Characteristics of condylar movements during mastication in stomatognathic dysfunction

In this investigation of the relationship between mastication and TMJ abnormalities, the movements of the incisal point and condyles during mastication were analyzed in two normal subjects and six patients with unilateral TMJ abnormalities. The path of the nonworking condyle was shorter than that of the working condyle when patients chewed on the side of the normal TMJ, causing the mandible to deviate to the abnormal side at the point of transition from opening to closing. Also, the mobility of the abnormal condyle influenced the convexity of the opening path, and posterior dislocation of the condyle resulted in a crossover chewing pattern.     

Temporomandibular joint articulations on working side during chewing in adult females with cross‐bite and mandibular asymmetry

Influence of mandibular asymmetry and cross‐bite on temporomandibular joint (TMJ) articulation remained unknown. This study aimed to investigate whether/how the working‐side condylar movement irregularity and articular spaces during chewing differ between patients with mandibular asymmetry/cross‐bite and control subjects. The cross‐bite group and the control group consisted of 10 adult female patients and 10 adult female subjects, respectively. They performed unilateral gum‐chewing. The mandibular movements were recorded using a video‐based opto‐electronic system. The 3D articular surface of the TMJ for each individual was reconstructed using CT/MRI data. For local condylar points, the normalised jerk cost (NJC) towards normal direction to the condylar surface, the angle between tangential velocity vector and condylar long axis and intra‐articular space were measured. Three rotatory angles at centre of the condyle were also measured. During closing and intercuspation, (i) movements of posterior portion of the deviated side condyle showed significantly less smoothness as compared with those for the non‐deviated side and control subjects, (ii) the rotations of the condyle on the deviated side induced greater intra‐articular space at posterior and lateral portions. These findings suggest that chewing on the side of mandibular deviation/cross‐bite may cause irregular movement and enlarged intra‐articular space at posterior portion of the deviated side condyle.     

Movement of temporomandibular joint tissues during mastication and passive manipulation in miniature pigs

Movement is an important aspect of the biomechanics of the temporomandibular joint (TMJ). To track the relative movements of TMJ components, radio-opaque markers were implanted in the left squamosal bone, mandible and retrodiscal tissue of miniature pigs. Medial-lateral (ML) and dorsal-ventral (DV) fluoroscopic records were made 8-10 weeks later during chewing and passive manipulation. Marker movements were digitized from the videotapes. During passive manipulation, the deformation of the lateral capsule was also measured with a differential variable-reluctance transducer. The results provide new details about porcine chewing pattern, which is distinguished by a regularly alternating chewing side. During masticatory opening, the mandible had a centre of rotation (CR) well inferior to the condyle and close to the angle. In contrast, the passive opening movement showed a higher CR location close to the condylar neck, indicating a different motion from masticatory opening. The retrodiscal tissue followed the movements of the mandibular condyle during both mastication and passive manipulation. The lateral capsule elongated during ipsilateral shifts and retrusion, implying a possible role in limiting such movements. These movement characteristics provide a useful reference for studies on the TMJ using pigs.     

Motion of the human mandibular condyle during mastication

It has been reported that loading to the mandible during closing movement makes the condylar path move more in the superior direction than that during the free closing movement. In this study, the hypothesis was tested that the displacement of the condyle on the chewing side is greater in the direction of the mandibular fossa than that on the non-chewing side. Using a six-degrees-of-freedom jaw movement recording system, we recorded condylar motion in 12 healthy adults without TMD, during the chewing of a large hard gummy jelly. The maximum displacements at the condyle on the chewing side from the maximum intercuspation (CO) position were significantly larger in the superior and medial directions at the initial stage and in the posterior direction at all stages (0.5 mm, 0.5 mm, and 0.6 mm, respectively) than those on the non-chewing side (0.0 mm, 0.1 mm, and 0.1 mm, respectively). This suggests that, in healthy adults, the condyles at CO are located in a position such that excessive load is not applied to the temporomandibular joint when there are the aforementioned displacements.     

