Understanding cell types and mechanisms of dental growth is essential for reconstruction and engineering of teeth. Therefore, we investigated cellular composition of growing and non-growing mouse and human teeth. As a result, we report an unappreciated cellular complexity of the continuously-growing mouse incisor, which suggests a coherent model of cell dynamics enabling unarrested growth. This model relies on spatially-restricted stem, progenitor and differentiated populations in the epithelial and mesenchymal compartments underlying the coordinated expansion of two major branches of pulpal cells and diverse epithelial subtypes. Further comparisons of human and mouse teeth yield both parallelisms and differences in tissue heterogeneity and highlight the specifics behind growing and non-growing modes. Despite being similar at a coarse level, mouse and human teeth reveal molecular differences and species-specific cell subtypes suggesting possible evolutionary divergence. Overall, here we provide an atlas of human and mouse teeth with a focus on growth and differentiation.

In non-growing teeth, such as mouse and human molars, primary odontoblasts are long-lived post-mitotic cells that secrete dentine throughout the life of the tooth. New odontoblast-like cells are only produced in response to a damage or trauma. Little is known about the molecular events that initiate mesenchymal stem cells to proliferate and differentiate into odontoblast-like cells in response to dentine damage. The reparative and regenerative capacity of multiple mammalian tissues depends on the activation of Wnt/β-catenin signaling pathway. In this study, we investigated the molecular role of Wnt/β-catenin signaling pathway in reparative dentinogenesis using an in vivo mouse tooth damage model. We found that Axin2 is rapidly upregulated in response to tooth damage and that these Axin2-expressing cells differentiate into new odontoblast-like cells that secrete reparative dentine. In addition, the Axin2-expressing cells produce a source of Wnt that acts in an autocrine manner to modulate reparative dentinogenesis.

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Innovation has always been part of dentistry and with that comes thinking outside the box to produce guidelines for implementation of new approaches. Regenerative dentistry (RD) is a young specialty within the profession, which gathers knowledge from stem cells, molecular biology, and tissue and material engineering to produce and apply novel biologically based therapies. Since RD is an emerging branch of dentistry, it is not yet understood whether active clinicians are aware of this field and know exactly what it does. The aim of this study is to explore the awareness, understanding, and beliefs about RD of active dentists. A random selection of active dentists in the UK was approached via e-mail and face-to-face and asked to fill in a questionnaire. A total of 45 responses were received and analyzed. The results showed that active dentists in the UK are aware of the field but are not prepared to apply personalized biologically based therapies and feel a desire to educate themselves about RD further. Also, the results shine a light on the opportunities for regulatory and educational bodies to work together to prepare the clinicians for this novel field. Our research suggests that active dentists are ill-prepared for an era of personalized biologically based dental treatments. Further thinking of how to implement basic and more advanced biological knowledge and their application in dentistry is needed, and suggestions are made here.