In this study, we examined the roles of IRE1α in odontoblast development and dentin formation in wild-type mice as well as in DsppP19L mutant mice, which express a pathogenic variant of dentin sialophosphoprotein (P19L-DSPP) and exhibit a dentinogenesis imperfecta (DGI)-like phenotype. Here, DSPP is linked to dentinogenesis imperfecta.