Lip and tongue pressures related to dental arch and oral cavity size in Australian aborigines.

Although the oral cavity and dental arches of the Australian aborigine are large, studies of lingual and labial pressures indicate that the tongue is neither unusually large nor strong. The Australian aborigine's pharyngeal cavity is smaller in height and depth than that of the American; just the opposite is true for the oral cavity. To the extent that environmental factors are important at all, the resting pressure of the lips, not tongue pressure during swallowing, is probably the significant determinant of dental arch dimensions.