Differentiated odontoblasts could not be identified by one unique phenotypic marker, but the combination of expression of dentin phosphoprotein (Dpp), dentin sialoprotein (Dsp), dentin matrix protein 1 (Dmp1), and nestin may be valuable for the assessment of these cells. However, the findings using these proteins remain controversial. This study aimed to compare two odontoblast differentiation markers: nestin and Dsp in the process of dentinogenesis in mice. We performed immunohistochemistry and/or in situ hybridization technique for nestin and Dsp using 3-week-old incisors as well as postnatal 1-day-to 8-week-old molars. Preodontoblasts began to express nestin and Dsp proteins and Dsp mRNA, which increased in their intensity according to the progress of odontoblast differentiation in both incisors and developing molars. Nestin was consistently expressed in the differentiated odontoblasts even after the completion of dentin matrix deposition. The expression of Dsp mRNA coincided with the odontoblast secretory activity for dentin matrix deposition. In contrast, other pulpal cells, predentin matrix and dentinal tubules also showed a positive reaction for Dsp protein in addition to differentiated odontoblasts. In conclusion, nestin is valuable as a differentiation marker for odontoblasts, whereas Dsp mRNA is a functional marker for their secretory activity.Dentin is a hard connective tissue that forms the bulk of the tooth, and it is a bone-like matrix characterized by multiple closely packed dentinal tubules that traverse its entire thickness and contain the cytoplasmic processes of odontoblasts, which are responsible for the formation and maintenance of the dentin. The cell bodies of the odontoblasts are aligned along the inner aspect of the dentin, beneath a layer of predentin, where they also form the peripheral boundary of the dental pulp (35). The odontoblasts are terminally differentiated ectomesenchymal cells that synthesize several collagenous and non-collagenous proteins (NCPs) (45). The morphologically discernible differentiation of the odontoblast begins with the dental papilla cells adjacent to the inner enamel epithelium (7). The dental papilla cells adjoining the acellular zone rapidly enlarge and elongate to become preodontoblasts first and then odontoblasts as their cytoplasm increases in volume to contain increasing amounts of proteinsynthesizing organelles. The morphology of odontoblasts reflects their functional activity and ranges from an active synthetic phase to a quiescent phase (35). However, the preferred use of terminology regarding the classification of odontoblasts is controversial, because several terms for differentiated odontoblasts have been used by different researchers, i.e., secretory, transitional, and aged odontoblasts (12), young and old odontoblasts (51), or