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PubMed2006

Potential of dental mesenchymal cells in developing teeth.

The tooth, composed of dentin and enamel, develops through epithelium-mesenchyme interactions. Neural crest (NC) cells contribute to the dental mesenchyme in the developing tooth and differentiate into dentin-secreting odontoblasts. NC cells are known to differentiate into chondrocytes and osteoblasts in the craniofacial region. However, it is not clear whether the dental mesenchymal cells in the developing tooth possess the potential to differentiate into a lineage(s) other than the odontoblast lineage. In this study, we prepared mesenchymal cells from E13.5 tooth germ cells and assessed their potential for differentiation in culture. They differentiated into odontoblasts, chondrocyte-like cells, and osteoblast-like cells. Their derivation was confirmed by tracing NC-derived cells as LacZ(+) cells using P0-Cre/Rosa26R mice. Using the flow cytometry-fluorescent di-beta-D-galactosidase system, which makes it possible to detect LacZ(+) cells as living cells, cell surface molecules of dental mesenchymal cells were characterized. Large number of LacZ(+) NC-derived cells expressed platelet-derived growth factor receptor alpha and integrins. Taken together, these results suggest that NC-derived cells with the potential to differentiate into chondrocyte-like and osteoblast-like cells are present in the developing tooth, and these cells may contribute to tooth organogenesis.

Animals↗

PubMed1989

[Prognosis for the deciduous molars of juvenile dogs after root canal filling using apatite root sealer].

There are various restrictions on the root canal filling of deciduous roots after root canal treatment unlike in the case of permanent teeth, because deciduous molars undergo physiological root resorption with aging. Among the restrictions, it is most important that the root canal filling material be similarly absorbed and disappear along with the deciduous root so that it does not prevent the eruption of the permanent successors. Hardly any of the root canal filling materials currently on the market, however, are suitable for deciduous molars because some of them disappear earlier than the deciduous root without becoming indurated in the root canal, while some delay tooth replacement because they are resorbed with great difficulty, and continue strongly to stimulate the surrounding tissue of the root apex. Root canal filling materials utilizing alpha-TCP and hydroxyapatite with excellent biocompatibility have recently been put on the market by Sankin Kygyo Co. Type-III, in particular, contains only 5% iodoform, causing only very slight stimulation, and is a relatively good product from a practical standpoint, i.e., filling the root canal using a lentulo. Root canal filling was performed immediately after dental pulp extraction from the deciduous mandibular molars of juvenile dogs to determine the feasibility of filling deciduous teeth with root canal filling materials. Three dogs were then observed for sequential changes in the resorption of the deciduous roots, presence/absence of adverse effects on permanent successors, and influence on the process of eruption by means of radiographic examination every week. The results obtained were as follows: 1. The type-III apatite root sealar or Vitapex used for root canal filling was not absorbed, and there was almost no resorption of the root. Thus, the deciduous teeth on the experimental side were ejected and shed. 2. There was no significant difference in the amount of tooth germ formed between the experimental and control sides. 3. The amount of eruption tended to be delayed because of insufficient resorption of the root of the deciduous predecessor, but this tendency was considered to be due to the influence of the timing of root canal filling and individual difference. In the final analysis, no definite conclusions could be drawn.

Animals↗

PubMed1975

The transplantation and surgical movement of developing teeth.

There has now been one hundred years of study, research and clinical application into the possibility of transplantation of tooth germs, and a short review of the literature is given. Two clinical cases are described in which replacement of upper incisors has been successfully achieved by auto transplantation of a developing lower bicuspid and upper canines respectively. Long term follow up of such cases now extends over a decade and it is suggested that this technique has reached a stage now hen it can be recommended to the dental profession generally as a worthwhile clinical approach.

Accidents↗

PubMed1994

Distal-less and other homeobox genes in the development of the dentition.

The mammalian tooth develops through an interaction between two tissue layers of different embryologic origin. A number of transcription factors and as well as two members of the Msx class of homeobox genes have been shown to be involved in the histogenesis of the mammalian tooth. This raised the possibility that other homeobox genes might be involved in dental morphogenesis. We have amplified mouse tooth germ cDNA from three different gestational ages by the polymerase chain reaction with degenerate primers for 18 classes of homeobox genes. Members of several classes have been isolated, including the Msx genes, two Dlx genes, and the Dbx, MHox, Mox2A genes. One of the Dlx genes, Dlx-7, had not previously been reported in mammals, and some details are presented of its cDNA sequence. This work plus that of other investigators has shown that at least six Dlx genes are expressed in developing teeth or in first branchial arches, suggesting the possibility that these genes are involved in specifying complexity within or between teeth. The screening approach with degenerate primers is a successful way to identify new as well as previously known regulatory genes expressed in developing tooth embryos.

