Cinematic Study of Temporomandibular Joint Motion Using Ultra-fast Magnetic Resonance Imaging

Magnetic Resonance Images (MRI) of the temporomandibular joint (TMJ) are usually performed to study the opening/closing movements of the mandible and have up to now been pseudodynamic step-by- step images simulating condylar motion by post-processing reconstruction. The aim of this study was: 1. to optimize a TMJ cine-imaging method to give a better clinical result than the step-by-step methods; 2. to develop an ultra-fast MRI Gradient Echo (GE) sequence for this purpose; and 3. to analyze condylar movements in the sagittal, coronal and para-axial planes during border mandibular displacements and chewing. Both TM joints were studied in six asymptomatic volunteers. The method involved a compromise between in-plane resolution, slice thickness, signal-to-noise ratio and time resolution. Routine clinical use was found to be a GE pulse sequence providing three images per second with an isometric voxel resolution of approximately two millimeters in ridge. This did not allow visualization of the disk. Using this sequence enabled real and simultaneous condylar displacement observation in the three planes of space and therefore contributed to a better functional diagnosis of pathologic TMJ motions.     

3T磁共振成像显示颞下颌关节盘的技术研究

目的探索3T磁共振成像（MRI）显示颞下颌关节盘的序列、参数及电影成像方式的技术特点,并为临床研究颞下颌关节盘病变提供形态与功能影像学参照。方法选择15例正常志愿者和7例颞下颌关节损伤患者为研究对象,采用GE Signa HD 3T MRI和颞下颌关节专用表面线圈对颞下颌关节进行扫描,获得斜矢状、斜冠状闭口位FSE-XL/T1WI、FLAIR/T1WI、FSE-XL/PDWI、FSE/PDWI+FS、FRFSE-XL/T2WI、FRFSE/T2WI+FS扫描及斜矢状张口位FSE-XL/T1WI、FSE-XL/PDWI图像。由口腔颌面外科医师和MRI医师共同对各序列进行打分,分析各序列不同加权像对颞下颌关节盘的显示效果。结果PDWI对关节盘的显示效果得分最高,能清楚显示关节盘的解剖结构与形态。T2WI对关节盘损伤、撕裂、穿孔和关节囊积液显示良好,对关节盘移位情况则以PDWI序列显示效果为好。结论3T MRI可以清楚地显示关节盘在关节运动中的动态改变与病变受累情况,对颞下颌关节软组织损伤的诊治有重要价值。T1WI、PDWI及T2WI应作为常规的扫描方法。     

Functional magnetic resonance imaging of temporomandibular joint disorders

Fifty-eight temporomandibular joints (TMJs) from 40 patients with TMJ-related symptoms were examined by means of magnetic resonance scans with modified gradient echo sequences and a special double coil. This technique yielded a good spatial resolution of the intra-articular soft tissues, especially the articular disc and the bone structure of the TMJ. In combination with an incremental jaw opener, the disc-condyle complex was analysed in various closed and open mouth positions, depending on the clinical examination. Open mouth movement with differentiation of disc-condyle rotational and translation movement was demonstrated. Disturbances of TMJ motion showed interrupted condylar translation combined with mandibular deviation during open mouth movement (n = 8/58). Early phases of internal derangement of the TMJ with partial anterior disc displacement with (n = 12/58) or without (n = 2/58) reduction, total anterior disc displacement without reduction (n = 10/58), disc deformation (n = 10/58), disc adhesion (n = 2/58), condylar hypermobility (n = 6/58), condylar displacement (n = 8/58), and late phases of internal derangement of the TMJ with osteoarthrosis (n = 14/58) were clearly identified. Bilateral TMJ disorder was found in 72.5 per cent of the patients. By using motion-adapted, semi-dynamic magnetic resonance imaging (MRI), it is possible to improve the understanding of the complexity of TMJ movements.     

Associations between the articular eminence inclination and condylar bone changes, condylar movements, and condyle and fossa shapes

Objectives

The purpose of the present study was to determine the inclination and height of the articular eminence with respect to the condylar bone changes, condyle shape, fossa shape and condylar movements in patients with and without temporomandibular joint (TMJ) dysfunction using cone-beam computed tomography (CBCT).

Methods

The associations between the eminence inclination and the condylar bone changes, condylar movements, condylar shape and fossa shape were evaluated in patients with TMJ disorders and control patients without TMJ disorders. The measurements of the articular eminence inclination were established on central sagittal slices of the TMJ. The central coronal slices were used to determine the condyle and fossa shapes. The types of movements of the condyles were determined on open-mouth images, and mandibular hypermobility or hypomobility was noted for each joint.

