Unilateral Disc Displacement Research Articles

Evaluation of masticatory muscles in temporomandibular joint disorder patients using quantitative MRI fat fraction analysis-Could it be a biomarker?

Temporomandibular joint disorders (TMDs) are closely related to the masticatory muscles, but objective and quantitative methods to evaluate muscle are lacking. IDEAL-IQ, a type of chemical shift-encoded magnetic resonance imaging (CSE-MRI), can quantify the fat fraction (FF). The purpose of this study was to develop an MR IDEAL-IQ-based method for quantitative muscle diagnosis in TMD patients. A total of 65 patients who underwent 3 T MRI scans, including CSE-MRI sequences, were retrospectively included. MRI diagnoses and clinical data were reviewed. There were 19 patients in the normal group and 46 patients in the TMD group with unilateral disc displacement. The TMD group was subdivided into those with and without clenching. The right and left FF values of the masseter, medial, and lateral pterygoid muscles were measured twice by two oral radiologists on CSE-MRI, and the average value was used. FF measurements using CSE-MRI showed excellent intra- and inter-observer agreement (ICC > 0.889 for both). There were no statistically significant differences between the right and left FF values in the masseter, medial pterygoid, and lateral pterygoid of the normal group (p > 0.05). A statistically significant difference was found in the TMD group without clenching, in which the masseter muscle had a statistically significantly lower FF value on the disc displacement side (3.94 ± 1.61) than on the normal side (4.52 ± 2.24) (p < 0.05). CSE-MRI, which can reproducibly quantify muscle FF values, is expected to be a biomarker for objective muscle evaluation in TMD patients. The masseter muscle is expected to be particularly useful compared to other masticatory muscles, but further research is needed.

The Asymmetry of the Mandible in Patients with Unilateral Temporomandibular Joint Disc Displacement Confirmed by Magnetic Resonance Imaging.

The study aimed to determine the relationship between the mandibular asymmetry index according to Kjellberg between patients with painful unilateral anterior disc displacement (DD) and asymptomatic volunteers without disc displacement. Vertical measurements were performed on a panoramic single-image radiograph, and the disc status was confirmed by magnetic resonance imaging (MRI). Two groups of subjects were retrospectively selected, 40 patients (the overall mean age was 35.5 years; 75% female) with temporomandibular disorder symptoms confirmed by RDC/TMD axis I and manual functional analysis. Unilateral DD was determined by MRI. A comparative group of asymptomatic volunteers (20 dental students with a mean age of 23.4 years; 72% female) had the physiological position of the disc determined by MRI. The vertical asymmetry of the condyle was determined by the method of Kjellberg et al. The symmetry of the gonial angle of the mandible was also measured. A comparison of the mean of the asymmetry index between patients (average 90.89±7.08%) and asymptomatic volunteers (mean 95.86±4.44%) showed a statistically significant difference (p=0.0029). There was no difference (p=0.088) in gonial angle symmetry between the patients (mean 96.48±2.96°) and the asymptomatic volunteers (mean 97.52±2.31°). The distribution of the presence of individual DD diagnoses (partial and total displacement with reduction, displacement without reduction) in patients diagnosed with asymmetry of the mandible was without statistical significance (p>0.05). This study actually points to the asymmetry of the mandible as a potential morphological risk of anterior DD.

Suprafoveal condylar arthroplasty in unilateral disc displacement without reduction – A retrospective study

