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At least 1,009 records · Page 56Linked to original sources
PubMed2002

Expression of Runx1, -2 and -3 during tooth, palate and craniofacial bone development.

We describe the expression of three Runt-related RUNX genes (previously termed AML, Cbfa, or Pebp2alpha) Runx1 and Runx3 during the development of teeth and other craniofacial tissues and compare them to Runx2 expression reported earlier. All three genes were expressed in mesenchymal condensates. Runx1 was expressed in several cartilage primordia earlier than Runx3, and Runx2 was intense in all mesenchymal condensations of bones and teeth. Only Runx1 was expressed in epithelia, and in tooth germs transcripts were detected in outer dental epithelium. Runx1 was also intensely expressed in the midline epithelium of palatal shelves. In early tooth morphogenesis Runx3 was coexpressed with Runx2 in a thin layer of mesenchymal cells underlying dental epithelium. Unlike Runx2, Runx3 was expressed in odontoblasts. However, Runx3 mutant mice did not show obvious tooth phenotype or deviations of Runx1 and Runx2 expression patterns in the tooth.

Animals↗
PubMed2002

Expression of Runx1, -2 and -3 during tooth, palate and craniofacial bone development.

We describe the expression of three Runt-related RUNX genes (previously termed AML, Cbfa, or Pebp2alpha) Runx1 and Runx3 during the development of teeth and other craniofacial tissues and compare them to Runx2 expression reported earlier. All three genes were expressed in mesenchymal condensates. Runx1 was expressed in several cartilage primordia earlier than Runx3, and Runx2 was intense in all mesenchymal condensations of bones and teeth. Only Runx1 was expressed in epithelia, and in tooth germs transcripts were detected in outer dental epithelium. Runx1 was also intensely expressed in the midline epithelium of palatal shelves. In early tooth morphogenesis Runx3 was coexpressed with Runx2 in a thin layer of mesenchymal cells underlying dental epithelium. Unlike Runx2, Runx3 was expressed in odontoblasts. However, Runx3 mutant mice did not show obvious tooth phenotype or deviations of Runx1 and Runx2 expression patterns in the tooth.

Animals↗
PubMed2002

Expression and regulation of hedgehog-interacting protein during early tooth development.

Sonic hedgehog (Shh) expression is highly localized to the epithelium at the future sites of tooth development. This restricted expression suggests that inhibition of Shh in areas where teeth do not form may be an important mechanism in tooth germ localization. Recently, Hip, a putative vertebrate antagonist of Shh, has been identified. We have investigated the expression of Hip during early tooth development and found it not to be localized in cells immediately adjacent to Shh-expressing cells, but rather at a distance, separated by cells expressing Ptc1. Hip is also regulated by Shh in the first branchial arch. Shh-soaked agarose beads are able to induce the expression of Hip in odontogenic mesenchyme. A role for Hip might be to prevent the spread of excess Shh ligand beyond an immediate Ptc1-induced zone in odontogenic mesenchyme. This mechanism would therefore restrict Shh signaling specifically to those regions along the oral axis that are destined to form teeth.

Animals↗
PubMed1993

Developmental disturbances of permanent teeth following trauma to the primary dentition.

The topographic relationship of the apices of the primary teeth to the permanent tooth germs explains the potential for possible developmental disturbances of the permanent teeth after injuries to their predecessors. The anatomical, histologic and clinical aspects of permanent tooth malformation following trauma to the primary teeth are described. One hundred and fourteen children with originally 255 traumatized primary teeth have been re-examined (with an average period of 5.1 years after the trauma) to assess any developmental disturbances of the corresponding permanent teeth. Twenty-three per cent of partially or completely erupted permanent teeth showed developmental disturbances. The most frequent malformation was enamel hypoplasia including enamel discoloration and/or enamel defects. The highest prevalence of developmental disturbances of permanent teeth was found after intrusive injuries of primary teeth.

Adolescent↗
PubMed1987

A hypothetical model of genetic control of tooth-crown growth in man.

Twins and families were investigated to obtain information about inheritance of tooth-crown size. Sixty twin pairs and 100 families were examined using four methods of estimation. The results suggest genetically controlled interactions between tooth germs during their formation. A hypothetical model of odontogenesis is presented.

Humans↗
PubMed1991

A scanning electron microscopic study of the enamel of neonatal teeth.

Neonatal teeth, two mandibulars incisors and one maxillary central incisor, from two separate patients were examined, by SEM. Besides typical enamel anomalies, the incisors exhibited partial or total absence of root formation. These findings suggest that the early eruption of natal and neonatal teeth is dependent on osteoblastic activity within the area of the tooth germ. The reported cases show that teeth may erupt without root formation and without periodontal ligament which correlate with the role of the dental follicle during tooth eruption.

