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The pathological changes of subchondral bone during osteoarthritis (OA) development in the temporomandibular joint (TMJ) are poorly understood. In the present study, we investigated the longitudinal alterations of subchondral bone using a rat TMJ-OA model developed in our laboratory. Changes in bone mass were examined by micro-CT, and changes in osteoblast and osteoclast activities were analyzed by real-time PCR, immunohistochemistry, and TRAP staining. Subchondral bone loss was detected from 8 weeks after dental occlusion alteration and reached the maximum at 12 weeks, followed by a repair phase until 32 weeks. Although bone mass increased at late stages, poor mechanical structure and lower bone mineral density (BMD) were found in these rats. The numbers of TRAP-positive cells were increased at 12 weeks, while the numbers of osteocalcin-expressing cells were increased at both 12 and 32 weeks. Levels of mRNA expression of TRAP and cathepsin K were increased at 12 weeks, while levels of ALP and osteocalcin were increased at both 12 and 32 weeks. These findings demonstrated that there is an active bone remodeling in subchondral bone in TMJs in response to alteration in occlusion, although new bone was formed with lower BMD and poor mechanical properties.

Introduction: Mice with brachymorphism (bm) have defective chondrogenesis, including abnormal growth of the spheno-occipital synchondrosis. Malocclusion (anterior transverse crossbite) sometimes spontaneously occurs in inbred BALB/c-bm/bm mice, before the mandibular incisors erupt and make contact with the maxillary incisors. The aim of this study was to determine whether functional lateral loads to incisors promote anterior transverse crossbites in BALB/c-bm/bm mice., Methods: BALB/c-bm/bm mice with normal occlusion (normal group), BALB/c-bm/bm mice with malocclusion in which the incisors were not cut (mal group), and BALB/c-bm/bm mice in which the incisors had been cut to eliminate the functional lateral load during continued growth (mal-cut group) were used. We examined the amounts of shift of the maxillary and mandibular incisors in each group using radiographic images., Results: The amount of shift of the maxillary incisors in the mal group was significantly greater than that in normal group. The total amount of shift from the maxilla to the mandible in the mal group was significantly greater than in the normal and mal-cut groups., Conclusions: The results suggest that a continuous functional lateral load to the incisors is strongly related to promoting and worsening anterior transverse crossbite in BALB/c-bm/bm mice., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

The aim of the present study was to establish whether the early signs of various orofacial dysfunctions, malocclusions, or occlusal interferences can predict the development of temporomandibular dysfunction (TMD) in young adults. Forty-eight subjects referred for speech therapy and 49 controls participated in all four stages of this longitudinal study. The subjects were examined at the ages of 7, 10, 15, and 19 years. The phoniatrician diagnosed errors in place of articulation and problems in the movement and co-ordination of the speech articulators. Occlusion, TMD signs (palpatory tenderness of the masticatory muscles, and of temporomandibular joints (TMJ), jaw deviation on opening, and clicking), mandibular movement capacity and occlusal interferences were registered by the orthodontist. Multiple logistic regression models were applied in order to evaluate whether single signs of TMD at the age of 19 years were related to previous/present malocclusions or interferences, to misarticulations of speech, problems in oral motor skills, or other signs of TMD. The effect of gender was also considered. The results showed that excessive overjet was the only variable which seemed to consistently increase the risk of TMD. In addition, girls seemed to be more prone to the development of TMD than boys. Although, during growth, there were both local and central factors associated occasionally with TMD development, the predictive value of those variables in the estimation of the individual risk of TMD was rather small.

The purpose of this study was to assess the tissue alterations in the temporomandibular joint (TMJ) of the New Zealand White rabbit (Oryctolagus cuniculus L.), after a unilateral occlusal interference insertion on the animal's right side back teeth. A total of 36 animals were used, thirty of which belonged to the experimental group and six to the control group. We established three experimental periods: 24 hours, three days and seven days. The control group animals were divided two by two; each pair followed the same experimental periods of the former one. The experimental group animals were submitted to the use of a 0.3 mm thick metallic cap with a visor. All animals were euthanized, and the TMJs were removed. Using a microscope for examination we observed, in all experimental periods, the presence of intra-articular hemorrhage in the supra- and infra-disk compartments as well as in the retro-disk zone. There were no inflammatory cells detected. The thickness of the condylar fibrocartilage presented significant alterations among the animals of the three experimental groups. In the left TMJs no inflammatory cells were detected. The results suggest that the insertion of a unilateral occlusal interference in rabbit back teeth does not cause any inflammatory intra-articular process within seven days; however, it does cause bilateral intra-articular hemorrhage and a larger compression of the condylar fibrocartilage in the joint opposite the side where the interference is placed. We also concluded that, in order to do research on the temporomandibular joint using animals, it is necessary have an independent (or separate) group of animals as controls.

