Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.
Humans ; Mastication/physiology* ; Temporomandibular Joint/physiology* ; Temporomandibular Joint Disorders/etiology* ; Mandible/physiology*

INTRODUCTIONTemporomandibular joint disorders (TMJDs) are caused by several factors such as anatomical, neuromuscular and psychological alterations. A relationship has been established between TMJDs and postural alterations, a type of anatomical alteration. An anterior position of the head requires hyperactivity of the posterior neck region and shoulder muscles to prevent the head from falling forward. This compensatory muscular function may cause fatigue, discomfort and trigger point activation. To our knowledge, a method for assessing human postural attitude in more than one plane has not been reported. Thus, the aim of this study was to design a methodology to measure the external human postural attitude in frontal and sagittal planes, with proper validity and reliability analyses.

METHODSThe variable postures of 78 subjects (36 men, 42 women; age 18-24 years) were evaluated. The postural attitudes of the subjects were measured in the frontal and sagittal planes, using an acromiopelvimeter, grid panel and Fox plane.

RESULTSThe method we designed for measuring postural attitudes had adequate reliability and validity, both qualitatively and quantitatively, based on Cohen's Kappa coefficient (> 0.87) and Pearson's correlation coefficient (r = 0.824, > 80%).

CONCLUSIONThis method exhibits adequate metrical properties and can therefore be used in further research on the association of human body posture with skeletal types and TMJDs.

Adolescent ; Adult ; Female ; Humans ; Male ; Movement ; physiology ; Posture ; physiology ; Reproducibility of Results ; Temporomandibular Joint Disorders ; diagnosis ; physiopathology ; Young Adult

The aim of this study was to design a simple, economic, with high Common Mode Rejection Ratio (CMRR), preamplifier and multi-channel masticatory muscle surface electromyography (sEMG) signal acquisition system assisting to diagnose temporomandibular disorders (TMD). We used the USB interface technology in the EMG data with the aid of the windows to operate system and graphical interface. Eight patients with TMD and eight controls were analyzed separately using this system. In this system, we analyzed sEMG by an optional combination of time domain, frequency domain, time-frequency, several spectral analysis, wavelets and other special algorithms under multi-parameter. Multi-channel sEMG System of Masticatory Muscles is a simple, economic system. It has high sensitivity and specificity. The sEMG signals were changed in patients with TMD. The system would pave the way for diagnosis TMD and help us to assess the treatment effect. A novel and objective method is provided for diagnosis and treatment of oral-maxillofacial disease and functional reconstruction.
Algorithms ; Computer Graphics ; Data Collection ; Electromyography ; Humans ; Masticatory Muscles ; physiology ; physiopathology ; Sensitivity and Specificity ; Signal Processing, Computer-Assisted ; Temporomandibular Joint Disorders ; diagnosis ; User-Computer Interface

OBJECTIVECondylectomy was performed to treat condylar osteoma or hyperplasia. Introduced two methods of condylectomy via intraoral approach and evaluated their clinical results.

METHODSThirty-five patients, aging from 22 to 57.21 years, were treated by condylectomy via intraoral approach, of which 21 were condyle osteoma, 14 hemimandibular hyperplasia and condylar hyperplasia. Intraoral vertical ramus osteotomy (IVRO) were used in 32 patients and intraoral condylectomy via coronoid process resection was used in 3 patients.

RESULTSThe treatment results including oral function and facial symmetry after the operation were good in all patients. The temporomandibular joint (TMJ) dysfunction syndrome alleviated or disappeared. The follow-up period was 6 months to 3 years, and no relapse of condylar osteoma or hyperplasia was found. The patients who had IVRO and TMJ reconstruction had some degree of transplanted bone resorption, and one patients had relapse of facial deformity. But the patients who had intraoral condylectomy via coronoid process resection only had mild condyle remodeling and no obvious bone resorption was noted.

CONCLUSIONSThe two methods of intraoral condylectomy introduced in this stugy can successfully correct the facial deformity and TMJ dysfunction caused by condylar osteoma or hyperplasia. But the surgeons need to have excellent surgical skills and careful selection of the indications.

Adult ; Facial Asymmetry ; surgery ; Female ; Follow-Up Studies ; Humans ; Hyperplasia ; Male ; Mandible ; diagnostic imaging ; pathology ; surgery ; Mandibular Condyle ; diagnostic imaging ; pathology ; surgery ; Mandibular Neoplasms ; diagnostic imaging ; pathology ; surgery ; Middle Aged ; Oral Surgical Procedures ; methods ; Osteoma ; diagnostic imaging ; pathology ; surgery ; Temporomandibular Joint ; physiology ; surgery ; Temporomandibular Joint Disorders ; surgery ; Tomography, X-Ray Computed ; Young Adult

OBJECTIVETo analyze the stress distribution in temporomandibular joint (TMJ) with different depth of curve of Spee (CS) by three-dimensional finite element model (3D-FEM).

