Healthy Temporomandibular Joint Research Articles

Trueness evaluation of three intraoral scanners for the recording of maximal intercuspal position.

This clinical study aimed to assess the trueness of three intraoral scanners for the recor-ding of the maximal intercuspal position (MIP) to provide a reference for clinical practice. Ten participants with good occlusal relationship and healthy temporomandibular joint were recruited. For the control group, facebow transferring procedures were performed, and bite registrations at the MIP were used to transfer maxillary and mandibular casts to a mechanical articulator, which were then scanned with a laboratory scanner to obtain digital cast data. For the experimental groups, three intraoral scanners (Trios 3, Carestream 3600, and Aoralscan 3) were used to obtain digital casts of the participants at the MIP following the scanning workflows endorsed by the corresponding manufacturers. Subsequently, measurement points were marked on the control group's digital casts at the central incisors, canines, and first molars, and corresponding distances between these points on the maxillary and mandibular casts were measured to calculate the sum of measured distances (DA). Distances between measurement points in the incisor (DI), canine (DC), and first molar (DM) regions were also calculated. The control group's maxillary and mandibular digital casts with the added measurement points were aligned with the experimental group's casts, and DA, DI, DC, and DM values of the aligned control casts were determined. Statistical analysis was performed on DA, DI, DC, and DM obtained from both the control and experimental groups to evaluate the trueness of the three intraoral scanners for the recording of MIP. In the control group, DA, DI, DC, and DM values were (39.58±6.40), (13.64±3.58), (14.91±2.85), and (11.03±1.56) mm. The Trios 3 group had values of (38.99±6.60), (13.42±3.66), (14.55±2.87), and (11.03±1.69) mm. The Carestream 3600 group showed values of (38.57±6.36), (13.56±3.68), (14.45±2.85), and (10.55±1.41) mm, while the Aoralscan 3 group had values of (38.16±5.69), (13.03±3.54), (14.23±2.59), and (10.90±1.54) mm. Analysis of variance revealed no statistically significant differences between the experimental and control groups for overall deviation DA (P=0.96), as well as local deviations DI (P=0.98), DC (P=0.96), and DM (P=0.89). With standardized scanning protocols, the three intraoral scanners demonstrated comparable trueness to traditional methods in recording MIP, fulfilling clinical requirements.

Biomechanical study of temporomandibular joints of patients with temporomandibular disorders under incisal clenching: A finite element analysis

Temporomandibular disorders (TMD) encompass a collection of pathologies. Within the multitude of etiological factors contributing to TMD, mechanical factors hold significant importance. The aim of this investigation was to assess the magnitude and distribution of stresses encountered by the temporomandibular joints (TMJs) during incisal clenching among TMD patients while also elucidating the mechanical pathogenesis underlying TMD. Ten asymptomatic subjects and ten TMD patients were recruited. The Control, Bilateral, and Unilateral groups were set. The contact stress, maximum principal stress, and minimum principal stresses of TMJ structures among the groups were compared. In addition, comparisons of the contact stress distribution among the groups were adopted. In the Control and Bilateral groups, the magnitudes of stresses (contact stress, maximum and minimum principal stresses) between the right and left sides showed no significant difference (P > 0.05). For unilateral TMD patients,the minimum principal stress on the condyle in the Uni-N group (the normal side) was significantly greater than thatin the Uni-T group (the TMD side)(P = 0.016, mean difference 9.99 MPa [95 %CI: 3.11 to 16.87]). Furthermore, stresses on the condyle and fossa of the patients were significantly greater than those of asymptomatic subjects (P < 0.05). The contact stress distributions were concentrated in the Control group while irregular in the TMD groups. In conclusion, asymmetrical contact stress distributions were observed in unilateral TMD, with excessive stresses on the healthy side. The protection of the healthy TMJ during treatment is recommended for patients with unilateral TMD.

Evaluation of the effect of unilateral mastication on the morphology of temporomandibular joint from the perspective of dynamic joint space.

