Three-dimensional finite element analysis of cartilaginous tissues in human temporomandibular joint during prolonged clenching

Objective

Bruxism, the parafunctional habit of nocturnal grinding of the teeth and clenching, is associated with the onset of joint degeneration. Especially prolonged clenching is suggested to cause functional overloading in the temporomandibular joint (TMJ). In this study, the distributions of stresses in the cartilaginous TMJ disc and articular cartilage, were analysed during prolonged clenching. The purpose of this study was to examine if joint degradation due to prolonged clenching can be attributed to changes in stress concentration in the cartilaginous tissues.

Design

Finite element model was developed on the basis of magnetic resonance images from a healthy volunteer. Condylar movements recorded during prolonged clenching were used as the loading condition for stress analysis.

Results

At the onset of clenching (time = 0 s), the highest von Mises stresses were located in the middle and posterior areas (6.18 MPa) of the inferior disc surface facing the condylar cartilage. The largest magnitude of the minimum principal stress (−6.72 MPa) was found in the condylar cartilage. The stress concentrations were relieved towards the superior disc surface facing the temporal cartilage. On the surfaces of the temporal cartilage, relatively lower stresses were found. After 5-min clenching, both stress values induced in the TMJ components were reduced to 50-80% of the stress values at the onset of clenching, although the concomitant strains increased slightly during this period.

Conclusions

It is suggested that both the condylar and temporal cartilage layers along with the TMJ disc, play an important role in stress distribution and transmission during prolonged clenching due to tissue expansion. Furthermore, our study suggests that a development of stress concentrations in the TMJ during prolonged clenching and risk factors for the initiation of TMJ degeneration could not be confirmed.     

2种咬合板治疗颞下颌关节紊乱病的临床疗效分析

目的：研究松弛型咬合板和稳定型咬合板治疗颞下颌关节紊乱病(TMD)的疗效。方法：选择以口颌面部疼痛为主诉的TMD患者68例(急性30例,慢性38例),每组分别戴用松弛型咬合板和稳定型咬合板,比较分析治疗前、后颞肌前束(TA)、咬肌(MM)肌电值及关节疼痛强度的变化。采用SPSS 11.0 软件包对数据进行方差分析和t检验。结果：①静息状态下,2种咬合板治疗后,患者双侧TA及MM肌电电位均较治疗前显著下降(P<0.05)。②紧咬状态下,松弛型咬合板治疗的急性组患者双侧TA及MM肌电电位均较治疗前显著上升,而慢性组患者仅双侧MM肌电电位较治疗前显著上升(P<0.05);稳定型咬合板治疗组患者双侧TA肌电电位治疗前后无显著差异,仅双侧MM肌电电位较治疗前显著上升。③2种咬合板治疗后,患者疼痛指数均较治疗前显著下降;但松弛型咬合板治疗后,在功能状态下,急性组患者疼痛缓解的程度更显著。结论：松弛型和稳定型咬合板均对咀嚼肌有松弛作用,能缓解TMD疼痛,但松弛型咬合板治疗急性TMD患者的疗效更加显著。     

Research diagnostic criteria for temporomandibular disorders (RDC/TMD) axis I diagnoses in an Italian patient population

The aim of this work was twofold: to evaluate the prevalence of different Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnosis in an Italian population of subjects seeking TMD treatment in a tertiary clinic; and to compare data with those from similar studies in the literature. Participants in this study were 433 consecutive patients seeking TMD treatment at the Section of Prosthetic Dentistry, Department of Neuroscience, University of Pisa, Italy; mean age of patients was 38.8 years, with a female:male ratio of 2.6:1 (276 females, 73.2%; 101 males, 26.8%). RDC/TMD guidelines for examination were adopted to assign axis I diagnosis. The prevalence of RDC/TMD diagnoses was 38.2% (144/377) for group I disorders (muscle disorders), 52.3% (197/377) for group II disorders (disc displacements), and 52.6% (198/377) for group III disorders (arthralgia, osteoarthritis, osteoarthrosis). The present investigation provided findings that, compared and integrated with literature data, can be useful to create a world-wide database, in accordance with the nature of the RDC/TMD classification system.     

