The relationship between parafunctional masticatory activity and arthroscopically diagnosed temporomandibular joint pathology

A Comparative Study of Temporomandibular Joints in Adults with Definite Sleep Bruxism on Magnetic Resonance Imaging and Cone-Beam Computer Tomography Images

Objective: The aim was to study the imaging characteristics of the temporomandibular joint (TMJ) of definite sleep bruxers through magnetic resonance imaging (MRI) and cone-beam computer tomography (CBCT). Methods: Nineteen definite sleep bruxers diagnosed by polysomnography and twenty asymptomatic non-bruxers matched by age, gender, and education level participated in this study. After obtaining MRI and CBCT images of all TMJs of the subjects, evaluation and measurement were conducted, respectively. The analyzed parameters included disc position, disc configuration, joint effusion (JE), joint space or condyle position, and condylar bony changes. Results: Of the 38 joints in the study group, disc deformity and disc displacement of TMJs were both 57.9% when the mouth was closed, and 76.3% showed condylar bony changes, while when the mouth was open, 82% of all TMJs showed physiological biconcave discs. Comparison of joint space revealed that the anterior space was larger in the study group. There was no significant difference between the mild and the moderate to severe sleep bruxism subgroups in the changes of TMJ. Conclusion: The results demonstrated that a higher prevalence of disc deformity, disc displacement, JE, and condylar bony changes occurred in temporomandibular joints of sleep bruxers. These changes were not related to the severity of sleep bruxism.

Osteoarthritis of the temporomandibular joint: A review of aetiology and pathogenesis

The aim of this review was to assess the level of evidence for genetic, biological, and functional predictive and predisposing factors for end-stage temporomandibular joint arthritis within the published literature. A comprehensive review based upon PRISMA guidelines was performed from all literature relevant to the topic. Case series and animal studies were included given the rare nature of the disease and goal of finding root-cause predictive factors. Clinical and radiographic measures were used specifically to identify factors which may have contributed to disease onset and progression. A total of 249 abstracts were identified based on search terms of major databases. After application of exclusion and inclusion criteria, 63 full-text articles were included in the analysis of this paper. There were few factors that could be reliably used to predict end-stage temporomandibular joint disease. Limited evidence is available to adequately predict end-stage temporomandibular joint osteoarthritis. No descriptive process exists that explains how and why this process can occur in younger adults. A better understanding of the aetiology and pathogenesis of TMJ-OA may lead to prevention and more effective management strategies that may reduce the need for drastic surgical intervention, particularly in young adults.

Incobotulinum toxin type A for treatment of chronic myofascial pain

PURPOSE

This study assessed the effectiveness of incobotulinum toxin type A (IBTx) for chronic myofascial pain affecting the masseter and temporal muscles.

METHODS

Twenty two patients who received a diagnosis of chronic masseter and temporalis myofascial pain were evaluated by using a visual analog pain scale (VAS), digital pressure algometry, and the SF-36 Health Survey at baseline (T0), before IBTx injection. Patients were again evaluated at 2 months (T1) and 7 months (T2) after IBTx injection.

RESULTS

VAS scores for pain significantly differed (P = 0.029, Friedman test). Post-hoc tests showed a significant reduction in pain at 2 months (T0-T1) and 7 months (T0-T2) (P = 0.011 and P = 0.028, respectively; Wilcoxon test) but not between 2 and 7 months (P = 0.676; Wilcoxon test). There was no significant difference in pressure algometry values (P = 0.385, Friedman test). Quality of life (QOL) assessment showed a significant difference (P = 0.002, Friedman test). Post-hoc tests showed a significant improvement in QOLat 2 months, but no significant difference at 7 months (P = 0.004 and P = 0.260, Wilcoxon test).

CONCLUSION

IBTx injection resulted in safe, effective short-term pain relief for patients with chronic facial pain affecting the masseter and temporalis muscles.

Influence of bolus size and chewing side on temporomandibular joint intra-articular space during mastication

Previous studies suggested that, during mastication, magnitude and location of mechanical load in the temporomandibular joint (TMJ) might depend on chewing side and bolus size. Aim of this study was to dynamically measure the TMJ space while chewing on standardized boluses to assess the relationship among minimum intra-articular distances (MID), their location on the condylar surface, bolus size, and chewing side. Mandibular movements of 12 participants (6f, 24±1y.o.; 6 m, 28±6y.o.) were tracked optoelectronically while chewing unilaterally on rubber boluses of 15 × 15 × 5, 15 × 15 × 10, and 15 × 15 × 15 mm³ size. MID and their location along the main condylar axis were determined with dynamic stereometry. MID were normalized on the intra-articular distance in centric occlusion. Repeated measures ANOVA (α = 0.05) showed that MID were smaller on the balancing (0.74±0.19) than on the working condyle (0.89±0.16) independently of bolus size (p < 0.0001). MIDs did not differ between 5 and 10 mm bolus thicknesses (0.80±0.17) but increased for 15 mm (0.85±0.22, p = 0.024) and were located mostly laterally, close to the condylar center. This study confirmed higher reduction of TMJ space on the balancing than on the working condyle during mastication. Intra-articular distances increased significantly for the greatest bolus thickness. Loaded areas were located laterally, for both working and balancing joint.

Temporomandibular joint osteoarthritis at Chelechol ra Orrak, Palau

OBJECTIVE

To explore the frequency and severity of temporomandibular joint osteoarthritis (TMJ-OA) and its causative factors in a skeletal assemblage from the prehistoric site of Chelechol ra Orrak, Palau, western Micronesia.