Unbalanced alterations of temporomandibular joint morphology were associated with unilaterally masticatory habits. This study aimed to investigate the effect of unilateral mastication on the remodelling of the temporomandibular joint using dynamic joint space. Twelve volunteers with non-maxillofacial deformity and healthy temporomandibular joints were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to masticate French fries and peanuts unilaterally, which was recorded by a 3D motion capture system. The dynamic joint space during unilateral mastication was analysed. During early closure, the joint space reduction on the non-masticatory side was significantly greater than on the masticatory side (p < .05). During later closure, the joint space reduction on the non-masticatory side was significantly lower than that on the masticatory side (p < .05). The difference in joint space reduction between both sides was greater than the French fries while masticating the peanuts. Unilateral mastication resulted in a different major pressure area on the bilateral TMJs. Therefore, unilateral mastication might be an essential factor in the bilateral asymmetrical remodelling of the TMJ.

Case report impact on orthognathic surgery for counterclockwise rotation and effect on airway, with or without temporomandibular joint total joint prostheses

PurposePresent case reports that have generated new treatment protocols improving treatment of patient outcomes with jaw deformities and airway compromises requiring counterclockwise rotation (CCWR) of the maxillo-mandibular complex (MMC) with or without a requirement for temporomandibular joint (TMJ) total joint prostheses (TJP). Presented are studies that verify the efficacy of these procedures. MethodsInitial case presentations were identified in reference to CCWR of the MMC without and with TMJ total joint prostheses in cases of co-existing end-stage TMJ pathology. A non-systematic literature search was conducted to identify studies pertinent to subject matter. ResultsTwo case reports are presented that have significantly affected our specialty: 1) CCWR of the MMC and effect on airway, and 2) TMJ TJP with concomitant maxillary osteotomies for CCWR of the MMC. Forty papers were identified meeting the filtered criteria. Twenty-nine papers were excluded as case reports, philosophy, technique, or small case series. Eleven studies met the inclusion criteria and are summarized according to the data included. These studies validate the efficacy and stability of CCWR of the MMC in the presence of healthy joints as well as patients with end-stage TMJ pathology using custom TMJ TJP in conjunction with orthognathic surgery. ConclusionsPatients with healthy TMJs can be treated with CCWR of the MMC with predictable outcomes and stability. Patients with end-stage TMJ pathology can benefit from TMJ TJP and orthognathic surgery for CCWR of the MMC with good stability, improved function, decreased pain, improved airway, and quality of life.

Numerical investigation of the biomechanical effects of orthodontic intermaxillary elastics on the temporomandibular joint

Temporomandibular joint disorder (TMD) often coincides with malocclusion, and in some cases TMDs are reported after orthodontic treatment. Intermaxillary elastics (also known as orthodontic elastics, OE) are a common way to apply force during orthodontic treatment, and they might cause mechanical effects on the temporomandibular joint (TMJ), thereby lead to joint remodeling. It is still a controversial topic whether the adapted remodeling of the TMJ or of the alveolar bone is the main cause for the alteration of occlusion after treatment with OEs. It was the aim of this study to analyze whether variations of OEs would develop harmful effects on the healthy TMJ. A TMJ model with a masticatory system based on Hill-type muscle actuators was established. Mouth opening and closure with and without OEs were simulated, and maximum principal stresses in the disc and condylar cartilage as well as the displacement of the mandible were analyzed. We found no considerably difference in the mandibular movement without and with symmetrical OEs during mouth opening and closing. At full mouth opening, stresses in the disc and condylar cartilage of some models with OEs were much smaller than without OEs, but we did not find consistency in the results from the left and right sides of the same model (e.g. the lowest compressive stress on the left side of disc from the model with Class II OEs is much smaller than without OEs, −17.3 MPa compared with −28.2, while on the right side, there was no obvious difference). Hence, we could not conclude that OEs would develop deleterious effects on the healthy TMJ.

Do cone-beam computed tomography low-dose protocols affect the evaluation of the temporomandibular joint?