Results

There were no significant differences in the eminence inclination and height with respect to the condylar bone changes and condylar movements in the TMJ disorder group. However, there was a significant association between the eminence inclination and the fossa shape in the TMJ disorder group and significant associations between the eminence inclination and both the condyle and fossa shapes in the control group. The articular eminence inclination was steeper in the control group than in the TMJ disorder group.

Conclusions

The eminence inclination was steeper in the control patients than in the patients with TMJ disorders, and was not correlated with the condylar bone changes or condylar movements.     

Condylar injury: magnetic resonance imaging findings of temporomandibular joint soft-tissue changes

Recent studies have suggested magnetic resonance imaging (MRI) as useful in the evaluation of soft-tissue changes that occur in the temporomandibular joint (TMJ) after acute condylar trauma. The aim of this study was to investigate whether MRI findings of disc displacement, capsular tear and haemarthrosis are linked to the degree of condylar injury. Nineteen patients were assigned a diagnosis of uni- or bilateral condylar fracture (n=17), or condylar contusion with a uni- or bilateral diagnosis of TMJ sprain/strain (n=2). Condylar injuries were classified as grade I (absence of condylar fracture), grade II (type I, II or III condylar fracture), and grade III (type IV, V or VI condylar fracture). Bilateral sagittal and coronal MR images were obtained immediately after injury to establish the presence or absence of disc displacement, haemarthrosis and capsular tear. The data revealed a significant relationship between the degree of condylar injury and the MRI findings of capsular tear (P=0.000) and haemarthrosis (P=0.000), and between the MRI diagnoses of capsular tear and haemarthrosis (P=0.000). There was good diagnostic agreement between the presence of grade III condylar injury and the MRI diagnoses of capsular tear (K=0.62) and haemarthrosis (K=0.60). The results suggest that degree of condylar injury is related to MRI findings of capsular tear and haemarthrosis, and that MRI to supplement diagnosis of grade III condylar injury is warranted.     

正常成人颞颌关节的CT和MRI影相分析

本文对10名正常成人双侧TMJ进行了CT扫描,其中3名作了MRI扫描。对所有CT片作了TMJ骨性结构的三维分析,观察了正常人髁状突和关节凹的形态类型,并发现双侧形态均为同型,双侧髁状突运动范围一致。同时,还用CT软组织窗位相(闪烁相)对关节盘进行了正中(牙合)位和尽力开口位的观察,并用MRI对其结果加以证实。本研究所得结果较其它方法准确,更具有可比性。因为本研究选用CT对双测TMJ进行同时扫描,消除了以往X光片需分侧和多种投照检查所造成的误差。     

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.     

A comparative study between clinical and instrumental methods for the recognition of internal derangements with a clicking sound on condylar movement

AIMS: To compare the results of 3 methods of recognizing internal derangements with a clicking sound on condylar movement: 2 function-based methods (clinical examination and condylar movement recording) and 1 anatomy-based method (magnetic resonance imaging [MRI]). METHODS: For the recognition of an anterior or posterior disc displacement with reduction and of hypermobility within the temporomandibular joint (TMJ), 42 participants underwent a clinical examination, an opto-electronic movement recording, and an MRI scan. The examinations were executed in a single-blind design, with different experienced examiners for each technique. In addition, for 10 randomly chosen participants, the condylar movement recordings and the MRI scans were carried out twice. Without the examiners' knowledge, these second recordings were added to the other data. RESULTS: Intraobserver reliability for the recognition of internal derangements was excellent for condylar movement recording (kappa = 0.86) and fair to good for MRI (kappa = 0.73). Intermethod agreement was fair to good (kappa = 0.59) between the 2 function-based techniques. However, intermethod agreement between the anatomy-based MRI technique and either of the 2 function-based techniques was poor (for condylar movement recording, kappa = 0.15; and for clinical examination, kappa = 0.12). CONCLUSION: There is a great discrepancy between the diagnoses for internal derangements based upon anatomical TMJ characteristics and those based on functional TMJ characteristics. For a function-based diagnosis, there is probably no need for the sophisticated technique of condylar movement recording, since that method shows fair to good agreement with a carefully performed clinical examination.     