Dental Enamel↗
PubMed1994

The three-dimensional structure of Tomes' processes and their relationship to arrangement of enamel prism in dog teeth.

The relationship between the course of enamel prisms and the direction of secretory face in Tomes' process of ameloblast was examined three-dimensionally in the dog tooth by light and electron microscopy, as well as by reconstruction. Scanning electron microscopic observation on the developing enamel surface after the dissolution of the enamel organ showed numerous groups of pits with bulbous faces inclined in the same sidewards direction, while those faces in neighboring groups were inclined in an opposite direction. Tangential semithin sections from demineralized tooth germs were serially cut from the enamel surface to the enamel-dentin junction. These sections showed numerous belt-like zones arranged perpendicular to the meridian of the tooth. A straight row of enamel prisms perpendicular to the boundaries of the belt-like zones was selected at 142 microns from the enamel-dentin junction. The row of prisms and their successive Tomes' processes were reconstructed from micrographs with a personal computer. The cut ends of the enamel prisms initially perpendicular to the boundaries appeared as a sine curve, viewed from the enamel-dentin junction. In a single belt-like zone, the horizontal tilt angles of the enamel prisms towards the enamel-dentin junction tended to be largest at the center of the zone, and smallest near the boundaries. The long axis of each enamel prism was at right angles to the secretory face of the Tomes' process. The secretory faces in a single belt-like zone were inclined in the same sidewards direction and the secretory faces in neighboring zones were inclined in opposite directions. The results suggest that the direction of the sidewards displacement in ameloblasts is related to that of the secretory face of Tomes' processes. Further, one group of ameloblasts with their secretory faces inclined in the same sidewards direction form one belt-like zone.

Ameloblasts↗
PubMed1975

The 47,XYY male, Y chromosome, and tooth size.

Permanent teeth of 12 individuals with a 47,XYY chromosome constitution have been examined. The tooth sizes of 47,XYY males were found to be larger than those of control males and females. In many instances the differences were statistically significant. Using these results, it was possible to conclude that a factor or factors which influence excess growth of 47,XYY males probably are in effect during prenatal life, but without doubt must be in effect very early in postnatal life. The time period needed for the achievement of final excess growth is relatively short, in the case of first permanent molars probably only from 2 1/2 to 3 1/2 years. On the basis of the finding that the Y chromosome apparently carries genes affecting tooth sizes in normal males [1], it was suggested that gene products of the extra Y chromosome could cause the observed size difference between normal and 47,XYY males. The nature of the influence of one versus two Y chromosomes on growth was discussed in terms of the possible influence of the Y chromosome on the cell divisions within the developing tooth germ.

Adolescent↗
PubMed2003

The role of epithelial remodelling in tooth eruption in larval zebrafish.

Based on light and transmission electron-microscopic observations on erupting first-generation teeth in the zebrafish, Danio rerio, we propose a biphasic mechanism for tooth eruption: (1). formation of an epithelial crypt prior to eruption of the tooth, possibly as a result of constraints in the epithelium resulting from the growth of adjacent tooth germs, and (2). detachment of cellular interdigitations both within the pharyngeal epithelium, at the pharyngeal epithelium/enamel organ boundary, and between the outer and inner dental epithelium, resulting in the exposure of the tooth tip in the crypt, immediately after tooth ankylosis. Later, further detachment of interdigitations between the inner and the outer enamel epithelium unfolds the epithelium even more and leads to a more pronounced exposure of the tooth tip. The presence of small patches of non-collagenous matrix on the outer surface of the tooth close to where it merges with the attachment bone is interpreted as a device to prevent complete detachment of the enamel organ. The biphasic nature of the mechanism for tooth eruption is supported by observations on in vitro cultured heads. First-generation teeth develop normally and crypts are formed, as under in vivo conditions, but the teeth fail to erupt. Taken together, our observations suggest that epithelial remodelling plays a crucial role in eruption of the teeth in this model organism.

Animals↗
PubMed2006

An unusual developmental disturbance of an unerupted permanent incisor due to trauma to its predecessor - a case report.

Developmental disturbances of unerupted permanent tooth result from trauma to primary tooth as there is a close proximity between the root of the primary tooth and its permanent successor. The damage to the unerupted permanent tooth occurs by the transmission of traumatic forces to the permanent tooth germ. In the present case, however, a developmental disturbance on the permanent maxillary central incisor resulting from a direct effect of the inversely intruded primary maxillary central incisor is presented. The intruded tooth was extracted under general anesthesia. Upon eruption of the permanent central incisor, a localized crown malformation along with enamel hypoplasia which was not classified as a developmental disturbance before was observed. The damaged sites were restored with a light-cured composite resin.

Child, Preschool↗
PubMed1993

An immunocytochemical study of the innervation of developing human fetal teeth using protein gene product 9.5 (PGP 9.5).

