RESTORATION OF DISTURBED TOOTH ERUPTION IN OSTEOPETROTIC (OP OP) MICEBY INJECTION OF MACROPHAGE-COLONY-STIMULATING FACTOR/

Osteopetrotic (op/op) mice show severe osteosclerosis caused by an inh erited deficiency of osteoclast and resultant failure of tooth eruptio n, which can be cured by the injection of macrophage colony-stimulatin g factor (M-CSF). The present study revealed that consecutive injectio ns of M-CSF in these mutant mice brought about a recovery of bone reso rption resulting in the resumption of growth of tooth root and periodo ntal ligament. Bone resorption at the inner surface of bony crypts was noted on the 5th day after the start of M-CSF injections. This activi ty was reduced with the progress of root and periodontal ligament form ation, being confined to the basal and crestal portion of bony crypts by the 15th day of the experiment. Second molars emerged into the oral cavity on the 15th day, but no eruption of first molars was observed until the 20th day. Throughout the experiment, first molars exhibited appreciable root deformity, which was less severe in second molars. De layed eruption of first molars was thought to be related to the severi ty of the disturbance of root formation.