There is no established acquisition protocol based on scientific evidence for the acquisition of cone-beam computed tomography (CBCT) exams to evaluate the temporomandibular joint (TMJ). To evaluate the influence of acquisition protocols and jaw positioning on the diagnostic accuracy of TMJ condylar morphological alterations (CMA), dimension, position and excursion. Thirty-six TMJs on 18 dry skulls were imaged using a CBCT unit (OP300 Maxio, Instrumentarium, Tuusula, Finland) at two exposure settings (4.5 and 6.3mA), three voxel resolutions (0.085, 0.125 and 0.280 mm), three jaw positions (concentric, anteriorised and posteriorised) and three jaw excursions (normoexcursion, hyperexcursion and hypoexcursion). The macroscopic anatomy examination and high-resolution CBCT images were used as ground truth for CMA. Twenty-five TMJs had at least one CMA with 11 healthy TMJs serving as controls. Three experienced oral and maxillofacial radiologists evaluated the parasagittal images for the presence of CMA, position and excursion and measured dimensions. The area under the ROC curve, sensitivity and specificity were calculated. Weighted Kappa (α=0.05) was used to determine intra- and interexaminer reliability and comparisons between dependent variables analysed by Analysis of Variance at an a prior level of significance of 0.05. The agreement of the evaluation of the position and excursion with the reference standard was high, independent of the protocol (range, 0.75-0.91). Various combinations of acquisition protocols and jaw position did not influence the CMA evaluation. Erosion was overdiagnosed in protocols with larger voxel sizes and the detection of osteophytes greater in images with smaller voxel sizes. The anteroposterior dimension was greater in the open jaw position (p < .05). CBCT protocols using reduced radiation exposure from the CBCT machine evaluated in this study can be used to assess condylar morphology, dimension, position and excursion, without compromising diagnostic performances for these parameters.

The effect of mandibular movement on temporomandibular joint morphology while eating French fries

BackgroundThe preferred masticatory side was reported to be almost always the same as the affected side of the temporomandibular disorder. Unbalanced alterations of temporomandibular joint morphology were found to be associated with unilaterally masticatory habits. The aim of this study was to investigate the effect of the mandibular movement on the remodeling of temporomandibular joint during eating French fries using a 3D motion capture system. MethodsTwelve volunteers with non-maxillofacial deformity and a healthy temporomandibular joint were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to eat French fries by unilaterally mastication, which was recorded by a 3D motion capture system. The trajectories of the incisors and the condyles and the condylar acceleration during unilateral mastication were analyzed. ResultsDuring incisal biting, there was no significant difference in the condylar trajectories between the left and right sides (P > 0.05). During unilateral mastication, the average displacement and acceleration of the masticatory condyles were significantly lower than those of the non-masticatory condyles (P < 0.05). The trajectory angles of the masticatory condyles were significantly steeper than those of the non-masticatory condyle (P < 0.05). During swallowing, there was no obvious movement of the mandible. ConclusionsBetween both temporomandibular joints, unilateral mastication resulted in significant differences in the regions of the condylar movement within the articular fossa, and then caused different compressive regions of the temporomandibular joints. Thus, unilateral mastication might result in a significantly different pattern of temporomandibular joint remodeling between the two sides.

Study of collagen remodeling in structural disorders of the temporomandibular joint using second-harmonic generation microscopy.

Structural disorder of the temporomandibular joint (TMJ) is a progressive disease with poor prognosis due to its physiological three-dimensional anatomical position and the complicated relationship among muscles, ligaments, and cartilage. The lack of detection methods for changes in the collagen structure of the TMJ disc makes the diagnosis untimely and unclear. This work aimed to explore the feasibility of using a promising detection technique, second-harmonic generation (SHG), to characterize collagen fibers in a TMJ disc with structural disorders. The TMJ discs with structural disorder were observed using SHG microscopy, and assessment of collagen orientation was conducted by analyzing digitized images. The SHG images were also compared with the scanning electron microscopy images and microscopic images acquired after hematoxylin and eosin and Masson's trichrome staining. The SHG imaging showed that the collagen fibers in diseased TMJ were distributed in a disorderly manner, and pixel intensities in diseased TMJ discs were significantly different from those acquired in healthy TMJs. Moreover, the three dimensions of collagen fibers and dynamic images acquired by SHG nonlinear optical microscopy showed the structural disorder of the collagen fibers in a diseased TMJ. In summary, SHG imaging could provide three-dimensional and quantitative data, with dynamic and critical pathological information for clinical diagnosis, showing its potential value in the diagnosis and evaluation of structural disorders of the TMJ disc.

