Influences of osteoclast deficiency on craniofacial growth in osteopetrotic (op/op) mice

well known that the defect in bone resorption in osteopetrotic (op/op) mice brings about deformation of the cranium and failure of tooth eruption. How ever, the influences on longitudinal growth of the craniofacial skeleton ha ve not been elucidated. This study was thus conducted to examine craniofaci al morphology and longitudinal changes in the op/op mice by means of morpho metric analysis with lateral cephalograms. Lateral cephalograms, taken ever y 10 days from 10- to 90-day-old mice, were analyzed on a personal computer for II measurement items. For the nasal bone region, the most prominent di fferences were found between the op/op and normal mice. The anterior crania l base and occipital bone height presented almost equivalent growth changes in both the op/op and normal mice. The size of mandible, meanwhile, was si gnificantly smaller in the op/op mice than in the normal controls. The geni al angle was also significantly larger in the ap/op mice than in the normal mice throughout the experimental period. Thus, substantial differences in craniofacial growth were demonstrated in various areas of the craniofacial complex, which are assumed essentially due to the lack of osteoclastic bone resorption during growing period. Since the difference became more promine nt in the anatomic regions relevant to the masticatory functions, it would be a reasonable assumption that reduced masticatory function is also a key determinant for the less-developed craniofacial skeleton in the op/op mouse .