Clinical study on the relationship between chewing movements and temporomandibular joint abnormalities

Chewing movements are accomplished by the harmonious function of the stomatognathic system. Therefore, TMJs play important roles in chewing movements. Recently, significant findings on TMJ abnormalities have been obtained from many studies. However, the relationship between chewing movements and TMJ abnormalities remains unclear. The purpose of this study was to examine how TMJ abnormalities were reflected in chewing movements. Incisor point movements during chewing (chewing pattern) were investigated in 150 abnormal and 25 normal subjects using Sirognathograph Analysing System. Abnormal subjects were composed of 45 patients with anterior disk displacement with reduction (reciprocal click), 20 patients with anterior disk displacement without reduction (closed lock), 50 patients with osteoarthrosis and 35 patients with MPD syndrome. Analysis of condylar movements during chewing were also performed in 9 normal and 20 abnormal subjects. The results were as follow; 1. Subjects with TMJ abnormalities tended to show abnormal chewing patterns when chewing at their non-abnormal sides. 2. TMJ abnormality of each different type tended to show its respective characteristic chewing pattern. 1) Subjects with osteoarthrosis and reciprocal click without condylar posterior dislocation tended to show deviation of the turning point to the non-chewing side, with a convex opening path in the frontal plane and a lack of anteroposterior width in the sagittal plane. This finding was associated with the limitation in movement of the abnormal-side condyle. 2) Subjects with reciprocal click with condylar posterior dislocation tended to show a concave opening path and reversed or cross-over patterns in the frontal and horizontal planes, respectively. This finding was associated with the movement of the abnormal-side condyle in the medio-anterior direction during the initial phase of opening. 3) Subjects with closed lock without condylar posterior dislocation tended to show deviation of the turning point to the non-chewing side, with a concave opening path in the frontal plane and a lack of anteroposterior width in the sagittal plane. This finding was associated with the severe limitation in movement of the abnormal-side condyle. 4) Subjects with closed lock with condylar posterior dislocation characteristically tended to show reversed or cross-over patterns in the horizontal plane. This finding was associated with the movement of the abnormal-side condyle in the medio-anterior direction during the initial phase of opening. However, this movement was smaller than that of the reciprocal click. 3. Subjects with MPD syndrome showed chewing patterns similar to those of normal subjects. From the results, close relationships were found between chewing movements and TMJ abnormalities.     

Clinical, radiographic and MRI findings of the temporomandibular joint in patients with different rheumatic diseases

The aim of this study was to investigate the condition of the temporomandibular joint (TMJ) in patients with different rheumatic diseases, and report correlations between the clinical, radiographic and magnetic resonance imaging (MRI) findings. The 67 patients were divided into four groups: 16 with rheumatoid arthritis (RA), 15 with mixed connective tissue disease (MCTD), 18 with ankylosing spondylitis (AS) and 18 with spondyloarthropathy (SPA). They were clinically examined, and panoramic tomography, lateral panoramic radiography and MRI of the TMJ were performed. MRI showed reduced articular cartilage in 25% (4/16) of RA, 0% (0/15) of MCTD, 17% (3/18) of AS and 17% (3/18) of SPA patients. Condylar changes included erosion, osteophytes and abnormal shape. Disc alterations included perforation, abnormal anterior position and decreased movement. These abnormalities were most frequent in RA patients, and least frequent in MCTD and SPA patients. Crepitation and reduced maximum opening of the mouth correlated with abnormalities of the disc and articular cartilage as shown by MRI. Severe condylar erosion in panoramic tomograms significantly correlated with MRI findings of condylar erosion (P<0.01), diminished thickness of condylar cartilage, abnormal condylar shape, and abnormal shape of the temporal surface of the TMJ (P< or =0.001). The presence of crepitation, limited mandibular movement and/or pain on movement of the jaw often indicated structural damage to the TMJ. Panoramic radiographs provide an alternative method to MRI but, to obtain a more detailed anatomic picture, MRI is recommended for patients with acute unexplained pain or as part of preoperative work up. A panoramic recording is not indicated when MRI is planned.     

自体耳廓软骨瓣置换或重建颞下颌关节盘MRI评价

目的　通过磁共振成像 ( MRI)对自体耳廓软骨瓣修复关节盘的术后情况进行评估 ,以观察软骨生长情况。方法　对 11例关节病患者 13侧关节进行自体耳廓软骨瓣移植修复关节盘手术 ,所有患者均经临床检查和信访答卷进行随访 ,症状均得到缓解 ,并对其中 5例患者 (滑膜软骨瘤病和关节强直各 1例 ,结构紊乱 2例 ,骨关节病 1例 )行 MRI检查。结果　 MRI矢状位、张闭口位及冠状位扫描均显示移植软骨无明显破碎或吸收。结论　 MRI可作为检测软骨生长情况的指标之一 ,自体耳廓软骨瓣置换 /重建关节盘是可行的手术方式     