MATERIALS

50 temporomandibular joint surfaces (mandibular condyles and articular eminences), representing a minimum of 22 adult individuals, 17 of which retain teeth.

METHODS

Joint surfaces were macroscopically evaluated for characteristics associated with TMJ-OA and joint morphology. Dental remains were scored for tooth wear and staining.

RESULTS

Nine individuals (40.1 %) displayed lesions typical of TMJ-OA. The strongest associations were between tooth wear and TMJ-OA.

CONCLUSIONS

Indirect effects of parafunctional dental activity appear to be a factor in TMJ-OA frequency at Chelechol ra Orrak. While betel nut chewing may be one of those activities, it does not appear to be solely driving the presence of TMJ-OA.

SIGNIFICANCE

This study highlights the association between a specific parafunctional use of the temporomandibular joint and the potential pathological consequences. It also reinforces the need to carefully evaluate the archaeological context of skeletal remains in order to evaluate specific etiological factors in the presence of TMJ-OA in present and past populations.

LIMITATIONS

Sample sizes are limited in this study. This will increase as excavations continue.

SUGGESTIONS FOR FURTHER RESEARCH

Because dental occlusion appears to be associated with TMJ-OA, focus on dental conditions affecting occlusal patterns, such as third molar agenesis, antemortem tooth loss, and malocclusion, and their relationship to TMJ-OA frequency, are recommended.

Association of malocclusion, self-reported bruxism and chewing-side preference with oral health-related quality of life in patients with temporomandibular joint osteoarthritis

OBJECTIVES

The aim of this study was to evaluate the association of oral health-related quality of life (OHRQoL) with malocclusion and self-reported bruxism and chewing-side preference (CSP) in patients with temporomandibular joint osteoarthritis (TMJ-OA).

METHODS

This study involved 511 patients diagnosed with TMJ-OA. Each participant completed the Chinese version of the 14-item Oral Health Impact Profile (OHIP-C14) questionnaire and received a clinical examination concerning malocclusion (posterior crossbite, overbite, overjet and anterior open bite). Also patients' self-reported awake bruxism (AB), sleep bruxism (SB) and CSP based on the Oral Behavior Checklist (OBC) were recorded. The associations of OHIP-C14 with malocclusion and self-reported bruxism and CSP were assessed using multiple linear regression analysis.

RESULTS

Posterior crossbite, overbite, overjet and anterior open bite were not significantly associated with either the total OHIP-C14 score or the scores of each domain of OHIP-C14. AB was significantly associated with both the total OHIP-C14 score and the scores of each domain with the largest standardised coefficients. CSP was significantly associated with both the total OHIP-C14 score and the scores of the psychological and social domains. SB was significantly associated with the scores of both the function limitation and psychological disability domains.

CONCLUSIONS

Malocclusion is not significantly associated with OHRQoL in patients with TMJ-OA. Self-reported AB is highly associated with OHRQoL in patients with TMJ-OA, while self-reported SB and CSP are both moderately associated with OHRQoL in patients with TMJ-OA.

Clinical protocol for occlusal adjustment: Rationale and application

BACKGROUND

Occlusal adjustment can optimize the result of orthodontics, orthognathic surgery, and comprehensive restoration, and resolve adverse forces to the dentition that affect the entire masticatory system. Mounted diagnostic casts and computerized occlusal analysis offer complementary advantages for evaluating occlusal problems. Predictable occlusal adjustment is facilitated by precise, measured documentation of occlusal force by computerized occlusal analysis.

CLINICAL PRESENTATION

A conservative, structural correction of a pronounced, chronic occlusal problem by additive and subtractive occlusal adjustment was performed after a previous failed occlusal adjustment. The patient's chief concerns were significant anterior teeth fremitus in maximum intercuspation and "pain in the teeth and a poor bite" after 30+ adjustments over 2.5 years.

CLINICAL RELEVANCE

Confirmation of specific criteria for a therapeutic occlusion resolved the anterior teeth fremitus and uneven bite. Traumatic occlusal contact on posterior teeth may elicit protective mandibular repositioning affecting anterior teeth relationships and should be considered during comprehensive diagnosis.

A controversy with respect to occlusion

There are very little controversies on occlusion in healthy individuals, where centric relation is regarded as the criterion for assessing the present occlusion and also for establishing a new occlusal relationship between the upper and the lower jaws. On the other hand, the occlusal position in patients with deformed condyles still remains to be clarified. In this review, the effectiveness and limits of centric relation in these patients are discussed. In addition, the muscle induced occlusal positions, such as the muscular position and the terminal positions of habitual closing movements, are suggested as a substitution for centric relation. Finally, the importance of a stable intercuspal position, where the habitual closing movements terminate without any premature tooth contact, is emphasized.

Prevalence of Bruxism in Patients with Different Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Diagnoses

The relationship between bruxism and temporomandibular disorders is complex and is not yet clearly understood. The purpose of this study was to investigate the prevalence of clinically diagnosed bruxism in 212 patients with different Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnoses, as compared with that in 77 sex- and age-matched TMD-free subjects. A significant association between bruxism and temporomandibular disorders emerged (p < 0.05). The highest prevalence of bruxism was found in patients with the following diagnoses: combined myofascial pain and disk displacement (87.5%); combined myofascial pain, disk displacement, and other joint conditions (73.3%); and myofascial pain (68.9%). In general, it is suggested that bruxism has a stronger relationship with muscle disorders than with disk displacement and joint pathologies, and that such a relationship seems to be independent from the presence of other RDC/TMD diagnoses along with myofascial pain.

