A (3H)-proline autoradiographic study of dentine bridge formation in transplanted mouse molar teeth

An in vitro model of human dental pulp repair

Pulp tissue responds to dentin injury by laying down reactionary dentin secreted by existing odontoblasts or reparative dentin elaborated by odontoblast-like cells that differentiated from precursor cells in the absence of inner dental epithelium and basement membrane. Furthermore, growth factors or active dentin matrix components are fundamental signals involved in odontoblast differentiation. In vitro, dental pulp cells cultured under various conditions are able to express typical markers of differentiation, but no culture system can re-create pulp response to dentin drilling. This paper reports the behavior of thick slices from human teeth drilled immediately after extraction and cultured from 3 days to 1 month. Results show that the damaged pulp beneath the cavity is able to develop, in vitro, some typical aspects correlated to tissue healing, evidenced by cell proliferation (BrdU-positive cells), neovascularization (positive with antitype-IV collagen antibodies), and the presence of functional (3H proline-positive) cuboidal cells close to the injured area. After 30 days of culture, elongated spindle-shaped cells can be seen aligned along the edges of the relevant dentin walls, whereas sound functional odontoblasts are well-preserved beneath healthy areas. This tissue recovery leads us to believe that such a culture model will be a useful system for testing factors regulating pulp repair.

Renewal and migration of rat incisor mesenchymal cells after doxorubicin administration

Ten female rats were intravenously injected with doxorubicin (20 mg/kg) and divided into two equal groups receiving a dose of tritiated thymidine either simultaneously with doxorubicin or 1 h before being killed after 5 days. Six control animals were correspondingly injected with 3H-thymidine. The left and right maxillary incisors were prepared for histologic and microautoradiographic investigation, respectively. The distribution of labeled cells in animals injected 1 h before death showed the regions of proliferation, whereas migration from these regions was evaluated by longer observation time. A zone of reduced dentin deposition lined by irregular odontoblasts being young odontoblasts and late preodontoblasts was observed at the time of doxorubicin injection. Pulpally to the dentinal lesion, islands of irregular predentin were deposited by non-progenitive pulp cells and depolarized odontoblasts. The late preodontoblasts were renewed from progenitive pulp cells, leading to a disturbed mantle predentin deposition.

A histological investigations of isografts of immature mouse molars to an intrabony and extrabony site

Partially-developed teeth with remnants of their periodontal ligaments isografted to the tibial shaft medulla and renal subcapsular site were capable of progressive regeneration characterized by renewed tubular dentine formation. Bone formation occurred in relation to grafts at the renal site as well as the tibial shaft; evidence of periodontal fibre reorganization was observed in grafts at both sites. Despite post-transplantation dentine and cementum formation, continued development of roots of normal morphology did not occur, perhaps due to disappearance of epithelial root sheath.

Capping of monkey pulps with Dycal and a Ca-eugenol cement

Capping of 120 teeth in four monkeys was performed with Dycal or with a calcium-eugenol cement. The observation periods were 8 days or 90 days. The monkeys were killed, and the teeth were examined histologically. After 8 days, the pulp-tissue reactions were basically the same in the two groups. The tissue adjacent to the exposure site was characterized by varying amounts of necrotic tissue, inflammatory cells, and extravasated erythrocytes. Capping material and dentin chips were displaced into the pulp tissue. Particles from the capping materials were found in vessels, macrophages, and foreign body cells. After 90 days, more hard-tissue formation occurred in the Dycal group than in the Ca-eugenol cement group. The hard tissue was formed by either fibroblasts or the original odontoblasts.

An autoradiographic study of experimental odontogenic cyst formation in the mouse

Proliferative populations of cells within the epithelial lining of developing experimental odontogenic cysts were identified by labeling with 3H-thymidine. Mouse molar teeth extracted from 10-day-old mice were transplanted subcutaneously and host animals were injected with 3H-thymidine 1 h prior to sacrifice. The cysts which developed around the crown of the transplanted teeth were prepared for autoradiographical examination. Labeling indices were high initially but decreased rapidly as the cysts enlarged. The pattern of labeling, however, bore no resemblance to the labeling of the reduced enamel epithelium from which the cysts developed. It was concluded that labeling activity reflects only the state of development and activity of the cyst and not the origin of the cyst.