Reduced joint distance during TMJ movement in the posterior condylar position

Relationship between the Mandibular Condyle Position and the Bite Force in the People with Normal Temporomandibular Joint

Statement of the Problem. The mandibular condyle position is important in temporomandibular joint (TMJ) disorders. The bite force is a mechanical force that may affect the condylar position. Purpose. To investigate the relationship between condylar position in the glenoid fossa and maximum bite force in adults with normal temporomandibular joint. Materials and Methods. In this cross-sectional study, 23 subjects (21 females and 2 males; mean age 38.88 $\pm$ 11.7 years) with 41 joints participated. Right and left joints were examined using cone-beam computed tomography. Maximum bite force was measured using the strain gauge transducer in the regions of right molar, left molar, and incisors. Pearson correlation coefficient, paired sample t-test, and binary logistic regression were employed for analysis. Results. The mean maximum bite force was 169.09 ± 87.7 N. The most common position of the condyle was anterior (n = 36) and inferior (n = 31). The mean of mandibular condyle joint spaces for right and left sides were not statistically significant ( $P>0.05$ ). There were no relationships between the condylar positions and the mean maximum bite force ( $P>0.05$ ). Conclusion. The condylar positions in the glenoid fossa are not related to the bite force in the people with normal temporomandibular joint.

The impact of occlusal support on temporomandibular disorders: a literature review

Temporomandibular disorders are a multifactorial disease. Occlusal support and the number of teeth in dentition have significant effects on the masticatory system. The current study aims to review the role of occlusal support in association with findings of temporomandibular disorders. Data sources were PubMed, Web of Science and Google Scholar, with 1411 citations published over the period 1992–2019. The selection criteria stipulated that articles must have reported the association between the number of teeth, occlusal unit, occlusal support and temporomandibular disorders. A total of 15 full-text articles was finally accessed for eligibility in the current review. The studies on temporomandibular disorders were collected from various sources, including articles reporting temporomandibular disorder symptoms ( n=1), temporomandibular disorder signs ( n=5), temporomandibular joint osseous changes ( n=1), temporomandibular joint dysfunction using the Helkimo index ( n=2), and temporomandibular disorder classification ( n=6). Of these articles, significant associations were found between: the number of missing teeth and temporomandibular disorders ( n=5); the number of occlusal units and occlusal supports and temporomandibular disorders ( n=3); the position of the lost occlusal units and temporomandibular disorders ( n=1). Loss of the occlusal unit has more impact on temporomandibular disorders than the loss of posterior teeth. The total loss of unilateral occlusal support seems to be an aetiological factor for temporomandibular disorders, and maintenance of balanced posterior occlusal support has a role in the prevention and management of temporomandibular disorders.

A new approach in three dimensions to define pre- and intraoperative condyle-fossa relationships in orthognathic surgery - is there an effect of general anaesthesia on condylar position?

Incorrect registration of the condylar position in orthognathic surgery is supposed to cause postoperative relapse, condylar resorption and temporomandibular disorders. The aim of this prospective study was to evaluate the influence of general anaesthesia on centric relation (CR). Therefore, CR registered preoperatively in the awake patient and CR registered intraoperatively under general anaesthesia were recorded in 30 patients (14 men, 16 women) undergoing orthognathic surgery (skeletal class I: n=3, II: n=13, III: n=14; symmetric: n=20; asymmetric: n=10). CR records were digitized and, through superimposition on the preoperative cone beam computed tomography of the patient's skull, the superior, anterior and posterior joint space and the volumetric congruence of 120 condyles were analysed. The linear measurements of joint spaces did not demonstrate any clinically relevant discrepancy between the CR measured in the awake and anaesthetized patient. In contrast, volumetric analysis revealed statistically significant differences between both states, with an intraoperative condylar sag predominantly in the posterior-inferior direction. The patient's skeletal class or symmetry had no significant influence on the intraoperative condylar displacement. Thus, the risk of fixing the condyle in an unphysiological position supports the idea of using intraoperative condylar positioning devices to achieve predictable and stable outcomes.

Design and fabrication of a 3D-printed oral stent for head and neck radiotherapy from routine diagnostic imaging

Background

Oral stents have been shown to reduce the deleterious effects of head and neck radiotherapy through the displacement of normal tissues away from the areas of high dose irradiation. While these stents are commonly used in the treatment of patients with head and neck cancer at many large academic cancer centers, their use is much more limited outside of these institutions due to the time and expertise required for their fabrication.

Results

In the study, we describe a novel method to design and manufacture oral stents from routine computed tomography (CT) imaging studies through the use of 3D printing technologies.