Assessment and comparison of condylar position based on joint space dimensions and gelb 4/7 grid using CBCT

Background: Temporomandibular joint (TMJ) is a unique joint. An optimal position of the mandibular condyle in the glenoid fossa is a fundamental question in dentistry, and there is no quantitative standard. Thus, the most common condylar position in the glenoid fossa can be determined by the dimension of the joint space and Gelb 4/7 grid using cone-beam computed tomography (CBCT). Aim: To analyze the position of the condyle and joint spaces in the normal temporomandibular joint and to compare the efficacy of the Gelb 4/7 grid over dimensions of joint spaces to assess optimum condylar position using CBCT. Materials and Methods: CBCT images of 40 patients (right and left) without a history of TMJ disorders were selected. Anterior (Ajs), superior (Sjs), and posterior joint spaces (Pjs) on sagittal slices, medial (Mjs), and lateral (Ljs) on coronal view were measured and Gelb 4/7 grid on sagittal slices used to assess the condylar position. Results: Significant difference between right and left sides in Ajs, Sjs, Mjs, and Ljs values. Significant differences were noticed in Mjs, Ajs values between males and females. Centric position is the most common position of the condyle, and 4/7 position is the most common according to Gelb 4/7 grid. Conclusion: Gelb 4/7 position was found to be the most common anatomical position of the condyle in healthy TMJs, and centric relation position was the most common based on joint space dimensions.

The evaluation of agreement between high-frequency ultrasonography and research diagnostic criteria for the diagnosis of temporomandibular joint internal derangements.

Aim:The aim of this study is to compare the diagnosis of patients with temporomandibular joint (TMJ) internal derangements which had been diagnosed using Research Diagnostic Criteria/Temporomandibular Disorders (RDC/TMD) with the dynamic high resolution sonography findings.Settings and Design:Axis I section of RDC/TMD form had been applied to participants. Participants were divided into three groups as healthy TMJ, disc displacement with reduction, and disc displacement without reduction. The diagnoses had been compared with the dynamic high-resolution sonography findings.Materials and Methods:Twelve of the patients had been treated with laser therapy, whereas 13 patients were treated with stabilization splint. Seventeen patients were treated with anterior repositioning splint (n = 42). After the application of different treatment modalities, the position of the articular disc had been determined with Axis I of RDC/ TMD form and dynamic high-resolution sonography. The findings were compared and statistically analyzed.Statistical Analysis Used:Statistical analyses of data were analyzed with Turcosa Cloud (Turcosa Ltd Co, Turkey).Results:For the right TMJ, pretreatment and posttreatment ultrasonography (USG) diagnoses and RDC/ TMD clinical diagnoses were found similar (κ = 0.125–0.008). No statistically significant relationship was found (P > 0.05). For the left TMJ, pretreatment USG diagnosis and RDC/TMD clinical diagnose were found similar (κ = 0.070). No statistically significant relationship was found (P > 0.05). For the left TMJ, posttreatment USG diagnosis and RDC/TMD clinical diagnose were compared. A statistically significant difference was found (κ = 0.256). A statistically significant relationship was found (P < 0.05).Conclusions:Axis 1 of RDC/TMD form which is used for the diagnosis of internal derangements and dynamic high resolution sonography was not found in the agreement.