Condylar movements of temporomandibular disorder patients with intermittent lock: a pilot study

The purpose of this study was to clarify which direction of the condylar path is advantageous for releasing TMJ intermittent lock. The subjects were ten patients with temporomandibular disorders (TMD) and intermittent lock caused by anterior displacement of disks without obvious medial or lateral displacement. The patients could not open their mouths fully in habitual opening but could open fully in an intentional winding opening with reduction of the anteriorly displaced disks (winding opening). The two kinds of movement at the kinematic condylar point were measured in each subject and compared. The length of the condylar path in winding opening was significantly larger than that in habitual opening. The affected side condyle of winding opening traced medio-inferior paths in the early part of the condylar translation in comparison with habitual opening. From the viewpoint of the condylar path, the medio-inferior direction of condylar translation is thought to be advantageous for releasing intermittent lock.     

Movement of the lateral and medial poles of the working condyle during mastication in patients with unilateral posterior crossbite.

Patients with unilateral posterior crossbite often show reverse sequential jaw movement patterns on the frontal view during mastication on the crossbite side. Recent studies show that such patients are prone to suffer from temporomandibular joint (TMJ) disc displacement, particularly the lateral portion. The purpose of this study was to examine the movement of the lateral and medial poles of the working condyle during mastication in such patients. Subjects were 12 consecutive patients with unilateral posterior crossbites and without TMJ disc displacements and 12 normal subjects. An optoelectronic jaw-tracking system with 6 degrees of freedom was used to record the motion of the lateral and medial poles of the working condyle during mastication of standardized hard, gummy jelly. The data from the first 10 cycles were analyzed. The lateral and medial poles of the condyle on the crossbite side moved more in the medial direction and less in the lateral direction during mastication in the crossbite patients than the condyle in the normal subjects. The lateral pole of the working condyle moved more in the posterior and inferior directions and less in the anterior direction than the medial pole in all subjects. These results suggest that these condylar movements in patients with unilateral posterior crossbites might be related to the susceptibility to TMJ disc displacement, particularly the lateral portion.     

Clinical symptoms of open lock position of the condyle. Relation to anterior dislocation of the temporomandibular joint.

Nine cases of open lock position of the condyle of the temporomandibular joint (TMJ) are reported. In two patients recurrent dislocation of the TMJ was diagnosed clinically, and four had previous episodes of anterior dislocation. An arthrotomographic examination revealed that the condyles of the affected TMJs were located anterior to the anterior bands of the disks at an open-mouth position. An arthrographic fluoroscopic examination showed that the anterior bands mechanically obstructed the anteriorly displaced condyles from posterior movement into the articular fossae to various degrees at open-mouth position. One cause of anterior dislocation of the TMJ is thought to be fixation of the condyle in the open lock position resulting from a disturbance of a neuromuscular mechanism. In the two patients with dislocation, occlusal treatment eliminated muscular symptoms and the dislocations completely disappeared.     

Influence of balancing‐side occlusal interference on smoothness of working‐side condylar movement and intra‐articular space in chewing efforts

Response of temporomandibular joint (TMJ) articulation adapting to occlusal alteration has been sparsely known. For 10 healthy adults with acceptably good occlusion, an artificial occlusal interference (OI) was introduced to the lower molar on the balancing side of unilateral chewing. Subjects were asked to chew a gum on their preferred side. The chewing jaw movements with/without the OI were recorded using a video‐based optoelectronic system. The mandibular movements were generated in each individual's TMJ model reconstructed by magnetic resonance images. The smoothness of local condylar point movements towards the normal direction of the condylar surface and interarticular space on the working side was measured. Overall, the smoothness of condylar point movements in the closing phase was impaired immediately after introduction of the OI. In the intercuspal phase, the OI increased the joint space. After about 60 chewing cycles, the movement smoothness and joint space began to recover. These findings suggest that OI on the balancing side induced irregular stress field translation on the working‐side condylar surface followed by acute recovery process.     

Influence of tooth contact on the path of condylar movements.