WITHDRAWN: Arthroscopy for temporomandibular disorders

The Cochrane Oral Health Group withdrew this review as of Issue 12, 2015. The review is out of date and does not meet current Cochrane methodological standards. It will be superseded by a new Cochrane review on Surgical interventions for managing temporomandibular disorders.

The editorial group responsible for this previously published document have withdrawn it from publication.

Computerized occlusal analysis as an alternative occlusal indicator

BACKGROUND

All disciplines of dentistry require that clinicians assess the articulation of the teeth/prosthesis with respect to simultaneous contacts, bite force and timing.

AIMS

This article intends to describe the advantages and limitations of the data acquired when using a computerized occlusal analysis as a dynamic occlusal indicator.

METHODOLOGY

A search of the literature was completed (Medline, PubMed) using the keywords occlusion, occlusal registration, computerized occlusal analysis and T-Scan for dental.

RESULTS

According to the evidence available, the computerized occlusal analysis system is the only occlusal indicator that demonstrates the ability to provide quantifiable force and time variance in a real-time window from the initial tooth contact into maximum intercuspation.

CONCLUSION

The reported advantages to accurately indicate occlusal contacts make the computerized occlusal analysis system a better occlusal indicator when compared with other non-digital convention indicator materials available.

Psychosocial aspects of bruxism: the most paramount factor influencing teeth grinding

In clinical practice, patients suffering from an occlusal parafunctional activity have increased. It can be observed that a negative influence of environment aggravates patient's health. The aim of this paper is to present the impact of environment and development of human civilization on the prevalence of bruxism and the correlation between them. The authors grasp the most relevant aspects of psychological and anthropological factors changing over time as well as their interactions and describe a relationship between chronic stress and bruxism. Current literature shows how contemporary lifestyle, working environment, diet, and habits influence the patient's psychoemotional situation and the way these factors affect the occluso-muscle condition.

A study of the temporomandibular joint during bruxism

A finite element model of the temporomandibular joint (TMJ) and the human mandible was fabricated to study the effect of abnormal loading, such as awake and asleep bruxism, on the articular disc. A quasilinear viscoelastic model was used to simulate the behaviour of the disc. The viscoelastic nature of this tissue is shown to be an important factor when sustained (awake bruxism) or cyclic loading (sleep bruxism) is simulated. From the comparison of the two types of bruxism, it was seen that sustained clenching is the most detrimental activity for the TMJ disc, producing an overload that could lead to severe damage of this tissue.

Psychophysiological Definitions of Clenching

This study tested the hypothesis that individuals show considerable variability in EMG activity produced by the masticatory muscles when they are instructed to clench than when they are instructed to make minimal or maximal contact. Twenty individuals without temporomandibular disorder (TMD) pain participated in a biofeedback-training task to establish a relaxed baseline. They were instructed to clench their teeth according to their personal definition of the term, while EMG data were collected. This process was repeated two more times, followed by similar instructions to make minimal and maximal contact between the teeth. Results showed that individual subjects were very consistent in their behavioral definition of clenching and that the subjects taken as a whole showed markedly greater variability. The precise behavioral meaning of clenching varies across individuals. The failure to account for these individual differences may explain in part reported discrepancies on the role of parafunctions in TMD.

Oral tori are associated with local mechanical and systemic factors: a case-control study

PURPOSE

To estimate if various dental factors, medications, and medical conditions are associated with an increased risk for the presence of oral tori.

MATERIALS AND METHODS

Using a case-control study design, the investigators identified and adjudicated a sample of cases with torus palatinus (TP) and/or torus mandibularis (TM) during a 1.5-year period. The medical records were abstracted and data on dental factors, temporomandibular dysfunction (TMD), medications, and medical conditions were recorded. Risk estimates were calculated as adjusted odds ratios (AORs) with 95% confidence intervals (CIs) using conditional logistic regression analyses, and the P value was set at .05.

RESULTS

The sample was composed of 66 subjects with TM, 34 subjects with TP, and 100 control subjects from the same database. Any form of oral torus (TP and/or TM) was associated significantly with TMD (AOR, 10.51; 95% CI, 4.46 to 24.78; P<.01) and tooth attrition (AOR, 5.22; 95% CI, 2.32 to 11.77; P<.01). TP was associated significantly with TMD (AOR, 4.14; 95% CI, 1.21 to 14.21; P<.05), tooth attrition (AOR, 38.18; 95% CI, 7.20 to 202.41; P<.01), and treated hypertension (AOR, 6.64; 95% CI, 1.31 to 33.57; P<.05). TM was associated significantly with TMD (AOR, 5.77; 95% CI, 2.38 to 13.98; P<.01), tooth attrition (AOR, 6.69; 95% CI, 2.78 to 16.14; P<.01), and a penicillin allergy (AOR, 4.45; 95% CI, 1.05 to 18.83; P<.05).

CONCLUSIONS

This study provides clinical evidence showing significant associations between oral tori and various dental factors, medications, and medical conditions. These findings add to the list of environmental factors believed to contribute to the formation of oral tori.

Arthroscopy for temporomandibular disorders

BACKGROUND

Temporomandibular disorders (TMDs) are considered a collection of disorders involving many organic, psychological and psychosocial factors. They can involve the masticatory muscles or the temporomandibular joint (TMJ) and associated structures, or both. It is estimated that 40% to 75% of the population displays at least one sign of the disease and 33% of the population reports at least one symptom. Arthroscopy has been used to reduce signs and symptoms of patients with TMD but the effectiveness has still not been totally explained.

OBJECTIVES

To assess the effectiveness of arthroscopy for the management of signs and symptoms in patients with TMDs.

