Scanning electron microscopy of casts of rat molar tooth pulp chambers

Pulpal progenitors and dentin repair

Mesenchymal stem cells are present in the dental pulp. They have been shown to contribute to dentin-like tissue formation in vitro and to participate in bone repair after a mandibular lesion. However, their capacity to contribute efficiently to reparative dentin formation after pulp lesion has never been explored. After pulp exposure, we have identified proliferative cells within 3 zones. In the crown, zone I is near the cavity, and zone II corresponds to the isthmus between the mesial and central pulp. In the root, zone III, near the apex, at a distance from the inflammatory site, contains mitotic stromal cells which may represent a source of progenitor cells. Stem-cell-based strategies are promising treatments for tissue injury in dentistry. Our experiments focused on (1) location of stem cells induced to leave their quiescent state early after pulp injury and (2) implantation of pulp progenitors, a substitute for classic endodontic treatments, paving the way for pulp stem-cell-based therapies.

Microradiographic and electron microscopic observations of the enamel-covered dentine in rat molars

The enamel-covered primary and secondary coronal dentine in the molars of 90-day-old and 360-day-old rats was examined using microradiography. Some preparations were subsequently examined by transmission and scanning electron microscopy (SEM). Fractured dentine surfaces and methacrylate casts of the tubular system in the primary dentine were also examined with SEM. No microradiographic evidence of a hypermineralized peritubular matrix, such as that seen in man and other species, was seen in either young or old rats. Transmission and SEM confirmed the microradiographic findings. The tubule obliteration and extensive intra-luminal mineral deposits which have been reported in the enamel-free coronal dentine of the rat molar were not seen in the enamel-covered coronal dentine but some evidence of tubule obliteration was seen in the secondary dentine.