T2 mapping with 3.0 T MRI of the temporomandibular joint disc of patients with disc dislocation

IntroductionT2 mapping, as a quantitative biochemical MRI-technique that provides information on water and collagen fiber content and composition, was shown to be clinically feasible for the evaluation of healthy temporomandibular joints. ObjectivesThe aim of our study was to compare the T2 values of whole discs in patients with and without disc dislocation, to evaluate the possible influence of morphological findings on T2 values and to assess the interrater agreement. MethodsSixty-six patients were included in the study. Three experienced examiners assessed the perceptibility of the morphological parameters and the position of the articular disc on the morphological MR images. On the T2 maps, the T2 values of the region-of-interest (ROI) were assessed. ResultsThe ICC (Intraclass Correlation Coefficient) for the reproducibility of the T2 values was 0.717. The assessment of the morphologic parameters was excellent or good in most of the discs. There was no significant difference in the T2 values based on disc position or signal intensity. But, a statistically significant moderation effect (p = .014) could be identified, indicating that the effect of disc position differs for different signal intensities. Condyle position, effusion, and degenerative changes showed pronounced moderation effects on the T2 values. ConclusionDue to the high sensitivity to effusion, T2 mapping currently seems to be unsuitable as a diagnostic tool for routine use in the temporomandibular joint. The moderation effect clearly shows the influence of factors such as signal intensity, effusion, arthrosis, and condyle position. Perhaps a solution for these problems could be the development of dedicated TMJ coils for higher field strengths at 7.0 T.

Three-dimensional quantitative assessment of surgical stability and condylar displacement changes after counterclockwise maxillomandibular advancement surgery: Effect of simultaneous articular disc repositioning.

In this study, we quantitatively assessed 3-dimensional condylar displacement during counterclockwise maxillomandibular advancement surgery (CMMA) with or without articular disc repositioning, focusing on surgical stability in the follow-up period. The 79 patients treated with CMMA had cone-beam computed tomography scans taken before surgery, immediately after surgery, and, on average, 15months postsurgery. We divided the 142 condyles into 3 groups: group 1 (n=105), condyles of patients diagnosed with symptomatic presurgical temporomandibular joint articular disc displacement who had articular disc repositioning concomitantly with CMMA; group 2 (n=23), condyles of patients with clinical verification of presurgical articular disc displacement who had only CMMA; and group 3 (n=14), condyles of patients with healthy temporomandibular joints who had CMMA. Presurgical and postsurgical 3-dimensional models were superimposed using voxel-based registration on the cranial base. Three-dimensional cephalometrics and shape correspondence were applied to assess surgical and postsurgical displacement changes. Immediately after surgery, the condyles moved mostly backward and medially and experienced lateral yaw, medial roll, and upward pitch in the 3 groups. Condyles in group 1 showed downward displacement, whereas the condyles moved upward in groups 2 and 3 (P≤0.001). Although condylar displacement changes occurred in the 3 groups, the overall surgical procedure appeared to be fairly stable, particularly for groups 1 and 3. Group 2 had the greatest amount of relapse (P≤0.05). CMMA has been shown to be a stable procedure for patients with healthy temporomandibular joints and for those who had simultaneous articular disc repositioning surgery.

Reproducibility of the Obtained Centric Relation Records in Patients with Disc Displacement with Reduction.

ObjectiveThe aim of this study was to investigate reproducibility of the position of centric relation in patients with disc displacement with reduction.Materials and methodsThe test group included 30 subjects, diagnosed with disc displacement with reduction in right, left or both joints. The control group included 12 individuals with no signs and symptoms of temporomandibular disorders. Using chin point guidance with a jig, centric relation record was made three times by every participant, in a single session. Left and right condylar position for each centric relation record was determined and recorded using the electronic ultrasonic measuring device. The data were transferred to the computer, processed and analyzed. Condylar distances between centric relation records were measured (anteroposterior, vertical, transversal and linear values), and the data were statistically analyzed using the t and the F tests.ResultsNo statically significant difference was found between the test and the control groups. Two thirds of study participants demonstrated condylar position of the repeated centric relation recording within the area of 0.3 mm in diameter. For more than 90% of participants that area was within 0.4 mm.ConclusionsThere is no difference in reproducibility of the centric relation between patients with disc displacement with reduction and healthy temporomandibular joint individuals (p>0.05). When doing centric relation record on a patient with disc displacement with reduction there is no need for previous splint therapy and standard precautions are acceptable. The obtained results must be interpreted within the experimental group, and not projected on the other groups of temporomandibular disorders.

