Osteoclastic resorption of3H-proline labelled bone,dentine and cementum in the rat

Six litter mate Wistar rats were injected intraperitoneally with 2 Ci/g body weight³H-proline at the age of 15 and 20 days. Six to seven weeks later resorption of cementum, dentine and bone was caused experimentally by luxation of the first right mandibular molar. The animals were killed 10 days later in glutaraldehyde perfusion fixation and 5 serial sections of the mandibles were processed for radioautography. Cementum, dentine and bone showed bands of labelling corresponding to the stage of odontogenesis and osteogenesis at the time of injection. Osteoclasts were found in contact with labelled cementum, dentine and bone but the number of grains over osteoclasts was insignificant.