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At least 1,027 records · Page 57Linked to original sources
PubMed2005

Structure, attachment, replacement and growth of teeth in bluefish, Pomatomus saltatrix (Linnaeus, 1776), a teleost with deeply socketed teeth.

Tooth replacement poses many questions about development, pattern formation, tooth attachment mechanisms, functional morphology and the evolution of vertebrate dentitions. Although most vertebrate species have polyphyodont dentitions, detailed knowledge of tooth structure and replacement is poor for most groups, particularly actinopterygians. We examined the oral dentition of the bluefish, Pomatomus saltatrix, a pelagic and coastal marine predator, using a sample of 50 individuals. The oral teeth are located on the dentary and premaxillary bones, and we scored each tooth locus in the dentary and premaxillary bones using a four-part functional classification: absent (A), incoming (I), functional (F=fully ankylosed) or eroding (E). The homodont oral teeth of Pomatomus are sharp, deeply socketed and firmly ankylosed to the bone of attachment. Replacement is intraosseus and occurs in alternate tooth loci with long waves of replacement passing from rear to front. The much higher percentage of functional as opposed to eroding teeth suggests that replacement rates are low but that individual teeth are quickly lost once erosion begins. Tooth number increases ontogenetically, ranging from 15-31 dentary teeth and 15-39 premaxillary teeth in the sample studied. Teeth increase in size with every replacement cycle. Remodeling of the attachment bone occurs continuously to accommodate growth. New tooth germs originate from a discontinuous dental lamina and migrate from the lingual (dentary) or labial (premaxillary) epithelium through pores in the bone of attachment into the resorption spaces beneath the existing teeth. Pomatomus shares unique aspects of tooth replacement with barracudas and other scombroids and this supports the interpretation that Pomatomus is more closely related to scombroids than to carangoids.

Animals↗
PubMed2006

Mandibular first and second molar tooth transposition: a case report.

A case is reported of what appears to be a transposition affecting the mandibular first, second, and third molars. The possible aetiology is discussed in relation to previously published studies. In the case described the primary actilogical factor appears to intraosseous migration of the developing tooth germ.

Child↗
PubMed1997

Multiple dens invaginatus affecting maxillary lateral incisors and a supernumerary tooth.

Dens invaginatus is a developmental variation resulting from an alteration in the normal growth pattern of the dental papilla of a tooth. This anomaly occurs predominantly in maxillary permanent lateral incisors. Multiple occurrence in maxillary incisor teeth in the same patient has frequently been reported, and examination of bilateral teeth for the anomaly is often carried out routinely. This paper reports an unusual case of multiple invaginations, including dens invaginatus affecting maxillary lateral incisors and a supernumerary tooth and minor invaginations of the upper canines. Moreover, the case illustrates the importance of examining all the teeth in patients who present with dens invaginatus and palatal pits in incisors and canines. The possibility that the supernumerary tooth had resulted from gemination of the lateral incisor tooth germ is discussed.

Dens in Dente↗
PubMed1989

Use of fluoride by young children and prevalence of mottled enamel.

The prevalence of mottled enamel in the permanent dentition of children participating in a fluoride (F-) program at the dental school of the Vrije Universiteit (Amsterdam) was investigated in a study utilizing the Thylstrup-Fejerskov (TF) index. The randomly chosen children received a F- regime considered optimal by the Dutch Advisory Committee for Prevention of Oral and Dental Diseases. From the children examined (n = 83; 49 boys and 34 girls; mean age, 13 years and 5 months), 74% exhibited mottled enamel in a slight to moderate degree. More teeth were affected and the degree of mottling was higher when children started to use F- at an earlier age. Unintentional ingestion of toothpaste containing 0.15% F- during frequent toothbrushing in combination with the daily intake of F- tablets before the age of four may explain the high prevalence of mottled enamel. After these treatments, F- concentrations in plasma of young children can reach values which can directly affect the developing tooth germ.

Adolescent↗
PubMed2004

Management of the infected, abscessed primary tooth--a report.

Despite modern advances in the prevention of dental caries and an increased understanding of the importance of maintaining the natural dentition in children, many abscessed and infected primary teeth, especially the deciduous molars, are still being prematurely lost through extractions. This report describes a simple, quick and effective technique that has been successfully used to manage infected, abscessed primary teeth. Results indicate that the non-vital primary pulp therapy technique is both reliable and effective. Not only is the procedure painless, it also helps to relieve the child of his immediate pain and achieves the primary goals of elimination of infection and retention of the tooth in a functional state without endangering the developing permanent tooth germ.

Abscess↗
PubMedDate not supplied

Oligodontia in the primary dentition with permanent successors: report of case.

