated in situ with broad potential applications in craniofacial tissue engineering.

CircGCN1L1 promotes synoviocyte proliferation and chondrocyte apoptosis by targeting miR-330-3p and TNF-α in TMJ osteoarthritis

Altered expression of circular RNAs (circRNAs) has been identified in various human diseases. In this study, we investigated whether circRNAs function as competing endogenous RNAs to regulate the pathological process of temporomandibular joint osteoarthritis (TMJOA). High-throughput sequencing of mRNA (RNA seq) was performed to detect the expression of circRNAs in TMJOA and control synovial tissues isolated from humans. The differentially upregulated circGCN1L1 (hsa_circ_0000448) in synoviocyte was validated in vitro and in vivo. Here we demonstrate the interactions between circGCN1L1 and both miR-330-3p and tumor necrosis factor-α (TNF-α) through bioinformatics predictions, luciferase report assays, and fluorescence in situ hybridization. mRNA expression profiles of TNF-α-stimulated synoviocyte showed that circGCN1L1 and p65 expressions were upregulated by TNF-α. Moreover, miR-330-3p was negatively correlated with TNF-α secretion. Further, we found that miR-330-3p directly targeted TNF and restrained the production of matrix-degrading enzymes (MMP3, MMP13, and ADAMTS4). Mechanistic studies unveiled that circGCN1L1 in TMJOA synovial tissues and cells may be associated with condylar chondrocyte apoptosis and synoviocyte hyperplasia. Moreover, intra-articular injection of shcircGCN1L1 alleviated TMJOA progression in rat models. Altogether, we elucidated the important roles of a novel circRNA, namely, circGCN1L1, which induced inflammation in TMJ synoviocytes and decreased anabolism of the extracellular matrix (ECM) through miR-330-3p and TNF-α gene. This circRNA may represent a potentially effective therapeutic strategy against TMJOA progression at an early stage.

Temporomandibular joint osteoarthritis at Chelechol ra Orrak, Palau

OBJECTIVE

To explore the frequency and severity of temporomandibular joint osteoarthritis (TMJ-OA) and its causative factors in a skeletal assemblage from the prehistoric site of Chelechol ra Orrak, Palau, western Micronesia.

MATERIALS

50 temporomandibular joint surfaces (mandibular condyles and articular eminences), representing a minimum of 22 adult individuals, 17 of which retain teeth.

METHODS

Joint surfaces were macroscopically evaluated for characteristics associated with TMJ-OA and joint morphology. Dental remains were scored for tooth wear and staining.

RESULTS

Nine individuals (40.1 %) displayed lesions typical of TMJ-OA. The strongest associations were between tooth wear and TMJ-OA.

CONCLUSIONS

Indirect effects of parafunctional dental activity appear to be a factor in TMJ-OA frequency at Chelechol ra Orrak. While betel nut chewing may be one of those activities, it does not appear to be solely driving the presence of TMJ-OA.

SIGNIFICANCE

This study highlights the association between a specific parafunctional use of the temporomandibular joint and the potential pathological consequences. It also reinforces the need to carefully evaluate the archaeological context of skeletal remains in order to evaluate specific etiological factors in the presence of TMJ-OA in present and past populations.

LIMITATIONS

Sample sizes are limited in this study. This will increase as excavations continue.

SUGGESTIONS FOR FURTHER RESEARCH

Because dental occlusion appears to be associated with TMJ-OA, focus on dental conditions affecting occlusal patterns, such as third molar agenesis, antemortem tooth loss, and malocclusion, and their relationship to TMJ-OA frequency, are recommended.

Newly developed mastication activity reduction procedure rapidly induces abnormal atrophic change of the mandibular condyle in young and elder experimental animal models

This study was performed to develop a new rat model of reduced masticatory activity in order to assess the effect of this reduction on the morphology of the temporomandibular joint (TMJ) over time. Female rats were used, and ovariectomy was performed to simulate aged/postmenopausal status. Twenty-four SD rats aged 6 weeks were divided into four groups: ovariectomy/sham procedure (Ov/S); ovariectomy/reduced masticatory activity (Ov/RMA); non-Ov/S (NO/S); and non-Ov/RMA (NO/RMA). The RMA procedure involved grinding down the edges of the upper and mandibular incisors by about 3 mm and supplying the rats with a powdered diet. The bilateral TMJ was examined by micro-computed tomography at 0, 1, 2, 4, 6, and 8 weeks after the start of RMA. Condylar width was greater in the NO/S group than in the Ov/S group after the 2nd week, showing that ovariectomy reduced the width of the condyle. After the 2nd week, significant differences in condylar width were apparent between the NO/S and NO/RMA groups, and between the Ov/S and Ov/RMA groups. This RMA procedure appeared to provide a good model of reduced masticatory activity. The present findings in female rats suggest that reduction of appropriate mastication activity in the growth period results in poor growth of the mandibular condyle and immediately induces atrophy of the mandibular condyle under conditions simulating aged/postmenopausal status.

