[Sequence of experimental remodeling of the mandibular periosteum in the rat]

The evolution of a synchronous bone remodeling sequence has been followed with time. This sequence was induced in the buccal mandibular cortex of the rat which undergoes modeling apposition after maxillary molar extractions. The sequence has been studied in the rat on day 0, 2, 4, 6, 8 and 12 after induction. Disappearance of the layer of osteoid tissue produced on day 0 was initially observed (day 2). The resorption phase reached a peak on day 4 and then decreased until day 12. The greatest inversion was observed on day 8 and then regressed. Apposition, completely absent on day 4, was again important on day 12. The variations with time of the 2 different osteoclast profiles, those in contact with bone (considered as active) and those at a distance from the bone surface (considered as inactive) allowed to study the kinetics of these cells. Whereas their total number was unchanged on day 4 and 6, on day 4 the active osteoclasts were more numerous: this situation was completely reversed on day 6. These facts suggest that the osteoclasts present were active for 1 to 2 days, then became inactive without change in number before their disappearance. This very reproducible model seems useful for understanding certain mechanisms occurring during bone remodeling and for testing the role of some mediators or pharmacological agents on the process.