Characteristics of developmental stages of deciduous molar 3 of miniature pig. (A-C') H&E staining of different stages during tooth germ morphogenesis; Boxed regions in A,B,C were magnified in A',B',C'. (A,A') The tooth germ developed into cap stage at embryonic day 40 (E40). The epithelium folded into the bud and the inner enamel epithelium (IEE) and outer enamel epithelium (OEE) were separated. The stellate reticulum (SR) was located between IEE and OEE. The mesenchymal cells concentrated and became dental papilla (DP). (B,B') At E50, the tooth bud reached bell stage and the secondary and third enamel knots began to form. The out layer of dental papilla cells attached to the basement membrane of IEE. (C,C') At E60, parts of IEE and dental papilla cells at the cusp tip had differentiated into ameloblasts and odontoblasts (O). Enamel (E) and pre-dentin (pD) were secreted. Scale bars represent 50μm (A,A',B,B') and 100μm(C,C').