SEARCH STRATEGY

The Cochrane Oral Health Group Trials Register (to 23 December 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2010), MEDLINE via OVID (1950 to 23 December 2010), EMBASE via OVID (1980 to 23 December 2010), LILACS via BIREME Virtual Health Library (1982 to 23 December 2010), Allied and Complementary Medicine Database (AMED) via OVID (1985 to 23 December 2010), CINAHL via EBSCO (1980 to 23 December 2010). There were no restrictions regarding the language or date of publication.

SELECTION CRITERIA

Randomized controlled clinical trials of arthroscopy for treating TMDs were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, and three review authors independently assessed the risk of bias of included trials. The authors of the selected articles were contacted for additional information.

MAIN RESULTS

Seven randomized controlled trials (n = 349) met the inclusion criteria. All studies were either at high or unclear risk of bias. The outcome pain was evaluated after 6 months in two studies. No statistically significant differences were found between the arthroscopy versus nonsurgical groups (standardized mean difference (SMD) = 0.004; 95% confidence interval (CI) -0.46 to 0.55, P = 0.81). Two studies, analyzed pain 12 months after surgery (arthroscopy and arthrocentesis) in 81 patients. No statistically significant differences were found (mean difference (MD) = 0.10; 95% CI -1.46 to 1.66, P = 0.90). Three studies analyzed the same outcome in patients who had been submitted to arthroscopic surgery or to open surgery and a statistically significant difference was found after 12 months (SMD = 0.45; 95% CI 0.01 to 0.89, P = 0.05) in favor of open surgery. The two studies compared the maximum interincisal opening in six different clinical outcomes (interincisal opening over 35 mm; maximum protrusion over 5 mm; click; crepitation; tenderness on palpation in the TMJ and the jaw muscles 12 months after arthroscopy and open surgery). The outcome measures did not present statistically significant differences (odds ratio (OR) = 1.00; 95% CI 0.45 to 2.21, P = 1.00). Two studies compared the maximum interincisal opening after 12 months of postsurgical follow-up. A statistically significant difference in favor of the arthroscopy group was observed (MD = 5.28; 95% CI 3.46 to 7.10, P < 0.0001). The two studies compared the mandibular function after 12 months of follow-up with 40 patients evaluated. The outcome measure was mandibular functionality (MFIQ). This difference was not statistically significant (MD = 1.58; 95% CI -0.78 to 3.94, P = 0.19).  

AUTHORS' CONCLUSIONS

Both arthroscopy and nonsurgical treatments reduced pain after 6 months. When compared with arthroscopy, open surgery was more effective at reducing pain after 12 months. Nevertheless, there were no differences in mandibular functionality or in other outcomes in clinical evaluations. Arthroscopy led to greater improvement in maximum interincisal opening after 12 months than arthrocentesis; however, there was no difference in pain.

Stress analysis in the mandibular condyle during prolonged clenching: a theoretical approach with the finite element method

Parafunctional habits, such as bruxism and prolonged clenching, have been associated with functional overloading in the temporomandibular joint (TMJ), which may result in internal derangement and osteoarthrosis of the TMJ. In this study, the distributions of stress on the mandibular condylar surface during prolonged clenching were examined with TMJ mathematical models. Finite element models were developed on the basis of magnetic resonance images from two subjects with or without anterior disc displacement of the TMJ. Masticatory muscle forces were used as a loading condition for stress analysis during a 10 min clenching. In the asymptomatic model, the stress values in the anterior area (0.100 MPa) and lateral area (0.074 MPa) were relatively high among the five areas at 10 min. In the middle and posterior areas, stress relaxation occurred during the first 2 min. In contrast, the stress value in the lateral area was markedly lower (0.020 MPa) than in other areas in the symptomatic model at 10 min. The largest stress (0.050 MPa) was located in the posterior area. All except the anterior area revealed an increase in stress during the first 2 min. The present result indicates that the displacement of the disc could affect the stress distribution on the condylar articular surface during prolonged clenching, especially in the posterior area, probably leading to the cartilage breakdown on the condylar articular surface.

Assessment of bruxism in the clinic

Bruxism is a much-discussed clinical issue in dentistry. Although bruxism is not a life-threatening disorder, it can influence the quality of human life, especially through dental problems, such as tooth wear, frequent fractures of dental restorations and pain in the oro-facial region. Therefore, various clinical methods have been devised to assess bruxism over the last 70 years. This paper reviews the assessment of bruxism, provides information on various assessment methods which are available in clinical situations and discusses their effectiveness and usefulness. Currently, there is no definitive method for assessing bruxism clinically that has reasonable diagnostic and technical validity, affects therapeutic decisions and is cost effective. One future direction is to refine questionnaire items and clinical examination because they are the easiest to apply in everyday practice. Another possible direction is to establish a method that can measure actual bruxism activity directly using a device that can be applied to patients routinely. More clinical studies should examine the clinical impact of bruxism on oral structures, treatment success and the factors influencing the decision-making process in dental treatment.

Masseter muscular weakness affects temporomandibular synovitis induced by jaw opening in growing rats

OBJECTIVE

To evaluate the influence of impaired masseter function during growth on the development of temporomandibular synovitis.

MATERIALS AND METHODS

Sixteen 3-week-old male Wistar rats were classified into four groups. The first group served as control; and in the second group, jaw opening was forced for 3 hours when the rats were 9 weeks old. In the third and fourth groups, the masseter muscles were bilaterally resected at 3 weeks of age, and the rats in the fourth group were additionally forced to open their jaw at 9 weeks of age. All rats were sacrificed at 9 weeks. Temporomandibular joint (TMJ) tissue samples were processed for histology, and evaluated for cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions by immunohistochemistry to examine the inflammatory changes in the synovial membrane.