METHODSFEM with different depth of CS were established. The depth was 2.50, 0 and 4.50 mm (model 0, 1, 2). The stress distribution were analyzed by software Abaqus. The change of stress were analyzed by paried t test.

RESULTSThe stress distribution patterns in TMJ with different depth of CS were similar. The Von Mises on the anterior surface of condyle and the Von Mises on the intermedial zone of the disc was higher. The S. Max. Principal of the condyle was mainly tensile stress. The S. Min. Principal of the condyle was mainly compressive stress. The S. Max. Principal of the disc was mainly tensile stress. The S.Min. Principal of the disc was mainly compressive stress.In model 0, the eviations of the Von Mises, the S.Max. Principal and the S.Min. Principal on the anterior surface of condyle were 0.1057 - 0.2298 MPa, -0.2243 - -0.3738 MPa and -0.3494 - -0.1165 MPa. The eviations of the Von Mises, the S.Max. Principal and the S. Min. Principal on the intermedial zone of the disc were 0.1099 - 0.6880 MPa, -0.3217 - 0 MPa and -1.2000 - -0.1000 MPa. The D-values of of Von Mises of condyle and disk between different models were extremely significant (P < 0.01).

CONCLUSIONSWith the same plane of occlusion, the stress distribution patterns of TMJ with different depth of CS is similar to that of normal occlusion. The final results also validate the anterior surface of condyle and intermediate zone of articular disc are the weight-bearing areas in TMJ. The changes of depth of CS change the value of the stress.

Cephalometry ; Dental Occlusion ; Dental Stress Analysis ; methods ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional ; methods ; Mandibular Condyle ; physiology ; Stress, Mechanical ; Temporomandibular Joint ; physiology ; Temporomandibular Joint Disc ; physiology

OBJECTIVETo explore the six degrees of freedom of jaw opening and closing movement with motion capture and analysis system to establish a quantitative method for studying mandibular movement and a digital basis for virtual reality study of mandibular movement.

METHODSIn a male adult with normal dentition without temporomandibular joint disorders, 3 fluorescent markers were pasted in the upper dentition and 4 in the lower dentition. Six cameras of the motion capture system were arranged in a semi-circular fashion. The subject sat in front of the camera at an 80-cm distance with the Frankfort plane kept parallel to the horizontal plane. The degree-of-freedom (3 linear displacement and 3 angular displacement) of jaw opening and closing movement was obtained by collecting the marker motion.

RESULTSSix degrees of freedom of jaw opening and closing were obtained using the motion capture system. The maximum linear displacements of X, Y and Z axes were 5.888 089 cm, 0.782 269 cm, and 0.138 931 cm, and the minimum linear displacements were -3.649 83 cm, -35.961 2 cm, -5.818 63 cm, respectively. The maximum angular displacements of X, Y and Z axes were 0.760 088°, 2.803 753°, and 0.786 493°, with the minimum angular displacements of -2.526 18°, -0.625 94°, and -25.429 8°, respectively. Variations of linear displacements during jaw opening and closing occurred mainly in the Y axis, and those of angular displacement occurred mainly in the Z axis.

CONCLUSIONThe six degree-of-freedom of mandibular movement can be accurately obtained with the motion capture system to allow quantitative examination of the mandibular movement.

Adult ; Humans ; Male ; Mandible ; physiology ; Movement ; physiology ; Range of Motion, Articular ; Temporomandibular Joint ; physiology ; Video Recording

BACKGROUNDFunctional magnetic resonance is a non-invasive method that can examine brain activity and has been widely used in various fields including jaw movement and pain processing. Temporomandibular disorder (TMD) is one of the most frequent facial pain problems. The objective of this study was to investigate the brain activities using functional magnetic resonance imaging (fMRI) during unilateral maximal voluntary clenching tasks in the TMD synovitis patients with biting pain.

METHODSFourteen TMD synovitis patients with unilateral biting pain and 14 controls were included in the study. Contralateral biting pain was defined as right molar clenching causing left temporomandibular joint (TMJ) pain. Ipsilateral biting pain was defined as right molar clenching causing right TMJ pain. Symptom Check List-90 (SCL-90) was administered to the patients and controls. Independent sample t-test was used to compare the SCL-90 subscales between the two groups. Unilateral clenching tasks were performed by the patients and controls. Imaging data were analyzed using SPM99.

RESULTSPatients were divided into contralateral TMD biting pain group (n = 8) and ipsilateral TMD biting pain group (n = 6). The SCL-90 subscales were significantly different between the two groups for somatization, depression, anxiety, phobic anxiety, and paranoid ideation. Group analysis of the controls demonstrated brain activations in the inferior frontal gyrus, precentral gyrus, middle frontal gyrus, superior temporal gyrus, and insular. The areas of activation were different between right and left clenching task. In TMJ synovitis patients with contralateral or ipsilateral biting pain, the group analysis showed activations in the inferior frontal gyrus, superior temporal gyrus, medium frontal gyrus, precentral gyrus, and anterior cingulate cortex.