Objective: To better understand the pathogenesis of TMD by studying microtrauma of the temporomandibular joint (TMJ), immune responses within TMJ, and psychosocial factors of the past ten years., Methods: Condyle and disc movements from 38 patients with temporomandibular disorders (TMD) were observed with the use of videotape recording and soundtape recording techniques after TMJ arthrography. Pathological changes following occlusal trauma were examined using an animal model. Immune complexes in condyle cartilage; antibody to collagen II; and cytokines such as interleukin 1, tumor necrosis factor, and interleukin 6 were detected in synovial fluid of TMD. Psychosocial characteristics were analyzed with the Minnesota Multiphasic Personality Inventory (MMPI) of 80 TMD patients and the Life Events Experience Survey (LEES) of 42 TMD patients., Results: Persistent and recurrent microtrauma did exist within joints of TMD patients, caused by occlusal trauma and occlusal interference. Occlusal trauma in animals could induce condyle and disc degenerative changes that are similar to the findings in TMJ osteoarthrosis patients. Sequestered antigens within cartilage could be exposed to the immune system after joint degeneration. Humoral and cellular immune responses did exist within TMJ and played an important role in the pathogenesis of TMD. Forty percent of TMD patients suffered from psychosomatic disorders, significantly more than in the healthy control., Conclusion: Microtrauma of TMJ, immune responses within TMJ, psychosocial factors, and anatomical structures of the TMJ itself are the four main contributing factors of TMD. Possible mechanisms of the interactions of the four factors are presented, and principles of preventing and treating TMD are also suggested.

The aim of this study was to analyze biomechanical reactions in the mandible and TMJ during clenching under various restraint conditions. A three-dimensional finite element model of the mandible, including the TMJ, was created for test purposes. The results were as follows: (1) Under any restraint conditions, displacement was greatest on the surface of the condyle and less on the articular disc and the surface of the glenoid fossa, in that order. Resultant stresses followed the same trend. (2) Displacement and stress were greatest when the lower central incisor was restrained and attenuated as the posterior teeth were restrained. Because the biomechanical reaction of the TMJ during clenching was greatest when the lower central incisor was restrained, premature contact of these teeth may be one of the factors involved in the initiation of temporomandibular arthrosis.

Tic Douloureux (Trigeminal Neuralgia) has afflicted mankind for centuries, perhaps for all time. This sharp stabbing paroxysm of pain along the branches of the trigeminal nerve is described as "...one of the most painful problems that plagues mankind." Many theories about the cause of trigeminal neuralgia have been previously presented. Often these theories build on the previous foundations when new research presents itself. The complete picture still eludes researchers today. Much of the mechanism has been proposed, but researchers lacked one essential component. There has never been an answer to why these pains only occur in cranial segments and why, thankfully, TN is rare. What sets the stage for the development of TN? The unique neurophysiology of the trigeminal nerve and the accompanying ability of the Temporomandibular Joints to create a sensitized neural system are the last piece of the puzzle. This central sensitization of the Trigeminal Nerve allows the development of a small cluster of neurons that act as a central trigger for the paroxysmal pain. The role of the TMJ in trigeminal neuralgia is illustrated by this case report.

In this study tooth contact sounds have been compared with temporomandibular joint (TMJ) sounds elicited during opening and closing movements. One hundred and eight subjects were instructed to open as far as possible and then close with sufficient force to produce a tooth contact sound. At least four cycles from each subject were recorded on tape, The first and last sounds in the recording were the tooth contact sounds, these were identified automatically. The mean duration and rise time of each tooth contact sound was calculated and their standard deviations for each subject were calculated to give a measure of the reproducibility. The number and mean amplitude of TMJ sounds occurring during tooth separation were also calculated for each cycle. Highly significant correlations were found between the number and amplitude of the TMJ sounds within a cycle and the duration and rise time, and particularly their standard deviations. Acoustic quiescence during the open-close cycle was associated with short, reproducible tooth contact sounds characterized by a short rise time. The longest and most variable tooth contact sounds were associated with TMJ sounds in all three phases of the open-close cycle. This supports previous clinical findings associating occlusal interferences with TMJ dysfunction.