Amino Acid Sequence↗

PubMed2002

Double tooth.

The form of primary and permanent teeth can differ morphologically from that which is considered normal, completely or in some parts. The changes in tooth form can be hereditary or caused by some disease or trauma. Fusion is a union of one or more teeth during development. Gemination means that two separate morphological units were created by division of the tooth germ. The intention of this study was to state the prevalence of double teeth (fusion and gemination) among the persons tested, as to gender, distribution in the maxilla or mandible, and whether the anomaly occurred bilaterally or unilaterally. The results of this investigation have shown that in a total of examined 3,517 plaster models, a prevalence of double teeth was 0.2%. 57.2% of them were fusioned and 42.9% geminated.

Female↗

PubMed1998

[Oro-dental injuries during intubation anesthesia].

Injuries to the oro-dental tissue are still one of the most frequent mishaps during endotracheal intubation and general anaesthesia. However, damage to the soft and hard tissues in most cases involves oral structures already showing advanced pathogenic alterations. Injuries to the teeth are therefore rather more often due to the disease of the teeth than to mistakes during anaesthesia. The risk of injuries to the teeth can be ascertained by means of a presurgical inspection of the oral cavity and evaluation of the individual anatomical conditions in the head and neck region, which may well interfere with the endotracheal intubation. In contrast to anaesthetic pitfalls causing severe disturbance of general health, dental trauma can be treated with quite satisfying functional and aesthetic results. However, in order to maintain conditions for the complete restitution of injured teeth immediate dental therapy is recommended. In preterm infants which need mechanical ventilation during the postnatal period direct laryngoscopy as well as mechanical alterations caused by an oral tube can cause injuries to the tooth germs of the first and second dentition and deformation of the maxillary skeleton. In consequence the patient will need intensive therapy of the resulting disturbances for several years. This review gives information about the causes and types of injuries to the oral and maxillofacial region during general anaesthesia. In addition, the anatomical conditions and pathological changes associated with an increased risk for oro-dental injuries and the facilities for prevention are discussed. Finally, the main aspects of emergency treatment of injuries to the dental hard tissues are presented.

Anesthesia, Inhalation↗

PubMed2004

Expression of ephrin-A ligands and EphA receptors in the developing mouse tooth and its supporting tissues.

Ephrins are cell-membrane-bound ligands for Eph receptor tyrosine kinases and regulate a variety of developmental processes. In order to investigate the potential roles of the ephrin-Eph system in tooth formation, we studied the cellular mRNA expression of Ephrin-A1-A5 and EphA2, EphA3, EphA4, EphA7, and EphA8 receptors during embryonic histomorphogenesis of the mouse first molar (embryonic days 11.5-18.5). Ephrin-A1, ephrin-A5, EphA2, EphA3, EphA4, and EphA7 were expressed in the tooth germ at the epithelial thickening stage, and later, ephrin-A1, ephrin-A5, EphA2, EphA4, and EphA7 showed distinct expression patterns in the enamel organ undergoing epithelial folding morphogenesis. Prior to birth, ephrin-A1, ephrin-A5, EphA2, and EphA4 transcripts were present in the cuspal area of the dental papilla including the preodontoblasts. In addition, ephrin-A1 and ephrin-A5 were seen in the forming blood vessels and alveolar bone, respectively. In contrast, ephrin-A2, ephrin-A3, and ephrin-A4 showed ubiquitous expression during odontogenesis, whereas EphA8 transcripts were not observed. During dental trigeminal axon pathfinding (embryonic days 12.5-13.5), ephrin-A2, ephrin-A4, and ephrin-A5 were evenly distributed in the trigeminal ganglion, whereas EphA7 was expressed in a subset of ganglion cells. These results suggest regulatory roles for ephrin-A/EphA signaling in the formation of the tooth organ proper and its supporting tissues.

Animals↗

PubMed2001

Otodental syndrome: a case report and genetic considerations.

A 5-year-old boy presented with otodental syndrome. His maxillary and mandibular incisors were within normal limits. The premolar/molar areas in all quadrants were occupied by markedly macrodontic teeth showing globular shape. The canines had a similar rounded shape. Two canines and 1 of the other abnormal teeth demonstrated areas of yellow hypoplastic enamel. Radiographs revealed that some of the abnormal teeth had bifurcated pulp chambers and pulp stones. Premolar tooth germs were absent. Audiometry demonstrated that the child had a marked bilateral sensorineural hearing loss for frequencies above 1000 Hz. No other members of the immediate family were clinically affected. The parents of the child were not aware of any similarly affected relatives. Suggestions with respect to possible genetic mechanisms and gene participation in the etiology of this syndrome are offered.

