The purpose of this investigation is to study the relationships between facial height; positioning of the mandible by the muscles of mastication; vertical lip, tongue, and occlusal forces; and tooth eruption. First, these relationships will be investigated in human subjects who exhibit normal face height, as well as those with long and short face vertical dysplasias. This will be accomplished by means of radiographic analyses, conventional intraoral transducers, and newly designed thin piezoelectric transducers which measure occlusal force. This information should not only better define these relationships, but offer insight for better recognition and eventual modification of these relationships. Second, in an animal model (rodent incisor) the force and rate of eruption of teeth will be measured by new transducers to determine how these parameters are affected by differences in magnitude, duration, and frequency of vertical loading of the teeth. The derivation of an accurate and workable methodology is a necessary step toward future data collection in primates. Information from the animal model also may allow better understanding of the relationships investigated in humans.