Protective effects of extracorporeal shockwave on rat chondrocytes and temporomandibular joint osteoarthritis; preclinical evaluation with in vivo99mTc-HDP SPECT and ex vivo micro-CT

OBJECTIVE

Extracorporeal shockwave therapy (ESWT) has been shown to have chondroprotective effects on arthritic diseases. We investigated the effects of ESWT on temporomandibular joint osteoarthritis (TMJOA) using rat chondrocytes and TMJOA rat models.

DESIGN

Cell viability and expression of pro-inflammatory cytokines, cartilage degradation, and apoptosis markers were measured in control, monosodium iodoacetate (MIA)-treated and ESWT plus MIA-treated chondrocytes in vitro, and intra-articular MIA injection (TMJOA) and ESWT on TMJOA rats in vivo. In vivo^99mTc-hydroxymethylene diphosphonate (HDP) single-photon emission computerized tomography/computerized tomography (SPECT/CT) and ex-vivo micro-CT and histologic examinations were performed in rat models.

RESULTS

ESWT plus MIA-treated chondrocytes showed increased cell viability significantly (P = 0.007), while decreased genetic expression of pro-inflammatory cytokines [tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6); P < 0.001 for each] and cartilage degradation markers [matrix metalloproteinase-3 (MMP3), matrix metalloproteinase-13 (MMP13), and bone morphogenetic protein 7 (BMP7); P < 0.001 for each], and number of apoptotic cells (P < 0.001) compared to MIA-treated chondrocytes. Changes in cytochrome c and cleaved caspase-3 levels relative to procaspase-3 were decreased over MIA-treated chondrocytes. ESWT on TMJOA rat models was associated with a significant decrease in pro-inflammatory and cartilage degradation markers, as demonstrated by real-time PCR and immunohistochemistry stains (P < 0.001 for each). On ^99mTc-HDP SPECT/CT, the ESWT group showed a significantly lower uptake ratio compared to the TMJOA group (P = 0.008). Micro-CT analysis revealed that the ESWT group showed improved structure and bone quality compared to the TMJOA control group.

CONCLUSIONS

ESWT was associated with a protective effect on cartilage and subchondral bone structures of TMJOA by reducing inflammation, cartilage degradation, and chondrocyte apoptosis.

Alternative cone-beam CT method for the analysis of mandibular condylar bone in patients with degenerative joint disease

OBJECTIVE

The aim of this study was to investigate the use of 3D microstructural bone analysis in patients with degenerative joint disorder (DJD) to enhance the diagnostic capacity of cone beam computed tomography (CBCT) in the evaluation of bone tissue.

METHODS

147 TMJ CBCT images of 88 participants were assessed with regard to DJD in the mandibular condyle. We divided each condyle into 3 groups (0, 1, 2) according to diagnosis of DJD: 0 indicates normal condyles (control individuals), 1 indicates mild erosive osteoarthritic change (EOC) and 2 indicates severe EOC. 3D fractal dimension (FD) was calculated on CBCT images of mandibular condyle and were compared with the radiographic diagnosis of patients.

RESULTS

ANOVA test showed that there was statistically significant difference in FD values among each groups. The average FD value of group 0 was 1.971, group 1 was 1.918 and group 2 was 1.863. Lower FD values and more severe degenerative changes were seen in patient group 2. To evaluate the reliability of fractal analysis (FA) method, receiver operating characteristic (ROC) curve analysis was performed. Area under the curve (AUC) was 0.717 (p < 0.001).

CONCLUSION

This study provides a preliminary conclusion that fractal analysis may be a helpful tool to enhance the diagnostic capacity of CBCT in the evaluation of DJD.

Masseter muscle atrophy impairs bone quality of the mandibular condyle but not the alveolar process early after induction

BACKGROUND

Masseter muscle function influences mandibular bone homeostasis. As previously reported, bone resorption markers increased in the mouse mandibular condyle two days after masseter paralysis induced with botulinum toxin type A (BoNTA), followed by local bone loss.

OBJECTIVE

This study aimed to evaluate the bone quality of both the mandibular condyle and alveolar process in the mandible of adult mice during the early stage of a BoNTA-induced masseter muscle atrophy, using a combined 3D histomorphometrics and shape analysis approach.

METHODS

Adult BALB/c mice were divided into an untreated control group and an experimental group; the latter received one single BoNTA injection in the right masseter (BoNTA-right) and saline in the left masseter (Saline-left). 3D bone microstructural changes in the mandibular condyle and alveolar process were determined with high-resolution microtomography. Additionally, landmark-based geometric morphometrics was implemented to assess external shape changes.

