Attachment to and phagocytosis of mineral by alveolar bone osteoclasts.

The mechanisms by which the osteoclast attaches to and resorbs bone are not fully understood. Morphologic techniques have primarily been used to examine these mechanisms, but many studies have been based on decalcified material. In this study, the attachment of the osteoclast to alveolar bone and its relationship to the mineral component during the active resorption associated with tooth eruption in the rat was examined using transmission electron microscopy and techniques designed to minimize demineralization effects during processing. Large conglomerates of bone mineral were found within both the ruffled border and the vacuoles adjacent to this area. These deposits were clearly more extensive than the isolated mineral fragments described in other sites by previous investigators. Examination of demineralized sections showed that collagen was largely absent within the ruffled border, and not present within vacuoles. These observations suggest that phagocytosis of bone mineral may supplement its extracellular dissolution in situations associated with rapid bone turnover, such as tooth eruption. Two types of clear zone attachment to mineral were also observed, permitting further speculation on the mechanism by which osteoclasts attach to and move along the bone surface.