RESULTS

The control group showed noninflammatory changes. In the jaw-opening group, vascular dilation and weak COX-2 immunoreactivity were induced by jaw opening in the synovium. In the masseter-resection group, the masseter-resected rats exhibited moderate synovial changes while in the resection with opening group, the masseter-resected rats revealed more significant inflammatory changes including synovial hyperplasia, dilated vasculature, fibrin deposits, and intense immunoreactivity for COX-2 and iNOS, all caused by jaw opening.

CONCLUSIONS

These results suggest that masseter activity in the growth period is an important factor in the induction of temporomandibular synovitis.

Effect of Hyperactivity of the Lateral Pterygoid Muscle on the Temporomandibular Joint Disk

In this study, the effect of hyperactivity of the lateral pterygoid muscle (LPM) on the temporomandibular joint (TMJ) disk during prolonged clenching was examined with a mathematical model. Finite element models of the TMJ were constructed based on magnetic resonance images from two subjects with or without internal derangement of the TMJ. For each model, muscle forces were used as a loading condition for stress analysis for 10 min clenching. Furthermore, an intermittent increase of the LPM force with intervals of 1 min was applied. In the asymptomatic model, large stresses were found in the central and lateral part of the disk at the onset of clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 min of clenching. When the force of the LPM increased temporarily, the disk moved anteriorly and returned to its original position afterward. In the symptomatic model, large stresses were observed in both the posterior region of the disk and the retrodiscal tissue throughout clenching. Upon temporary increase of the LPM force, the disk was elongated anteriorly, which appeared to be irreversible. These results indicate that hyperactivity of the LPM may be involved in the progression of disk displacement.

Plain Film Arthrography Applied to the Diagnosis of Intra-Articular Adhesions of the Temporomandibular Joint

PURPOSE

To evaluate the diagnostic accuracy of plain film arthrography (PFA) on the presence of intra-articular adhesions of the temporomandibular joint (TMJ).

PATIENTS AND METHODS

The study population included 105 consecutive patients (105 TMJs) and data collected in our department. All patients were examined by PFA and arthroscopy. The findings of interpreting PFA were recorded as positive, suspicious, or negative according to the PFA radiographic criteria. After comparing the findings of PFA with those of arthroscopy, the comparison data were assessed by generating receiver operating characteristic curve (ROC curve) and analyzing the area (A(z)) under the curves with SPSS 11.0 (SPSS, Inc, Chicago, IL), and the area under the ROC curve was calculated. According to the area, the diagnostic value of PFA was evaluated. Meanwhile, the causes of misdiagnosis and underdiagnosis of intra-articular adhesions were analyzed.

RESULTS

Arthroscopic surgery results confirmed that 56 TMJs in 105 patients had adhesions. The area under ROC curve was 0.73 (confidence interval, 0.64, 0.82; P < .05). The adhesions located in the medial groove could hardly be detected through PFA, while those located in the lateral two thirds of upper joint compartment could easily be detected.

CONCLUSION

Although the diagnostic accuracy of PFA was fair, it was a simple and effective modality to diagnose intra-articular adhesions of the TMJ. The causes of misdiagnosis and underdiagnosis were related to the size and location of the intra-articular adhesions.

Dental attrition models predicting temporomandibular joint disease or masticatory muscle pain versus asymptomatic controls

AIMS

To determine whether patients with temporomandibular joint disease or masticatory muscle pain can be usefully differentiated from asymptomatic controls using multifactorial classification tree models of attrition severity and/or rates.

METHODS

Measures of attrition severity and rates in patients diagnosed with disc displacement (n = 52), osteoarthrosis (n = 74), or masticatory muscle pain only (n = 43) were compared against those in asymptomatic controls (n = 132). Cross-validated classification tree models were tested for fit with sensitivity, specificity, accuracy and log likelihood accountability.

RESULTS

The model for identifying asymptomatic controls only required the three measures of attrition severity (anterior, mediotrusive and laterotrusive posterior) to be differentiated from the patients with a 74.2 +/- 3.8% cross-validation accuracy. This compared with cross-validation accuracies of 69.7 +/- 3.7% for differentiating disc displacement using anterior and laterotrusive attrition severity, 68.7 +/- 3.9% for differentiating disc displacement using anterior and laterotrusive attrition rates, 70.9 +/- 3.3% for differentiating osteoarthrosis using anterior attrition severity and rates, 94.6 +/- 2.1% for differentiating myofascial pain using mediotrusive and laterotrusive attrition severity, and 92.0 +/- 2.1% for differentiating myofascial pain using mediotrusive and anterior attrition rates. The myofascial pain models exceeded the > or =75% sensitivity and > or =90% specificity thresholds recommended for diagnostic tests, and the asymptomatic control model approached these thresholds.

CONCLUSION

Multifactorial models using attrition severity and rates may differentiate masticatory muscle pain patients from asymptomatic controls, and have some predictive value for differentiating intracapsular temporomandibular disorder patients as well.