The aim of this study was to evaluate the efficacy of suprafoveal condylar arthroplasty (SFCA) in the management of patients with unilateral temporomandibular joint (TMJ) disc displacement without reduction (DDWoR). A retrospective study comprising patients who underwent unilateral SFCA for clinically and radiologically confirmed unilateral DDWoR from 2008 to 2020 was conducted. Patients older than 18 years at the time of diagnosis with a minimum of 6 months of unsuccessful non-surgical and minimally invasive management (including diet and life style modification, physiotherapy, appliance therapy, pharmacotherapy, arthrocentesis and arthroscopic lysis and lavage) before undergoing surgery with a minimum of 1 year follow-up post-surgery were included in the study. Patients with other articular and extra-articular causes of restricted mouth opening, prior history of mandibular surgery and/or trauma, growth abnormalities, systemic, metabolic, infective, neoplastic conditions affecting TMJ, including gross occlusal disharmony, untreated existing para-functional habits and bilateral DDWoR, were excluded from the study. Patients were assessed in terms pain on a visual analog scale (VAS), interincisal mouth opening (MO) and subjective assessment of mandibular range of movements including deviation of mouth opening, protrusion and ability for contralateral laterotrusion. 23 patients (10 males and 13 female) were included in the study, with a mean age of 35.09 years and mean follow up period of 37.7 months (range = 12–58; SD = 15.3). The mean pain scores on the VAS reduced from 6.35 preoperatively to 1.13 postoperatively and were found to be statistically significant (p < 0.0001). The improvement of the mean pre-operative mouth opening of 21.83 mm to a mean post-operative mouth opening of 42.09 mm was also found to be statistically significant (p < 0.0001). The subjective improvement in protrusive (p = 0.0003), laterotrusive (p = 0.0005) and opening movements (p = 0.0001) after 1 year were also found to be statistically significant. No patient developed any significant changes in occlusion post-operatively. Four of 23 (17.3%) patients developed transient neuromotor deficit of the temporal branch of the facial nerve. Within the limitations of the study, it seems that SFCA (without addressing the disc) might be an alternative to less invasive treatment approaches, if the latter turned out not to be successful.

Unilateral disc displacement as a risk factor for development of contralateral disc displacement

<h3>Objective</h3> The aim of this study was to investigate whether unilateral temporomandibular joint disorders (TMD) are associated with increased risk of contralateral TMD development. <h3>Study Design</h3> In total, 401 subjects with and without TMD completed baseline and follow-up MRI and CT imaging 8 years apart on average. Consensus diagnoses of disc displacement (DD) and degenerative joint disease (DJD), made by radiologists who performed the image analyses, were extracted from records. At baseline, 75 subjects had unilateral DD and/or DJD. Fifty-six subjects had bilateral normal joints, forming the control group. Generalized estimating equations were used to account for correlation between joints within a subject and control for age and sex. Odds ratios and 95% confidence intervals were calculated to compare odds of developing DD or DJD in baseline normal joints. <h3>Results</h3> The odds of developing DD were 1.9 times higher in normal joints of those with unilateral DD, with or without DJD, than in those of controls (p=0.14). The odds of DD development among those with unilateral DD and DJD were 3.2 times higher than controls (p=0.049). Among those with baseline unilateral DD, the odds of developing contralateral DD were 7.32 times higher for those without reduction than with reduction (p=0.02). There was no evidence that unilateral DD is associated with contralateral DJD development or vice versa. Additionally, there was no evidence that unilateral DJD is associated with contralateral DJD development regardless of severity. The odds of developing contralateral DD or DJD were not associated with diagnostic progression or improvement of joints with baseline unilateral DJD. However, contralateral DD development was 88% less likely in those with improvement of unilateral DD (p=0.09). <h3>Conclusion</h3> There is some evidence supporting unilateral DD as a risk factor for development of contralateral DD. There is no evidence supporting DJD as a risk factor for development of contralateral DD or DJD. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Stability of the contralateral temporomandibular joint disk position after disk repositioning on one side

To evaluate the stability of the contralateral temporomandibular joint disk position after disk repositioning on 1 side. Patients with unilateral anterior disk displacement (ADD) treated by disk repositioning from 2015 to 2019 were included in the study. The contralateral disk status was classified as follows: normal, ADD with reduction (ADDwR), and medial/lateral displacement. At 1-year follow-up, changes in the contralateral disk position were evaluated by MRI. Two hundred thirty-four patients were included in the study. There were 84 disks with normal position, 51 with ADDwR, and 99 with medial/lateral displacement (M/LD) in the contralateral joint. At 1-year follow-up, all the repositioned disks were stable without relapse. In the contralateral joints, 75% of the disks with normal position were unchanged compared with 43.1% of the ADDwR and 54.5% of the M/LD. ADDwR had the highest rate of changing to ADDwoR compared with the disks in normal position (4.8%) and M/LD (7.1%, χ2=16.13, P < .001). There were 28.3% of M/LD disks and 3.9% of ADDwR that changed to normal position. After unilateral disk repositioning, most of the contralateral disks with normal position were stable. M/LD disks tended to move to normal position, whereas ADDwR was largely changed to ADDwoR.

