Abstract: Objective:To investigate the expression difference of Btbd7 gene in the different developmental stages of neonatal SD mice roots and discuss its role in the process. Methods: The tooth germ specimens of neonatal SD mice containing the first mandibular molar were prepared on the 8th,11th,15th,19th day after birth. Using conventional HE staining,we observed HERS morphology during the root developmental stages and tested Btbd7 expression by immunohistochemistry technology. Results:Btbd7 gene expressed highly in HERS cells and it decreased in the wake of its grown . Conclusion: Btbd7 gene specifically expressed in the structure of HERS in space-time and may anticipate the formation and stretch of tooth root branches during the neonatal SD mice root development.

Key words: Btbd7 gene, tooth root development, Hertwig 's epithelial root sheath