Human Masticatory Muscle Forces during Static Biting

Abstract

Muscle forces determine joint loads, but the objectives governing the mix of muscle forces involved are unknown. This study tested the hypothesis that masticatory muscle forces exerted during static biting are consistent with objectives of minimization of joint loads (MJL) or muscle effort (MME). To do this, we compared numerical model predictions with data measured from six subjects. Biting tasks which produced moments on molar and incisor teeth were modeled based on MJL or MME. The slope of predicted vs. electromyographic (EMG) data for an individual was compared with a perfect match slope of 1.00. Predictions based on MME matched best with EMG activity for molar biting (slopes, 0.89-1.16). Predictions from either or both models matched EMG results for incisor biting (best-match slopes, 0.95-1.07). Muscle forces during isometric biting appear to be consistent with objectives of MJL or MME, depending on the individual, biting location, and moment.

Validation of a musculoskeletal model of wheelchair propulsion and its application to minimizing shoulder joint forces

“…Results from Nickel et al (2003) support current findings with the fact that the criterion minimization of muscle effort gives reasonable correlations with experimental results. The present model can be used to analyze shoulder joint forces throughout propulsion, and may be useful as a prescriptive tool in determining ideal axle placement for those either newly injured, or may be used in an intervention for those seeking relief from shoulder pain.…”

Validation of a musculo-skeletal model of the mandible and its application to mandibular distraction osteogenesis

“…So it seems that only using the min/max criterion might not be valid in all cases. However, when studying the results of Nickel et al (2003) one can observe that the criterion minimization of muscle effort gives reasonable correlations with experimental results for all cases. Only for incisor biting the criterion minimization of joint loads gave a somewhat better result in some subjects, while at the same time this criterion gave bad results for the other subjects.…”

“…The muscle recruitment was predicted using a min/max criterion, which is the same as minimization of muscle effort. Nickel et al (2003) and Iwasaki et al (2003) found that predicted muscle outputs during unilateral biting were consistent with minimization of joint loads or minimization of muscle effort, or both, depending on the subject. So it seems that only using the min/max criterion might not be valid in all cases.…”

Biomechanical properties of the mandibular condylar cartilage and their relevance to the TMJ disc

“…Another prime limitation with regard to the development of accurate FEM models pertains to taking the interindividual differences into account. In this regard, models developed via in vivo measurements in single humans (Hirose et al, 2006;Koolstra, 2003;Koolstra andvan Eijden, 1997a, 1997b) can be validated for accuracy with data obtained from validated models of inter-individual differences in joint loads Nickel and Iwasaki, 2004;Nickel et al, 2003).…”