Double-Needle Arthrocentesis with Viscosupplementation in Patients with Temporomandibular Joint Disc Displacement without Reduction

OBJECTIVES:Arthrocentesis is the simplest surgical intervention for the temporomandibular joint (TMJ). It can be performed on an outpatient basis at a low cost and with low morbidity. The objective is to release the articular disc by disrupting the adhesion formed between its surfaces and the mandibular fossa through hydraulic pressure generated by irrigation of the upper compartment of the TMJ. Viscosupplementation with hyaluronic acid during or after arthrocentesis improves clinical outcomes, increases mouth opening, and reduces pain levels. The aim of this study was to evaluate the efficiency of arthrocentesis plus hyaluronic acid viscosupplementation through clinical examination and preoperative magnetic resonance imaging in patients with unilateral disc displacement without reduction (DDwoR).METHODS:This analytical retrospective cross-sectional study clinically and radiologically evaluated 72 patients of both sexes with unilateral DDwoR. The following data were collected: sex, pain, age, duration of pain, maximum mouth opening, and patient pain perception on a visual analog scale. TMJ arthrocentesis was performed only once for each of the indicated joints. Data were collected before arthrocentesis (baseline) and at 7, 14, 30, 60, 90, and 180 days after the procedure (final evaluation).RESULTS:Between the baseline and final evaluation, there was a significant reduction in pain (p=0.001) and restoration of articular function. In addition, there was a significant increase in maximum mouth opening (p=0.001).CONCLUSION:Patients with DDwoR undergoing arthrocentesis combined with hyaluronic acid injection showed significant improvement in the perceived pain and maximum mouth opening in the mid-term follow-up periods.

The effect of TMJ disk repositioning by suturing through open incision on adolescent mandibular asymmetry with and without a functional orthodontic appliance

The objective of this study was to evaluate the effect of combined temporomandibular joint (TMJ) disk repositioning by suturing through open incision and orthodontic functional appliance (OFA) treatment for adolescents with mandibular asymmetry. Adolescent patients (12-20 years old) with mandibular asymmetry combined with unilateral TMJ disk displacement without reduction were treated with disk repositioning by suturing through open incision with and without postoperative OFA. Magnetic resonance imaging and posteroanterior cephalometric radiographs (PA) were used to measure and compare the changes in condylar height, joint space, and menton deviation pre- and postoperatively. Twenty-six patients were included in the study. Joint space was significantly increased postoperatively and new bone mostly formed at the superior or posterior superior part of the condyle after 6 to 18 months in all surgically treated joints. Fourteen patients with OFA had a significant increase in condylar height and menton deviation compared to 12 patients without OFA (2.29 ± 0.91 mm vs 1.22 ± 0.69 mm, P=.003; 4.56 ± 1.48 mm vs 2.01 ± 0.74 mm, P=.000). Combined treatment with TMJ disk repositioning by suturing through open incision and OFA can promote condylar growth and correct mandibular deviation in adolescent patients. Postoperative OFA can maintain the increased joint space created by disk repositioning and promote new bone formation at the superior and posterior parts of the condyle.

"RA.DI.CA." Splint for the Management of the Mandibular Functional Limitation: A Retrospective Study on Patients with Anterior Disc Displacement without Reduction.

The study aimed at assessing the effectiveness of the RA.DI.CA. splint in the management of temporomandibular joint disc displacement without reduction (ADDwoR) and jaw functional limitation. The authors developed a retrospective clinical study. A total of 2739 medical records were screened. One hundred and forty-one patients with chronic unilateral disc displacement without reduction and jaw limitation, treated with a multifunctional RA.DI.CA. splint, were enrolled. Temporomandibular pain, headache, familiar pain, neck pain, and emotional strain, maximum spontaneous mouth opening, and lateral excursions were evaluated at baseline (T0), after therapy (T1), and during the follow-up (T2). Descriptive statistical analysis was performed. Wilcoxon test assessed changes in symptomatology and functional aspects before and after treatment and between T1 and T2, with p < 0.05. Ninety-nine patients (70%) declared themselves “healed” from jaw functional limitation with no residual painful symptoms, 31 (22%) improved their symptoms and jaw function, 11 (8%) reported no changes compared to T0 and no one worsened. As for all parameters analyzed, the comparison between the ones before and after treatment was statistically significant (p < 0.05). The RA.DI.CA. splint proved to be highly performing and promoting functional and symptomatologic recovery, also in the medium and long term, through the restoration of the functional disc-condyle relationship and the healing of joint tissues.

