In a research of immature apex closure carried out in 6 young mongrel dogs, polyglycolic acid (PGA) and amelogenin protein (RAP), generated by recombinant DNA technology, were compared.s. Pulp tissues of mandibular and maxillary premolars were completely removed during root canal treatment of all teeth. (n = 120). The cavities were left opened for 14 days. Canals were cleaned, watered, and divided equally for RAP or PGA treatment (n = 60). The treated teeth were removed from the mice after 1 and 3 months for histological analysis and immunological detection of protein markers linked to odontogenic cells. The animals were then killed. A pulp chamber with epulp-like tissue was found in amelogenin-treated canals after one month, and apical tissue that was functionally connected to the bone by a periodontal ligament PDL was also seen in amelogenin-treated canals analysed after three months. In contrast, although a calcified apical tissue was formed in the PGA group, neither soft connective tissue within the pulp chamber nor the periodontal ligament was observed. The findings suggest that recombinant amelogenin protein is the component that can signal for the lost dental tissue regeneration via activation of the Wnt signaling pathway and promoting cell survival and proliferation of neural stem/progenitor cells.