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Orientation of the masseter muscle and the curve of Spee in relation to crushing forces on the molar teeth of primates
Author(s) -
Osborn J. W.
Publication year - 1993
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.1330920108
Subject(s) - molar , sagittal plane , tilt (camera) , masseter muscle , bite force quotient , anatomy , orthodontics , posterior teeth , geometry , biology , medicine , mathematics
A highly significant correlation is demonstrated between the forward inclination of the superficial masseter muscle and the forward tilt of molar teeth in the sagittal plane, conforming to the posterior end of the curve of Spee. The skulls studied included New and Old World monkeys, anthropoid apes, man, and a selection of other mammals. There was a wide variation between the angles measured in different animals (from 54° to 115°). The tilt of the curve of Spee increases the crush/shear ratio of the force produced on food between the posterior molars. The parallel tilt of superficial masseter maximizes the efficiency with which this muscle contributes to the crush component of the bite force in the sagittal plane. © 1993 Wiley‐Liss, Inc.