Subjects with temporomandibular joint disc displacement and body posture assessment via rasterstereography: a pilot case-control study.

The possible relationship between temporomandibular disorders (TMDs) and body posture is still controversial. Rasterstereography has been introduced as a radiation-free, reliable and non-invasive method to analyze three-dimensional spinal posture. The aim of this case-control study is to evaluate, through rasterstereography, body posture parameters in a group of patients with reducible unilateral dislocation of the articular disc, compared to healthy volunteers. Rasterstereographic recordings obtained were compared between the two groups with a paired t-student test. Furthermore, the relationship between Rasterstereographic recordings and clinical data in the TMD group were analyzed by means of multiple regression analysis. Only lateral deviation was statistically significant different between the two groups (rms VPDM Control group 40% > TMD group, p=0.02; 43% control group VPDM max > TMD group, p<0.02). In the TMD group, a significant relationship (p<0.05) was found out between lateral and rotational deviations of the column and muscular pain, therefore suggesting a possible overactivity of the masticatory muscles, especially of lateral pterygoids' bilaterally and the left masseter. Patients with reducible unilateral disc displacement showed limited postural alterations compared to healthy volunteers, only lateral deviations (VPDM rms and VPDM-max) were statistically significant (Π<0.05) between the two groups.

Relations between anterior disc displacement and maxillomandibular morphology in skeletal anterior open bite with changes to the mandibular condyle.

In this study we investigated the relation between anterior disc displacement (ADD) and maxillomandibular morphology in skeletal anterior open bite with changes to the mandibular condyle. Thirty female patients (60 joints) with both conditions were evaluated. Magnetic resonance imaging of the temporomandibular joint (TMJ) was used to diagnose both ADD and changes to the mandibular condyle (erosion, osteophyte, and deformity). The relations among ADD, changes to the mandibular condyle, and maxillomandibular morphology were examined statistically. Changes to the mandibular condyle had a higher score than sym anterior open bite, the deviated side in asymmetric anterior open bite, and the non-deviated side. The score for disc displacement on the non-deviated side was lower than both the sym side and the deviated side. Unilateral changes to the mandibular condyle and unilateral disc displacement were not apparent in sym anterior open bite, but a unilateral non-displaced disc was seen only on the asymmetric side. Mandibular condylar changes were significantly more common on the deviated, than on the non-deviated, side. The SNB angle was significantly smaller, and the ANB, GZN, and SN-mandibular plane angles were significantly larger in sym anterior open bite. Overjet, ANB angle, GZN angle, and SN-MP angle were significantly larger, and the SNB angle was significantly smaller, in the presence of ADD without reduction and mandibular condylar deformity. We conclude that the prevalence of ADD without reduction and changes to the mandibular condyle were related to mandibular asymmetry and mandibular morphology in anterior open bite. This retrospective study suggests that ADD without reduction and mandibular condylar bone changes may be related to the progression of skeletal class II open bite and mandibular asymmetry in cases of skeletal open bite.

MRI observation of condylar location and morphology in the patients with temporomandibular disc displacement

