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At least 775 records · Page 43Linked to original sources
PubMed2000

Crown dilaceration of a first premolar caused by extraction of its deciduous predecessor: a case report.

This report describes a rare case of crown dilaceration of the mandibular first premolar caused by trauma during extraction of the precedent primary first molar. The mandibular first primary molar had been extracted at the age of 4 years 7 months. Compared to the pre-operative radiograph, the post-operative film showed that the direction of the first premolar tooth germ had changed, suggesting that crown dilaceration had been induced by the surgical procedures during tooth extraction. From radiographic examinations, the premolar was considered to have erupted spontaneously.

Bicuspid↗
PubMed1986

Localization of type V collagen with monoclonal antibodies in developing dental and peridental tissues of the rat and hamster.

The distribution of collagen type V in developing dental and peridental tissues was investigated with the indirect immunofluorescence technique using unfixed, frozen sections of jaws from 1-2 day old neonatal rats and hamsters. Immunostaining for type V collagens was found both intracellularly and extracellularly in dental tissues of mesenchymal origin. In non-dental tissues, weak immunostaining was observed in the mesenchymally derived stroma surrounding the developing molar tooth germs but was more pronounced in larger cells, probably young osteoblasts in close vicinity to alveolar bone, and in some cells within developing salivary glands. Decalcification revealed a strong immunostaining in the extracellular bone matrices. In the dental tissues, the mesenchymally derived cells of the papilla exhibited an intracellular staining for type V collagen. In odontoblasts, increased immunostaining over that of other pulpal cells was observed just prior to or coinciding with the onset of predentin secretion and reactivity remained high in fully differentiated odontoblasts. A weak staining was observed in predentin but only after the onset of mineralization. As was the case for bone, after demineralization the dentin matrix stained intensely for type V collagen. The results demonstrate that type V collagen is actively synthesized by mesenchymal cells of developing hard tissues and that this type of collagen is an intrinsic component of hard connective tissue matrices. The data suggest that in developing tooth germs type V collagen is not involved in the differentiation process of either odontoblasts or ameloblasts.

Animals↗
PubMed2003

Sonic hedgehog functions as a mitogen during bell stage of odontogenesis.

Epithelial-mesenchymal interactions are required for tissue growth and gene expression patterns during odontogenesis. We showed previously that Sonic hedgehog (SHH) is detectable in both dental epithelium and mesenchyme, while Shh transcripts are present in dental epithelium only, suggesting that SHH functions as an autocrine signal in epithelium and a paracrine signal in mesenchyme. This hypothesis was tested here. We found by in situ hybridization that the SHH autocrine receptor Ptch-2 is indeed expressed in dental epithelium whereas the paracrine receptor Ptc is expressed in mesenchyme. Bovine bell stage tooth germs were microsurgically separated into epithelial and mesenchymal portions and the resulting tissue fragments were organ-cultured. In epithelium fragments cultured by themselves, gene expression of Shh and Gli-1 (a putative transcriptional mediator of hedgehog signaling) was significantly decreased in both inner dental epithelium and stratum intermedium layers; this was accompanied by a sharp drop in epithelial cell proliferation. However, in companion control tissue fragments containing both epithelium and mesenchyme, Shh and Gli-1 expression as well as cell proliferation were maintained. Treatment of dental epithelial or mesenchymal cell populations in monolayer cultures with exogenous recombinant SHH stimulated cell proliferation. Together, the data provide clear evidence that Shh is synthesized by dental epithelium, reaches the underlying mesenchyme, and appears to act as an autocrine mitogen for epithelial cells and a paracrine mitogen for mesenchymal cells, thus exerting crucial functions in tooth germ growth, morphogenesis, and tissue-tissue interactions of bell stage of odontogenesis.

Animals↗
PubMed1993

Alteration of in vitro bone metabolism and tooth formation by zinc.

1. The effects of zinc on bone metabolism and tooth formation was examined in organ cultures of calvaria and tooth germ, and in cell cultures of osteoblast-like cells, MC3T3-E1. 2. Treatment of calvaria with zinc (10, 100 microM) for 4 days both increased alkaline phosphatase (ALP) activity in bone and reduced the secretion of N-acetyl beta-glucosaminidase from bone, without affecting bone mineral or collagen content. The increase in ALP activity produced by zinc (10 microM) was inhibited neither by actinomycin D (5 micrograms/ml) nor by cycloheximide (0.5 micrograms/ml). 3. Treatment of MC3T3-E1 cells with zinc (50, 100 microM) for 25 days also increased ALP activity, but reduced calcium content in cells and in the matrix layer. 4. These results indicate that zinc increases ALP activity in osteoblasts without affecting de novo enzyme synthesis, and that it inhibits bone mineralization, in accordance with the inhibition of osteoclastic activity. 5. Treatment of tooth germ with zinc (100 microM) for 7 days also produced an increase in ALP activity and inhibition of mineralization. These results indicate that the increased ALP activity produced by zinc is a common phenomenon in hard tissues, and, further, that zinc inhibits mineralization during tissue formation.

