Abstract: Objective: To study the expression characteristics of Dickkopf1 (DKK1) in different time and space during tooth development of the postnatal mice, and to provide the theoretical basis for clarifying the mechanism of Wnt signaling pathway in regulating the tooth development. Methods: The postnatal Kunming mice at days 0.5, 6.5, 12.5, 18.5, 24.5, and 30.5 respectively after birth were selected and divided into various groups by time,three in each group.The mice in each group were sacrificed and the paraffin sections of mandibular bone including the first molar were prepared at the thickness of 5 μm, followed by HE staining and immunohistochemical staining in order to detect the expressions of DKK1 in tooth tissue and periodontal tissue. Results: At 0.5 d after birth, the mandibular first molar tooth germ was in the bell stage. At 6.5 d the enamel development of mandibular first molar was almost completed, and the epithelium root sheath extended to the root direction. At 12.5 d the dentin development of crown was completed, with the root formatted about 1/3. At 18.5 d the root had formatted about 2/3. At 24.5 d the root had reached the full length. At 30.5 d the apical foramen was narrow, and the root development was basically completed. There was no DKK1 expression at 0.5 d, but it expressed in the odontoblasts and predentin at 6.5 d. From days 12.5 to 30.5,the expressions of DKK1 were positive in periodontal ligament, alveolar bone, and cellular cementum as odontoblasts, which were gradually increased with the prolongation of time. However, no expression of DKK1 was detected in the pulp. Conclusion: DKK1 shows regular expressions at different tooth developmental stages after birth, suggesting its potential role in the growth of dentin and periodontal tissues.

Key words: hematoxylin and eosin staining, immunohistochemistry, periodontal tissue, dental development, DKK1