In 46 non-patients and 46 patients, the authors examined the presence (+) and the absence (-) of laterotrusive (LG) and mediotrusive (MG) tooth guidance, i.e. dynamic dental articulation events in contrast to static dental occlusion events. During a right and left laterotrusion/mediotrusion of the mandible, the number of compound, mutually exclusive and exhaustive tooth guidance events (possibilities) was six. In addition, the presence and the absence of temporomandibular joint (TMJ) sounds, provoked TMJ pains, and the associations between TMJ sounds and tooth guidance events were examined. In non-patients, LG+ and MG+ was relatively infrequent (30%) while LG+ and MG- was relatively frequent (70%). In patients, LG+ and MG+ was relatively frequent (58%) while LG+ and MG- was relatively infrequent (42%). LG- and MG+ was absent in non-patients and rare in patients (3%). Either unilateral or bilateral MG+ was relatively infrequent in non-patients (30%) and relatively frequent in patients (59%). Bilateral MG+ was relatively infrequent in non-patients (20%) and relatively frequent in patients (52%). Either unilateral or bilateral TMJ sounds were relatively infrequent in non-patients (39%) and relatively frequent in patients (74%). Either unilateral or bilateral provoked TMJ pains were absent in non-patients and relatively frequent in patients (72%). The authors found no evidence that TMJ sounds were associated with the ipsilateral absence of so-called balancing contacts (MG-) in non-patients and patients. Finally, no evidence supporting the use of a so-called positive predictive value, and "extension concept' of probability theory was found.

In the typical dental office, at least one third of the patients present with indications for an occlusal appliance. Eighty percent of craniomandibular patients observed in general practice can and should be treated by the general practitioner. Unfortunately, because of time constraints in dental school curricula and prevailing controversies concerning occlusion, many dentists lack the skills and confidence necessary to provide these services. In this article, the authors use the Fourth Molar Paradigm and the Dental Joystick Paradigm to facilitate an understanding of how occlusion relates to the temporomandibular joint and craniomandibular disorders. This knowledge is necessary to correctly interpret temporomandibular radiographs, diagnose and treat craniomandibular disorders, and plan and execute any dental therapy that alters the mandibular position. In addition, in the absence of scientific research to confirm or disqualify the Occlusion Hypothesis, which states that malocclusion is a risk factor for craniomandibular disorders, the authors offer the stated paradigms to support the Occlusion Hypothesis.

This study focuses on the association between psychological factors and TMJ sounds, and the most suitable research design to establish this relation. A traditional research design is simulated to demonstrate how self-report may bias findings. A refined design is presented to obtain unbiased estimates of the role of psychological variables. In the 'naïve' design the importance of psychological variables was overestimated and the role of physiological variables was underestimated. It was concluded that future studies in the aetiology of TMJ clicking should abandon the use of self-report as a proxy for objective findings. With the refined design it was found that psychological factors play only a minor role in the prevalence of TMJ sounds. Findings do not support speculation about mechanisms that relate psychological factors to the presence of TMJ sounds.

This pilot study describes responses of Sprague Dawley rats to mandibular retrusion. Lingually overcontoured crowns were cemented onto maxillary incisors to produce 3.5 mm of autoretrusion. Monitoring data indicate that activity was suppressed and nutritional intake was reduced. Histological evaluation of the 2-, 4-, 7-, and 59-day test specimens detected only a monocytic infiltrate response in the 4-day group.

Magnetic resonance imaging (MRI) is excellent for visualizing soft tissues of the temporomandibular joint (TMJ) . Because it has no harmful effects, it can be used in asymptomatic subjects. MRI and clinical findings relating to TMJs were correlated with findings relating to occlusion in 20 medical and dental students (13 women, 7 men) who volunteered to participate in our study. Subjects with clinically evident joint signs such as clicking, crepitation or tenderness on palpation also exhibited pathologic MRI findings, especially in regards to configuration, position and function of the disk, and, often, disturbances of occlusal relationships between the upper and lower teeth.

Fifty-two consecutive male patients with a medical diagnosis of Reiter's disease (RD) and 52 individually matched controls with no known general joint disease were examined for subjective symptoms and clinical signs of craniomandibular disorders (CMD) using routine stomatognathic methods. Patients with RD had more frequent and more severe subjective symptoms than did controls (P < .05). According to Helkimo's Clinical Dysfunction Index, subjects in the RD group had more severe clinical signs than those in the control group (P < .05). The most characteristic sign or symptom of CMD in the RD group was pain in the TMJ during function.