CONCLUSIONSThe inferior frontal gyrus and precentral gyrus play essential roles during the unilateral clenching task. Activation of anterior cingulate cortex in the synovitis patients with biting pain was associated with higher levels of psychological distress.

Adolescent ; Adult ; Brain ; metabolism ; physiology ; Facial Pain ; metabolism ; physiopathology ; Female ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Middle Aged ; Synovitis ; pathology ; Temporomandibular Joint ; pathology ; Young Adult

AIMThe purpose of this study is to compare the effects of the two clutches on recording the condylar movement.

METHODOLOGYTen subjects (6 women, 4 men; mean age 25.4 years) participated in the study. The mandibular movement, sagittal condylar inclination angle, and transversal condylar inclination angle of each subject were recorded with the CADIAX using the two clutches, respectively. The characteristics of the tracings of the protrusion, opening, and mediotrusion were analyzed with the t-test statistics at a = 0.05 level. The Kappa values were calculated for an assessment of the congruence of the tracings.

RESULTSThe results showed that the contour, direction, and dimension of the tracings in the two clutches were approximately same, but the tracings determined by the functional occlusal clutch were more regular and congruent. In the group segment recorded with the tray clutch, opening/closing paths of one subject showed crossed and time curves of three subjects appeared peak-like changes of velocity, but none were statistically different (P>0.05).

CONCLUSIONThe research suggests that the functional occlusal clutch should be preferred in the evaluation of the mandibular function, as the tracings with the tray clutch are more likely to produce false positive results.

Adult ; Dental Occlusion ; Diagnosis, Computer-Assisted ; instrumentation ; Female ; Humans ; Jaw Relation Record ; instrumentation ; Male ; Mandibular Condyle ; physiology ; Movement ; Temporomandibular Joint ; physiology

OBJECTIVETo evaluate the application of lateral lag screw and reduction of articular disk in management of intracapsular sagittle fractures of the condylar process.

METHODSThe study group consisted of 16 cases (19 joints), including 10 males (12 joints) and 6 females (7 joints). Condylar sagittal fracture and displaced articular disk were detected in all patients. The condylar segments were repositioned and fixed by using lateral lag screw and the displaced articular disk were repositioned at the same time. The mean postoperative follow-up was 16 months (range 6-28 months). During the follow up, facial nerve function was monitored and radiologic re-examinations were performed to evaluate reposition of condylar process fractures and articular disk, while the mouth opening and occlusion were registered.

RESULTSThe reduction of the displaced condylar fragments and articular disks in all patients were excellent on 3D CT and MRI. No severe complications were observed (including permanent facial nerve palsies, malocclusion, ankylosis). Three months after surgery, all patients showed their better mobility with condylar and disk, and mouth opening reached 43 mm on maximum, 32 mm on minimum, with a mean of 37 mm.

CONCLUSIONThe results by application of lateral lag screw and reduction of articular disk are helpful in anatomical and functional recovery of temporomandibular joint for patients with displaced sagittal condylar process fractures.

Adolescent ; Adult ; Bone Screws ; Child ; Female ; Follow-Up Studies ; Fracture Fixation, Internal ; instrumentation ; methods ; Humans ; Male ; Mandibular Condyle ; injuries ; Mandibular Fractures ; surgery ; Middle Aged ; Range of Motion, Articular ; physiology ; Temporomandibular Joint Disc ; injuries ; surgery ; Young Adult

This study was conducted to establish a functional mandibular biomechanical model for use in the follow-up biomechanical study of the integrated and fractured mandible. The integrated and dry human mandible was used, and the corresponding maxilla and cranial base was duplicated by resin and plaster. 2-mm silicon rubber was used for simulation of the temporomandibular joint (TMJ) disc. A simulated TMJ and physiological mandibular model was developed by four pairs of muscular loadings (Masseter= 180 N, Temporalis = 190 N, Medial Pterygoideus = 120 N, Lateral Pterygoideus = 40 N) in each muscular center, and the functional loading corresponding with physiological condition was reflected and simulated more realistically when compared with that of the previously reported mandibular models which were developed by occlusion loading or by only one pair of muscles loading. In summary, we have established a functional mandibular model which can be used to analyze the biomechanical behavior in various functional conditions.
Biomechanical Phenomena ; Humans ; Mandible ; physiology ; Masseter Muscle ; anatomy & histology ; physiology ; Masticatory Muscles ; physiology ; Models, Biological ; Pterygoid Muscles ; anatomy & histology ; physiology ; Stress, Mechanical ; Temporal Muscle ; anatomy & histology ; physiology ; Temporomandibular Joint ; physiology