The action of anti-inflammatory agents in healthy temporomandibular joint synovial tissues is sex-dependent

This study evaluated the effects of dexamethasone, parecoxib, and glucosamine on cartilage thickness and cytokine levels in the temporomandibular joint (TMJ). Forty-eight rats (24 female, 24 male) were assigned to four treatments administered once daily for 7 days: control (saline intramuscularly), parecoxib (0.3mg/kg intramuscularly), dexamethasone (0.1mg/kg intramuscularly), and glucosamine (80mg/kg orally). The thickness of TMJ cartilage and levels of four cytokines were measured. Median cartilage thickness was higher in males than in females in the control (253.2 vs. 240.4μm, P=0.0036), parecoxib (227.3 vs. 192.1μm, P<0.0001), and dexamethasone (227.1 vs. 170.5μm, P=0.017) groups, but was lower in males in the glucosamine group (214.5 vs. 239.6μm, P=0.0001). IL-1β was not detected. Median IL-1α levels differed between males and females in the parecoxib group (0.08 vs. 0.04ng/ml, P=0.0055), but not in the control (0.07 vs. 0.06ng/ml), dexamethasone (0.06 vs. 0.04ng/ml), or glucosamine (0.08ng/ml vs. 0.06ng/ml) groups (all P>0.05). Only dexamethasone induced lower IL-6 levels in males than in females (median 4.6 vs. 2.1ng/ml, P=0.0044). Median TNF-α levels did not differ between males and females in the control (0.07 vs. 0.05ng/ml) or parecoxib (0.07 vs. 0.05ng/ml) groups (both P>0.05), but dexamethasone (0.09 vs. 0.05ng/ml, P=0.0002) and glucosamine (0.09 vs. 0.07ng/ml, P=0.0259) induced higher TNF-α levels in females. Thus, the effects of the three treatments on the levels of cytokines and thickness of condylar cartilage were sex-dependent.

TMJ energy densities in healthy men and women.

Cartilage fatigue, due to mechanical work, may account for the early development of degenerative joint disease (DJD) in the temporomandibular joint (TMJ), and why women are three times more likely to be afflicted. This study tested for gender differences in mechanical energy densities in women and men with healthy TMJs. Eighteen women and eighteen men gave informed consent. Research diagnostic criteria including imaging were used to ensure that subjects' TMJs were normal, without disc displacement or signs of DJD. Numerical modeling determined TMJ loads (Fnormal). Jaw tracking and three-dimensional dynamic stereometry characterized individual-specific data of stress-field dynamic mechanics during 10 symmetrical jaw closing cycles. These data were used to estimate tractional forces (Ftraction). Energy densities were then calculated, where: Energy Density=W/Q (W=work done or mechanical energy input=Ftraction*distance of stress-field translation, Q=volume of cartilage). Two-way analysis of variance (ANOVA) and follow-up two-group comparisons tested mean energy densities for ipsilateral and contralateral TMJs in women vs men. Mean energy densities ± standard deviations in ipsilateral and contralateral TMJs in women were 9.0±9.7 and 8.4±5.5mJ/mm3, respectively, and were significantly larger (P=0.004 and 0.001, respectively) compared to ipsilateral and contralateral TMJs in men, which were 5.6±4.2 and 6.3±4.2mJ/mm3, respectively. Energy densities were significantly larger in healthy TMJs of women than men. Larger TMJ energy densities during normal jaw functions could predispose earlier mechanical fatigue of the TMJ disc.

Does Temporomandibular Joint Pathology With or Without Surgical Management Affect the Stability of Counterclockwise Rotation of the Maxillomandibular Complex in Orthognathic Surgery? A Systematic Review and Meta-Analysis.

