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At least 829 records · Page 46Linked to original sources
PubMed1989

[Traumatic injuries to the teeth for children].

For modern medical care, social background may be an essential factor, and medical care through out the individual's life time appears to have significant meaning. From this point of view, total dental care throughout childhood is being carried out in the field of pediatric dentistry. It can be stated that we pedodontists have a degree of farsight in the treatment of traumatic injuries to the teeth regarding children (the theme of the lecture), since the injured teeth are treated not only as items to be restored but also as a part of the growing body with careful consideration on the effects with regard to orlo-facial growth. It is obvious that epidemiological surveilance is necessary to understand the cause of dental injuries, and also careful attention ought to be paid to the activity of the children to grasp the potential background of dental trauma. Here, I would like to explain the consequences of the serial work on the traumatic injuries to teeth which were carried out in our department. 1) The prevalence of dental injuries in children appeares to be on the increase according to a judgement based on the surveilances form in and out of the country. Also as the parental recognition for dental injuries became higher, more patients visited dental clinic or hospital looking for improved treatment techniques. 2) Careful consideration must be paid to the succedaneus permanent tooth germ, when a deciduous tooth suffered from traumatic injury. The effect of the direction applied and the area of the traumatic force on the root of the deciduous tooth, the successor and the surrounding tissue was investigated by means of kinetic analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1990

Influence of colchicine on the addition of a sugar to the enamel protein in secretory ameloblasts of cultured germs of rat molar tooth by 3H-galactose radioautography.

The influence of colchicine on the addition of 3H-galactose to the enamel protein in secretory ameloblasts of cultured germs of rat molar tooth was investigated by light- and electron-microscopic radioautography. In tooth germs cultured without colchicine, the reaction products of 3H-galactose were observed over Golgi cisternae at early chase times and then localized over the enamel with time. In tooth germs cultured with colchicine, the silver grains were seen over the Golgi cisternae, condensing granules and accumulated secretory granules. Some grains also appeared with time over the pale granular material precipitated in the intercellular space with colchicine treatment. In quantitative analysis with light microscopic radioautography, values of silver grain counts over the unit area (100 microns2) on ameloblasts and enamel of colchicine-treated tooth germs were significantly lower at both 0 min and 30 min chase after 30 min pulse than those of control tooth germs, respectively. This finding indicates that colchicine diminished the incorporation of 3H-galactose into the secretory ameloblast of cultured tooth germs. It is suggested that colchicine decreases the activity of the Golgi apparatus with regard to the addition of sugar to the synthesizing glycoprotein in the secretory ameloblast.

Ameloblasts↗
PubMed1998

Association of developmental regulatory genes with the development of different molar tooth shapes in two species of rodents.

While the evolutionary history of mammalian tooth shapes is well documented in the fossil record, the developmental basis of their tooth shape evolution is unknown. We investigated the expression patterns of eight developmental regulatory genes in two species of rodents with different molar morphologies (mouse, Mus musculus and sibling vole, Microtus rossiaemeridionalis). The genes Bmp-2, Bmp-4, Fgf-4 and Shh encode signal molecules, Lef-1, Msx-1 and Msx-2, are transcription factors and p21CIP1/WAF1 participates in the regulation of cell cycle. These genes are all known to be associated with developmental regulation in mouse molars. In this paper we show that the antisense mRNA probes made from mouse cDNA cross-hybridized with vole tissue. The comparisons of gene expression patterns and morphologies suggest that similar molecular cascades are used in the early budding of tooth germs, in the initiation of tooth crown base formation, and in the initiation of each cusp's development. Furthermore, the co-localization of several genes indicate that epithelial signalling centres function at the three stages of morphogenesis. The earliest signalling centre in the early budding epithelium has not been reported before, but the latter signalling centres, the primary and the secondary enamel knots, have been studied in mouse. The appearance of species-specific tooth shapes was manifested by the regulatory molecules expressed in the secondary enamel knots at the areas of future cusp tips, whilst the mesenchymal gene expression patterns had a buccal bias without similar species-specific associations.

Animals↗
PubMed2006

Morphological and clinical considerations of first and second permanent molar eruption disorders.

Tooth eruption is a complex biological process which starts from the site of development in the jaw bone until the teeth reach their final functional position in the chewing plane. Various factors can disturb this process. Besides mechanical obstacles on the eruption path, a pathological position or axial orientation of the tooth germ, morphological aberrations of the tooth or pathological alterations of the periodontium, primary disorders of the eruption mechanism may lead to complete or partial retention of the tooth in the jaw bone. These morphological features bear upon the prognosis of orthodontic correction which is dependent upon the underlying cause. First and second molars are rarely affected by eruption disorders, with a prevalence of 0.01 to 0.08 per cent, however, marked consequences for function such as posterior open bite or elongation of the antagonists may result. Following an overview of pathogenetic factors of tooth eruption disorders, selected cases of impacted first and second permanent molars are presented with respect to their morphological causes.

Child↗
PubMed2000

Dental follicle cell-conditioned medium enhances the formation of osteoclast-like multinucleated cells.

An influx of mononuclear cells and the subsequent increase of osteoclasts around tooth germs suggests that the dental follicle (DF) regulates or influences bone resorption required for tooth eruption. In order to study the effects of DF cell products on osteoclast formation during tooth eruption, a conditioned medium (CM) was created in which DF cells were added to mouse bone marrow cultures. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like multinucleated cells were formed in the presence of 10 nM 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The CM, dose-dependently, stimulated the formation of TRAP-positive cells in the presence of 1,25(OH)2D3 for 14 days culture. The number of these cells decreased due to degradation in the control culture. A semi-solid methylcellulose assay in the presence of CM showed little expression of colony-stimulating activity. These results suggest that the DF cells of a developing tooth produce factor(s) that enhance osteoclast formation and bone resorption necessary for tooth eruption.

