Is the Temporomandibular Joints' Reciprocal Clicking Related to the Morphology and Position of the Mandible, as Well as to the Sagittal Position of Lower Incisors?-A Case-Control Study

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

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

Oral Glucosamine in the Treatment of Temporomandibular Joint Osteoarthritis: A Systematic Review

Temporomandibular disorders (TMDs) occur frequently within the general population and are the most common non-dental cause of orofacial pain. Temporomandibular joint osteoarthritis (TMJ OA) is a degenerative joint disease (DJD). There have been several different methods of treatment of TMJ OA listed, including pharmacotherapy among others. Due to its anti-aging, antioxidative, bacteriostatic, anti-inflammatory, immuno-stimulating, pro-anabolic and anti-catabolic properties, oral glucosamine seems to be a potentially very effective agent in the treatment of TMJ OA. The aim of this review was to critically assess the efficacy of oral glucosamine in the treatment of TMJ OA on the basis of the literature. PubMed and Scopus databases were analyzed with the keywords: (temporomandibular joints) AND ((disorders) OR (osteoarthritis)) AND (treatment) AND (glucosamine). After the screening of 50 results, eight studies have been included in this review. Oral glucosamine is one of the symptomatic slow-acting drugs for osteoarthritis. There is not enough scientific evidence to unambiguously confirm the clinical effectiveness of glucosamine supplements in the treatment of TMJ OA on the basis of the literature. The most important aspect affecting the clinical efficacy of oral glucosamine in the treatment of TMJ OA was the total administration time. Administration of oral glucosamine for a longer period of time, i.e., 3 months, led to a significant reduction in TMJ pain and a significant increase in maximum mouth opening. It also resulted in long-term anti-inflammatory effects within the TMJs. Further long-term, randomized, double-blind studies, with a unified methodology, ought to be performed to draw the general recommendations for the use of oral glucosamine in the treatment of TMJ OA.

Vitamin D3 Metabolism and Its Role in Temporomandibular Joint Osteoarthritis and Autoimmune Thyroid Diseases

The aim of this review was to present the metabolism of vitamin D₃, as well as to discuss the role of vitamin D₃ in bone metabolism, temporomandibular joint osteoarthritis (TMJ OA), and autoimmune thyroid diseases (AITD) on the basis of the literature. Vitamin D₃ plays a significant role in human health, as it affects the calcium-phosphate balance and regulates the bone metabolism. Calcitriol impresses the pleiotropic effect on human biology and metabolism. Its modulative function upon the immune system is based on the reduction of Th1 cell activity and increased immunotolerance. Vitamin D₃ deficiency may lead to an imbalance in the relationship between Th1/Th17 and Th2, Th17/Th reg, and is considered by some authors as one of the possible backgrounds of autoimmune thyroid diseases (AITD), e.g., Hashimoto's thyroiditis or Graves' disease. Moreover, vitamin D₃, through its direct and indirect influence on bones and joints, may also play an important role in the development and progression of degenerative joint diseases, including temporomandibular joint osteoarthritis. Further randomized, double blind studies are needed to unequivocally confirm the relationship between vitamin D₃ and abovementioned diseases and to answer the question concerning whether vitamin D₃ supplementation may be used in the prevention and/or treatment of either AITD or OA diseases.

Development of a new category system for the profile morphology of temporomandibular disorders patients based on cephalograms using cluster analysis

Objective

This study aims to develop a new category scheme for the profile morphology of temporomandibular disorders (TMDs) based on lateral cephalometric morphology.

Methods

Five hundred and one adult patients (91 males and 410 females) with TMD were enrolled in this study. Cluster tendency analysis, principal component analysis and cluster analysis were performed using 36 lateral cephalometric measurements. Classification and regression tree (CART) algorithm was used to construct a binary decision tree based on the clustering results.

Results

Twelve principal components were discovered in the TMD patients and were responsible for 91.2% of the variability. Cluster tendency of cephalometric data from TMD patients were confirmed and three subgroups were revealed by cluster analysis: (a) cluster 1: skeletal class I malocclusion; (b) cluster 2: skeletal class I malocclusion with increased facial height; (c) cluster 3: skeletal class II malocclusion with clockwise rotation of the mandible. Besides, CART model was built and the eight key morphological indicators from the decision tree model were convenient for clinical application, with the prediction accuracy up to 85.4%.

Conclusion

Our study proposed a novel category system for the profile morphology of TMDs with three subgroups according to the cephalometric morphology, which may supplement the morphological understanding of TMD and benefit the management of the categorical treatment of TMD.

Position of the Hyoid Bone and Dimension of Nasopharynx and Oropharynx after Occlusal Splint Therapy and Physiotherapy in Patients Diagnosed with Temporomandibular Disorders

Background: The aim of the study was to assess the position of the hyoid bone, as well as the width of the nasopharynx and oropharynx after occlusal splint therapy combined with physiotherapy in patients diagnosed with temporomandibular disorders (TMD). Methods: This was a clinical trial study. The study group consisted of 40 patients diagnosed with TMD, who were qualified for the treatment combining physiotherapy and occlusal splint therapy. Hyoid bone position as well as the width of the nasopharynx and oropharynx were assessed in lateral cephalograms taken before and after the end of the treatment. There were 15 generally healthy participants included into the control group, who had taken lateral cephalograms twice within the period of 1 to 2 years and did not receive any occlusal treatment in the meantime. Results: The position of the hyoid bone was significantly lowered and the dimension of the lower part of the oropharynx was significantly decreased after the end of the long-term occlusal splint therapy combined with physiotherapy in patients diagnosed with TMD. Conclusions: Long-term occlusal splint therapy combined with physiotherapy affected the position of the hyoid bone and the dimension of the lower part of the oropharynx.