Bicuspid↗

PubMed1979

[A case contribution to the Gardner syndrome].

As to its course the Gardner syndrome is similar to a chronic disease and has the following symptoms: 1. Fibro-epithelial tumours of the skin with first symptoms in early childhood. 2. Osteomes, osteofibromas, desmoids mainly located in the cranial region. 3. Disturbances of the dental development in the form of tooth retentions, persistence of milk teeth and supernumerary tooth germs. 4. Intra- and retroperitoneal or intramesenteric fibromatoses which scarcely become clinically manifest. 5. Intestinal polyposis occurring in most cases only in the third decade of life. The tumours of the skin, of the connective tissue and of the bone are always benign, whereas the intestinal polypi show a considerable tendency toward malignant degeneration. For this reason, the prognosis of the Gardner syndrome must be considered unfavourable. On the basis of a case report, the clinical symptoms and findings in the maxillofacial region are outlined.

Adult↗

PubMed1989

[The surgical-orthodontic classification of retained and dystopic teeth of the second dentition in dysostosis cleidocranialis].

Dysostosis cleidocranialis concerns both teeth and jaw and is characterized by supernumerary teeth, dentitio tarda, tooth impaction and eventually follicular cysts. The concept of treatment can be divided in two stages: 1. At the beginning of the delayed secondary dentition (dentitio tarda) the operative removal of the supernumerary tooth germs and 2. corresponding to the belated morphological development (dentitio tarda) the operative exposure of the impacted teeth of the secondary dentition. The first operation facilitates a morphological development and especially a vertical drift without any obstacles. The second becomes necessary when only the morphological development, but not the vertical drift of the teeth of the secondary dentition takes place. The operative exposure is done using a self-developed technique [13, 18]. At the same time as the exposed teeth undergo a spontaneous vertical drift, orthopedic treatment for anomaly is started.

Adolescent↗

PubMed1990

Complete root resorption of an upper central incisor due to ectopic eruption of canine in a deaf-mute child.

Unilateral complete root resorption of the permanent central incisor was experienced in a boy with deaf and dumb. Transposition of tooth germ or abnormally directed eruption of the canine caused not only an entire root but a part of enamel resorption. The patient was diagnosed clinically and radiographically as an ectopic eruption of the right maxillary upper canine and then treatments were provided to improve esthetic and functional conditions in terms of eruption guidance. It should be emphasized that the early diagnosis and the subsequent eruption guidance is essential in the patient with these kinds of eruption disorder of the mixed dentition.

Adolescent↗

PubMed2002

Tooth eruption into the newly generated bone induced by recombinant human bone morphogenetic protein-2.

OBJECTIVE: The purpose of this study was to observe tooth eruption pattern into the newly generated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2). METHOD: Three 12-week-old beagle dogs were used. Following wound healing of the extracted maxillary third deciduous incisor at the age of 13 weeks, a resection of maxillary alveolar bone (8 mm by 8 mm by 8 mm) was carried out, accompanied by extraction of the maxillary second incisor tooth germ. The rhBMP-2 (5 microgram/100 microL or 10 microgram/100 microL) was implanted in the resected area. A group that was not implanted after resection and a nonresected group were used as controls. Serial changes of the eruption pattern of the maxillary third incisor in the implanted area were observed radiographically. Oxytetracycline and calcein were employed as bone markers. Nine weeks after the implantation, the animals were sacrificed. The samples were observed histologically and analyzed using peripheral quantitative computerized tomography to acquire the bone mineral density (BMD). RESULTS: In the rhBMP-2 (5 microgram/100 microL)-treated group, histological findings and the BMD of the newly generated bone were almost same as in the nonresected group. The maxillary third incisor erupted through the implanted area. However, in the rhBMP-2 (10 microgram/100 microL)-treated group, more osteoinductive activity and significantly higher BMD were observed in the newly generated bone. The maxillary third incisor erupted mesially so as to avoid this implanted area. CONCLUSION: Results showed that bone remodeling and tooth eruption through the newly generated bone appear to be dose dependent. Accordingly, proper dosage of rhBMP-2 should be determined for successful clinical application.