Three-dimensional finite-element model of the human temporomandibular joint disc during prolonged clenching

In the temporomandibular joint (TMJ), overloading induced by prolonged clenching appears to be important in the cascade of events leading to disc displacement. In this study, the effect of disc displacement on joint stresses during prolonged clenching was studied. For this purpose, finite-element models of the TMJ, with and without disc displacement, were used. Muscle forces were used as a loading condition for stress analysis during a time-period of 10 min. The TMJ disc and connective tissue were characterized as a linear viscoelastic material. In the asymptomatic model, large stresses were found in the central and lateral part of the disc through clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 min of clenching. In the symptomatic model, large stresses were observed in the posterior part of the disc and in the retrodiscal tissue, and the stress level was kept constant through clenching. This indicates that during prolonged clenching the disc functions well in the asymptomatic joint, meanwhile the retrodiscal tissue in the symptomatic joint is subject to excessive stress. As this structure is less suitable for bearing large stresses, tissue damage may occur. In addition, storage of excessive strain energy might lead to breakage of the tissue.

The Relationship Between Temporomandibular Joint Synovitis and Adhesions: Pathogenic Mechanisms and Clinical Implications for Surgical Management

PURPOSE

The purpose of this investigation was to determine the relationship between arthroscopically diagnosed synovitis and adhesions in a population of patients with significant limitation of mandibular opening and temporomandibular joint pain.

PATIENTS AND METHODS

Temporomandibular joint arthroscopy was performed on 126 joints in 80 patients (female:male = 5.7:1; mean age = 35.5 years; mean duration of symptoms = 50 months). All patients were diagnosed with severe temporomandibular joint disease recalcitrant to conservative therapy. Each joint was evaluated arthroscopically for the presence of synovitis and adhesions. Chi-squared analysis was performed to determine if there was a significant relationship between the presence of synovitis and adhesions.

RESULTS

Diagnostic arthroscopic examination showed the following: no synovitis and no adhesions in 18/126 joints (14%), no synovitis with adhesions present in 33/126 joints (26%), synovitis with no adhesions in 13/126 joints (10%), and synovitis and adhesions present in 62/126 joints (49%). Statistical analysis showed a significant relationship between arthroscopically diagnosed synovitis and adhesions.

CONCLUSION

Synovitis and adhesions are commonly present in the temporomandibular joints of patients requiring arthroscopic surgery due to painful limitation of mandibular movement. Excessive mechanical stress on the temporomandibular joint leads to maladaptive responses in the articular and synovial tissues, ultimately leading to synovitis, osteoarthritis and the formation of adhesions. An understanding of the pathogenic mechanisms that lead to synovitis, osteoarthritis and adhesions has important clinical implications for the nonsurgical as well as surgical management of patients suffering from these disorders.

Influence of arthroscopically observed fibrous adhesions before and after joint irrigation on clinical outcome in patients with chronic closed lock of the temporomandibular joint

The aim of this study was to investigate the changes in the state of arthroscopically observed fibrous adhesions (FA) after visually guided irrigation (VGIR) and the influence of FA on clinical outcome in patients with chronic closed lock of the temporomandibular joint (TMJ). Forty-eight TMJs of 48 patients with unilateral chronic closed lock were enrolled in this study. All 48 joints underwent VGIR twice. After the first VGIR (immediately before the second VGIR), clinical outcome was assessed as regards maximal interincisal opening (MIO) and self-evaluated TMJ pain (VAS). Thirty patients were symptom-free (good outcome group) and the remaining 18 patients had symptoms (poor outcome group). In each group, the changes of the MIO, VAS and severity of FA (FA score) after the first VGIR were studied. The influence of FA score in the first and second VGIR on clinical outcome was analyzed by logistic regression analysis. There was no joint with disappearance or reduction of FA after the first VGIR. In both groups, MIO and VAS were significantly improved after the first VGIR even though the state of FA became significantly worse. The multivariate logistic regression analysis showed that the risk of poor outcome for FA scores in the first and second VGIR were 0.89-times (95% CI: 0.33-2.40, P=0.82) and 1.76-times (95% CI: 0.54-5.73, P=0.35), respectively. The dose-response relationships between FA scores in the first or second VGIR were not significant. In conclusion, our results indicate that the presence of FA or a postoperative worsening of FA (including postoperative new FA formation) seems not to affect the clinical outcome as regards MIO and VAS in patients with chronic closed lock of the TMJ.

Observation of three cases of temporomandibular joint osteoarthritis and mandibular morphology during adolescence using helical CT

Temporomandibular joint (TMJ) osteoarthritis (OA) is a potential cause of craniofacial deformity. If TMJ OA appears during orthodontic treatment, the mandible usually rotates posteriorly, resulting in an unsatisfactory profile, especially in patients with pre-treatment mandibular retrusion. Although it is important to confirm the kind of TMJ pathosis at the start of orthodontic treatment, the relationship between TMJ OA, condylar remodelling and changes in craniofacial morphology remains unclear because of a lack of longitudinal studies. Elucidating this relationship might allow better prediction of post-treatment craniofacial morphology. In the present case reports, helical computed tomography and cephalometry were used to analyse relationships between the pattern and location of condylar remodelling and the changes in craniofacial morphology in three patients with TMJ OA.

Magnetic resonance evaluation of the disk before and after arthroscopic surgery for temporomandibular joint disorders

OBJECTIVE

The purposes of this study were (1) to assess functional and pain outcomes after arthroscopic surgery on patients with temporomandibular joint disorders (TMD); (2) to evaluate postsurgical changes in disk position, mobility, and morphology on magnetic resonance imaging (MRI); and (3) to measure the association between changes in disk position, mobility, and morphology on MRI and clinical outcomes.