A case of oligodontia in the primary dentition with corresponding permanent successors is described. A two-year-old Japanese boy was admitted to the pedodontic clinic with the chief complaint of congenitally missing primary teeth. The boy appeared to be normally developed and was in good physical health. There was no history of trauma, extraction, or exfoliation of primary teeth. Clinical examination showed that eight anterior teeth were missing. Also, a canine and three first molars were much smaller in size and were malformed. However, radiographic examination at age four years, ten months showed that all of the permanent tooth germs--including the corresponding successors of congenitally missing primary teeth--were evident.

Anodontia↗
PubMed1984

Fluctuating asymmetry in the deciduous dentition of Dominican mulatto children.

An assessment of deciduous tooth-size asymmetry showed no evidence of sex differences. When asymmetry was compared between the various tooth dimensions, the buccolingual dimensions of mandibular incisors consistently displayed high asymmetry values. This finding may reflect a developmental interaction between the deciduous incisor tooth germs and their lingually-placed permanent successors.

Child, Preschool↗
PubMed1994

Development of several organs that require inductive epithelial-mesenchymal interactions is impaired in LEF-1-deficient mice.

Lymphoid enhancer factor 1 (LEF-1) is a sequence-specific DNA-binding protein that is expressed in pre-B and T lymphocytes of adult mice, and in the neural crest, mesencephalon, tooth germs, whisker follicles, and other sites during embryogenesis. We have generated mice carrying a homozygous germ-line mutation in the LEF-1 gene that eliminates its protein expression and causes postnatal lethality. The mutant mice lack teeth, mammary glands, whiskers, and hair but show no obvious defects in lymphoid cell populations at birth. The LEF-1-deficient mice also lack the mesencephalic nucleus of the trigeminal nerve, the only neural crest-derived neuronal populations. Together, the pattern of these defects suggest an essential role for LEF-1 in the formation of several organs and structures that require inductive tissue interactions.

Animals↗
PubMed1984

Supernumerary teeth in anthropoid primates and models of tooth development.

Supernumerary teeth are usually regarded as de-novo structures that result from abnormal development by the splitting of a tooth germ. The notions of abnormal and de novo appear to be applicable in only one instance, the morphological dental twin. All other types of supernumerary deciduous teeth can be explained by either a progress zone or an interstitial budding model of tooth differentiation. The development of extra structures as well as the loss of normally-present teeth can be explained by differences in potential within the context of normal development.

Animals↗
PubMed1992

Expression patterns of the homeobox gene, Hox-8, in the mouse embryo suggest a role in specifying tooth initiation and shape.

We have studied the expression patterns of the newly isolated homeobox gene, Hox-8 by in situ hybridisation to sections of the developing heads of mouse embryos between E9 and E17.5, and compared them to Hox-7 expression patterns in adjacent sections. This paper concentrates on the interesting expression patterns of Hox-8 during initiation and development of the molar and incisor teeth. Hox-8 expression domains are present in the neural crest-derived mesenchyme beneath sites of future tooth formation, in a proximo-distal gradient. Tooth development is initiated in the oral epithelium which subsequently thickens in discrete sites and invaginates to form the dental lamina. Hox-8 expression in mouse oral epithelium is first evident at the sites of the dental placodes, suggesting a role in the specification of tooth position. Subsequently, in molar teeth, this patch of Hox-8 expressing epithelium becomes incorporated within the buccal aspect of the invaginating dental lamina to form part of the external enamel epithelium of the cap stage tooth germ. This locus of Hox-8 expression becomes continuous with new sites of Hox-8 expression in the enamel navel, septum, knot and internal enamel epithelium. The transitory enamel knot, septum and navel were postulated, long ago, to be involved in specifying tooth shape, causing the inflection of the first buccal cusp, but this theory has been largely ignored. Interestingly, in the conical incisor teeth, the enamel navel, septum and knot are absent, and Hox-8 has a symmetrical expression pattern. Our demonstration of the precise expression patterns of Hox-8 in the early dental placodes and their subsequent association with the enamel knot, septum and navel provide the first molecular clues to the basis of patterning in the dentition and the association of tooth position with tooth shape: an association all the more intriguing in view of the evolutionary robustness of the patterning mechanism, and the known role of homeobox genes in Drosophila pattern formation. At the bell stage of tooth development, Hox-8 expression switches tissue layers, being absent from the differentiating epithelial ameloblasts and turned on in the differentiating mesenchymal odontoblasts. Hox-7 is expressed in the mesenchyme of the dental papilla and follicle at all stages. This reciprocity of expression suggests an interactive role between Hox-7, Hox-8 and other genes in regulating epithelial mesenchymal interactions during dental differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Characterization and localization of epidermal growth factor receptors in human developing tooth.