Effect of condylar osteochondroma resection through an intraoral approach on the masticatory functions: a preliminary evaluation based on occlusion and temporomandibular joint functions

With this research, we aimed to evaluate the effect of condylar osteochondroma (OC) resection through an intraoral approach on the masticatory functions. Resection of condylar OC was carried out via an intraoral approach with the help of three-dimensional (3D) design, endoscope, and navigation system. The T-Scan III computerised occlusal analysis system was used to evaluate the occlusal force distribution, recorded at pre-treatment (T1) and post-treatment (T2) intervals. Records of the clinical examination of the temporomandibular joint (TMJ), including maximal interincisal opening, mandibular lateral and forward movements, were also collected. Ten patients with condylar OC were enrolled in this study. The difference of force distribution between bilateral occlusion was reduced in T2 compared with T1 (11.92% ± 4.41% vs 48.52 % ± 28.37%, p<0.05), indicating better occlusal force distribution obtained after surgery. There was no significant difference in functions of the TMJ, such as maximal interincisal opening, and mandibular lateral and forward movements between T2 and T1 (p>0.05). Accordingly, condylar OC resection through an intraoral approach would obtain a satisfactory occlusal balance with no impairment of the temporomandibular joint functions.     

Magnetic resonance imaging assessment of positional relationship between the disk and condyle in asymptomatic young adult mandibular prognathism

The aim of this study was to clarify disk position relative to the condyle and condylar position relative to the glenoid fossa in clinically asymptomatic and orthodontically untreated young adult Class III patients by magnetic resonance imaging (MRI). In addition, the relationship between skeletal Class III morphology and positional changes of the temporomandibular joint (TMJ) components were investigated. The material consisted of 34 bilateral sagittal oblique TMJ MR images (MRIs) and lateral cephalometric radiographs taken in a closed mouth position. The mean age of the patients was 20.71 +/- 0.82 years (range 16-29 years). Only clinically symptom-free subjects were included in this study. Measurements made on the MRIs and lateral cephalographs were used to calculate means and minimum and maximum values. The right and left TMJ variables were compared with the Student's t-test. Correlation coefficients between bilateral TMJ variables and skeletal variables were calculated. In the right TMJ, the disk was positioned anteriorly and the condyle was positioned posteriorly, whereas the left TMJ was normal. A negative correlation existed between the vertical skeletal morphology and the anterior joint space of the TMJ. A positive correlation was found between the left disk position and the vertical skeletal morphology because of the differentiation of the condylar head angle in each side. As a result, clinically asymptomatic Class III patients may be candidates for TMJ derangements. For this reason, clinical and visual examinations should be performed simultaneously to eliminate diagnostic errors before orthognathic treatment.     

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.     

MR abnormalities of the lateral pterygoid muscle in patients with nonreducing disk displacement of the TMJ

The aim of this study was to investigate the pathological changes of the lateral pterygoid muscle (LPM) using magnetic resonance imaging (MRI) in patients with anterior disk displacement with nonreduction (ADDnr) of the temporomandibular joint (TMJ) and to compare the abnormal findings of the LPM with the clinical symptoms and other pathological MRI alterations of the TMJ. Bilateral or unilateral ADDnr was demonstrated in 142 patents by MRI (176 TMJs; 106 females; 36 males; range 19 to 72 years; mean 43.9 years). In 123 TMJs, the LPMs were clearly observed in MRIs and analyzed in this study. Pathological changes of the LPM were found in 92 TMJs (74.8%) in MRI. Hypertrophy, atrophy and/or contracture were detected in the superior belly of the LPM (SBLPM) (35.8%, 44/123) or in the inferior belly of the LPM (IBLPM) (9.8%, 12/123) or in both bellies (29.3%, 36/123). The pathological changes of the LPM in MRI presented a significant association with the main clinical symptoms of TMJs with ADDnr, i.e. pain on jaw movement (P<0.01), pain in the LPM (P<0.01), pain in TMJ (P<0.05) and restricted jaw opening (P<0.05). The proportion of the abnormalities in LPM was significantly lower in TMJs with condylar limitation (63.6%) than in TMJs with condylar hypermobility (83.3%) and normal motion (88.9%)(P=0.008). Osteoarthritis was found to be correlated with condylar limitation (P<0.01). The results of this study indicate that the pathological changes of the LPM in TMJs with ADDnr could be detected by MRI and have a significant association with the main clinical symptoms of the patients. When condylar limitation happened, on the contrary, the pathological changes of the LPM in MRI were reduced. The alteration of the clinical symptoms in the patents with ADDnr might be associated with the pathological situations and symptoms of the LPM.     

