Change of dentin formation during the reproductive cycle in mice

The volume of incisor dentin formation was investigated semilongitudinally using the time-marking method during the reproductive cycle of pregnancy, parturition, lactation, and post-weaning in mice, and was compared with unmated, non-pregnant control mice. DDD/Qdj mice were injected with nitrilo-tri-acetate lead acid solution subcutaneously at 4-day intervals. Serial cross sections of 100 microns thickness were prepared from the edge of the tooth to the apical portion. Each area of dentin, 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 quantified as a volume in all animals. In the control animals, there was no significant difference at each period throughout the experiment. However, the volume of dentin formation increased during the reproductive cycle over that of the control. The increase in volume was significant (P < 0.0001). In addition, during pregnancy, the volume increased gradually with the greatest increase seen in the last 4 days of pregnancy, including the day of parturition, as compared with the first half-term of pregnancy (P < 0.05). The volume decreased immediately after parturition as compared with the latter half-term of pregnancy (P < 0.05). The results of the present study suggest that the volume of dentin formation is affected by the change of maternal metabolism during the reproductive cycle in mice.