Microprobe analysis of human masseter muscle biopsies.

Biopsies of the human masseter muscle were made using an intraoral approach. Sections were cut in a cryostat and freeze-dried. Using the myosin ATPase method at pH 9.3 the recognized heterogeneity of the muscle with respect to type I and type II fibers was confirmed. Sections were examined in an SEM by the method of energy dispersive X-ray analysis using a computer assisted semi-quantitative method (bulk analysis-thick sections) to determine the distribution of Na, P, S, Cl and K and their relative masses. Element concentrations in descending order were K, S, P, Na and Cl. Some element ratios were compared with results in the literature for other muscle (biochemical and microprobe analysis) and found to be generally in reasonable agreement. The results form a basis for the study of a prominent and accessible masticatory muscle in altered states.