Craniovertebral and Craniomandibular Changes in Patients with Temporomandibular Joint Disorders after Physiotherapy Combined with Occlusal Splint Therapy: A Prospective Case Control Study

Background and Objectives: The aim of the study was to assess the craniovertebral and craniomandibular changes in patients diagnosed with temporomandibular joint disorders (TMD) after physiotherapy combined with occlusal splint therapy. Materials and Methods: There were forty patients (32 females, 80%), diagnosed with TMD, included into the study group. After the initial series of physiotherapy, patients received maxillary occlusal splints to be worn day and night. Participants continued physiotherapy simultaneously with occlusal splint therapy for 6 months. Lateral cephalograms taken in natural head position before and after the end of the therapy were used for measurements. The control group consisted of 15 healthy participants (12 females, 80%), who had taken lateral cephalograms twice, and did not receive any type of occlusal treatment nor physiotherapy in the meantime. Results: Occlusal splint therapy and physiotherapy combined together significantly affected: the vertical position of the mandible (significant increase, p < 0.0001), the sagittal position of mandible (significant decrease, p = 0.0065), as well as the width of the functional space between C1 and C2 (significant decrease, p = 0.0042). Moreover, the cervical lordosis was restored after the end of the treatment (p < 0.0001). Conclusions: Cooperation of physiotherapists with dental practitioners is necessary in the treatment of patients with TMD, including temporomandibular joint osteoarthritis.

Quantitative analysis of the mouth opening movement of temporomandibular joint disorder patients according to disc position using computer vision: a pilot study

BACKGROUND

Temporomandibular joint disorder (TMD), which is a broad category encompassing disc displacement, is a common condition with an increasing prevalence. This study aimed to develop an automated movement tracing algorithm for mouth opening and closing videos, and to quantitatively analyze the relationship between the results obtained using this developed system and disc position on magnetic resonance imaging (MRI).

METHODS

Mouth opening and closing videos were obtained with a digital camera from 91 subjects, who underwent MRI. Before video acquisition, an 8.0-mm-diameter circular sticker was attached to the center of the subject's upper and lower lips. The automated mouth opening tracing system based on computer vision was developed in two parts: (I) automated landmark detection of the upper and lower lips in acquired videos, and (II) graphical presentation of the tracing results for detected landmarks and an automatically calculated graph height (mouth opening length) and width (sideways values). The graph paths were divided into three types: straight, sideways-skewed, and limited-straight line graphs. All traced results were evaluated according to disc position groups determined using MRI. Graph height and width were compared between groups using analysis of variance (SPSS version 25.0; IBM Corp., Armonk, NY, USA).

RESULTS

Subjects with a normal disc position predominantly (85.72%) showed straight line graphs. The other two types (sideways-skewed or limited-straight line graphs) were found in 85.0% and 89.47% in the anterior disc displacement with reduction group and in the anterior disc displacement without reduction group, respectively, reflecting a statistically significant correlation (χ2=38.113, P<0.001). A statistically significant difference in graph height was found between the normal group and the anterior disc displacement without reduction group, 44.90±9.61 and 35.78±10.24 mm, respectively (P<0.05).

CONCLUSIONS

The developed mouth opening tracing system was reliable. It presented objective and quantitative information about different trajectories from those associated with a normal disc position in mouth opening and closing movements. This system will be helpful to clinicians when it is difficult to obtain information through MRI.

Personalized Orthodontics: From the Sagittal Position of Lower Incisors to the Facial Profile Esthetics

Background: One of the goals of orthodontic treatment is to obtain maximum facial harmony. The sagittal position of the lower incisors plays a significant role in the planning of orthodontic treatment. The aim of the study was to evaluate the relationship between the sagittal position of lower incisors and facial profile esthetics with reference to the skeletal vertical dimension. Methods: There were 200 patients included in the study. Patients were allocated into three groups, depending on the vertical growth pattern: normal-angle, low-angle, and high-angle cases. Tweed–Merrifield cephalometric analysis was used to assess the sagittal and vertical position of the mandible, as well as to assess the sagittal position of the lower incisors. Results: Z-angle and Frankfort mandibular incisor plane angle (FMIA) decreased significantly (p < 0.001) with the increase of the skeletal vertical dimension. Incisor mandibular plane angle (IMPA) was significantly higher (p < 0.001) in low-angle patients compared to the high-angle ones. Z-angle appeared to be the most accurate parameter (area under curve, AUC = 0.957) describing patients with a convex profile. The cutoff value of Z-angle 68.0° was characterized by the sensitivity of 94.1% and the specificity of 84.3%. Conclusions: The sagittal position of the lower incisors significantly affects the facial profile convexity. The Z-angle is the parameter which most accurately describes the patients with a convex profile.