This study was designed to determine the stability of counterclockwise rotation (CCWR) of the maxillomandibular complex (MMC) in orthognathic surgery with or without surgical correction of coexisting temporomandibular joint (TMJ) pathology. The authors implemented a systematic review and meta-analysis. A search of major databases through PubMed, EMBASE, and Cochrane CENTRAL was performed. Inclusion criteria were studies that analyzed CCWR of the MMC in regard to skeletal stability after orthognathic surgery in patients with or without pre-existing TMJ pathology that was or was not surgically corrected concomitantly. The predictor variables were patients who underwent CCWR of the MMC in the following subgroups: 1) healthy TMJs (presumed healthy based on history, clinical evaluation, and radiographic analysis but without magnetic resonance imaging [MRI] confirmation), 2) no TMJ assessment, 3) untreated TMJ disc displacement (confirmed by MRI), 4) TMJ disc displacement (confirmed by MRI) repositioned using Mitek anchors, and 5) reconstruction with TMJ total joint prosthesis. Outcome variables were surgical relapse for angular and linear measurements. Postsurgical mean changes for the occlusal plane (OP) and linear measurements using a fixed-effects model with a 95% confidence interval were analyzed. A total of 345 patients enrolled in 12 studies were included in this study. There was significant OP relapse and horizontal relapse at the B point and menton for studies with untreated TMJ disc displacement and studies without TMJ assessment (P < .005). There was significant horizontal relapse at the A point for studies with healthy TMJs, without assessment of the TMJs, and with TMJ reconstruction with total joint prostheses (P < .005). There was no significant vertical relapse at the B and A points for all subgroup analyses (P < .005). The result of the meta-analysis suggests that CCWR of the MMC is a stable procedure for patients with healthy TMJs, patients undergoing concomitant TMJ disc repositioning with Mitek anchors, and patients with TMJ patient-fitted total joint prostheses but unstable in the presence of untreated TMJ disc displacements and when TMJ status is not assessed.

Biomechanical and biochemical outcomes of porcine temporomandibular joint disc deformation

ObjectiveThe structure–function relationship in the healthy temporomandibular joint (TMJ) disc has been well established, however the changes in dysfunctional joints has yet to be systematically evaluated. Due to the poor understanding of the etiology of temporomandibular disorders (TMDs) this study evaluated naturally occurring degenerative remodeling in aged female porcine temporomandibular joint (TMJ) discs in order to gain insight into the progression and effects on possible treatment strategies of TMDs. DesignSurface and regional biomechanical and biochemical properties of discal tissues were determined in grossly deformed (≥Wilkes Stage 3) and morphologically normal (≤Wilkes Stage 2) TMJ discs. ResultsCompared to normal disc structure the deformed discs lacked a smooth biconcave shape and characteristic ECM organization. Reduction in tensile biomechanical integrity and increased compressive stiffness and cellularity was found in deformed discs. Regionally, the posterior and intermediate zones of the disc were most frequently affected along with the inferior surface. ConclusionsThe frequency of degeneration observed on the inferior surface of the disc (predominantly posterior), suggests that a disruption in the disc-condyle relationship likely contributes to the progression of joint dysfunction more than the temporodiscal relationship. As such, the inferior joint space may be an important consideration in early clinical diagnosis and treatment of TMDs, as it is overlooked in techniques performed in the upper joint space, including arthroscopy and arthrocentesis. Furthermore, permanent damage to the disc mechanical properties would limit the ability to successfully reposition deformed discs, highlighting the importance of emerging therapies such as tissue engineering.

IL-1β mediating high mobility group box protein-1 expression in condylar chondrocyte during temporomandibular joint inflammation.