Absorbable Implants↗

PubMed1998

FGFs and BMP4 induce both Msx1-independent and Msx1-dependent signaling pathways in early tooth development.

During early tooth development, multiple signaling molecules are expressed in the dental lamina epithelium and induce the dental mesenchyme. One signal, BMP4, has been shown to induce morphologic changes in dental mesenchyme and mesenchymal gene expression via Msx1, but BMP4 cannot substitute for all the inductive functions of the dental epithelium. To investigate the role of FGFs during early tooth development, we examined the expression of epithelial and mesenchymal Fgfs in wild-type and Msx1 mutant tooth germs and tested the ability of FGFs to induce Fgf3 and Bmp4 expression in wild-type and Msx1 mutant dental mesenchymal explants. Fgf8 expression is preserved in Msx1 mutant epithelium while that of Fgf3 is not detected in Msx1 mutant dental mesenchyme. Moreover, dental epithelium as well as beads soaked in FGF1, FGF2 or FGF8 induce Fgf3 expression in dental mesenchyme in an Msx1-dependent manner. These results indicate that, like BMP4, FGF8 constitutes an epithelial inductive signal capable of inducing the expression of downstream signaling molecules in dental mesenchyme via Msx1. However, the BMP4 and FGF8 signaling pathways are distinct. BMP4 cannot induce Fgf3 nor can FGFs induce Bmp4 expression in dental mesenchyme, even though both signaling molecules can induce Msx1 and Msx1 is necessary for Fgf3 and Bmp4 expression in dental mesenchyme. In addition, we have investigated the effects of FGFs and BMP4 on the distal-less homeobox genes Dlx1 and Dlx2 and we have clarified the relationship between Msx and Dlx gene function in the developing tooth. Dlx1,Dlx2 double mutants exhibit a lamina stage arrest in maxillary molar tooth development (Thomas B. L., Tucker A. S., Qiu M. , Ferguson C. A., Hardcastle Z., Rubenstein J. L. R. and Sharpe P. T. (1997) Development 124, 4811-4818). Although the maintenance of molar mesenchymal Dlx2 expression at the bud stage is Msx1-dependent, both the maintenance of Dlx1 expression and the initial activation of mesenchymal Dlx1 and Dlx2 expression during the lamina stage are not. Moreover, in contrast to the tooth bud stage arrest observed in Msx1 mutants, Msx1,Msx2 double mutants exhibit an earlier phenotype closely resembling the lamina stage arrest observed in Dlx1,Dlx2 double mutants. These results are consistent with functional redundancy between Msx1 and Msx2 in dental mesenchyme and support a model whereby Msx and Dlx genes function in parallel within the dental mesenchyme during tooth initiation. Indeed, as predicted by such a model, BMP4 and FGF8, epithelial signals that induce differential Msx1 and Msx2 expression in dental mesenchyme, also differentially induce Dlx1 and Dlx2 expression, and do so in an Msx1-independent manner. These results integrate Dlx1, Dlx2 and Fgf3 and Fgf8 into the odontogenic regulatory hierarchy along with Msx1, Msx2 and Bmp4, and provide a basis for interpreting tooth induction in terms of transcription factors which, individually, are necessary but not sufficient for the expression of downstream signals and therefore must act in specific combinations.

Animals↗

PubMed1993

Immunocytochemical demonstration of nerve growth factor receptor (NGF-R) in developing human fetal teeth.

Evidence is accumulating that nerve growth factor receptor (NGF-R or p75NGFR) can mediate cell growth and differentiation of non-neuronal cells. NGF-R expression was studied in developing teeth of human embryos and fetuses between the 6th and 18th weeks of gestation, using a monoclonal mouse-anti-human NGF-R antibody. In contrast to earlier findings in rodents, the NGF-R expression of the human dental papilla was found to be transient. NGF-R was present in the condensing ecto-mesenchymal cells of the dental papilla in the early cap stage tooth germ. In later developmental stages, a shift of the NGF-R expression from the papilla to the cytoplasmic membrane of the inner enamel epithelium (IEE) was demonstrated. As in rodent odontogenesis, the NGF-R immunoreactivity of the IEE remained until the odontoblasts started secretion of predentinal matrix in the late bell state. The mitotic activity in the IEE was detected by an antibody against proliferating cell nuclear antigen (PCNA) and showed that the NGF-R expression of the IEE decreased as the cell proliferation ceased. We propose that NGF-R may, be involved in differential and/or proliferative events of human odontogenesis.

Embryo, Mammalian↗

PubMed2005

Isolation of precursor cells (PCs) from human dental follicle of wisdom teeth.