In this study the characterization and localization of Epidermal Growth Factor (EGF) receptor in human jaws, from fetuses ranging in age from 9 to 12 weeks is reported for the first time. Binding of [125I]-EGF to membranes obtained from three separate pools of fetal jaws was specific and time- and temperature-dependent. Analysis of the binding data revealed the presence of a single class of binding site with high affinity (Kd, 9.2 x 10(-10) mol/L) and mean binding capacity of 128 fmoles/mg protein. Immunohistochemical study demonstrated the presence of EGF receptors in the early developmental stages of human tooth. In the bud stage, the positivity was localized in the epithelial cells. In the cap stage, EGF receptors was present in the outer and inner enamel cells, in some cells of the stellate reticulum and in the mesenchymal papilla and follicle cells. In the bell stage, positivity for EGF receptors was present in the outer enamel epithelium, in some cells of the stellate reticulum and in the mesenchymal cells of the follicle and papilla. The presence of EGF receptors in the proliferative stages in both epithelial and mesenchymal cells suggests that EGF is involved in the early developmental stages of the human tooth germ.

Dental Enamel↗
PubMed1999

Comparative study of MSX-2, DLX-5, and DLX-7 gene expression during early human tooth development.

Msx and Dlx family transcription factors are key elements of craniofacial development and act in specific combinations with growth factors to control the position and shape of various skeletal structures in mice. In humans, the mutations of MSX and DLX genes are associated with specific syndromes, such as tooth agenesis, craniosynostosis, and tricho-dento-osseous syndrome. To establish some relationships between those reported human syndromes, previous experimental data in mice, and the expression patterns of MSX and DLX homeogenes in the human dentition, we investigated MSX-2, DLX-5, and DLX-7 expression patterns and compared them in orofacial tissues of 7.5- to 9-wk-old human embryos by using in situ hybridization. Our data showed that MSX-2 was strongly expressed in the progenitor cells of human orofacial skeletal structures, including mandible and maxilla bones, Meckel's cartilage, and tooth germs, as shown for DLX-5. DLX-7 expression was restricted to the vestibular lamina and, later on, to the vestibular part of dental epithelium. The comparison of MSX-2, DLX-5, and DLX-7 expression patterns during the early stages of development of different human tooth types showed the existence of spatially ordered sequences of homeogene expression along the vestibular/lingual axis of dental epithelium. The expression of MSX-2 in enamel knot, as well as the coincident expression of MSX-2, DLX-5, and DLX-7 in a restricted vestibular area of dental epithelium, suggests the existence of various organizing centers involved in the control of human tooth morphogenesis.

Animals↗
PubMed2001

The role of effectors of the activin signalling pathway, activin receptors IIA and IIB, and Smad2, in patterning of tooth development.

The gene for activin betaA is expressed in the early odontogenic mesenchyme of all murine teeth but mutant mice show a patterning defect where incisors and mandibular molars fail to develop but maxillary molars develop normally. In order to understand why maxillary molar tooth development can proceed in the absence of activin, we have explored the role of mediators of activin signalling in tooth development. Analysis of tooth development in activin receptor II and Smad2 mutants shows that a similar tooth phenotype to activin betaA mutants can be observed. In addition, we identify a novel downstream target of activin signalling, the Iroquois-related homeobox gene, Irx1, and show that its expression in activin betaA mutant embryos is lost in all tooth germs, including the maxillary molars. These results strongly suggest that other transforming growth factor beta molecules are not stimulating the activin signalling pathway in the absence of activin. This was confirmed by a non-genetic approach using exogenous soluble receptors to inhibit all activin signalling in tooth development, which reproduced the genetic phenotypes. Activin, thus, has an essential role in early development of incisor and mandibular molar teeth but this pathway is not required for development of maxillary molars.

Activin Receptors, Type II↗
PubMed1995

[The limits of conservative care in pedodontics].

Despite progress in the decrease of caries by means of many preventive dental programs, children's teeth of poor socio-economic groups are still strongly affected. The well known role of children's teeth in oro-facial growth and harmony, as well as in the development of functions as chewing, speaking or phonation and swallowing, has justified their preservation during all their functional periods. Several conservative therapies allow to reach this purpose. However, extensive dental caries, difficulty to get child tooth infection under control, injuries on permanent tooth germs and child's general health deficiency, can limit preservation of infected teeth, leading to their extraction.

Algorithms↗
PubMed2001

Orthodontic tooth movement in the mixed dentition. Histological study of a human specimen.

