Identification of osteoclasts and their mononuclear precursors. A comparative histological and histochemical study in hamster periodontitis.

Quantification of osteoclast resorption, a good index of periodontitis destruction, is primarily based on osteoclast identification. As their identification is sometimes dubious, we compared osteoclastic counts in hamster specimens processed for either routine histology or tartrate-resistant acid phosphatase (TRAP) staining. No difference was found between the two approaches concerning the number of osteoclasts. However the mean bone-osteoclast interface was higher in the TRAP-stained specimens (+30%, p less than 0.02). As osteoclast precursors are also TRAP+ cells, they were quantified too. Compared with controls, there was a dramatic increase (p less than 0.0001) in periodontitis-affected animals. Precursors were strongly correlated to active osteoclasts (r = 0.97). Our data suggest that precursors are recruited only when the disease is active in a given site.