Tooth transplantation in the mouse. I. The use of procion dyes and tritiated proline in a study of syngeneic tooth germ transplantation

Mechanisms controlling secondary initiation of dentinogenesis: a review

Dentinogenesis can be initiated secondarily as an intrinsic ability of the dental pulp to repair, or after interaction of pulp cells with specific exogenous inductive factors. In the present article the basic developmental aspects, highlighting the mechanism by which dentinogenesis is initiated during tooth development, are discussed. Furthermore, clinical and experimental observations concerning the events taking place during secondary initiation of dentine formation, as part of exposed or non-exposed pulp tissue repair, or as a result of dentine matrix or other chemical-pulp cell interactions, are reviewed. Discussion includes hypotheses relating to the crucial biological steps leading to expression of odontoblastic-like cell phenotype and secondary initiation of dentine histogenesis.

Calcification capacity of dental papilla mesenchymal cells transplanted in the isogenic mouse spleen

The capacity of the dental pulp to form calcified tissue was examined in papilla cells dissociated from first molar tooth germs of the neonatal mouse and isografted in the spleen for up to 7 days. To obtain papilla cell populations without odontoblasts, pulpal mesenchyme was isolated mechanically from the enamel organ after 0.1% trypsin treatment and rolled on a membrane filter. On day 3 after transplantation, the grafted papilla cells had changed into large, spindle-shaped cells, and initial calcification with needle-like crystals began in association with the collagenous matrix surrounding those cells. On day 7 after transplantation, the spindle cells transformed into odontoblast-like cells containing well-developed secretory organelles, and irregular, but nontubular, calcified tissues were commonly observed surrounding the extracellular collagenous matrix. The calcified tissue matrix with cellular inclusions displayed a structure similar to that of osteodentin. During this period, an intense positive reaction for alkaline phosphatase (ALPase) activity was demonstrated along the cell membranes of the odontoblast-like cells aligned at the periphery of forming calcified tissue. Enzymatic activity could not be detected on the cells incorporated completely into osteodentin-like matrix. The present results show that the papilla cell population transplanted into the spleen formed osteodentin-like material, thus demonstrating the capacity of papilla cells to produce calcified tissue.

Differentiation of odontoblasts in mouse dental papillae recombined with normal or chemically-treated dentinal matrices

Separation and recombination experiments were made with manually or trypsin-dissociated dental papillae (day 15, 16, 17, 18 in utero and 2, 7, 14 postnatal) and manually isolated hard tissues of the third molar crown (14 postnatal days). Several series of hard tissues were further treated with citric acid, hyaluronidase or sodium hypochlorite. The recombinations were transplanted into the subcutaneous tissue of new-born mice. Grafts were removed 7, 14 and 21 days later and prepared for light and electron microscopy. Whatever the age of the papilla and whatever the treatment of the crowns, well-characterized odontoblasts differentiated and deposited new layers of tubular dentine, except when the recombined dental papilla was 15 days old. These findings indicate that odontoblasts are very early committed (since day 16 in utero) and that they may differentiate in dental papillae in contact with chemically altered dentinal matrices.

Dentin and osteodentin matrix formation in apicoectomized replanted incisors in cats

The reestablishment and rate of osteodentin and dentin matrix formation in 27 apicoectomized replanted and 20 control incisors in cats were studied after Procion H8-BS vital staining. In control teeth the pattern of matrix formation differed in the various pulpal zones, with a higher rate of matrix formed toward apical areas, most dominantly in maxillary incisors. Osteodentin formation could be traced after a lag period of more than 10 days after replantation. Thirty and 60 days postoperatively osteodentin matrix was found in the total pulpal length in 83% and 73% of the teeth, respectively. A common finding was a tubular osteodentin matrix in the pulpal apical third in the replanted teeth. Tubular osteodentin matrix was, however, present most incisally in some teeth 60 days postoperatively. Internal resorption corresponding to outer cervical lesions dominated the pulpal reactions in the maxillary replanted teeth after 60 days. It is concluded that under the present experimental conditions the pulp tissue possesses a high healing potential and that the osteodentin formation reflects the pulpal healing pattern after replantation traumas. The results also indicate that successful pulpal healing depends on unexposed dentinal tubules.

