CHANGE OF DENTIN FORMATION DURING THE REPRODUCTIVE-CYCLE IN MICE

The volume of incisor dentin formation was investigated semi-longitudi nally using the time-marking method during the reproductive cycle of p regnancy, parturition, lactation, and post-weaning in mice, and was co mpared with unmated, non-pregnant control mice. DDD/Qdj mice were inje cted with nitrilo-tri-acetate lead acid solution subcutaneously at 4-d ay intervals. Serial cross sections of 100 mu m thickness were prepare d from the edge of the tooth to the apical portion. Each area of denti n, encircled by adjoining lines labeled with the lead that was formed at 4-day intervals, was measured by means of an image scanning system. The total amount of dentin formation per 4-day intervals was quantifi ed as a volume in all animals. In the control animals, there was no si gnificant difference at each period throughout the experiment. However , the volume of dentin formation increased during the reproductive cyc le over that of the control. The increase in volume was significant (P < 0.0001). In addition, during pregnancy, the volume increased gradua lly with the greatest increase seen in the last 4 days of pregnancy, i ncluding the day of parturition, as compared with the first half-term of pregnancy (P < 0.05). The volume decreased immediately after partur ition as compared with the latter half-term of pregnancy (P < 0.05). T he results of the present study suggest that the volume of dentin form ation is affected by the change of maternal metabolism during the repr oductive cycle in mice.