The Role of the Lateral Pterygoid Muscle in Articular Disc Displacement: A Cross-Sectional Magnetic Resonance Imaging Study

Background: Determination of the role of the Lateral Pterygoid Muscle LPM in the articular disc displacement ADD is controversial referring to the variations in the pattern of insertion of the Superior Lateral Pterygoid Muscle SPLM. Introduction: it was well understood that the superior head of the lateral pterygoid muscle has only a single insertion pattern among individuals in which the muscle is attached to the articular disc and capsule. However, recent findings in many studies have shown a noticeable variation in the insertion pattern of the upper LPM. Method: MRI examinations were collected at King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia. Scans of 61 patients (41 females, 20 males, mean age 33 years old) with symptoms of temporomandibular dysfunction were reviewed retrospectively. The direction of their articular disc displacement was evaluated through sagittal and coronal views in both open and closed mouth positions. Results: There was no statistical significance found between the LPM attachment types and TMJ disc position. The chi-square test also showed no significant difference between the type of LPM attachment and the condylar location. Forty-five percent of the articular discs were located between the articular eminence and the glenoid fossa. The majority of the disc displacement was in the anterior direction. Conclusion: There was no statistically significant association between the type of LPM attachments and the direction of disc displacement.

Magnetic Resonance Imaging Evaluation of Closed-Mouth TMJ Disc-Condyle Relationship in a Population of Patients Seeking for Temporomandibular Disorders Advice

Objective. To characterize the closed-mouth temporomandibular joint (TMJ) disc-condyle relationship in a population of individuals who sought hospital services for temporomandibular disorders (TMD). Methods. Two hundred and twenty-four TMJ magnetic resonance images (MRIs) of 112 patients were assessed in all spatial planes to classify disc position with respect to the condyle in a closed-mouth position. Results. Disc displacement (DD) was present in 62.1% and superior disc position in 29.9% of the patients. Position could not be determined in 8% of the cases. Among DD, pure anteriorized position was the most common condition (34.4%), with different combined translational and rotational displacements in all the other joints (27.7%). Conclusion. There is a wide biological variability in disc position in closed mouth among patients seeking for TMD advice. Getting deeper into the correlation with clinical symptoms is recommended to refine the potential relevance of any diagnostic and management strategies based on the imaging evaluation of TMJ disc position.

Hand-Carried Ultrasonography Instrumentation in the Diagnosis of Temporomandibular Joint Dysfunction

Internal derangement (ID) in the temporomandibular joint (TMJ) is defined as a mechanical problem of the joint that interferes with its function. It is attributed to an abnormal interaction among the articular disc, condyle, and joint eminence. The aim of this study is to evaluate diagnostic efficacy of non-invasive hand-carried ultrasonography instrumentation (US) to provide high-level images for a correct diagnosis of ID. Twenty-eight ID patients, 15 female and 13 males, were examined both clinically and by MRI images in order to achieve a diagnosis of ID (using Helkimo index). Then, they were submitted to US examination with a 12 MHz transducer by using hand-carried instrumentation by a clinician that was blind to their diagnosis and clinical data. TMJ US examination was performed with the mouth closed and mouth open, with proper technique. Each position was then evaluated with two different orientations of the transducer. US showed acceptable results in identifying bone structures. Lower values of diagnostic efficacy were obtained for disc position during joint movements with respect to MRI images. MRI still represents the gold standard for the identification of joint structures. If not corroborated by clinical and anamnestic data, the diagnostic efficacy of US in identifying the position of the disc during opening and closing jaw movements appears limited than compared to MRI.

Assessment of anterior positioning splint in conjunction with lateral pterygoid BTX injection to treat TMJ disc displacement with reduction — a preliminary report

Objective Treatment of temporomandibular disc displacement with reduction is controversial. This study assesses the use of an anterior positioning splint with botulinum toxin in the lateral pterygoid muscle (BTX) for such cases. Methods Twelve joints were included; groups I and II received BTX injection while group II also received an anterior positioning splint. Pain scores and clicking status were recorded at regular intervals then a postoperative MRI was done after 4 months. Results Clinical improvement was noted in both groups. Mean pain scores dropped significantly and clicks in the twelve joints disappeared in 83% of group I and 33% of group II. MRIs showed significant disc position improvement with the higher mean change (1.33 ± 0.76) in group I. Group I showed better improvement of discal position and only one joint regained a click. Patients of group II reported discomfort from the splint which may have caused psychological distress and so worst pain scores. Conclusions Group I showed slightly better results but the cost of BTX injections and the complications of the splint should be kept in mind and the decision of treatment selection made according to each condition.

Prognostic Indicators of Yang’s Arthroscopic Technique for Management of Temporomandibular Joint Anterior Disc Displacement: Part 1- Clinical Predictors.