Temporomandibular joint (TMJ) osteoarthritis(OA)characterized with cartilage degen-eration is associated with inflammation. High mobility group box chromosomal protein-1(HMGB-1)is a potent mediator of inflammation and the trigger of OA. The expression of HMGB-1 in TMJ OA was uncovered, but the role of HMGB-1 in TMJ cartilage degeneration is not fully understood. In this study, the regulation of HMGB-1 in TMJ condylar cartilage was revealed. A complete Freund's adjuvant (CFA)-induced TMJ inflammation animal model was employed and the expression of HMGB-1 was detected at 1st, 2nd, and 6th weeks by immunohistochemistry. TMJ condylar chondrocytes were incubated with IL-1β (10 and 40 ng/ml) at 24, 48, and 72 h, and the translocation and protein level of HMGB-1 were evaluated by immunofluorescence and Western blot. Nuclear HMGB-1 staining was predominantly located in chondrocytes of both the fibrosis and proliferative zones in healthy TMJ. 1st week and 2nd week after CFA injection, immunoreaction could be detected in the cytoplasms of HMGB-1-positive cells and cartilage matrix especially in hypertrophic zone. At 6th week after CFA injection, cartilage matrix expression was disappeared and the cytoplasm expression of HMGB-1 was very weak in hypertrophic zone. HMGB-1 was translocated from the nucleus to the cytoplasm at 48 h after incubated with IL-1β (10 ng/ml and 40 ng/ml). The protein level of HMGB-1 was increased after stimulation and had a peak at 48 h. HMGB-1 might be associated with TMJ inflammation and OA. Insight into the role of HMGB-1 in TMJ inflammation is helpful to add the new knowledge into the pathogenesis of TMJ OA.

Effects of several temporomandibular disorders on the stress distributions of temporomandibular joint: a finite element analysis

The aim of this study was to evaluate stress distributions in the temporomandibular joints (TMJs) with temporomandibular disorders (TMDs) for comparison with healthy TMJs. A model of mandible and normal TMJs was developed according to CT images. The interfaces between the discs and the articular cartilages were treated as contact elements. Nonlinear cable elements were used to simulate disc attachments. Based on this model, seven models of various TMDs were established. The maximum stresses of the discs with anterior, posterior, medial and lateral disc displacement (ADD, PDD, MDD and LDD) were 12.09, 9.33, 10.71 and 6.07 times magnitude of the identically normal disc, respectively. The maximum stresses of the posterior articular eminences in ADD, PDD, MDD, LDD, relaxation of posterior attachments and disc perforation models were 21, 59, 46, 21, 13 and 15 times greater than the normal model, respectively. TMDs could cause increased stresses in the discs and posterior articular eminences.

Cytokines in healthy temporomandibular joint synovial fluid

Analysis of temporomandibular joint (TMJ) synovial fluid may elucidate the aetiology of temporomandibular disorders and arthritic conditions, as well as the inflammatory mechanisms involved. Knowledge about healthy synovial fluid is necessary to understand TMJ pathologies. We aimed to quantify the proinflammatory cytokines interleukin (IL)-1β, IL-2, IL-6 and tumour necrosis factor (TNF), and the anti-inflammatory cytokines IL-10 and interferon (IFN)-γ in healthy TMJ synovial fluid to serve as reference values for future studies on TMJ pathologies. Twenty healthy, young adult volunteers without temporomandibular dysfunction were included. Bilateral synovial fluid samples were obtained using the push-pull technique with hydroxocobalamin described by Alstergren in 1999. Cytokines were quantified with Luminex multiplex assays and compared using nonparametric statistical analysis. No serious adverse effects were reported. Of 40 possible samples, 14 fulfilled the strict sampling criteria and were included in the analysis. Cytokine values (reported as medians with interquartile ranges) were as follows: TNF, 23 (13-37)pgmL(-1) ; IL-2, 1·8 (0-22)pgmL(-1) ; and INF-γ, 10 (0-47)pgmL(-1) . IL-1β, IL-6 and IL-10 were almost undetectable. In addition, TNF and INF-γ cytokine levels correlated. We demonstrated that TNF was consistently detected and IFN-γ and IL-2 sporadically detected in the TMJ synovial fluid of healthy individuals using the hydroxocobalamin method and a multiplex assay. The cytokines IL-10, IL-1β and IL-6 were barely detectable in this sample of healthy TMJs.