The relationship of bone marrow edema pattern in the mandibular condyle with joint pain in patients with temporomandibular joint disorders: longitudinal study with MR imaging

The purpose of this study was to investigate the course of bone marrow edema pattern (decreased signal intensity on T1- or proton-density-weighted images and increased signal intensity on T2-weighted fat-suppressed images) in the mandibular condyle after improvement in clinical symptoms, and to clarify its relationship with temporomandibular joint (TMJ) pain. This study was based on 14 joints of 11 patients (all female, mean age 37.5 years) with TMJ disorders showing condylar bone marrow edema pattern on initial magnetic resonance (MR) images. All joints were re-evaluated clinically and using MR images after relief of joint pain following arthrocentesis combined with non-surgical treatment. The time interval between the initial and follow-up MR images ranged from 14 to 27 months (mean 17 months). Of the 14 joints, 4 joints (28.6%) showed a normal bone marrow signal, whereas 10 joints (71.4%) showed persistent bone marrow edema pattern on follow-up MR images (P = 0.125). Therefore, the reduction in TMJ pain did not correlate with resolution of bone marrow edema pattern in most joints. The results of this study suggest that the bone marrow edema pattern in the mandibular condyle does not always contribute to the occurrence of joint pain in patients with TMJ disorders.     

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.     

A three-dimensional method of visualizing the temporomandibular joint based on magnetic resonance imaging in a case of juvenile chronic arthritis

Summary. Aim . The purpose of this study was to present a new visualizing method for temporomandibular joint (TMJ) pathology in 3D at several condylar positions and to apply the method to a case of juvenile chronic arthritis (JCA) with previously diagnosed bilateral TMJ disorder and to a subject without signs and symptoms from the TMJ.
Subject . The 20-year-old female patient had suffered from polyarticular JCA from the age of 6 years 8 months. The present study is based on a follow-up examination after the completion of orthodontic treatment with the Herbst appliance. Both TMJs were examined using magnetic resonance imaging (MRI) at closed and open mouth positions. The mandibular condyle, the glenoid fossa and the articular disc were segmented and 3D reconstruction of these structures was carried out.
Results. The condyle was characterized by an increased sagittal diameter with osteophyte-like formation at the anterior aspect of the condylar head and flattening of the superior surface. The depth of the glenoid fossa was reduced and the articular eminence was remarkably flat. The articular disc was markedly diminished and posteriorly placed on the condylar head. The distance of the condylar path during mouth opening was reduced and the curvature of the condylar path was quite flat. The disc moved slightly posteriorly on the condylar head and remained in the glenoid fossa during mouth opening.
Conclusion. The imaging modality described improves visualization of TMJ morphology and gains insight into the TMJ pathology of the JCA patient, adding to understanding of the clinical problems.     

Three-dimensional comparative evaluation of articular disc position and other temporomandibular joint morphology in Class II horizontal and vertical cases with Class I malocclusion:: A magnetic resonance imaging study

ObjectiveTo evaluate and compare articular disk position, condylar position, and joint spaces in Class II vertical, Class II horizontal, and Class I cases. The purpose was to assess the potential for development of temporomandibular disorders (TMDs) in the three groups.Materials and MethodsA sample of 75 cases, 25 cases in each group of Class I, Class II vertical, and Class II horizontal, were selected based on inclusion and exclusion criteria. Magnetic resonance imaging (MRI) assessments were made with a 1.5-Tesla basic system with a closed-mouth technique for evaluating articular disk position in the sagittal and transverse planes, condylar position, and joint spaces in the sagittal plane. Philips 3.0 software was used to analyze the MR images.ResultsThere was evidence of alterations in the temporomandibular joint (TMJ) morphology in both Class II vertical and Class II horizontal cases, with maximum discrepancy in Class II vertical cases. MRI evaluation suggested a tendency for antero-medial disk displacement with anteriorly positioned condyles in Class II vertical cases. The discrepancy was milder in the Class II horizontal group.ConclusionsClass II vertical cases are more susceptible to the development of TMDs and should be subjected to TMJ evaluation before starting any orthodontic treatment to intercept and prevent a mild asymptomatic TMD from developing into a more severe form. Class II vertical cases should be subjected to MRI evaluation before starting any orthodontic treatment.