Acetylglucosaminidase↗
PubMed1975

[The lateral dental lamina and the enamel niche. 6th and last paper on the embryology of human teeth].

Up to the cap-stage the lateral enamel strand extends from the dental lamina to the tip of the tongue-like projection of the enamel organ, forming there a swelling. It does not reach the free margin of the enamel organ at the bell-stage. The lateral enamel strand gradually becomes smaller in regard to the tooth germ, changing its relative position to the mesial half of the latter, and finally degenerates. In the molar germ, as the epithelial tongue-like projection at the cap-stage increases in length to become an interradical process, the lateral enamel strand extends as a crest on the buccal interradical process. The direction of the lateral enamel strand is inverse in the maxillary molar germs.

Animals↗
PubMed1993

A chondroitin sulfate epitope in mammalian dental pulp and its developmental expression in mouse dental papilla.

The molecular specificity of the dental papilla of a bell-stage tooth was studied by production of dental-papilla-reactive monoclonal antibodies (Mabs). One of the Mabs, designated 7C5, recognized an epitope present in glycosaminoglycan. Several lines of evidence suggested that the 7C5-epitope consists of chondroitin 6-sulfate. The Mab did not react with mouse dental epithelium, but reacted uniformly with mesenchymal tissue in the mandibular process and accumulated in the dental sac and in the papilla of bell-stage tooth germs. The 7C5-staining was lost from the differentiating odontoblasts, while the staining in the molar tooth papilla was accumulated in the subodontoblastic layer. In the developing mouse incisor, the 7C5-epitope was restricted to the lingual-posterior area. The 7C5-epitope was also present in pulpal tissue and predentin of different types of teeth of various mammalian species, including man, sheep, swine, and rat. Collagenase pre-treatment of tissue sections abolished the bulk of the 7C5-reactivity in peridental mesenchyme during embryonic stages while leaving the staining of the dental papilla intact. In newborn and adult teeth, collagenase also impaired the reactivity in the pulp except for the subodontoblastic layer. This suggests the existence of different subpopulations of the 7C5-epitope containing proteoglycans in dental papilla and pulp. A high-molecular-weight proteoglycan, sensitive to chondroitinase ABC but not to heparinase or heparitinase, was immunoprecipitated by 7C5 from extracts of bell-stage mouse tooth germs. We suggest that the evolutionary conservation of chondroitin 6-sulfate in the dental pulp reflects its properties as non-terminally differentiated tissue and perhaps the retention of a potential to differentiate to odontoblasts.

Animals↗
PubMed1989

Enamel proteins within two preferentially used animal models.

Two different models have been used to study enamel proteins: rodent incisors and bovine or porcine tooth germs. In the present experiment proteins were sequentially extracted from forming enamel of rat incisors and bovine tooth germs and examined using SDS-PAGE. The Coomassie-blue staining of amelogenins from both species revealed very similar patterns, which indicates a rather common processing, although developed at different rates. Non-amelogenin proteins behave differently when Concanavalin-A probing was used. Bovine non-amelogenins contain amido-black stainable proteins which are not recognized by lectin, contrary to rat enamel. If those proteins are albumin or albumin derived, as recently suggested, the observed discrepancy might be explained by the non enzymatic glycation known to occur on circulating albumin. In that case it would be a consequence of the use of adult rats in which circulating albumin is partly glycated versus bovine foetuses in which albumin would not be significantly glycated. Finally both species contain glycoproteins within non-amelogenins, which remain to be more precisely defined.

Amelogenesis↗
PubMed1976

The secretory ameloblast of the mini-pig foetus: Morphology, and effect on morphology of various aldehydes and of delayed fixation.

Electron microscopic investigations of secretory ameloblasts from deciduous tooth germs of mini-pig foetuses and investigations of the ability of various fixatives to preserve these cells in tooth germs immersion-fixed in to 5 min, 10 min, 15 min, 20 min and 40 min after death of the mother gave the following results: 1. The ameloblasts exhibit ultrastructural characteristics typical of exocrine secretory cells of merocrine type. 2. The localization of organelles is as in rodent secretory ameloblasts, but differs from the location in the human analogues. 3. Fixation with 4% formaldehyde invariably gives unacceptable ameloblast preservation. 4. Fixation with 2.5% glutaraldehyde gives fair preservation of the ameloblasts when the germs are fixed within 10 min of the death of the mother. 5. Fixation with a fixative mixture 2% formaldehyde-1.25% glutaraldehyde gives good preservation when the ameloblasts are fixed within 15 min of the death of the mother. 6. Fixation with a fixative mixture 2% formaldehyde-1% glutaraldehyde-1% acrolein gives good ameloblast preservation when the germs are fixed within 15 min of the death of the mother.

Acrolein↗
PubMed1991

Short-term mineralization of dentin and enamel in the mouse embryonic molars cultured in serum-free, chemically-defined medium.