Objective: To evaluate the mandibular condylar location and morphology in the temporomandibular joint disorders. Methods: One hundred thirty-seven TMD patients (age 37.5±16.1 years, male/female=39/98) were performed with MRI scan for temporomandibular joint (TMJ) from November, 2011 to April, 2019 in Department of Radiology,Hainan Hospital of General Hospital of Chinese PLA and General Hospital of Chinese PLA. The patients were classified into 3 groups according the disc displacement: disc without displacement (DWoD) (185 TMJ), disc displacement with reduction (DDWR) (17 TMJ) and disc displacement without reduction (DDWoR) (72 TMJ). The location (anterior position, central position and posterior position) and morphology (oval shape, flat shape and beaklike shape) of the condylar head were observed on the sagittal PDWI, and the long and short axes were measured on the axial T2WI. Another groups were classified into 3 subgroups according to the disc displacement of bilateral TMJ: bilateral normal disc location (biND) (74 cases), unilateral disc displacement (uniDD) (40 cases) and bilateral disc displacement (23 cases). The inter-condyle angle was measured on the axial T2WI. Results: There was no significant difference for the location of condylar head among DWoD, DDWR and DDwoR groups (χ(2)=7.435, P=0.115). The rate for flat condylar shape was significantly higher in DWoD group [83.9%(115/137)] than that in DDWoR group [50.7%(34/67)], and the rate for beaklike condylar shape was significantly lower in DWoD group [16.1%(22/137)] than that in DDWoR group [49.3%(33/67)] (χ(2)=23.521, P<0.001). The length of long axis presented significantly longer in DWoD group [(17.2±2.4) mm] than that in DDWR group [(15.4±2.0) mm] and that in DDWoR group [(14.7±2.7) mm] (P<0.05). The length of short axis presented significantly longer in DWoD group [(7.3±1.2) mm] than that in DDWR group [(6.5±1.3) mm] and that in DDWoR group [(6.1±1.4) mm] (P<0.05). The inter-condyle angle presented significantly larger in biND group (136°±13°) and uniDD group (132°±14°) than that inbiDD group (124°±17°) (P<0.05). Conclusions: The mandibular condylar morphology changes significantly presented in the patients with temporomandibular disc displacement for the temporomandibular disorders.

Predictors of arthrocentesis outcome on joint effusion in patients with disk displacement without reduction

The aim of this study was to investigate the preoperative variables in patients with articular disk displacement without reduction that may influence the results of arthrocentesis on joint effusion (JE). The records of 203 patients with clinical signs and symptoms of unilateral painful disk displacement without reduction and JE, confirmed by magnetic resonance imaging (MRI), and treated with arthrocentesis were selected. The following preoperative data were recorded: sex; age; joint side; pain duration; pain intensity, measurement with the visual analogue scale; and maximum interincisal distance (MID). All patients underwent a second MRI examination 3 to 4 months postoperatively to assess JE. The sample was then divided into 2 groups: group 1 (n = 160) comprised patients with no signs of JE; and group 2 (n = 43) comprised patients still showing signs of JE. Univariate and multivariate analyses were used to compare the groups. Among the studied variables, pain duration (P = .0175), pain intensity (P < .0001), and MID (P = .0085) were shown to affect arthrocentesis outcomes. The longer the pain duration (odds ratio [OR] = 0.930), the more intense was the pain (OR = 0.346), and the smaller the MID (OR = 0.562), the less were the chances of arthrocentesis completely eliminating JE. Pain duration, pain intensity, and MID can be used as predictors for the effect of arthrocentesis on JE outcomes and considered during treatment planning.

Distraction of the temporomandibular joint condyle in patients with unilateral non-reducing disc displacement: Fact or fiction?

Objectives: This study investigated the distractive effect of a unilateral pivot splint on patients with unilateral disc displacement without reduction.Methods: The study group was comprised of 18 patients who had no history of treatment with removable prosthetic restorations of molars, premolars, or canine teeth, and no previous treatment for temporomandibular disorder. Joint spaces measurements made on magnetic resonance images indicated the affected side to be narrower than the healthy side. Unilateral distraction splints were made for all patients. An ultrasonic motion analyzer was used to measure the vertical shift occurring on the affected side as patients closed their mouths with maximal force with the splint in their mouths.Results: Closing with maximal force on the unilateral distraction splint led to a noticeable downward movement of the affected condyle.Discussion: The findings of this study indicate that the TMJ condyle of patients with unilateral disc displacement without reduction may be unilaterally distracted if the articular space is narrowed.

Diagnosis of disk displacement using real-time MRI: Clinical report of two patients

The clinical application of real-time magnetic resonance imaging (MRI) for the diagnosis of temporomandibular joint disk displacement (DD) with and without reduction is presented. In 2 patients with presumed DD, real-time MRI at 15 frames per second was performed during the natural opening and closing of the mouth. In one patient unilateral DD with reduction and in the other patient bilateral DD without reduction were observed. In contrast with conventional static MRI, real-time MRI moving images of temporomandibular joint DD offer comprehensive information about the dynamics of all involved structures, which in turn promises more reliable diagnoses. Real-time MRI is more rapid, more reliable, more informative, and less stressful for patients with temporomandibular disorders (TMDs).