TMD in class III patients referred for orthognathic surgery: Psychological and dentition-related aspects

ObjectiveTo investigate temporomandibular disorders (TMD), psychosocial, and occlusal variables in class III orthognathic surgery patients with respect to the control subjects, and to compare psychosocial and occlusal features in class III patients with different Research Diagnostic Criteria for TMD (RDC/TMD) diagnoses.Materials and methodsThe study enrolled 44 class III patients referred for orthognathic surgery and 44 individuals without a malocclusion. TMD, depression and somatization were assessed by RDC/TMD. Occlusal analysis included Helkimo's Occlusal Index items, overjet and overbite.ResultsIn the controls, patients with class III deformities had higher prevalence of myogenic TMD, increased grade of chronic pain, and more occlusal deviations. Within the study group, TMD patients reported higher depression score (P < 0.01), myofascial pain was related to higher depression and somatization grades (P < 0.01, P < 0.05 respectively), and disc displacement showed relation with RCP-ICP slide interferences (P < 0.05).ConclusionWith respect to subjects without a malocclusion, TMD in class III dentofacial deformities is similar in prevalence, but differs in clinical appearance. Occlusal, but not psychosocial features deviate from those in the controls. While psychosocial variables accompanied TMD and myofascial pain, increased RCP-ICP slide was related to disc displacement in class III patients.     

下颌第三磨牙近中阻生患者垂直向咬合状况与TMD的关系探讨

目的 探讨下颌第三磨牙近中阻生患者垂直向咬合情况与颞下颌关节紊乱病( temporomandibular joint disorders,TMD)的关系. 方法 选取37例下颌第三磨牙近中阻生患者纳入观察组,另选20例非下颌第三磨牙近中阻生的口腔疾病患者纳入对照组,评估其垂直向、颊舌向、近远中向咬合状况,运用AutoCAD软件进行下颌牙列Spee曲线测量. 结果 观察组 TMD患病率(51. 4%)显著高于对照组(15. 0%),差异具有统计学意义(χ2 =7. 24,P=0. 007);观察组垂直向咬合异常率(40. 5%)高于对照组(10. 0%),差异有统计学意义(χ2 =5. 79, P=0. 056),观察组和对照组颊舌向、近远中向咬合异常率差异无统计学意义(P>0. 05);观察组和对照组Spee曲线平均深度分别为(2. 41 ± 0. 26) mm、(2. 05 ± 0. 18) mm,观察组Spee曲线深度较对照组有增加,差异具有统计学意义(t=4. 51,P=0. 009). 结论 下颌第三磨牙近中阻生患者TMD发生率高于非近中阻生患者;下颌第三磨牙近中阻生引发垂直向咬合异常.     

Diagnostic accuracy of three screening questions (3Q/TMD) in relation to the DC/TMD in a specialized orofacial pain clinic

Objective: To determine the diagnostic accuracy of three screening questions (3Q/TMD) in relation to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), in a specialized clinic.

Material and methods: Consecutive patients,?>18 years, referred with a possible TMD complaint to the Orofacial Pain and Dysfunction clinic, Academic Centre for Dentistry Amsterdam, the Netherlands, were included in the study. All patients (n?=?449; mean age 44 years; 72% females), answered the 3Q/TMD and the DC/TMD questionnaire before a DC/TMD examination. The 3Q/TMD constitutes of two questions on weekly pain from the jaw, face and temple region (Q1), and on function (Q2), and one function-related question on weekly catching and/or locking of the jaw (Q3). Q1 and Q2 were evaluated in relation to a DC/TMD pain diagnosis and Q3 in relation to a subgroup of DC/TMD intra-articular diagnosis, referred to as the reference standard.

Results: In total, 44% of patients received a pain-related DC/TMD diagnosis and 33% an intra-articular reference DC/TMD diagnosis. Sensitivity for the two pain screening questions was high (0.83–0.94), whereas specificity was low (0.41–0.55). For the function-related question, sensitivity was low (0.48), whereas specificity was high (0.96).

Conclusions: In a specialized pain clinic, the two pain questions (Q1, Q2) are positive in most patients with pain-related TMD. Therefore, in case of a positive response, further diagnostic procedures for TMD pain are warranted. For the functional screening question (Q3), a positive response is indicative for an intra-articular DC/TMD diagnosis, while in case of a negative outcome, an intra-articular TMD might still be present.     

Management of pain in TMD patients: Bio-oxidative ozone therapy versus occlusal splints

Objective: To compare the effects of bio-oxidative ozone application with occlusal splints in temporomandibular disorder (TMD) patients with pain.

Methods: Forty participants were selected after the diagnosis of TMD and randomly divided into two groups: ozone group (OG, n = 20) and occlusal splint group (OCSG, n = 20). Ozone was applied to patients three times per week, for a total of six sessions. Patients in the OCSG were instructed to use occlusal splints every night over a period of four weeks.

