Muscle and temporomandibular joint forces associated with chincup loading predicted by numerical modeling

Laura R. Iwasaki, Brian W. Baird, W. D. McCall, Jeffrey C. Nickel

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Development of the components of the temporomandibular joint (TMJ) is thought to reflect joint loading. The aims of this project were to test 3 hypotheses: whether effective eminence morphology, masticatory muscle forces, and predicted TMJ forces during chincup loading of the mandible were consistent with the objectives of minimization of joint loads (MJL) or muscle effort (MME), or both. Regression relationships of MJL model-predicted versus measured eminence shapes in 9 subjects indicated a high degree of correlation (mean slope = 0.99, compared with perfect-match slope = 1.00). Model predictions of muscle output during chincup loading of the mandible were tested by comparison with data gathered in 6 subjects. Midsagittal plane chin loads were applied over a range of 60° while bilateral masticatory muscle surface electromyography was quantified. The regression relationships of predicted versus measured masseter and anterior digastric muscle outputs indicated that model predictions were highly correlated (mean slopemasseter muscle = 1.02; mean slopedigastric muscle = 0.96). TMJ forces predicted by modeling showed intersubject differences of up to 34% for similar chincup loading conditions. Intrasubject variation in TMJ forces was as high as 57%, depending on chin load angle. The results demonstrated that TMJ eminence shape and masticatory muscle forces were consistent with objectives of both MJL and MME. Variation in TMJ forces depended on the subject and the direction of chincup loading.

Original languageEnglish (US)
Pages (from-to)530-540
Number of pages11
JournalAmerican Journal of Orthodontics and Dentofacial Orthopedics
Issue number5
StatePublished - Nov 2003
Externally publishedYes

ASJC Scopus subject areas

  • Orthodontics


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