Is Anterior Disc Displacement Without Reduction Associated With Temporomandibular Joint Condylar Height in Juvenile Patients Younger Than 20 Years?

Because disc displacement might be accompanied by degenerative changes in the condyle, this study explored the association between condylar height and anterior disc displacement without reduction in juvenile patients. This was a retrospective cohort study that enrolled a sample of patients younger than 20 years with unilateral disc displacement without reduction. All patients had 2 magnetic resonance imaging records taken from January 2010 to June 2013 (interval, >6 months). Condylar height, disc length, and displacement distance were measured. The predictor variable was joint status (healthy vs affected side), and the outcome variables were changes in condylar height, displacement distance, and disc length over time. SAS 9.13 was used for analysis and the P value was set at .05. One hundred twenty-four patients (101 female and 23 male; mean age, 16.4 yr; mean interval, 13.6 months) were included. During the interval, the condylar height of the healthy side increased 0.75 mm, whereas the condylar height of the affected side decreased 0.41 mm. The disc of the affected side was shortened and more anteriorly displaced. Anterior disc displacement without reduction could be accompanied by a decrease in condylar height in juvenile patients, and the disc might be shortened and more anteriorly displaced.

Is mandibular asymmetry more frequent and severe with unilateral disc displacement?

PurposeTo investigate the prevalence of mandibular asymmetry (MA) within the symptomatic unilateral anterior disc displacement (ADD) patients, and analyze the influence TMJ factors of the MA severity. MethodsPatients aged under 20 years old with symptomatic unilateral ADD and asymptomatic volunteers with normal disc-condyle relationship diagnosed by magnetic resonance imaging (MRI) were included in this study. Posteroanterior cephalometric radiographs were taken to measure MA. Condylar height, disc length and disc displacement were measured by MRI. The prevalence and severity of MA were compared between the ADD and the control groups. The correlation between the severity of MA with the amount of condylar height shortage, disc deformity and distance of disc displacement were also evaluated within the ADD group. ResultsThere were 165 cases in the unilateral ADD group, and 156 cases in the control group. One hundred and nineteen cases had MA which accounted 72.12% (119/165) in the ADD group; while in the control group, only 25.64% (40/156) exhibited MA. The mean horizontal menton deviation and condylar height shortage in the unilateral ADD group were significantly larger than that in the control group (5.62 mm vs. 4.19 mm; 3.14 mm vs. 1.32 mm, p < 0.01). The severity of MA was significantly correlated with the amount of disc displacement, disc deformity and condylar height shortage (correlation coefficient: 0.80, 0.70, and 0.82). ConclusionMA is much more common and severe in young unilateral ADD patients. The severity of MA is correlated with the height of condyle and the status of the disc.

The influence of unilateral disc displacement on stress in the contralateral joint with a normally positioned disc in a human temporomandibular joint: An analytic approach using the finite element method

ObjectivesTo investigate the influence of unilateral disc displacement (DD) in the temporomandibular joint (TMJ) on the stress in the contralateral joint, with a normally-positioned disc, during clenching. Study designA finite element model of the TMJ was constructed based on MRI and 3D-CT of a single patient with a unilateral DD. A second model with bilateral normally-positioned discs served as a reference. The differences in stress distribution in various TMJ components during clenching were predicted with these models. ResultsIn the unaffected joint of the unilateral DD model, the largest von Mises stress at the start of clenching was predicted in the inferior surface of the disc and increased by 30% during clenching. In the connective tissue the largest stress (1.16 MPa) did not reduce during clenching, in contrast to the (unaffected) joints of the reference model. In the affected joint, the largest stress was predicted in the temporal cartilage throughout clenching. In the surrounding connective tissue, the largest stress (1.42 MPa) hardly changed during clenching indicating no, or negligible, stress relaxation. ConclusionsThis suggested that a unilateral DD could affect the stresses in the unaffected (contralateral) joint during clenching, where it may lead to weakening of the tissues that keep the disc on the top of the condyle. The results may be helpful in counseling worried patients, since they give insight into possible future developments of the disorder.

