A comparison between osteoclasts in vitro and in vivo in the periodontal ligament of the adult mouse

Abstract

Twelve expiants of the first mandibular molar and surrounding periodontium of young adult mice were cultured for 7 days in vitro. The number and size of osteoclasts, the number of nuclei per osteoclast and the distribution of the osteoclasts in the periodontal ligament were compared with osteoclasts in periodontal ligament in vivo in mice of the same age as the mice from which the expiants were taken. Light microscope comparison of the two groups indicated that resorption of bone had occurred in vitro. There was a significant increase in the number and size of osteoclasts in the cultured expiants compared with the in vivo material. The numbers of nuclei per osteoclast and the distribution of osteoclasts in the periodontal ligament was similar in the two groups, but the greatest increase in osteoclast numbers occurred on the distal aspect of the distal root where there were most osteoclasts in vivo. It was concluded that there was active bone resorption and that osteoclasts formed de novo during culture of these expiants.