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Modeling of muscle forces in humans with and without temporomandibular joint disorders
Author(s) -
Iwasaki L. R.,
Liu H.,
Gonzalez Y. M.,
Marx D. B.,
Nickel J. C.
Publication year - 2015
Publication title -
orthodontics and craniofacial research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 55
eISSN - 1601-6343
pISSN - 1601-6335
DOI - 10.1111/ocr.12075
Subject(s) - pterygoid muscles , bite force quotient , masseter muscle , temporomandibular joint , masticatory force , lateral pterygoid muscle , biting , medicine , temporalis muscle , anatomy , orthodontics , molar , biology , ecology
Structured Abstract Objectives Subjects with/without temporomandibular joint disorders ( TMJD ) were tested for differences in muscle forces. Setting and Sample Population School of Dental Medicine, University at Buffalo. Ninety‐one subjects were classified in four groups based on the presence/absence (±) of chronic myofascial and/or TMJ pain (P) and bilateral disc displacement ( DD ). Material and Methods Validated numerical models employed an organizational objective and subjects' anatomy to calculate masticatory muscle forces during static biting. anova and Holm's step‐down procedure post hoc tests assessed group differences. Theoretical geometries, representing the range of subjects' muscle orientations, were surveyed via numerical models to identify key combinations resulting in high muscle forces. Effect size (Cohen's d ) and anova / post hoc tests assessed group differences in key muscle orientations. Results +P− DD subjects had significantly higher muscle forces, especially for lateral pterygoid muscles, compared to the other groups ( p < 0.01) for bite forces that were directed posteromedially or posterolaterally on mandibular molars and posteriorly and slightly medially on mandibular incisors. Key muscle orientations for peak lateral pterygoid muscle forces were identified, and group comparisons showed mean orientation in +P− DD compared to other diagnostic groups was ≥5° more upright for masseter and ≥3° more posteriorly directed for temporalis muscles (all Cohen's d ≥ 0.8). Conclusion Predicted lateral pterygoid muscle forces were significantly higher in +P− DD compared to other groups for specific biting conditions and were attributable, in part, to differences in masseter and temporalis muscle orientations.