Ruptured disc after arthroscopic repositioning in the temporomandibular joint: a retrospective magnetic resonance imaging study

Our aim was to explore the incidence of rupture after arthroscopic repositioning of the disc of the temporomandibular joint (TMJ) by reviewing magnetic resonance images (MRI) of the TMJ taken before and after operation, and to investigate correlations retrospectively. We studied 247 patients with anterior disc displacement of the TMJ, and categorised them into 3 groups based on the postoperative MRI. The first group comprised those whose disc ruptured after repositioning, the second those who had a possible rupture of the disc after repositioning, and the third had no rupture of the disc after repositioning. Age, sex, duration of symptoms, maximum incisal mouth opening, whether the anterior disc displacement was unilateral or bilateral, and the Wilkes stage, were included in the analysis. The incidence of rupture (5/247) was 2%. Weak points at the intermediate zone of the disc were found in 4 of the 5 joints. The patients whose discs ruptured were significantly younger than the other 2 groups (p=0.001). There was no statistically significant difference in preoperative duration of symptoms and mouth opening among the groups. The proportions of unilateral and bilateral disc displacement (p=0.047) and Wilkes stage (p=0.027) differed among the 3 groups. The Wilkes stages was significantly more advanced in the ruptured group than in the other 2 groups (p=0.027) with 4/5 being bilateral. The weak point in the intermediate zone of the disc on MRI could be a sign of rupture. Teenagers and young adults with anterior disc displacement without reduction, particularly those in whom it is bilateral, are at a higher risk of a rupture after repositioning of the disc by arthroscopy.

Magnetic resonance imaging-verified temporomandibular joint disk displacement in relation to sagittal and vertical jaw deformities

This retrospective study was designed to analyze the relationships between temporomandibular joint (TMJ) disk displacement and skeletal deformities in orthodontic patients. Subjects consisted of 460 adult patients. Before treatment, lateral cephalograms and TMJ magnetic resonance imaging (MRI) were recorded. Subjects were divided into six groups based on TMJ MRI according to increasing severity of TMJ disk displacement, in the following order: bilateral normal TMJs, unilateral disk displacement with reduction (DDR) and contralateral normal, bilateral DDR, unilateral disk displacement without reduction (DDNR) and contralateral normal, unilateral DDR and contralateral DDNR, and bilateral DDNR. Subjects were subdivided sagittally into skeletal Class I, II, and III deformities based on the ANB (point A, nasion, point B) angle and subdivided vertically into hypodivergent, normodivergent, and hyperdivergent deformities based on the facial height ratio. Linear trends between severity of TMJ disk displacement and sagittal or vertical deformities were analyzed by Cochran–Mantel–Haenszel test. The severity of TMJ disk displacement increased as the sagittal skeletal classification changed from skeletal Class III to skeletal Class II and the vertical skeletal classification changed from hypodivergent to hyperdivergent. There were no significant differences in the linear trend of TMJ disk displacement severity between the sexes according to the skeletal deformities. This study suggests that subjects with skeletal Class II and/or hyperdivergent deformities have a high possibility of severe TMJ disk displacement, regardless of sex.

Evaluation of the Effects of Temporomandibular Joint Disc Displacement and Its Progression on Dentocraniofacial Morphology in Symptomatic Patients Using Posteroanterior Cephalometric Analysis

The aim of this study was to evaluate the effects of disc displacement (DD) and its progression on dentocraniofacial morphology in symptomatic patients, and to compare the results with asymptomatic volunteers. Female patients with DD, diagnosed with magnetic resonance imaging (MRI) and posteroanterior cephalometric analysis, were included in this study. Subjects were grouped as follows: control group with bilateral normal disc position (group 1, n=20), unilateral DD with reduction (group 2, n=17), bilateral DD with reduction (group 3, n=32), unilateral DD without reduction (group 4, n=16), and bilateral DD without reduction (group 5, n=19). Thirteen cephalometric variables were measured. A significant increase in the ANS (Anterior nasal spine)-Me (Menton)-MSP (Midsagittal plane) angle in unilateral DD groups and decreases in the Ag (Antegonial notch)-Me dimension on the affected side in all DD groups were observed. Also, the maximum values of the Me-MSP dimension and ANS-Me-MSP angle were observed in group 4. The results of this study showed that the deviation of the menton point toward the disc displacement side causes a mandibular asymmetry. It can be concluded from these results that the presence of DD in female patients affects facial morphology, and its progression makes the differences more significant and remarkable. These results emphasize the importance of early diagnosis and treatment in the management of DD.