In vitro formation of cementum in mouse molar germs cultured in newly-developed organ culture system.

A new organ culture system for in vitro study of cementogenesis in mouse molar teeth was developed. Mandibular first molar germs at postnatal day 14 were exposed by removing off one side of the mandibular bone and were then placed cut surface down onto filter papers. The filter papers had a hole in their center, and were maintained above the bottom of the culture chambers. A serum-free, chemicallydefined medium was then added, with fresh supplements at every change of the medium. This culture method maintained the three-dimensional architecture of the tooth germ as well as that of the peripheral tissues during the whole culture period. By the 43rd culture day, acellular cementum-like layer, clearly different from the periodontal ligament proper, was formed on the acellular cementum. The mineralization of the newly formed cementum-like matrix was confirmed by electron microscopy and X-ray microanalysis.