STUDY DESIGN

A retrospective analysis was conducted of temporomandibular joints with internal derangement and osteoarthritis that were refractory to nonsurgical treatments and underwent arthroscopic surgery and on which MRI was performed within 1 month after the initial visit and 1 year after arthroscopic surgery. Clinical findings were assessed on the basis of mandibular range of motion and joint pain level on a visual analog scale at the initial visit and 1 year after arthroscopic surgery. The disk position, mobility, and morphology on MRI were compared with clinical findings and were statistically analyzed before and after arthroscopic surgery. The treatment outcome was judged according to our success criteria. The associations between changes in disk position, mobility, and morphology and clinical outcomes after arthroscopic surgery were statistically analyzed.

RESULTS

Forty-three joints of 43 patients who underwent arthroscopic surgery were assessed in this study. After arthroscopic surgery, mandibular range of motion and visual analog scale results improved statistically. According to the criteria for clinical resolution, 32 surgeries were successful and 11 were unsuccessful. Preoperative and postoperative MRI showed that most joints had anterior disk displacement (ADD) without reduction. Postoperative MRI revealed that, statistically, the number of mobile disks had increased and deformity of the disks had progressed. In the successful group, postoperative MRI revealed that all joints had mobile disks. In both groups, most joints had ADD without reduction before and after arthroscopic surgery, and, statistically, deformity of the disks progressed after arthroscopic surgery.

CONCLUSIONS

Arthroscopic surgery was an effective treatment for TMD refractory to nonsurgical treatments. This study provides important information of clinical significance. Disk position remained ADD without reduction, disk mobility increased, and deformity of the disks progressed after arthroscopic surgery.

Morphologic changes in the unloaded temporomandibular joint after mandibulectomy

PURPOSE

The aim of this study was to examine intra-articular conditions in unloaded temporomandibular joints (TMJs) after mandibulectomy including the condyle or segmental mandibulectomy.

PATIENTS AND METHODS

Seventeen joints were defined as unloaded TMJs. Eleven of the 17 joints were classified into the "without condyle" (WOC) group in which TMJs had the condyle removed but the disc and superior joint compartment were preserved, and remaining 6 joints were classified into the "with condyle" (WC) group in which TMJs were connected to the condylar process. Disc configuration, bony changes, and joint effusion were examined by magnetic resonance imaging. In 8 of the 17 joints, arthroscopic examination of the superior joint compartment was performed. Correlation between data of the WOC and WC groups was evaluated. The relationship between arthroscopic findings and joint effusion was also analyzed.

RESULTS

Deformed discs were observed in 7 of the 11 joints (63.6%) of the WOC group but were not observed in the WC group, in which there was a normal relationship between the disc and condyle. Bony changes were not detected in any joints. Joint effusion and arthroscopically diagnosed fibrous adhesion were observed in nearly all joints of both groups.

CONCLUSIONS

We conclude that alteration of the relationship between the disc and condyle is more important for the initiation of disc deformation than loading conditions on the disc. The present findings suggest that, in the unloaded TMJs, articular degeneration is induced by disturbance of synovial fluid metabolism but that bony conditions are not affected.

Reliability of clinician judgements of bruxism

Bruxism is considered to be a parafunctional disorder requiring treatment and is viewed as a risk factor for the development of temporomandibular disorders (TMDs). The purpose of this investigation is to examine the reliability of clinician judgements of bruxism severity. Twenty dentists who are faculty members in a dental school examined 29 stone casts and gold-plated models of individual teeth for evidence of bruxism. Ordinal ratings of bruxism severity for the 29 augmented models were made on two occasions, approximately 3 months apart. Inter-rater reliability among all clinicians, evaluated using intraclass correlation coefficients (ICCs), was poor at both time one and time two (i.e. ICC = 0.33 and 0.32, respectively), with somewhat better reliability found among those clinicians with above-average time elapsed since completion of dental training (i.e. ICC = 0.48 and 0.50 for time 1 and time 2, respectively). Three-month test-retest reliabilities were fair (ICC = 0.46) for the full group of raters and were unrelated to clinicians' degree of confidence in their ratings. These results indicate a need to standardize methods for clinical assessment of bruxism. Additionally, they have implications for studies using clinical assessments of bruxism to test the association between bruxism and other conditions such as TMDs.

Is bruxism severity a predictor of oral splint efficacy in patients with myofascial face pain?

Both the efficacy and mechanism of any effect of oral splint therapy for patients with temporomandibular disorders (TMDs) are a matter of controversy. To address these issues, this study tested the hypothesis that oral splints produce the most marked pain relief for those TMD patients with myofascial face pain (MFP) who also brux (i.e. grind or clench) more than other MFP patients. In a 6-week randomized controlled clinical trial, 52 women with MFP were randomly assigned to receive either a full-coverage hard acrylic splint or a palatal-only splint. Bruxism was assessed both by self-report and by an objective assessment of molar microwear changes over a 2-week period prior to the start of the trial. Tested across multiple outcome measures, results indicated that those receiving the full-coverage splint had marginally better improvement on some pain-related measures than those receiving the palatal splint, but severity of bruxism did not moderate the therapeutic effect of the full-coverage splint. These findings strongly argue against the belief that oral splints reduce MFP by reducing bruxism and raise questions about the importance of bruxism in the maintenance of MFP.

Adhesions in the temporomandibular joint: formation and significance

BACKGROUND

Adhesions are frequently seen in the deranged temporomandibular joint (TMJ). In the early stage of the degenerative process the adhesion does not seem to be a significant factor in reduced mandibular movement. This is reversed in advanced degenerative joint disease where the adhesion requires release to achieve a satisfactory clinical result. Correlation of clinical history and findings within the joint should increase understanding of limited jaw movement.