Acid Phosphatase↗
PubMed2003

Identification of a secreted BMP antagonist, ectodin, integrating BMP, FGF, and SHH signals from the tooth enamel knot.

We have identified mouse and human cDNAs encoding a novel secreted BMP inhibitor, which we have named ectodin. It is most homologous (approximately 37% amino acid identity) to sclerostin that is a secreted BMP antagonist. Recombinant ectodin protein produced in cultured cells was efficiently secreted as a antagonist. Ectodin inhibited the activity of BMP2, BMP4, BMP6, and BMP7 for mouse preosteoblastic MC3T3-E1 cells, and bound to these BMPs with high affinity. Ectodin is intensely expressed in developing ectodermal organs, including teeth, vibrissae, and hair follicles. However, it is absent from the hair placodes and from the enamel knot signaling centers in teeth. In addition, several cell layers surrounding the enamel knots were completely devoid of ectodin transcripts. We analyzed the regulation and function of ectodin in tooth germs. Recombinant ectodin protein antagonized the BMP-mediated induction of Msx2 expression in cultured tooth explants, indicating that ectodin is a secreted BMP inhibitor. BMP2 and BMP7 stimulated ectodin expression in tooth explants, showing that it is part of a feedback mechanism controlling the activity of BMPs. The stimulation of ectodin expression by BMP was prevented by SHH and FGF4 but not by Wnt6. Hence, the feedback mechanism whereby BMPs upregulate their own inhibitor is counteracted by signals coexpressed with BMPs in the enamel knot. We conclude that ectodin is a novel BMP inhibitor which integrates BMP signaling with the SHH and FGF signal pathways and contributes in defining the exact spatiotemporal domain of BMP target field around the ectodermal signaling centers.

3T3 Cells↗
PubMed1977

[Tooth regeneration in the guinea pig (Cavia porcellus)].

The first inferior molar has been extracted, a part of its being reimplanted or not. A new molar of normal form regenerated, apparently from the apex of the tooth germ, in all cases in which the alveolus was left free or implanted with a tooth freagment deprived of pulpa.

Animals↗
PubMed1986

Odontogenesis and amelogenesis in interacting lizard-quail tissue combinations.

In this study we examined the possible inductive role of the dental papilla from polyphyodont lizard tooth germs. Flank skin sheets of quail ectoderm enzymatically separated from dermal tissue were recombined with lizard tooth papillae and placed on semisolid medium and cultured for 2 days. Subsequently, the recombinants were removed and placed on the chorioallantoic membrane of chick hosts and incubated for 6 days. After this period of 8 days in explant, control tissues differentiated according to their own phenotypes. Lizard dental papilla alone differentiated as fibroblasts. Quail flank skin ectoderm differentiated into epithelial sheets. Intact lizard tooth buds developed into teeth with dentine and incipient enamel. In the best experimental recombinants, advanced and relatively well-constructed teeth were observed, with clear indications of hard tissue deposition in association with quail epithelium. The results show that mesenchyme of the adult lizard dental papilla and embryonic quail ectoderm of heterotopic origin are capable of carrying out the complex sequence of morphogenetic interactions involved in normal odontogenesis.

Amelogenesis↗
PubMed1979

Tooth morphogenesis: the role of the innervation during induction and pattern formation.

The hypothesis is discussed that the innervation of the early mandibular and maxillary processes influences the initiation and patterning of tooth germs. Silver staining of embryonic mouse tissue supports the notion that the innervation is present before tooth buds appear. Data from other experimental studies is discussed in support of this hypothesis. The importance of the early events of tooth morphogenesis in initiating and patterning the dentition is discussed in the context of tooth morphogenesis as a whole. The processes involved in odontogenesis are categorized as Phase I: Initiating events; Phase II: Histogenetic events; and Phase III: Cytodifferentiative events. The complications of the interrelationship of these three seemingly discrete segments of tooth development are discussed in the context of inductive tissue interaction.

Ameloblasts↗
PubMed1979

SDH activity in the developing incisors or irradiated mouse fetuses.

Pregnant CD1 Swiss albino mice were irradiated with 400 rads of whole body X-irradiation on the twelfth gestational day. The animals were then sacrificed beginning on day 14 through 20 of gestation by chloroform inhalation. The fetuses were extirpated via laparotomy and decapitated. The severed heads were rapidly frozen and sectioned in a cryostat. The sections were affixed to glass slides and incubated for succinic dehydrogenase activity according to the method of Nachlas et al. (1957) and counterstained in Safranin 0, routinely dehydrated and mounted. Data from observations indicated that siccinic dehydrogenase activity appeared normal in the tissue layers of the developing tooth germ when compared to control animals. When the experimental procedure had invoked damage to the developing tooth, succinic dehydrogenase activity was lessened relative to the degree of damage. Presumably the X-irradiation had affected the cellular maturation process thereby reducing the functional competency of the cells as illustrated by the reduced enzyme activity.

Animals↗
PubMed1988

A peculiar complication in Le Fort I osteotomy.

In two cases of routine Le Fort I osteotomy in secondary cleft palate surgery, a swelling noted in the antral mucosa was biopsied. In both cases, histological examination resulted in a diagnosis of odontogenic myxoma. After analysis of the radiographs, it was concluded that the biopsies were taken from displaced tooth germs. The close histological similarity between myxoma on the one hand and dental papilla tissue, a thickened tooth follicle and a thickened or polypoid antral mucosal lining on the other is discussed.

Adolescent↗