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Mechanobehavioral Scores in Women with and without TMJ Disc Displacement.

ABSTRACT: Cartilage fatigue may be a factor in the precocious development of degenerative changes in the temporomandibular joint (TMJ). This cross-sectional study estimated potential for cartilage fatigue via TMJ energy densities (ED) and jaw muscle duty factors (DF), which were combined to calculate mechanobehavioral scores (MBS) in women with (+) and without (-) bilateral TMJ disc displacement (DD). All subjects gave informed consent to participate and were examined using Diagnostic Criteria (DC) for Temporomandibular Disorders (TMD) and magnetic resonance (MR) and computed tomography (CT) images. Forty-seven subjects were categorized into +DD ( n = 29) and -DD ( n = 18) groups. Dynamic stereometry (MR images combined with jaw-tracking data) characterized individual-specific data of TMJ stress-field mechanics to determine ED (ED = W/ Q mJ/mm³, where W = work done, Q = volume of cartilage) during 10 symmetrical jaw-closing cycles with a 20-N mandibular right canine load. Subjects were trained to record masseter and temporalis electromyography over 3 days and 3 nights. Root mean square electromyography/bite-force calibrations determined subject-specific masseter and temporalis muscle activities per 20-N bite-force (T_{20 N}, µV), which defined thresholds. Muscle DF (DF = % duration of muscle activity/total recording time) were determined for a range of thresholds, and MBS (ED² × DF) were calculated. Intergroup differences in ED, DF, and MBS were assessed via analyses of variance with Bonferroni and Tukey honest significant difference post hoc tests. Average ED for contralateral TMJs was significantly larger ( P = 0.012) by 1.4-fold in +DD compared to -DD subjects. Average DF were significantly larger (all P < 0.01) for +DD compared to -DD subjects by 1.7-, 2.5-, and 1.9-fold for day, night, and overall, respectively. Daytime MBS were significantly larger (all P < 0.04) by up to 8.5-fold in +DD compared to -DD subjects. Significantly larger ED, DF, and MBS were shown in women with compared to women without bilateral TMJ DD.

SUBMITTER: Iwasaki LR

PROVIDER: S-EPMC5502957 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Various interventions have been used for the management of patients with temporomandibular joint (TMJ) disc displacement without reduction (DDwoR), but their clinical effectiveness remains unclear. This systematic review investigated the effects of these interventions and is reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic and manual searches up to November 1, 2013, were conducted for English-language, peer-reviewed, publications of randomized clinical trials comparing any form of conservative or surgical interventions for patients with clinical and/or radiologic diagnosis of acute or chronic DDwoR. Two primary outcomes (TMJ pain intensity and maximum mouth opening) and a number of secondary outcomes were examined. Two reviewers performed data extraction and risk of bias assessment. Data collection and analysis were performed according to Cochrane recommendations. Twenty studies involving 1,305 patients were included. Data analysis involved 21 comparisons between a variety of interventions, either between interventions, or between intervention and placebo or no intervention. Meta-analysis on homogenous groups was conducted in 4 comparisons. In most comparisons made, there were no statistically significant differences between interventions relative to primary outcomes at short- or long-term follow-up (p > .05). In a separate analysis, however, the majority of reviewed interventions reported significantly improved primary outcome measures from their baseline levels over time (p < .05). Evidence levels, however, are currently insufficient for definitive conclusions, because the included studies were too heterogeneous and at an unclear to high risk of bias. In view of the comparable therapeutic effects, paucity of high-quality evidence, and the greater risks and costs associated with more complex interventions, patients with symptomatic DDwoR should be initially treated by the simplest and least invasive intervention.

Project description:The temporomandibular joint (TMJ) disc nutrient environment profoundly affects cell energy metabolism, proliferation, and biosynthesis. Due to technical challenges of in vivo measurements, the human TMJ disc extracellular nutrient environment under load, which depends on metabolic rates, solute diffusion, and disc morphometry, remains unknown. Therefore, the study objective was to predict the TMJ disc nutrient environment under loading conditions using combined experimental and computational modeling approaches. Specifically, glucose consumption and lactate production rates of porcine TMJ discs were measured under varying tissue culture conditions (n = 40 discs), and mechanical strain-dependent glucose and lactate diffusivities were measured using a custom diffusion chamber (n = 6 discs). TMJ anatomy and loading area were obtained from magnetic resonance imaging of healthy human volunteers (n = 11, male, 30 ± 9 y). Using experimentally determined nutrient metabolic rates, solute diffusivities, TMJ anatomy, and loading areas, subject-specific finite element (FE) models were developed to predict the 3-dimensional nutrient profiles in unloaded and loaded TMJ discs (unloaded, 0% strain, 20% strain). From the FE models, glucose, lactate, and oxygen concentration ranges for unloaded healthy human TMJ discs were 0.6 to 4.0 mM, 0.9 to 5.0 mM, and 0% to 6%, respectively, with steep gradients in the anterior and posterior bands. Sustained mechanical loading significantly reduced nutrient levels (P < 0.001), with a critical zone in which cells may die representing approximately 13.5% of the total disc volume. In conclusion, this study experimentally determined TMJ disc metabolic rates, solute diffusivities, and disc morphometry, and through subject-specific FE modeling, revealed critical interactions between mechanical loading and nutrient supply and metabolism for the in vivo human TMJ disc. The results suggest that TMJ disc homeostasis may be vulnerable to pathological loading (e.g., clenching, bruxism), which impedes nutrient supply. Given difficulties associated with direct in vivo measurements, this study provides a new approach to systematically investigate homeostatic and degenerative mechanisms associated with the TMJ disc.

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Mechanobehavioral Scores in Women with and without TMJ Disc Displacement.

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