Histopathology of the temporomandibular joint disc: Findings in 30 samples from joints with degenerative disease

The temporomandibular joint disc: A complex fable about an elusive butterfly

INTRODUCTION

Discussions related to the diagnosis and management of temporomandibular joint (TMJ) disorders (TMDs) have always been interesting, and at times controversial, since they involve combinations of dental, medical, and surgical etiological theories and management strategies. Amongst the various recommendations that emerged over the years was that any dental and surgical procedures that are primarily focused on mandible repositioning and irreversible changes to dental occlusion should be avoided. This statement has important implications for appraising the validity of physiopathology concepts and treatment proposals centered around the evaluation of TMJ disc position, since they also generally lead to performing irreversible procedures.

METHODS

A review of the pertinent TMJ literature related to the articular disc position and its association with TMD symptoms was carried out by the authors.

RESULTS

For many practitioners, the position of the TMJ disc has been regarded as a primary cause of TMJ pain and dysfunction. For decades, incoordination between the TMJ disc, the condylar head and the articular eminence was indeed considered the main factor for the etiology of intracapsular TMD symptoms and consequently an important target for therapy. However, research has shown that synovitis is the more important variable in dealing with those conditions.

CONCLUSION

In this commentary, the biological rationale to consider synovitis, rather than disc position, as the linchpin for clinical symptoms is presented in detail. Hopefully, this might contribute to putting the elusive butterfly characteristics of this topic finally to rest.

BMSC Derived Exosomes Attenuate Apoptosis of Temporomandibular Joint Disc Chondrocytes in TMJOA via PI3K/AKT Pathway

Bone marrow mesenchymal stem cell-derived exosomes (BMSC-Exos) are crucial means of intercellular communication and can regulate a range of biological processes by reducing inflammation, decreasing apoptosis and promoting tissue repair. We treated temporomandibular joint (TMJ) disc chondrocytes with TNF-α and performed local injection of sodium iodoacetate (MIA) in the TMJ of rats to establish in vitro and in vivo models of TMJ osteoarthritis (TMJOA). BMSC-Exos were isolated and extracted to evaluate their proliferation and trilineage differentiation abilities, and their antiapoptotic and chondroprotective effects were assessed. This study revealed that BMSC-Exos can be endocytosed by TMJ disc chondrocytes in vitro and that BMSC-Exos pretreatment strongly attenuated the inhibitory effect of TNF-α on the proliferative and chondrogenic potential of TMJ disc chondrocytes. The administration of BMSC-Exos significantly suppressed TNF-α-induced apoptosis in TMJ disc chondrocytes by increasing the phosphorylation level of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) pathway-related proteins, whereas the PI3K inhibitor LY294002 neutralized this antiapoptotic effect. Intradiscal injection of BMSC-Exos alleviated the degeneration and inflammation of TMJ discs in a rat model of TMJOA. Our study revealed that BMSC-Exos can attenuate the apoptosis of TMJ disc chondrocytes and destruction of TMJ discs partially by inhibiting the apoptotic pathway and activating the PI3K/AKT pathway, thereby providing a promising treatment strategy for the regeneration of damaged TMJ discs.

TMJ Replacement in Degenerative Disease: A Systematic Review

Objectives: This study aims to describe and analyze the indications and clinical results of total TMJ replacement in participants with degenerative and/or inflammatory joint diseases, defining patient and intervention conditions. Methods: A systematic review was conducted according to the Cochrane Handbook for Systematic Reviews of Intervention and reported according to the PRISMA Items update. The search strategy was from 1997 to July 2024 in Pubmed, Embase, Scopus, and Web of Science. A search for gray literature was conducted in the databases Google Scholar and Open Access Theses and Dissertations (OATD), and there were no limitations on the language or study design. We incorporated studies involving human patients over 15 years of age with degenerative and/or inflammatory joint conditions who underwent joint prosthesis replacement, either concurrently or separately from orthognathic surgery, as an initial intervention or after prosthesis installation. Participants with a postoperative follow-up of 12 months or longer were included. A risk of bias analysis was performed for non-randomized studies using the ROBINS-I tool, and GRADE profiler (GRADEpro) software was used to assess the quality of evidence and synthesize the data. Results: All the selected studies performed postoperative follow-up with quantitative and qualitative parameters; 10 performed a follow-up of 2 to 5 years. The indication for joint prosthesis replacement due to system failure was only 4.07%. Concerning diagnoses, 579 presented degenerative and/or inflammatory joint diseases, with osteoarthritis being the most frequent, followed by osteoarthrosis, juvenile idiopathic arthritis, and rheumatoid arthritis. The maximum mouth opening of the participants with TMJ disease presented an average of 24.32 ± 5.8 mm with a range of 18 to 36.4 mm. Of the 579 participants, the studies mention that they presented a soft to liquid diet and pain associated with decreased mandibular functionality. Conclusions: A total of 76.18% of the participants presented a range of moderate to severe pain associated with a decrease in functionality and, after joint replacement, all participants mentioned a decrease in pain or absence of pain, a change in diet by incorporating solid foods, and an increase in opening with an average of 40.74 ± 3.1 mm. Total joint replacement shows favorable long-term results. It is not possible to identify the best time to perform joint replacement surgery, considering the time since diagnosis of the disease, the time since the start of non-surgical treatment, or the number of previous surgeries.

