Effect of developmental stage of explants on further in-vitro development of hamster molars.

With morphometrical and biochemical methods the in-vitro development of 1-4-day-old 2nd maxillary molars was studied up to 10 days and compared with previously reported in-vivo development. Incorporation of [3H]-thymidine and increase in dry weight were used as biochemical parameters for cell proliferation and growth respectively specific alkaline phosphatase activity and uptake of 45Ca as the measure for mineralization. In explants of 2-4-day-old hamsters, formation of dentine and enamel matrix was consistent: both mineralized. These explants attained stages beyond enamel matrix formation, possibly the transitional stages of amelogenesis. The amounts of matrices produced appeared to be related to the final size the explants attained. Best in-vitro development histologically was in explants of 2 and 3-day-olds. Thus in-vitro development was qualitatively similar to in vivo.