Conclusion

Our proposed method may help to greatly expand access to these beneficial devices for patients undergoing radiation treatment at centers without access to dental and oral/maxillofacial specialists.

Condylar distances in hypermobile temporomandibular joints of patients with excessive mouth openings by using computed tomography

Objectives: hypermobility in Temporomandibular joint (TMJ) can manifest higher range of motions in mandible. The aim of this study was to compare the position and distances of the head of condyle to glenoid fossa in TMJs of healthy individuals and patients with mild, moderate and severe TMJ hypermobility. Material and Methods: In this clinical study, 69 patients (between the ages of 22 to 42) with manifestation of joint hypermobility were included and Computed tomography were administered for both TMJs. The patients were divided into three groups based on their maximum mouth opening (MMO): (A) with MMO of 50-55 mm; (B) with MMO between 55 to 65 mm; and (C) with MMO >65 mm. Also, 15 healthy people with profiled tomography in the last 6 months were assumed as control group (N) with normal MMO (<50 mm). The position of condyle from articular eminence while MMO; and the distances from anterior, superior and posterior border of condyle and facing wall of glenoid fossa were measured in closed mouth from the tomography of all contributors. The collected data were analyzed by one-way ANOVA, Post Hoc and Chi-Square tests using SPSS software version 15 at significant level of 0.05. Results: The superior and posterior distances were significantly higher in groups A, B and C than healthy individuals (all P values<0.01). The anterior distance was significant between groups B and N only in right TMJ (P=0.013). Conclusions: TMJ hypermobility showed the characteristic of increased condylar distance in posterior and superior specially in higher excessive mouth opening.

Key words:Computed tomography, joint hypermobility, mandibular condyle, mouth opening.

Evaluation of intra-articular distance narrowing during temporomandibular joint movement in patients with facial asymmetry using 3-dimensional computed tomography image and tracking camera system

INTRODUCTION

Functional overloading can lead to disc displacement in the temporomandibular joint (TMJ), and a high incidence of disc displacement has been reported in patients with facial asymmetry. The aim of this study was to assess the dynamic condylar movement in patients (n = 26) with facial asymmetry using a simulation system with 3-dimensional computed tomographic images and tracking camera system.

MATERIAL AND METHODS

The intra-articular distance (IAD) between the condyle and glenoid fossa was recorded during TMJ movement as a parameter for functional overloading and compared between Group I with severe asymmetry and Group II with mild asymmetry.

RESULTS

The average IAD was shorter in Group I than Group II, especially at the lowest point (P < 0.05). The ratio of IAD narrowing in Group I was significantly larger than in Group II (P < 0.05). The mean IAD were slightly smaller on the deviated side (3.41 mm) than on the nondeviated side (3.55 mm) in Group I, even though there was no statistical significance. The maximum displacement in Group I was longer than in Group II and had no significant difference between deviated side and nondeviated side.

CONCLUSION

We suggested that the reduced IAD resulting from TMJ overloading can lead to internal derangement in severe facial asymmetry.

Computed tomographic study of the patterns of oesteoarthritic change which occur on the mandibular condyle

The aim of this study was to investigate which parts of the articular surface of the mandibular condyle are involved in osteoarthritic (OA) change (the occurring pattern) and the relationship of these patterns to clinical signs and symptoms. The computed tomographic (CT) images and clinical records of patients with OA involvement of one or both of their temporomandibular joints (TMJs) were reviewed (OA changes confirmed by CT; 684 TMJs included). The condylar articular surface was divided into nine imaginary sections on the CT images: antero-medial (AM), antero-central (AC), antero-lateral (AL), centri-medial (CM), centri-central (CC), centri-lateral (CL), postero-medial (PM), postero-central (PC), and postero-lateral (PL) section. The occurring patterns were classified with hierarchical cluster analysis based on the distribution of the sections involved by OA changes. OA changes were observed the most frequently on the AC (62.4%) followed by the AM (55.0%), CC (48.2%), AL (43.0%), CL (43.3%), CM (33.3%), PC (28.9%), PL (25.3%), and PM (23.1%). The occurring patterns were classified into three types among which subjective joint pain (P < 0.001) and noise (P < 0.05) were more frequently reported in the entire-involved type followed by lateral- and antero-medial types in descending order, while no significant differences for age, gender, side, pain on palpation, clicking, crepitus, mouth opening range and craniomandibular index were observed. OA changes are more likely to occur on the anterior than the posterior and on the medial than the lateral surface of the mandibular condyle, while subjective joint pain and noise are more frequently reported with OA changes involving the lateral or entire part. Pain on palpation, noise, and mouth opening range were not related to the occurring pattern of OA changes.