METHODS

Arthroscopic examination of deranged TMJs was performed on 75 patients with limited jaw opening and correlated with the history of the derangement.

RESULTS

A progressive maturation of adhesion formation was observed with longer standing symptoms. A different adhesion pattern was noted with derangement caused by direct trauma on the joint.

CONCLUSIONS

Internal derangement of the TMJ is associated with formation of intra-articular adhesions. These are unlikely to be associated with reduced condyle movement in the early phase of the derangement. Later stage adhesions are more substantial and require release to achieve a satisfactory clinical outcome.

Expression of 25 kDa heat shock protein by synovial type B cells of the mouse temporomandibular joint

Earlier studies have demonstrated immunoreactivity for heat shock protein 25 (Hsp25) in type B synovial lining cells of the rat temporomandibular joint, and also the presence of characteristic cytoplasmic processes in these cells, but it is unclear whether or not the type B cells in other animals possess such elaborate cytoplasmic projections and as there is as yet no evidence for the synthesis of this protein by these cells. For these reasons, the expression of Hsp25 was investigated in the synovial membrane of the mouse temporomandibular joint by immunocytochemistry and by in situ hybridization using a specific cRNA probe. Intense immunoreaction for Hsp25 was found in the cytoplasm of certain synovial lining cells that were identified as type B by immunoelectron-microscopy. These Hsp25-positive cells had slender cytoplasmic processes, either projecting towards or covering the synovial surface. Morphological differences between cytoplasmic processes seemed to depend on the location of the type B cell bodies. In situ hybridization showed intense signals for Hsp25 mRNA in the synovial lining cells, suggesting that the type B cells produce, rather than resorb, Hsp25. These findings indicate that Hsp25 is a useful marker for the identification of the synovial type B cells in the temporomandibular joint. It is further hypothesized that Hsp25 in type B cells is involved in maintaining their specific profile and epithelial-like arrangement, and in protecting against mechanical stress.

Disc mobility and arthroscopic condition of the temporomandibular joint associated with long-term mandibular discontinuity

PURPOSE

The present study aimed to explore disc mobility and arthroscopically diagnosed morphologic changes in the temporomandibular joint (TMJ) associated with long-term mandibular discontinuity.

PATIENTS AND METHODS

Twelve patients (24 TMJs) who had undergone mandibulectomy including the unilateral condyle or segmental mandibulectomy without mandibular reconstruction, more than 8 months before this study were examined. The 24 TMJs were classified into 3 groups as follows: group 1, TMJs with a major mandibular fragment including the mandibular body (n = 11); group 2, TMJs with a mandibular ramus including the coronoid process (n = 5); and group 3, TMJs with only a condylar process, a mandibular ramus not including the coronoid process, or without a condyle (n = 8). Disc mobility was evaluated by magnetic resonance imaging, and arthroscopic observation of the superior joint compartment (SJC) was performed in all TMJs. The relationship between disc mobility and the arthroscopic findings was also studied.

RESULTS

The frequency of immobile discs differed significantly among groups 1 (0%), 2 (40.0%), and 3 (100%). Arthroscopic findings were normal in all SJCs of group 1. Various types of fibrous adhesions were observed in 40.0% of group 2 and in 75.0% of group 3. The development of fibrous adhesions in the SJC was significantly related to the presence of an immobile disc.

CONCLUSIONS

Long-term immobilization of the TMJ in a nonfunctional state seems to promote the development of fibrous adhesions in the SJC. Preservation of the mandibular fragment including the coronoid process, during mandibulectomy appears to contribute to postoperative TMJ mobility. To ensure recovery of a physiologic TMJ after mandibulectomy, it seems important to re-establish TMJ mobility by establishing mandibular continuity as soon as possible.

Condylar bony change and self-reported parafunctional habits in prospective orthognathic surgery patients with temporomandibular disorders

OBJECTIVE

The purpose of this study was to investigate the relationship between self-reported parafunctional habits and condylar bony change and disk displacement in orthognathic surgery patients with signs and symptoms of temporomandibular joint disorders.

STUDY DESIGN

This is a cross-sectional retrospective study of pretreatment helical computed tomography scans and questionnaires of 94 female orthognathic surgery patients.

RESULTS

Condylar bony change, unilaterally or bilaterally, was found in 56.4% of the subjects, or 43.6% of the joints. Disk displacement, unilaterally or bilaterally, was seen in 59.6% of the subjects, or 45.7% of the joints. Bruxism and clenching was significantly associated with condylar bony change and disk displacement. Subjects with 3 or more parafunctional habits showed a significantly higher rate of bilateral condylar bony change.

CONCLUSION

Our results suggest that bruxism and clenching might be related to deterioration of the temporomandibular joint and that the greater the number of parafunctional habits a subject has, the higher the risk of condylar bony change.

Different effects of nocturnal parafunction on the masticatory system: the Weak Link Theory

It is proposed that damage to the masticatory system from intense parafunction can be assessed more accurately by the Weak Link Theory. The theory predicts that the more intense and the more prolonged the forces, the more the tendency of damage to either. 1. the periodontal tissue; 2. the teeth; or 3. the orofacial structures. To test the theory, 22 subjects were selected based on reports of nocturnal bruxism. Each was assessed for masticatory system breakdown on the Russell Periodontal Index, the Helkimo Dysfunction Index, and a Tooth Wear Index. A Bruxcore (Forgione, A. 1974 J Dent Res 53:127) was used to obtain an objective score of bruxism. Five of eleven subjects with mild bruxism scored high on only one index. Significantly more subjects (ten of eleven) with moderate to severe bruxism scored high on one index only.