The development of dentin microstructure is controlled by the type of adjacent epithelium.

Considerable amount of research has been focused on dentin mineralization, odontoblast differentiation, and their application in dental tissue engineering. However, very little is known about the differential role of functionally and spatially distinct types of dental epithelium during odontoblast development. Here we show morphological and functional differences in dentin located in crown and roots of mouse molar and analogous parts of continuously growing incisors. Using a reporter (DSPP-cerulean/DMP1-cherry) mouse strain and knockout mice with ectopic enamel (Spry2+/- ;Spry4-/- ) we show that the different microstructure of dentin is initiated in the very beginning of dentin matrix production and is maintained throughout the whole duration of dentin growth. This phenomenon is regulated by the different inductive role of adjacent epithelium. Thus, based on the type of interacting epithelium we introduce more generalized terms for two distinct types of dentins: cementum vs. enamel-facing dentin. In the odontoblasts which produce enamel-facing dentin we identified uniquely expressed genes (Dkk1, Wisp1 and Sall1) which were either absent or downregulated in odontoblasts which form cementum-facing dentin. This suggests the potential role of Wnt signalling on the dentin structure patterning. Finally, we show the distribution of calcium and magnesium composition in the two developmentally different types of dentins by utilizing spatial element composition analysis (LIBS). Therefore, variations in dentin inner structure and element composition are the outcome of different developmental history initiated from the very beginning of tooth development. Taken together, our results elucidate different effect of two main types of dental epithelium, important for either crown or root formation, on adjacent odontoblasts which give rise to dentin of different quality. This article is protected by copyright. All rights reserved.