Developing teeth of 32 human fetuses (crown-rump length 11-205 mm) were examined immunohistochemically by antisera to protein gene product 9.5 (PGP 9.5) in an attempt to shed light upon the possible role of innervation in odontogenesis. As a control for the specificity of PGP 9.5 as a neuronal marker, the results were verified by immunocytochemical co-localization in peripheral nerves of neurone-specific enolase, neurofilaments and S-100 protein. The dental follicle received the first nerve fibres in the early cap stage. At this stage, fibroblasts differentiated in the presence of nerve fibres and formed the dental follicle surrounding the developing tooth. In the dental papilla, however, no fibres were demonstrated until the dentine and enamel matrices had formed, about half of the present height of the tooth germ. Most nerve fibres were localized in the basal part of the papilla until the last stage examined and usually followed the blood vessels of the papilla. Thus the effect of innervation on tooth development may be associated with the development of the dental follicle. A novel finding was that functional odontoblasts were not only positive for S-100 but also for PGP 9.5, indicating their neural crest origin.

Antibodies, Monoclonal↗
PubMed1989

[Severe root resorption of maxillary incisors and ectopic eruption of maxillary canine].

A 12-year-old female with severe root resorption in the maxillary left central and lateral incisors (Case 1) and a 27-years-old female with the maxillary left canine erupted in the position of the central incisor (Case 2) were examined and treated. The findings and treatment procedures were as follows: 1. In Case 1, severe root resorption was caused by the ectopic eruption of the canine. On the lingual surface, the resorption had proceeded to a part of enamel. 2. In the Case 1, after the central and lateral incisors were extracted, the canine was carefully guided into the position of the lateral incisor. 3. In Case 2, treatment was not performed, because the chief compliant was carious lesions and the patient did not mind the malposition of the canine. 4. In both Case 1 and 2, the main reason of ectopic eruption of canines was presumably not a discrepancy between the tooth material and the basal arch length but the malposition of the tooth germ and/or abnormal eruption process of the canine.

Adolescent↗
PubMedDate not supplied

Mixed odontogenic tumors: an analysis of 23 new cases.

The ameloblastic fibroma, ameloblastic fibrodentinoma, and ameloblastic fibro-odontoma are mixed odontogenic tumors that are considered to arise from both epithelial and mesenchymal elements of the tooth germ. This article presents the clinical and histopathologic characteristics of 23 new cases. The patients' ages ranged from 3 to 19 years (median 9). Most tumors were asymptomatic and were associated with an unerupted tooth or teeth. All patients were treated with simple enucleation of the tumor. We found that histologically these lesions comprise a spectrum. Some were probably benign odontogenic tumors (neoplasms) and others were odontomas undergoing maturation (hamartomas); however, in any given case we were, on histologic grounds, unable to differentiate the two. The majority, if not all, of our cases were nonaggressive with little or no tendency to recur, whereas some reported cases have exhibited local aggressiveness and recurrence, suggestive of neoplasia. In our opinion, it is clinically important to distinguish the mixed odontogenic tumors from ameloblastoma since the mixed tumors, found mostly in children, are relatively benign when compared to ameloblastoma, which is found in all age groups (usually adults). The usually innocuous behavior of these lesions does not justify aggressive treatment initially, and simple enucleation should be appropriate in most cases.

Adolescent↗
PubMed2000

Inhibition of apoptosis in the primary enamel knot does not affect specific tooth crown morphogenesis in the mouse.

The enamel knot (EK), located in the center of cap-stage tooth germs, is a transitory cluster of non-dividing epithelial cells, eventually linked to the outer dental epithelium by the enamel septum (ES). It might act as a signaling center providing positional information for tooth morphogenesis and could regulate the growth of tooth cusps through the induction of secondary signaling EKs. The EK undergoes apoptosis, which could constitute a mechanism whereby the signaling functions of this structure are terminated. Recently, we demonstrated the segregation of 5-bromo-2'-deoxyuridine (BrdU) negative inner dental epithelial (IDE) cells of the EK into as many individual groups of cells as cusps will form and suggested a morphogenetic role for these particular IDE cells. Using Z-VAD-fmk, a specific caspase inhibitor, apoptosis in the primary EK of first mouse lower cap-staged molars and lower incisors cultured in vitro was abrogated. No obvious histological alterations were observed in the incisors, whereas a prominent EK and an ES connecting the outer dental epithelium (ODE) and the BrdU negative IDE cells capping cusp L2 were observed in the molars. EK specific transcription (Shh, Msx-2, Bmp-2, Bmp-4) was down-regulated in the body of these structures with the exception of the associated IDE cells. In these experimental conditions, segregation of non-dividing transcriptionally active IDE cells occurred and a normal cusp pattern was expressed.

Animals↗
PubMed2003

Tooth and jaw: molecular mechanisms of patterning in the first branchial arch.

