DIETARY CONSISTENCY AND CRANIOFACIAL DEVELOPMENT RELATED TO MASTICATORY FUNCTION IN MINIPIGS

Since the 1890s oral biological researchers have been interested in th e idea that strenuous mastication of unprocessed food will stimulate p roper oral-facial growth and occlusal relationships. Conversely, lack of such function due to consumption of refined food is one hypothesis among many for the etiology of malocclusion in industrialized humans. Adequately controlled experimental resting of the idea has been limite d to rats. To investigate the ''disuse'' theory in a larger-bodied and more occlusally relevant animal model, we raised four Yucatan minipig s from weaning on hard diet (HD) and another four on softened but equi valent diet (SD). The animals were monitored for eight months, sacrifi ced, and then occlusal and osteometric data collected. Variations due to dietary regime are pervasive and not due to caries, periodontitis, or attrition differences. Whereas HD body weight is 10% greater than S D, the deep masseter is 25% greater, with similar disproportion in sup erficial masseter and temporalis weight. Facial prognathism, arch narr owness, tooth crowding/maleruption and posterior cranial tapering are markedly different in the two groups. A curious posterior torsional di fference in the mandibular rami, as well as broadness and flatness of be mandibular symphysis, also occur in SD. We performed a Q-mode princ ipal coordinates analysis of the 19 logged variables for the specimens , bootstrapping the variable list, to demonstrate a statistically sign ificant (P < .01) overall pattern of dramatic differences. Having cont rolled other celebrated orthodontic etiologies (genetic background, re spiratory mode, infectious degeneration and interproximal attrition), these results support the proposition that dietary consistency relates directly to human craniofacial growth.