The dental follicle is an ectomesenchymal tissue surrounding the developing tooth germ. It is believed that this tissue contains stem cells and lineage committed progenitor cells or precursor cells (PCs) for cementoblasts, periodontal ligament cells, and osteoblasts. In this study, we report the isolation of PCs derived from dental follicle of human third molar teeth. These fibroblast-like, colony forming and plastic adherent cells expressed putative stem cell markers Notch-1 and Nestin. We compared gene expressions of PCs, human mesenchymal stem cells (hMSCs), periodontal ligament cells (PDL-cells) and osteoblasts (MG63) for delimitation of PCs. Interestingly, PCs expressed higher amounts of insulin-like growth factor-2 (IGF-2) transcripts than hMSCs. Differentiation capacity was demonstrated under in vitro conditions for PCs. Long-term cultures with dexamethasone produced compact calcified nodules or appeared as plain membrane structures of different dimensions consisting of a connective tissue like matrix encapsulated by a mesothelium-like cellular structure. PCs differentially express osteocalcin (OCN) and bone sialoprotein (BS) after transplantation in immunocompromised mice but without any sign of cementum or bone formation. Therefore, our results demonstrate that cultured PCs are unique undifferentiated lineage committed cells residing in the periodontium prior or during tooth eruption.

Adolescent↗

PubMed1986

Characterization and immunocytochemical localization of dentine phosphoprotein in rat and bovine teeth.

Dentine phosphoprotein (DPP) was isolated from unerupted bovine molars and from rat incisors. The proteins were characterized biochemically and used to immunize rabbits and guinea pigs. Antibody activity was investigated by enzyme-linked immunosorbent assay (ELISA). Guinea-pig anti-rat DPP did not cross-react with bovine DPP, but rabbit anti-bovine DPP did cross-react with rat DPP. Anti-rat DPP antiserum was applied to cryotome sections of rat molar tooth germs and DPP immunoreactivity was seen in dentine, odontoblasts, odontoblast processes and pre-ameloblasts. Anti-bovine DPP antiserum reacted positively in bovine dentine and dentinal tubules. When this antiserum was applied to rat tissue, predentine was positive but dentine was negative. Adsorption experiments with DPP, purified by methods including and excluding precipitation with calcium, suggested that non-calcium precipitable DPP is present in rat predentine. Rat and bovine DPP are thus species-specific and DPP is synthesized by the odontoblasts, transported through their processes and secreted into the dentine.

Amino Acids↗

PubMed1993

[Lysosomal storage diseases, genetic or drug-induced? effect of glycosaminoglycan and sphingolipid disorders on dental tissues].

In vivo studies were carried out on dental tissues of rat incisor after a single injection of suramin, a drug which induces mucopolysaccharidosis-like disease. Accumulation of lysosome-like structures was seen in secretory ameloblasts and odontoblasts. In vitro studies on embryonic tooth germ buds showed similar changes when they were cultured in presence of suramin. Anti-phospholipid immunolabelling revealed a developmentally regulated temporo-spatial pattern. Radiolabeling with 3H-suramin indicated cytosolic and nuclear incorporation. The drug acting as polyanion interacted directly with predentine. 35S sulphate incorporation was impaired by the drug. Another lysosomal storage disease, the sphingolipidosis, Krabbe's disease was also investigated in human. Changes were observed in pulp cells and as a consequence in dentin. Enamel also displayed many changes. Pharmacological or genetically acquired diseases constitute models providing insights on the role played by glycosaminoglycans and phospholipids in biomineralization.

Ameloblasts↗

PubMed1975

In vitro studies of bone resorption by the root-resorbing tissue from the bovine deciduous tooth.

Granulation tissue which is responsible for root resorption of deciduous tooth lies between root of the deciduous tooth and its permanent tooth germ. This tissue is called "root-resorbing tissue". Its bone-resorbing activity was investigated in vitro. Bovine root-resorbing tissue was cultured in close contact with 45Ca-labeled dead calvaria of rats. Bone-resorbing activity was determined by measuring 45Ca released from labeled calvaria during culture. It was found that only the root-resorbing tissue which was rich in odontoclasts and had a good blood supply in its surface layer had bone-resorbing ability, and that bone resorption occurred only when it was placed in close contact with calvarium. The root-resorbing tissue which was poor in odontoclasts and blood vessels failed to stimulate by 25-hydroxy-vitaim D3 or heparin, but not by larger amounts of parathyroid hormone, vitamin D3, and dihydrotachysterol when added to the culture.

Alveolar Process↗