In order to optimize the patient selection for specific treatment modality and to achieve favorable treatment outcomes, prognostic indicators impacting the results are important to analyze. This longitudinal retrospective study aimed to analyze various prognostic factors impacting the surgical outcomes following Yang’s arthroscopic discopexy for management of temporomandibular joint anterior disc displacement using success criteria based on pain, maximal interincisal opening, diet, and quality of life. Furthermore, a quantitative MRI assessment of disc position and condylar height was performed pre- and postoperatively. Multinomial analysis was used to evaluate various prognostic variables including gender, age, duration of illness, Wilkes staging, parafunctional habits, and splint/orthodontic therapy. A total of 169 patients (234 joints) were included. The outcome was categorized as excellent (n = 67/39.6%), good (n = 72/42.6%), improved (n = 22/13.01%) or poor (n = 8/4.73%) with a success rate of 95.26%. Patients aged from 11–15 years old were significantly more likely to be in the good outcome group (odds ratio (OR), 0.20; P < 0.05). Also, patients with shorter duration of illness (OR, 0.29; P < 0.05) and with Wilkes stage III (OR, 0.11; P < 0.05) were more likely to be in the improved outcome group. Better outcomes can be achieved at younger patients with shorter disease history and earlier Wilkes staging.

Contemporary Imaging Modalities for Temporomandibular Joint

There are different imaging methods used in the evaluation of bone structure, disc, ligaments and muscles that make up Temporomandibular Joint (TMJ). The aim of this review is give information about choice of suitable imaging methods for TMJ diseases from past to present. In the past, conventional radiographs have often been used for TMJ imaging, but nowadays magnetic resonance imaging is the gold standard for soft tissue imaging and disc position determination. Another new technology, ultrasonography can be used for disc displacement, effusion, diagnosis of intraarticular defects. Cone beam computed tomography, it is used for the evaluation of cortical and trabecular structure of bone components of TMJ, developmental anomalies and traumatic injuries affecting TMJ, pathological changes such as osteophyte, erosion, fractures, ankylosis, glenoid fossa-condyle relationship. Nowadays, in parallel with the developing technology, a single imaging method is not used for TMJ imaging and evaluation is performed with several imaging methods. Imaging methods should be selected by evaluating the factors such as radiation dose, contribution to diagnosis and treatment plan, easy applicability.

Natural Frequency Analysis of a Jeffcott Rotor Having Stepped Shaft

The Rotating shafts are mechanical elements used to transmit power or motion. A shaft with a step or steps is widely used instead of a shaft with a fixed (non-variable) diameter when operating at high speeds. The aim of this research is to study the effect of the step amount and its location in the shaft on the natural frequencies of the Jeffcott rotor model. Analytical methods are used to find an approximate formulation to obtain the natural frequencies of the Jeffcott rotor model neglecting the shaft mass. Lagrange equations are used to develop dynamic equations assuming elastic shaft with steps carrying a disk. The finite element method by using ANSYS is used to validate and compare the results obtained in the analytical method. The results obtained analytically and numerically were compatible and in good agreement. In addition, some parameters such as the step amount and the stepped shaft length are changed to check its effects on the natural frequencies. the results showed that the natural frequencies increase with an increase in the amount and length of the stepped part, while they decrease the closer the disc position to the center.

Symptoms, disc position, occluding pairs, and facial skeletal characteristics of older patients with temporomandibular disorders

Objective To describe the proportions of different osseous diagnoses in older patients with temporomandibular disorders (TMD) and to analyze the symptoms, disc position, occluding pairs, and facial skeletal characteristics of patients with bilateral osteoarthrosis (BOA) and bilateral normal joints (BNJ). Methods This retrospective cross-sectional study constituted 88 older patients (age ≥60 years). The osseous diagnosis, symptoms, disc position, occluding pairs, and facial skeletal characteristics were evaluated. Variables in BOA patients and BNJ patients were compared using the t-test and chi-square test. Results Forty-eight patients had BOA, 7 had unilateral osteoarthrosis, 11 had intermediate osteoarthrosis, and 22 had BNJ. The prevalence of disc displacement without reduction (DDw/oR) in BOA patients was significantly higher than in BNJ patients. BOA patients exhibited greater ANB angle, PP-MP, U1-NPo, L1-NPo, and facial convexity angle; shorter posterior cranial base; and decreased ramus height. Conclusion BOA patients with associated DDw/oR had more complaints of orofacial pain and exhibited a shorter posterior cranial base, and greater mandibular retrusion, anterior tooth protrusion, and protruded profile than BNJ patients.

Evaluating the Effect of Conservative Therapy in Patients with Wilkes Stage III Temporomandibular Joint Derangement

The authors evaluated effects of physiotherapy in patients experiencing Wilkes III temporomandibular joint (TMJ) derangement with clinically limited joint mobility, but no pain. The group consisted of 31 patients with unilateral temporomandibular joint involvement, 3 men and 28 women (average age was 30.93, ranging from age 12 to 61). None of the patients in the group had experienced any previous TMJ therapy. The patients underwent conservative therapy in the form of home exercise (mobilisation and isometric exercises) as the first step in treatment. The authors evaluated the improvement in jaw movement (maximal interincisal opening – MIO) and the patients’ subjective assessments of their condition. Disc position before and after two months of exercise was also evaluated using ultrasound examination. The average MIO value in patients before starting the exercises was 33.5 mm, and after two months of exercises, 42.4 mm. Subjective assessment by patients: 26 patients (83%) described their condition as completely satisfactory, not requiring further therapy. Of these patients, ultrasound examination showed 10 patients with complete disc reduction, 9 patients with a change in disc displacement with reduction, and 7 patients with a continuing (unchanged) state of disc displacement. Results of our study show the effect of conservative therapy in patients with painless TMJ due to disc displacement (WIII). Effect of home exercises which were easy to perform, simple and acceptable to the patient were demonstrated.