RESULTS

After 2 weeks, masseter mass was significantly reduced (P-value <0.001). When compared to Saline-left and untreated condyles, BoNTA-right condyles showed significant bone loss (P-value <0.001) and shape changes. No significant bone loss was observed in the alveolar processes of any of the groups (P-value >0.05).

CONCLUSION

Condyle bone quality deteriorates at an early stage of BoNTA-induced masseter muscle atrophy, and before the alveolar process is affected. Since the observed bone microstructural changes resemble those in human temporomandibular joint degenerative disorders, the clinical safety of BoNTA intervention in the masticatory apparatus remains to be clarified.

Estrogen Promotes Mandibular Condylar Fibrocartilage Chondrogenesis and Inhibits Degeneration via Estrogen Receptor Alpha in Female Mice

Temporomandibular joint degenerative disease (TMJ-DD) is a chronic form of TMJ disorder that specifically afflicts people over the age of 40 and targets women at a higher rate than men. Prevalence of TMJ-DD in this population suggests that estrogen loss plays a role in the disease pathogenesis. Thus, the goal of the present study was to determine the role of estrogen on chondrogenesis and homeostasis via estrogen receptor alpha (ERα) during growth and maturity of the joint. Young and mature WT and ERαKO female mice were subjected to ovariectomy procedures and then given placebo or estradiol treatment. The effect of estrogen via ERα on fibrocartilage morphology, matrix production, and protease activity was assessed. In the young mice, estrogen via ERα promoted mandibular condylar fibrocartilage chondrogenesis partly by inhibiting the canonical Wnt signaling pathway through upregulation of sclerostin (Sost). In the mature mice, protease activity was partly inhibited with estrogen treatment via the upregulation and activity of protease inhibitor 15 (Pi15) and alpha-2-macroglobulin (A2m). The results from this work provide a mechanistic understanding of estradiol on TMJ growth and homeostasis and can be utilized for development of therapeutic targets to promote regeneration and inhibit degeneration of the mandibular condylar fibrocartilage.

Temporomandibular Joint Disorders in Older Adults

OBJECTIVES

To review the literature and summarize the evidence of temporomandibualar joint (TMJ) disorders (TMDs) in older adults, focusing on clinical manifestations of TMDs in older adults, highlighting the incidence and sexual dimorphism of TMJ degeneration and the role of sex hormones in this process, and providing potential treatment options for TMD in older adults.

DESIGN

Two review authors performed the literature search, study inclusion, and data extraction. PubMed, Embase, and Google scholar were searched for literature until August 2017 (Figure ). We adopted a combination of Medical Subject Headings with related free text words for the search in PubMed and optimized the search in other search engines.

RESULTS

Traditionally, it was believed that TMDs predominantly affected women of childbearing age, but recent large studies in Europe and the United States have shown that the prevalence of TMD peaks after childbearing age (45-64) and then gradually decreases with age, although not much is known about the disease in older adults.

CONCLUSION

Most older adults have TMJ degeneration, which affects women more than men. In most older adults, the symptoms of TMD are mild and self-limiting and can usually be treated with self management.

Inhibition of notch signaling pathway temporally postpones the cartilage degradation progress of temporomandibular joint arthritis in mice

PURPOSE

The aim of this study is to explore the role of Notch signaling pathway in the initiation and progression of temporomandibular joint osteoarthritis (TMJOA).

METHODS

48 mice were divided into DAPT-TMJOA, Control-TMJOA and Control-Sham groups. Animals received discectomy/Sham surgery in their right TMJ, following the DAPT/saline intra-articular injections every week. Mice were sacrificed at 1/4/8 weeks post-surgery. Safranin-O and H&E staining were performed on the TMJ sections for the modified Mankin's score. qPCR and immunohistochemistry were used to evaluate Notch1, Jagged1 and Hes5 expressions.

RESULTS

The mRNA expressions of Notch1, Jagged1 and Hes5 were significantly increased in Control-TMJOA group compared with Control-Sham group. Immunostaining revealed a dramatic elevation of Notch1, Jagged1 and Hes5 signals distributed in the cartilage at 1 and 4 weeks after discectomy. However, the increased number of those immuno-positive cells turned down at 8 weeks after surgery. DAPT treatment partially rescued the elevated mRNA expression and immuno-positive cell numbers of Notch1, Jagged1 and Hes5. More importantly, the cartilage destruction during TMJOA was delayed by DAPT treatment, analyzed by modified Mankin's score.

CONCLUSION

Notch signaling participates in the onset and development of TMJOA. Inhibiting Notch signaling activation by DAPT can partially delay the progress of TMJOA.