Ultrastructure of a new generation of odontoblasts in grafted coronal tissues of mouse molar tooth germs

Third molar tooth germs were removed from 14-day-old mice and freed from the enamel organ and follicle. After section of the apical tissues, including Hertwig's sheath, they were transplanted in 1-day-old newborn mice of the same lineage. Electron microscopy of grafts removed 7, 14 and 21 days later showed that, following the disappearance of the initial layer of odontoblasts and a period of adaptation, 14 days after transplantation newly differentiated odontoblasts deposited tubular dentine. The dentine matrix production was increased over that of controls, demonstrating that synthesis was accelerated, possibly because of lack of nerves in the grafts. Numerous characteristic structures that might be involved in the transit of proteoglycans from the Golgi apparatus were seen, as far as the extremity of the odontoblast processes. The particular experimental conditions allowed the observation in the neck region of the odontoblast of a concentration of coated vesicles which might be involved in cellular lengthening. Thus, in the presence of a fine and regular vascular network, a new generation of odontoblasts may differentiate, even in the absence of epithelial and nervous elements, and so predentine may contain inductive factors that allow the odontoblastic differentiation of pulp cells in contact with it.

Morphogenesis of mineralized tissues induced by neonatal mouse molar pulp isografts in the spleen

Tooth pulps dissociated intact with EDTA were isografted for up to 40 days, and examined by light and electron microscopy for hard tissue morphodifferentiation. Grafts formed tubular dentine and osteodentine. Tubular dentine, penetrated regularly by elongated odontoblast processes, resembled normal dentine and was formed when the original odontoblasts continued normal matrix secretion. Osteodentine was formed by spindle-shaped cells with large round nuclei which presumably were transformed pulp cells, and incorporated the same elements as found in cells of non-tubular dentine. Occasionally, odontoblasts were contiguous with both the regular dentine and the osteodentine. Thus in EDTA-dissociated pulps transplanted to the spleen, the original odontoblasts produce tubular dentine and other pulp cell differentiate to form osteodentine.

The development of mandibular molar tooth germs isografted in the mouse spleen

Tooth germs taken from 13-day-old embryonic mice and isografted in the spleen of adult mice were examined by light and electron microscopy. Well-organized tooth structures from the early cap stage to fully developed and mineralized mature teeth were obtained up to day 60 after transplantation. Germs on day 2 were similar to those prior to the onset of grafting but reached the late cap stage of development on day 4. On day 6, enamel and dentine formation were initiated and inner enamel epithelium and dental papilla cells were polarized. On days 10-15, enamel-matrix secretion was completed and almost all ameloblasts had become resorptive enamel epithelium. India ink injected from the recipient caudal vein accumulated to the capillaries within the pulp throughout the newly-formed vessels. On day 20, defined root formation had begun but occasionally irregular and cellular osteodentine was formed in root areas. On day 30, transplants were covered with reduced enamel epithelium and acellular cementum was formed at the root areas together with rudimentary periodontal ligament fibres. Cellular cementum became thicker up to day 40. There was little evidence of cellular infiltration from recipient tissue up to day 60. The spleen seems to be a suitable site for transplantation of tooth germs.

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.

Production of keratinizing cysts within mandibles of rats with autogenous gingival epithelial grafts. A histologic study

A method for the consistent production of epithelial-lined cysts in the mandibles of rats is described. Attached gingiva from the interdental papilla was excised and implanted into prepared cavities in the mandible. The animals were examined at time periods varying from 0 to 45 days later. Twenty-seven of the 28 animals examined after 7 days or longer had developed cysts. An interpretation of the pathogenesis of these cysts was made based on histologic observations and measurements of the cysts at the various time intervals.