Results: Mandibular movements showed significant differences for the time factor in OG and OCSG. Pressure pain thresholds of the temporal and masseter muscles at follow-up were significantly higher in the OCSG group. Both treatments statistically decreased the visual analog scale (VAS) scores. However, no statistically significant difference was observed between groups after the application of treatments.

Discussion: Occlusal splint treatment is still the gold treatment modality for objective pain relief in patients with TMD pain.     

MRI evaluation of the classification,frequency, and disc morphology of temporomandibular joint disc displacements: a multicenter retrospective study in a Turkish population

Objectives  Magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) and temporomandibular disorders (TMDs) have been discussed in detail for various populations. As no such study has examined the Turkish population, we determined the frequency of TMDs in the Turkish population through a multicentric investigation using MRI. Methods  This retrospective study examined 504 TMJs of 252 symptomatic patients who had undergone bilateral MRI investigation in four different dental schools. The image analysis included the assessment of disc position and morphology, and recaptured the coronal and sagittal planes in the closed and open mouth positions. The TMJ disorders were classified using the Clinical Diagnostic Criteria for Temporomandibular Disorders (CDC/TMD). The correlations among the groups of TMJs and disc morphologies were analyzed statistically using the chi-square test (P ≤ 0.05). Results  Disc displacement and abnormal disc morphology were detected in 69.5% of the symptomatic TMJ patients. Of the joints examined using MRI, 154 were normal, 135 had anterior disc displacement with reduction (ADDwR), 145 had anterior disc displacement without reduction (ADDwoR), 30 had partial anterior disc displacement, and 18 had sideways disc displacements. Regarding disc morphology, enlargement in the posterior band was the most commonly encountered type and was observed in 152 TMJs. Overall, the average time for referral for treatment, which was defined as the time from symptom onset until the time of referral, was 1.5 years. Conclusions  The most common type of disc displacement found in the Turkish population studied was ADDwoR. In addition, patients did not perceive the symptoms of TMDs as a disease and did not seek help until the TMJ derangement caused a major complaint.     

Prevalence and risk factors of sleep bruxism and wake-time tooth clenching in a 7- to 17-yr-old population

Carra MC, Huynh N, Morton P, Rompré PH, Papadakis A, Remise C, Lavigne GJ. Prevalence and risk factors of sleep bruxism and wake‐time tooth clenching in a 7‐ to 17‐yr‐old population.
Eur J Oral Sci 2011; 119: 386–394. © 2011 Eur J Oral Sci Sleep‐related bruxism (SB) and wake‐time tooth clenching (TC) have been associated with temporomandibular disorders (TMDs), headache, and sleep and behavioral complaints. This study aimed to assess the prevalence and risk factors of these signs and symptoms in a 7‐ to 17‐yr‐old population (n = 604) seeking orthodontic treatment. Data were collected by questionnaire and by a clinical examination assessing craniofacial morphology and dental status. Sleep‐related bruxism was reported by 15% of the population and TC was reported by 12.4%. The SB group (n = 58) was mainly composed of children (67.3% were ≤12 yr of age) and the TC group (n = 42) was mainly composed of adolescents (78.6% were ≥13 yr of age). The craniofacial morphology of over 60% of SB subjects was dental class II and 28.1% were a brachyfacial type. Compared with controls (n = 220), SB subjects were more at risk of experiencing jaw muscle fatigue [adjusted OR (AOR) = 10.5], headache (AOR = 4.3), and loud breathing during sleep (AOR = 3.1). Compared with controls, TC subjects reported more temporomandibular joint clicking (AOR = 5), jaw muscle fatigue (AOR = 13.5), and several sleep and behavioral complaints. Sleep‐ and wake‐time parafunctions are frequently associated with signs and symptoms suggestive of TMDs, and with sleep and behavioral problems. Their clinical assessment during the planning of orthodontic treatment is recommended.     

Changes in reported orofacial symptoms over a ten-year period as reflected in two cohorts of fifty-year-old subjects

Objective. The study presents changes in reported orofacial symptoms over the course of a 10-year period. It was hypothesized that there was an increase of temporomandibular disorder (TMD) and orofacial pain symptoms during the period concurrent with social and demographic changes. Material and Methods. All 50-year-old subjects living in two Swedish counties were asked to answer a mail questionnaire in 1992 and 2002. In the two cohorts, 6,343 and 5,798, respectively, responded (response rate 71.3% and 70.2%). Results. Striking differences in demographic, occupational, general, and oral health conditions were found. General health was reported to be less good, utilization of dental care decreased, whereas number of teeth increased. The prevalence of a number of intra-oral symptoms and orofacial symptoms increased significantly between 1992 and 2002. Reported bruxism increased from 18% in 1992 to 28% in 2002. Conclusion. The observed increase in reported orofacial pain symptoms during the 10-year period, concurrent with changes in society, deserves further attention by society and the dental community.     