MATERIAL AND METHOD: We present a retrospective analysis of periodontal tissue reactions and clinically relevant phases of permanent tooth eruption and deciduous tooth resorption after half a year of orthodontic tooth movement in the upper and lower jaw of a deceased male (age 9 years 3 months). Specimens of the horizontal plane (lower jaw) and sagittal plane (upper jaw) were prepared by the ground microsection technique without prior decalcification. RESULTS: Histologically, reactions in the periodontal ligament presented as characteristic appositional/resorptive metaplastic processes in the areas of tension and pressure, with side effects such as root resorption and periodontal necrosis being only minor. In the upper jaw, an erupting permanent canine was closely associated with the tooth germ of the first premolar. Resorptive follicle activity had resulted in extensive erosion of the interradicular bone and root resorption in the area of the first premolars. CONCLUSION: These findings suggest that it might prove useful to take critical topographic findings as parameters for differential therapeutic decisions. Follicle-driven deciduous tooth resorption presenting partly as resorption lacunae and partly with linear characteristics was accompanied by resorptive/appositional remodeling of the alveolar socket as well as regressive changes in the supracrestal fibers of the marginal gingiva.

Child↗
PubMed1999

Developmental regulation and ultrastructure of glycogen deposits during murine tooth morphogenesis.

The distribution and ultrastructure of glycogen deposits were investigated in the murine tooth germ by histochemical periodic acid-Schiff (PAS) staining and transmission electron microscopy. Lower and upper first molars were examined in mouse embryos at embryonic days 11.5-17 (E11.5-E17) and in 2-day-old postnatal (P2) mice. The oral and dental epithelia and the mesenchymal cells were generally PAS-positive during tooth morphogenesis. PAS-negative cells were present at E13 in the distal tip of the tooth bud epithelium and in the contacting mesenchyme, and this complete lack of PAS reactivity continued in the dental papilla mesenchyme and inner enamel epithelium during the cap and bell stages. The lack of glycogen deposits in the interacting epithelium and mesenchyme during early morphogenesis may be associated with their demonstrated high signaling activities. Mesenchymal cells in the dental follicle consistently possessed small clusters or large pools of glycogen, which disappeared by P2. Since an intense PAS reaction was seen in mesenchymal cells at future bone sites, the glycogen in the dental follicle cells may be associated with their development into hard-tissue-forming cells. Ultrastructural observation of the enamel organ cells from the cap to early bell stages (E14-E15) revealed the occurrence of glycogen pools, which were associated with the Golgi apparatus and with vesicles having amorphous contents. Glycogen particles were also occasionally present inside vesicles or in the extracellular matrix. These may be associated with the exocytosis of glycosaminoglycan components into extracellular spaces and the formation of the stellate reticulum.

Animals↗
PubMed2000

Teeth and their sex-dependent dimorphic shape in three species of Costa Rican plethodontid salamanders (Amphibia: Urodela).

The shape of the teeth and their sex-dependent dimorphic expression in three species of Costa Rican plethodontids (Bolitoglossa subpalmata, Oedipina uniformis and Nototriton abscondens) were studied using light microscopy and scanning electron microscopy. The teeth of the vomerine tooth patches are about one third larger than the teeth of the jaws in B. subpalmata and O. uniformis, whereas all teeth of N. abscondens are of about uniform size. The occurrence of bicuspid tooth germs in the fetus proves that primary teeth are bicuspid in these directly developing plethodontids. Females possess only bicuspid teeth consisting of a pedicel and a crown, as is considered characteristic for urodeles after metamorphosis. Adult males possess conical monocuspid teeth on the premaxillary. These teeth--which are similar to the typical late larval tooth of salamanders presenting a larval stage--are about twice as big as the neighbouring bicuspid maxillary teeth. N. abscondens males possess some monocuspid teeth and teeth of aberrant shapes on the premaxillary and the maxillaries. A tendency to build more monocuspid teeth in the premaxillary region than in the maxillary region can be observed in this species. We suppose that different degrees of sensitivity to androgens in each section of the dental lamina of the upper jaw cause the secondary occurrence of conical monocuspid teeth predominantly on the premaxillary section.

Animals↗
PubMedDate not supplied

A spontaneous mutation: amelogenesis imperfecta with cysts in rats.

Amelogenesis imperfecta (AI) is an inherited dental disease of enamel formation in humans, and there are various phenotypes due to the combination of enamel quality and quantity. We encountered four female IGS rats with spontaneous AI including odontogenic cysts in the incisor teeth. Histopathologically, in the incisors of the rats, the enamel organ was disorganized with the remaining enamel matrix residing within the enamel space. The expanding cysts derived from the enamel organ were formed in the periosteal connective tissue on the labial side. At the bottom of the tooth germs, the precursor cells of the epithelial root sheath were arranged regularly and the enamel organs were preserved to the same degree as those of normal rats. In the molar teeth of the affected rats an enamel matrix remained on the neck and crown of the erupted teeth; however, no abnormality was observed at the tooth root. Although an animal model of AI has been developed from mutants of the SHR-SP rat strain, the present cases represent another potential model of the disease because of the differences in the way the enamel matured and the odontogenic cyst formation in the incisors.

Amelogenesis Imperfecta↗