The correlation between condylar inclination and tooth guidance was tested by comparison of recordings of condylar movement in right and left parasagittal planes during lateral excursion, opening, and protrusive movements in 13 subjects with temporomandibular joint (TMJ) clicks and 15 subjects without TMJ clicks. The characteristic tracing of mandibular movements at the condyle with tooth-guided versus non-tooth-guided conditions were investigated by use of a computerized Axiograph graph. The generated tracings of each subject were graphed and analyzed to calculate the horizontal condylar inclinations as related to the axis orbital reference plane. Information from a standardized questionnaire provided evidence of a definite correlation between the presence of TMJ clicking and a specific prior medical event (tonsillectomy). The data from computerized tracings of all subjects revealed no significant difference (p 0.05) in the mean angles of condylar guidance at any of the millimeter intervals examined regardless of whether the craniomandibular contact was an articulation of natural teeth or an articulation of maxillary natural teeth against a tray clutch. These results do not suggest that dynamic interarch tooth guidance or the change in vertical dimension reflect a significant alteration in the recordings of condylar guidance in clicking or nonclicking groups.     

三维超声下颌定位技术在(牙合)垫治疗颞颌关节绞锁中的应用

目的应用三维超声下颌定位技术,观察颞颌关节绞锁应用于（牙合）垫治疗前后髁突运动轨迹的变化。方法对21例单侧颞颌关节绞锁患者使用下颌稳定性（牙合）垫治疗。运用三维超声下颌定位技术观察绞锁性颞颌关节在（牙合）垫治疗前后健患侧髁突运动轨迹在最大开口运动、最大前伸运动和侧方运动中运动范围的变化。结果通过三维超声下颌定位技术可观察到患者髁突运动轨迹表现为双侧的不对称性。患侧关节在（牙合）垫治疗前后运动范围的比较发现,在最大开口运动的矢状位、冠状位、轴位的髁突运动范围增大（P〈0．05）;前伸和侧方运动的矢状位、冠状位的髁突运动范围增大（P〈0．05）。结论（牙合）垫治疗后绞锁性颞颌关节健患侧髁突的运动轨迹更加对称,患侧关节运动轨迹的范围增大。三维超声下颌定位技术可作为（牙合）垫治疗颞颌关节绞锁髁突运动轨迹改变有效的观测与评价手段。     

Horizontal Condylar Path in Patients with Disk Displacement with Reduction

In 32 patients with disk displacement with reduction, the condylar path in the horizontal plane during opening and closing movements of the mandible were analyzed with a computerized axiograph. The horizontal condylar tracings during opening were divided into 15 types. There was no clear relationship between the types and clinical symptoms. The specific correspondence of the types were revealed between the right and left joint. In 21 of 32 patients, the condyle on one side deviated medially, while the contralateral condyle deviated laterally at maximum opening. In most of the patients showing medio-lateral condylar deviation at maximum opening, a straight condylar path was observed from the maximum opening to the position just before the closing click. In some of the patients, the type of horizontal condylar tracing during opening was related to the displacement pattern of the disk assessed by magnetic resonance imaging (MRI).     

Case report of a posterior disc displacement without and with reduction

This article presents the case of a patient with an acute posterior disc displacement without reduction (PDDWR), whose temporomandibular joint (TMJ) showed, after physiotherapeutic manipulation, the characteristics of a posterior disc displacement with reduction (PDDR). Opto-electronic condylar movement recordings in both the PDDR state and the PDDWR state, and magnetic resonance imaging (MRI) scans of the TMJ in the PDDR state were carried out to document the case. The first 2 physiotherapeutic manipulations were initially successful in reducing the disc, but a few days later the joint showed a relapse to the PDDWR state. From the third manipulation on, now 12 months ago, the patient has been free of symptoms of the PDDWR state. Condylar movement traces of the joint in the PDDWR state indicated that the condyle was prevented from entering the fossa completely. The downward condylar movement deflections during the early phase of closing, recorded after the second manipulation, showed the reduction of the posteriorly displaced disc during closing. The movement recordings also showed that the PDDR could be eliminated by submaximal opening and closing movements. The MRI scans, taken after the third, successful manipulation, showed the disc to be in a normal position with respect to the condyle when the mouth was closed, and to be posteriorly displaced when the mouth was maximally opened. The case shows that manipulation techniques may successfully reverse an acute PDDWR into a PDDR. The technique of MRIs and condylar movement recordings show promise in further unraveling the morphological and clinical features of posterior disc displacements.     

Is condylar position a predictor for functional signs of TMJ hypermobility?

