The mice on the embry on days 13.5 （E13.5）， E14.5， E16.5， E18.5 and postnatal days 5 （PN5） were obtained， and used as E13.5，E14.5，E16.5E18.5，and PN5 groups，with 5 mice in each group；their heads were separated， immobilized， decalcified， dehydrated， embedded and sliced， and the morphology of tooth embryo tissue at different stages was observed by HE staining. The expression levels of integrin β1 and LAMR1 in the molar germ tissue at different stages of mouse molar development were observed by immunohistochemical staining.

The HE staining results showed that the tooth germ tissue development of the mice in E13.5 group corresponded to the bud stage， the epithelial cells protruded into the ectodermal mesenchyma and formed epithelial buds like flower buds；the tooth germ tissue development of the mice in E14.5 group corresponded to the cap stage， the epithelial bud volume was increased， which was called the enamel organ at the cap stage， and the density of ectomesenchymal cells around the enamel organ was increased， forming the dental papilla； the tooth germ tissue development of the mice in E16.5 group corresponded to the bell shaped early stage， the enamel organ further grew， resembled a hanging bell， and initially had the shape of the cusp； the tooth germ tissue development of the mice in E18.5 group corresponded to the late bell shaped stage， the ameloblast further developed， the inner ameloblast differentiated forward， and the shape changed from cubic to high columnar； the tooth crown of the mice in PN5 group developed into cervical loop， epithelial root sheath， epithelial septum and other structures， the ameloblasts and odontoblasts differentiated and matured and arranged neatly in high columnar shape， and enamel and dentin were formed. The results of immunohistochemical staining showed that integrin β1 and LAMR1 were expressed in the epithelium and dental papilla of mouse molars at different stages of molar development， and the expression intensities of integrin β1 and LAMR1 in different parts gradually were increased with the process of cell differentiation. The expression levels of integrin β1 protein in the ameloblasts of the mice in PN5 group was higher than those in the inner ameloblasts / preameloblasts in germ tissue of the mice in E14.5， E16.5 and E18.5 groups（P<0.05）； the expression levels of integrin β1 protein in the odontoblasts in tooth germ tissue of the mice in PN5 group were higher than those in the preodontoblasts in dental germ of the mice in E14.5， E16.5 and E18.5 groups（P<0.05）. The expression levels of LAMR1 protein in the inner ameloblasts / preameloblasts in E16.5 and E18.5 groups were higher than that in the inner ameloblasts in E14.5 group（P<0.05）， and were lower than that in the ameloblasts in dental germ of the mice in PN5 group（P<0.05）； the expression level of LAMR1 protein in the preodontoblasts in E18.5 group was higher than that in the preodontoblasts in E16.5 group（P<0.05）， and was lower than that in the odontoblasts in dental germ of the mice in PN5 group（P<0.05）. In PN5 group， the expression levels of integrin β1 and LAMR1 proteins in the mature odontoblasts at the cusp were higher than those in the immature odontoblasts between the apical and the neck （P<0.05）.

Integrin β1 and LAMR1 are expressed in the basement membranes， （pre）ameloblasts and （pre）odontoblasts during molars development in the mice. They may be involved in signal transduction of extracellular matrix and play a promoting role in the differentiation and polarity formation of the ameloblasts and odontoblasts.