Tooth morphogenesis is a well-known developmental system related to epithelial-mesenchymal interactions. In mice, the dental epithelium has the potential to induce tooth formation prior to the bud stage, whereas this potential shifts to the dental mesenchyme from the dental epithelium. The reaggregation of mesenchymal tissue leads to previous memories of individual cells being reset, which is useful for studying the predetermination of mesenchyme. Here, the mesenchyme was triturated into single cells after separation of the epithelium and the mesenchyme. These single cells were repelleted and combined with the epithelium. The reaggregated tooth was transplanted into a mice kidney capsule. In order to investigate the essential functions of both the dental epithelium and the dental mesenchyme regarding their mutual interaction, a reaggregation system was introduced using the late bud stage of the mouse first molar. Amelogenin expression was examined to confirm the cytodifferentiation in the reaggregated tooth. The results showed that a new tooth formed after reaggregating the dental mesenchyme. This tooth contained enamel, dentin, dentinal tubules and dental pulp. The inner enamel epithelium of the reaggregated tooth differentiated into ameloblasts. Immunohistochemistry for amelogenin was observed both in the ameloblasts and the enamel. However, the structure of the enamel was different from that of the normal tooth, with the thickness of the predentin becoming wider. These findings suggest that reaggregated dental mesenchyme cells can produce a tooth. The fate of dental epithelium was not affected by reaggregated dental mesenchyme, although the dental mesenchyme appears to lose the information from the dental epithelium.