Dental malocclusion is not related to temporomandibular joint clicking: a logistic regression analysis in a patient population

Objectives:To assess the association of several dental malocclusion features with temporomandibular joint (TMJ) click sounds in a population of temporomandibular disorder (TMD) patients.Materials and Methods:Four hundred forty-two TMD patients (72% female; 32.2 ± 5.7 years, range 25–44 years) were divided into a TMJ clicking and a no-TMJ clicking group, based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) assessment. Seven occlusal features were recorded for each patient: (1) posterior crossbite, (2) overbite, (3) open bite, (4) overjet, (5) mediotrusive and (6) laterotrusive interferences and (7) retruded contact position to maximum intercuspation (RCP-MI) slide length. A logistic regression model was created to estimate the association of occlusal features with TMJ clicking.Results:The difference between the groups as for the prevalence of the various occlusal features was generally not statistically significant, with minor exceptions. Mediotrusive interferences (P  =  .015) and RCP-MI slide ≥2 mm (P  =  .001) were the two occlusal features that were associated with the probability of having TMJ clicking, even if the adjusted odds ratios for TMJ clicking were low for both variables (1.63 and 1.89, respectively). Moreover, the amount of variance in the prevalence of TMJ clicking that was predicted by the final model was as low as 4.5% (R²  =  0.045).Conclusions:Findings from the present investigation suggested that in a population of TMD patients, the contribution of dental malocclusion features to predict TMJ click sounds is minimal with no clinical relevance.     

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

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

Validity of three screening questions (3Q/TMD) in relation to the DC/TMD

Temporomandibular disorders (TMD) are common but seem to be largely undetected within general dental care. To improve dentists’ awareness of these symptoms, three screening questions (3Q/TMD) have been introduced. Our aim was to validate 3Q/TMD in relation to the diagnostic criteria for TMD (DC/TMD), while taking into account the severity level of the symptoms. The study population consisted of 7831 individuals 20–69 years old, who had their routine dental check‐up at the Public Dental Health Service in Västerbotten, Sweden. All patients answered a health declaration, including the 3Q/TMD regarding frequent temporomandibular pain, pain on movement and catching/locking of the jaw. All 3Q‐positives (at least one affirmative) were invited for examination in randomised order. For each 3Q‐positive, a matched 3Q‐negative was invited. In total, 152 3Q‐positives and 148 3Q‐negatives participated. At examination, participants answered 3Q/TMD a second time, before they were examined and diagnosed according to DC/TMD. To determine symptom's severity, the Graded Chronic Pain Scale and Jaw Functional Limitation Scale‐20 (JFLS‐20) were used. In total, 74% of 3Q‐positives and 16% of 3Q‐negatives met the criteria for DC/TMD pain or dysfunction (disc displacements with reduction and degenerative joint disorder were excluded). Fifty‐five per cent of 3Q‐positives had a TMD diagnosis and CPI score ≥3 or a JFLS‐20 score ≥5, compared to 4% of 3Q‐negatives. The results show that the 3Q/TMD is an applicable, cost‐effective and valid tool for screening a general adult population to recognise patients in need of further TMD examination and management.     

Treatment for TMD with occlusal splint and electromyographic control: application of the FARC protocol in a Brazilian population

The purpose of this study was to apply Functional Anatomy Research Center (FARC) Protocol of TMD treatment, which includes the use of a specific type of mandibular occlusal splint, adjusted based on the electromyographic index, in a group of 15 patients with disc displacement, classified according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and then analyzing the results compared with the control group. The clinical evaluations were completed both before and after the treatment. Electromyographic (EMG) data was collected and recorded on the day the splint was inserted (visit 1), after one week (visit 2) and after five weeks of treatment (visit 3). The control group consisted of 15 asymptomatic subjects, according to the same diagnostic criteria (RDC/TMD), who were submitted to the same evaluations with the same interval periods as the treatment group. Immediately after splint adjustment, masseter muscle symmetry and total muscular activity were significantly different with than without the splint (p < 0.05), showing an increased neuromuscular coordination. After treatment, significant variations (p < .05) were found in mouth opening and in pain remission. There were no significant differences among the three sessions, either with or without the splint. There were significant differences between the TMD and control groups for all analyzed indices of muscular symmetry, activity and torque, with the exception of total muscular activity. The use of the splint promoted balance of the EMG activities during its use, relieving symptoms. EMG parameters identified neuromuscular imbalance, and allowed an objective analysis of different phases of TMD treatment, differentiating individuals with TMD from the asymptomatic subjects.     

