The generation of the entire tooth structure depends upon the developmental stage of tooth when the cells are harvested.
We also investigated the possible roles of BMP4 in HERS during the early stage of tooth root development.
Generally, dental development can be assessed by either the phase of tooth eruption or the stage of tooth calcification, with the latter being more reliable.
In the early stage of tooth germ development, the bud of the dental epithelium is invaginated by the underlying mesenchyme, resulting in the formation of a cap-like folded shape.
Moreover, embryonic body weight is a reliable indicator of prenatal 'tooth age', i.e. the stage of tooth development (Fig. 7).
These findings were concurrent with the gene expression of mesenchymal origin cells, such as odontoblasts, during the early stage of tooth development [ 19, 20].
Signals from the underlying dental mesenchymal compartment initiate this differentiation process by inducing PABs to SABs after basement membrane degradation during the bell stage of tooth development [ 4].
In a large-scale gene expression study (www.eurexpress.org), Ltbp3 transcripts were detected at E14.5 cap stage of tooth development (6).
However, if the re-activation of such an odontogenic pathway is a prerequisite to initiating tooth development and to reaching an advanced stage of tooth morphogenesis, it is insufficient for forming functional teeth with a dentin cone covered with enamel.
Under a stereomicroscope (Leica MZ7.5; Leica Microsystems, Wetzlar, Germany), we microsurgically dissected first molar tooth germs from the mandibular arch of stage E14.5 (equal to cap stage of tooth germ in development) embryos.
The upgoing expressions of those markers indicate that mechanical stress is vital not only in the early stage of osteogenesis but also in the later stage of tooth and bone formation.