Temporomandibular joint (TMJ) hypermobility is noted only when it interferes with smooth mandibular movements. These interferences (viz. clicking sounds and jerky mandibular movements) result from condylar dislocation in front of the eminence at wide mouth opening, or alternatively in front of the articular disc (posterior disc displacement). The aim of this study was to test the hypothesis that condyles of hypermobile persons are positioned more anterosuperiorly to the crest of the eminence during maximum mouth opening than those of persons without TMJ hypermobility. Possible posterior disc displacement was also evaluated. Nine persons with symptomatic hypermobility and nine control persons free of internal derangements were included, their diagnoses being based upon opto-electronic movement recordings. Condylar positions during maximum mouth opening were analysed on magnetic resonance images with two slightly different methods, showing the degree to which the condyles are displaced around the eminence. No posterior disc displacements were found in any of the magnetic resonance images. After excluding an outlier and using both measurement methods, a small difference in condylar position was found between the two groups of subjects. The condyles of all hypermobile persons travelled beyond the eminence; however, so were the condyles of nearly half of the non-hypermobiles. The large overlap between both groups suggests that condylar position alone is not a good predictor for symptomatic TMJ hypermobility. It is probably the combination of condylar location in front of the eminence with a particular line of action of the masticatory muscles, which gives rise to functional signs of hypermobility.     

Clinical classification of maximal opening and closing movements

Opening and closing mandibular border movements of 250 subjects, 130 with clinical signs of TMJ pathosis and 120 normal subjects, were evaluated by measuring incisal interocclusal distance and recording mandibular movement on a tracking device. Both maximal opening and closing pathways were divided into initial and secondary phases, and were further classified into seven patterns on the basis of anomalous mandibular movements. Subjects with TMJ sounds tended to show mandibular deviations in the second phase, while those with tenderness to muscle palpation tended to show deviations in both phases. Subjects with bruxism demonstrated twice as many deviations in the second phase.     

A new surgical approach for the treatment of chronic recurrent temporomandibular joint dislocation

Chronic recurrent temporomandibular joint (TMJ) dislocation is defined as the complete loss of articular relationships, during mouth-wide opening, between the articular fossa of the temporal bone and the condyle-disk complex. The most frequent pathogenetic factors involved in chronic recurrent dislocation of the TMJ are supposed to be trauma, abnormal chewing movements, TMJ ligaments, capsule laxity, and masticatory muscles disorders. In fact, TMJ dislocation occurs more frequently in people with general joint laxity and in patients with internal derangement of the TMJ or with occlusal disturbance.Management of TMJ dislocation remains a challenge. Eminectomy, whose validity has been demonstrated by several authors, acts on the bony obstacle, preventing condylar locking, but does not have a therapeutic effect on TMJ ligament and capsular laxity or masticatory muscle incoordination, which seem to be the real cause of TMJ dislocation in most cases.The authors present a mini-invasive modified technique of eminectomy, which aims to act on both the obstacle and the cause with respect and restoration of TMJ biomechanical constraints.     

A clinical study on the relationship between chewing movements and masticatory muscle activities

Chewing movement is one of the most important functional and physiological jaw movements, and it is coordinated by the three elements of the functional occlusion system (teeth, TMJs and masticatory muscles). However, the relationship between chewing movement and these elements has not been clarified. The purpose of this study was to investigate the relationship between chewing movement and the activity of the masticatory muscles which directly control jaw movements. 25 subjects with normal stomatognathic function, 5 patients with MPD syndrome (muscle dysfunction group) and 5 patients with unilateral TMJ internal derangement (TMJ dysfunction group) were selected. 6 gums with different hardness were used as the test bolus. Sirognathograph Electromyograph Analysing System was used to simultaneously record chewing movements and electromyograms of the right and left masseter, anterior temporal, posterior temporal and anterior belly of digastric muscles. Using the analysing software which was developed for this study, chewing movements and muscle activities were analysed. The results were as follow; A. In normal subjects 1. Gum hardness influenced durations of the closing and occluding phases, maximum opening and closing speed, opening degree and deviation of opening and closing path. 2. Gum hardness influenced muscle activities except of the time factors of digastric bursts. 3. Durations of the closing and occluding phases were found to be related with the elevator muscle activities. Maximum closing speed was related with the masseter and anterior temporal muscle activities. Deviation of closing path was related with the anterior and posterior temporal muscle activities. B. In abnormal subjects 1. The changes mainly observed in the muscle activities were found to be significantly different between the muscle dysfunction group and normal group. Similarly, the changes mainly observed in the chewing movements were different between the TMJ dysfunction group and normal group. 2. When compared with the relationships in normal subjects, changes were observed in the relationships for closing movement in the muscle dysfunction group. In contrast, changes were observed in the relationships for opening movement in the TMJ dysfunction group. From the results, close relationships were found between chewing movements and muscle activities, and were characteristically influenced by stomatognathic dysfunction.     