Predictors of signs and symptoms of temporomandibular disorders: a 20-year follow-up study from childhood to adulthood

The aim of this study was to find possible predictors of signs and symptoms of temporomandibular disorders (TMD) in a long-term perspective. Baseline questionnaire and clinical examinations focusing on function and dysfunction of the masticatory system were performed in a sample of 402 subjects 7, 11, and 15 years old. After 20 years, 320 subjects (80% of the original sample) completed a similar questionnaire as at baseline. From the oldest age group, now aged 35 years, 100 subjects (74% of the original sample) also attended a clinical examination. Three variables from the 20-year follow-up were chosen as dependent variables in logistic regression analyses, with independent variables selected from the baseline examinations. Three variables at baseline were significant predictors for reported TMJ clicking at the 20-year follow-up, tooth wear index being the strongest (odds ratio = 4.3). Reported TMJ clicking at the start was the only significant predictor for TMD symptoms without clicking 20 years later (odds ratio = 2.3). The third logistic regression model, using the Helkimo Clinical Dysfunction Score as dependent variable, resulted in four significant predictors from the baseline examinations (bruxism, oral parafunctions, TMJ clicking, and deep bite). The results indicated that some signs and symptoms might predict TMD signs and symptoms in a long-term perspective. However, it cannot be concluded from this study whether these symptoms recorded in childhood - oral parafunction, tooth wear, TMJ clicking, and deep bite - can be used for predicting manifest TMD in adult age.     

Prevalence of TMD symptoms in Turkish migrants and re-settlers from the former Soviet Union in comparison to a German group

Objectives: The objective of this study was to investigate the prevalence of temporomandibular disorder (TMD) symptoms among Turks and re-settlers with German origin from Russia and to compare those findings with a German group from the same area.

Method: Sixty-nine Turkish migrants, 50 re-settlers, and 96 Germans were clinically examined according to a short version of the Research Diagnostic Criteria (RDC/TMD) protocol. The subjects participated in a feasibility study of the German National Cohort and were recruited from the study center Heidelberg/Mannheim of the cluster Baden-Württemberg/Saarland.

Results: Significant differences emerged between the three ethnic groups for unassisted opening without pain, maximum unassisted opening, and overbite, with highest values for the German group. No significant differences were found for muscle pain on palpation or muscle and joint pain during opening.

Discussion: As the authors identified significant differences between the different ethnic groups for metric measurements, it might be beneficial to include questions concerning the ethnicity to the German version of the RDC/TMD for further research, to make the results more comparable.     

Effect of low-level laser therapy on pain levels in patients with temporomandibular disorders: a systematic review

Temporomandibular disorders (TMD) are characterized by the presence of temporomandibular joint (TMJ) and/or masticatory muscle pain and dysfunction. Low-level laser is presented as an adjuvant therapeutic modality for the treatment of TMD, especially when the presence of inflammatory pain is suspected.

Objective

To systematically review studies that investigated the effect of low level laser therapy (LLLT) on the pain levels in individuals with TMD.

Material and Methods

The databases Scopus, embase, ebsco and PubMed were reviewed from January/2003 to October/2010 with the following keywords: laser therapy, low-level laser therapy, temporomandibular joint disorders, temporomandibular joint dysfunction syndrome, temporomandibular joint, temporomandibular, facial pain and arthralgia, with the inclusion criteria for intervention studies in humans. exclusion criteria adopted were intervention studies in animals, studies that were not written in english, Spanish or Portuguese, theses, monographs, and abstracts presented in scientific events.

Results

After a careful review, 14 studies fit the criteria for inclusion, of which, 12 used a placebo group. As for the protocol for laser application, the energy density used ranged from 0.9 to 105 J/cm², while the power density ranged from 9.8 to 500 mW. The number of sessions varied from 1 to 20 and the frequency of applications ranged from daily for 10 days to 1 time per week for 4 weeks. A reduction in pain levels was reported in 13 studies, with 9 of these occurring only in the experimental group, and 4 studies reporting pain relief for both the experimental group and for the placebo.

Conclusion

Most papers showed that LLLT seemed to be effective in reducing pain from TMD. However, the heterogeneity of the standardization regarding the parameters of laser calls for caution in interpretation of these results. Thus, it is necessary to conduct further research in order to obtain a consensus regarding the best application protocol for pain relief in patients with TMD.