The mammalian jaw apparatus is ultimately derived from the first branchial arch derivatives, the maxillary and mandibular processes, and composed of a highly specialised group of structures. Principle amongst these are the skeletal components of the mandible and maxilla and the teeth of the mature dentition. Integral to the development of these structures are signalling interactions between the stomodeal ectoderm and underlying neural crest-derived ectomesenchymal cells that populate this region. Recent evidence suggests that in the early mouse embryo, regionally restricted expression of homeobox-containing genes, such as members of the Dlx, Lhx and Gsc classes, are responsible for generating early polarity in the first branchial arch and establishing the molecular foundations for patterning of the skeletal elements. Teeth also develop on the first branchial arch and are derived from both ectoderm and the underlying ectomesenchyme. Reciprocal signalling interactions between these cell populations also control the odontogenic developmental programme, from early patterning of the future dental axis to the initiation of tooth development at specific sites within the ectoderm. In particular, members of the Fibroblast growth factor (Fgf), Bmp, Hedgehog and Wnt families of signalling molecules induce regionally restricted expression of downstream target genes in the odontogenic ectomesenchyme. Finally, the processes of morphogenesis and cellular differentiation ultimately generate a tooth of specific class. Many of the same genetic interactions that are involved in early tooth development mediate these effects through the activity of localised signalling centres within the developing tooth germ.

Animals↗
PubMed1984

Injury to developing canines as a complication of intranasal antrostomy. Report of a case.

A case is presented in which a 7-year-old boy had an intranasal antrostomy made, during which operation both developing permanent canines were injured. Despite complete resection of the roots, both canines erupted normally, supporting recent experimental studies of the eruption mechanism which suggested the importance of the tooth follicle instead of root growth as the essential mechanism for tooth eruption. Methods to prevent damage to permanent tooth germs during intranasal osteotomy are described.

Child↗
PubMed2006

Ectopia or concomitant hypohyperdontia? A case report.

This report describes the unusual appearance seen on a panoramic radiograph of an orthodontic patient which the authors argue may represent ectopia or concomitant hypohyperdontia of the mandibular premolar teeth. A literature review describes the frequency of such anomalies in this area from previous studies. The presenting features of the patient and the differential diagnoses are explored. Treatment planning is discussed and treatment carried out in this particular case is detailed. The unusual symmetrical bilateral anomalies in this patient may point to a genetic determinant of tooth germ position and/or movement.

Anodontia↗
PubMed1991

Expression of syndecan gene is induced early, is transient, and correlates with changes in mesenchymal cell proliferation during tooth organogenesis.

Syndecan is an integral cell surface proteoglycan which contains an extracellular matrix-binding domain and a cytoskeleton-associated domain and may therefore transfer changes in the extracellular environment to cellular behavior. Changes in syndecan gene expression during embryonic and early postnatal mouse tooth development were analyzed by in situ hybridization and compared with the distribution of syndecan core protein and cell proliferation studied by immunohistochemistry. Syndecan RNA became accumulated in the condensing mesenchymal cells around the invaginating epithelial tooth bud during early development, and this accumulation became more intense when morphogenesis advanced to the cap stage. During the bell stage, when the cuspal pattern of the tooth is established, syndecan transcripts were lost, and RNA was not detected in the terminally differentiated or postmitotic odontoblasts. In the epithelium, syndecan RNA was intensely expressed in the invaginating epithelial bud, but the expression was reduced during the cap and bell stages. However, local stimulation in syndecan gene expression was observed in the epithelial preameloblasts immediately preceding their terminal differentiation into ameloblasts, which was accompanied by a complete loss of transcripts. There was a close correlation between the changes in syndecan transcripts and the distribution of syndecan core protein. Furthermore, analysis of cell proliferation by immunohistochemical detection of BrdU incorporation revealed that in the mesenchyme, but not in the epithelium, syndecan was intensely expressed by proliferating cells. The analysis of mRNA by Northern blot indicated that the transcripts in mesenchymal and epithelial cells were of similar size. In the slot-blot analysis the changes in syndecan transcripts correlated with the overall changes observed in the in situ hybridization analysis. The role of tissue interactions in the regulation of the syndecan gene was studied by using tissue recombination cultures of separated epithelial and mesenchymal components of the early tooth germ. The in situ hybridization and Northern blot analysis of these explants showed that the expression was increased in the mesenchyme cultured in contact with the epithelium. Our results indicate that syndecan gene expression in the embryonic tooth mesenchyme is induced by epithelial-mesenchymal interactions and thereafter expressed stage-dependently and transiently by the differentiating cells during organogenesis. The association of syndecan expression with mesenchymal cell proliferation raises the possibility that, in addition to behaving as a matrix receptor, syndecan may have a role in controlling growth and that syndecan may have different functions in epithelial and mesenchymal cells.

Animals↗