Mesenchymal stem cells-derived exosomes alleviate temporomandibular joint disc degeneration in temporomandibular joint disorder

Temporomandibular joint (TMJ) disorder (TMD) is a chronic progressive disease that is commonly seen in clinical settings. TMJ disc degeneration is an important manifestation of TMD, and further aggravates the progression of TMD. However, treatments on TMJ disc degeneration are very limited till now. In this study, we first observed the effects of bone marrow stem cells (BMSC) conditioned medium on functions of TMJ disc fibroblasts. Then BMSC-derived small extracellular vesicles (BMSC-EVs) were isolated and exposed to TMJ disc fibroblasts. RNA-sequencing was used to further investigate the mechanisms. BMSC-EVs were finally injected into a rat model with TMD. Results showed that in the transwell co-culture system, the medium derived from BMSC reduced inflammation and enhanced chondrogenesis in TMJ disc fibroblasts. BMSC-EVs promoted proliferation, migration, and chondrogenic differentiation of TMJ disc fibroblasts, and inhibited apoptosis and inflammatory responses. Local injection of BMSC-EVs into the TMD model alleviated TMJ disc degeneration. Therefore, BMSC-EVs were a potentially effective, sustainable and clinically translational-promising option for TMJ disc degeneration, and further reduce the progression of TMD.

Intramuscular Botulinum Toxin as an Adjunct to Arthrocentesis with Viscosupplementation in Temporomandibular Disorders: A Proof-of-Concept Case-Control Investigation

BACKGROUND

The reduction in joint load is a potential beneficial factor in managing osteoarthritis of the temporomandibular joint (TMJ). This paper aims to compare the effectiveness of the intramuscular injection of botulinum toxin (BTX-A) as an adjunct to TMJ arthrocentesis plus viscosupplementation with arthrocentesis plus viscosupplementation alone in the management of TMJ osteoarthritis.

METHODS

A pilot clinical retrospective study examined TMJ osteoarthritis treatments. Patients were divided into two groups: Group A received BTX-A injections and arthrocentesis with viscosupplementation, while Group B received only arthrocentesis with viscosupplementation. The study assessed outcomes based on mouth opening (MO), pain at rest (PR), pain at mastication (PF), and masticatory efficiency (ME) at various time points (baseline (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), and 4 weeks (T4)) up to 2 months after treatment.

RESULTS

The study included two groups, each with five patients. Group A received five weekly sessions of arthrocentesis plus viscosupplementation and a single BTX-A injection during the first arthrocentesis appointment. Group B underwent the five-session protocol of arthrocentesis plus viscosupplementation alone. MO, PF, PR, and ME improved quickly in T2 in both groups, but the improvement was of greater importance over the following weeks and lasted longer in Group A.

CONCLUSIONS

Arthrocentesis with viscosupplementation associated with BTX-A was found to be more effective than arthrocentesis alone in improving clinical outcomes. This suggests that patients with TMJ osteoarthritis and myofascial pain may benefit from reduced muscle tone and joint load.

Specific tissue engineering for temporomandibular joint disc perforation

BACKGROUND

The temporomandibular joint (TMJ) disc is a critical fibrocartilaginous structure with limited regenerative capacity in the oral system. Perforation of the TMJ disc can lead to osteoarthritis and ankylosis of the TMJ because of the lack of disc protection. Clinical treatments for TMJ disc perforation, such as discectomy, hyaluronic acid injection, endoscopic surgery and high position arthroplasty of TMJ, are questionable with regard to long-term outcomes, and only three fourths of TMJ disc perforations are repairable by surgery, even in the short-term. Tissue engineering offers the potential for cure of repairable TMJ disc perforations and regeneration of unrepairable ones.

OBJECTIVES

This review discusses the classification of TMJ disc perforation and defines typical TMJ disc perforation. Advancements in the engineering-based repair of TMJ disc perforation by stem cell therapy, construction of a disc-like scaffold and functionalization by offering bioactive stimuli are also summarized in the review, and the barriers developing engineering technologies need to overcome to be popularized are discussed.

Overtreatment "Successes"--What Are the Negative Consequences for Patients, Dentists, and the Profession?

AIMS

To describe how some management practices in the field of orofacial musculoskeletal disorders (also described as temporomandibular disorders [TMDs]) are based on concepts about occlusal relationships, condyle positions, or functional guidance; for some patients, these procedures may be producing successful outcomes in terms of symptom reduction, but in many cases, they can be examples of unnecessary overtreatment.

METHODS

The authors discuss the negative consequences of this type of overtreatment for both doctors and patients, as well as the impact on the dental profession itself. Special focus is given to trying to move the dental profession away from the old mechanical paradigms for treating TMDs and forward to the more modern (and generally more conservative) medically based approaches, with emphasis on the biopsychosocial model.

RESULTS

The clinical implications of such a discussion are apparent. For example, it can be argued that the routine use of Phase II dental or surgical treatments for managing most orofacial pain cases represents overtreatment, which cannot be defended on the grounds of symptom improvement (ie, "successful" outcomes) alone. Similarly, there is enough clinical evidence to conclude that complex biomechanical approaches focusing on the search for an ideal specific condylar or neuromuscular position for the management of orofacial musculoskeletal disorders are not needed to produce a positive clinical result that is stable over time.

CONCLUSION

Typically, overtreatment successes cannot be easily perceived by the patients or the treating dentists because the patients are satisfied and the dentists feel good about those outcomes. However, neither party knows whether an excessive amount of treatment has been provided. Therefore, both the practical and ethical aspects of this discussion about proper treatment vs overtreatment deserve attention.

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

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

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.