Clinical, radiographic, and electromyographic study of patients with internal derangement of the temporomandibular joint

Fifteen patients with internal derangement of the temporomandibular joint (TMJ) were examined clinically, radiographically, and electromyographically. Electromyographic recordings were also obtained from 11 subjects without signs or symptoms associated with their TMJs or masticatory musculature. All the patients with internal derangement demonstrated interferences on the ipsilateral side. This was interpreted as the result of disc displacement producing a reduced joint space and, consequently, a decreased vertical dimension on the symptomatic side. Slow opening and closing mandibular movements without clenching could be performed by healthy persons without noticeable EMG activity in the temporalis and masseter muscles. In association with disc displacement, electromyographic activity of the temporalis and masseter muscles occurred when the condyle slid over the posterior band of the disc and could be interpreted as an arthrokinetic reflex caused by distraction. Continuous muscle activity could be provoked by TMJ disc displacement and ceased when the disc position was normalized on mouth opening, only to occur again every time the disc became displaced on mouth closure. Anterior disc displacement without reduction (closed lock) could cause spastic activity in the temporalis muscle on the affected side. Spastic activity of the masseter and temporalis muscles occurring on the same side as a joint with anterior disc displacement hinders or inhibits the condylar movement necessary to achieve reduction.     

The advantageous direction of jaw movement for releasing TMJ intermittent lock

The purpose of this study was to clarify which direction of jaw movement is advantageous for releasing TMJ intermittent lock. The subjects included ten patients with TMJ intermittent lock who could not open their mouths fully in habitual opening paths (habitual opening), but could open fully in intentionally winding opening paths (winding opening). The following movements were analyzed: habitual opening, winding opening, lateral border opening to the contralateral side (contralateral opening), lateral border opening to the affected side and anterior border opening. The incisal points in winding opening tended to trace antero-lateral paths that were shifted toward the side opposite the affected joints in comparison with habitual opening. In addition to winding opening, the success rate in releasing locking of contralateral opening was significantly greater than that of habitual opening. The findings demonstrated that contralateral movements directed toward the nonaffected side are advantageous for releasing the intermittent lock. The patients will have a better chance of releasing the intermittent lock by themselves, when opening path shifted to the nonaffected side is recommended as the first choice.     

Influence of friction at articular surfaces of the temporomandibular joint on stresses in the articular disk: a theoretical approach with the finite element method

The present study was designed to assess stress and displacement of the temporomandibular joint (TMJ) disk during jaw opening with different frictional coefficients (micro) from 0.0001 to 0.5 at the TMJ disk and bony component interfaces using three-dimensional finite element (FE) models of individual TMJs based on magnetic resonance (MR) images. An asymptomatic female volunteer and a female patient with anterior disk displacement without reduction were selected, and serial sagittal and frontal slices of their MR images were used for the TMJ reconstruction procedure. The condylar movement was recorded during jaw opening by a Gnatho-hexagraph and used as the loading condition for the subsequent stress analysis of the model. In the asymptomatic subject, relatively high von Mises stresses were observed in the anterior and lateral regions of the disk during jaw opening, and the superior boundary, contacting with the glenoid fossa, exhibited lower stresses than those on the inferior boundary facing the condyle. In the symptomatic subject, although the stress value in the disk was relatively low, the posterior connective tissue exhibited high stress throughout jaw opening. Additional increments in stress values and disk displacement were observed as the coefficient of friction increased, especially in the asymptomatic subject. It is concluded that an augmentation in the friction between the disk, glenoid fossa, and condyle produces an increment in stress and displacement of the disk.