The present study was designed to demonstrate the short term mineralization of dentin and enamel, and to investigate the effects of sodium beta-glycerophosphate (Na-beta-GPO4) on calcification in a serum-free, chemically-defined medium. The first mandibular molars at the bell stage dissected from 18-day-old mouse embryos were used as explants, which were cultured by an improved flotation method. Calcification of enamel in the 18-day-old embryonic molars occurred within the 6th day of culture. In another experiment, the molar germs were cultured in a serum-free, chemically-defined medium supplemented with 1, 5 and 10 mM Na-beta-GPO4. Promotion of tooth mineralization was recognizable at very low concentrations, such as 1 mM Na-beta-GPO4, in 18-day-old embryonic tooth germs. The culturing system reported here shortens the time required for dentin and enamel calcification to one half or one third of that reported previously and therefore should prove useful for examining regulations for cytodifferentiation and morphogenesis in tooth germs and the mineralization of dentin and enamel.

Ameloblasts↗
PubMed1998

Neurturin mRNA expression suggests roles in trigeminal innervation of the first branchial arch and in tooth formation.

Neurturin (NTN) is a recently characterized member of the glial cell line-derived neurotrophic factor (GDNF)-family which, like GDNF, can promote the survival of certain populations of neuronal cells in peripheral and central nervous systems. To elucidate the roles of NTN and a novel glycosyl-phosphatidylinositol (GPI)-linked receptor protein GFRalpha-3, a member of GDNF-family receptor alpha, in the regulation of peripheral trigeminal innervation and tooth formation, their expression patterns during mouse embryonic (E) and early postnatal (P) development (E10-P5) of the first branchial arch were analyzed by in situ hybridization. NTN mRNAs were observed in oral and cutaneous epithelia of the mandibular process at all studied stages and expression became gradually restricted to the suprabasal epithelial cells. In addition, transcripts were also detected in the epithelium of whisker follicles. In the developing first molar tooth germ, NTN showed a developmentally regulated, spatiotemporally changing expression pattern, which partially correlated with the development of innervation. During the initiation of tooth formation NTN mRNAs were expressed in dental epithelium and during later embryonic development transcripts appeared in the dental papilla mesenchyme. In addition, some transcripts were seen in the dental follicle. During postnatal development, NTN expression was restricted to the dental follicle of the incisor tooth germs. GFRalpha-3 mRNAs were not detected in teeth, but an intense expression was seen in non-neuronal cells surrounding trigeminal nerve fibers and in the trigeminal ganglia during E11-E15. Ganglion explant cultures showed that trigeminal neurons start to respond to exogenous NTN at E12, which correlates to the earlier reported appearance of the Ret-tyrosine kinase receptor in the trigeminal ganglion. Local application of NTN with beads on isolated dental mesenchyme did not stimulate cell proliferation or prevent apoptotic cell death. In addition, exogenous NTN had no effects on tooth morphogenesis in in vitro cultures. Taken together, because trigeminal neurons respond to NTN after first axons have reached their primary epithelial target fields, NTN is apparently not involved in the guidance of pioneer trigeminal nerves to their peripheral targets. However, our results show that NTN is a potent neuritogenic factor and, therefore, may act as a target-field-derived neurotrophic factor for trigeminal nerves during innervation of the cutaneous and oral epithelia as well as dental follicle surrounding the developing tooth. In addition, although NTN appears not to be directly involved in the regulation of tooth morphogenesis, it may have non-neuronal, organogenetic functions during tooth formation.

Animals↗
PubMed1999

A review of 47 cases of unerupted maxillary incisors.

OBJECTIVES: To study the prevalence of aetiological factors associated with unerupted maxillary incisors and to follow the outcome of treatment in a study of 47 cases. DESIGN: A retrospective study. SETTING: The Dental Department, St Luke's Hospital, Malta, the School Dental Clinic of Malta and the private practices of two orthodontists in Malta. SAMPLE AND METHODS: Forty-seven patients with a total of 53 unerupted maxillary incisors were classified according to the aetiological factors causing non-eruption. The relative prevalence of the various aetiologies were ascertained, and the outcome after treatment was recorded to assess the efficacy of the treatment methods being used. RESULTS: The most common cause of lack of eruption was the presence of supernumerary teeth (47% of patients). The other 53% of cases were distributed more or less equally between the remaining aetiological factors, which were odontomes (9%), dilacerations (9%), tooth germ malposition (12%), crowding (4%), one case of a calcifying odontogenic cyst (2%) and one case of trauma to the preceding deciduous tooth (2%). The aetiology of 15% of cases could not be ascertained. Once supernumerary teeth were removed, maxillary incisors usually erupted successfully with the help of conventional treatment methods such as surgical exposure and orthodontics. A relatively large number of incisors that failed to erupt due to other aetiological factors had to be extracted. CONCLUSIONS: Maxillary incisors that fail to erupt due to the presence of supernumerary teeth have a better prognosis than unerupted incisors with less common aetiologies.

Adolescent↗
PubMed1984

[Results of dental homografts. Nine years after a publication on 25 homografts, what remains and what should be considered].

Several years ago I was pleased to announce the introduction of homografts, and in spite of the numerous reservations of authors (including those of Professor Dechaume ), I was strongly convinced of their feasibility. Following the publication by Dr. Brunel of a report on one of his patients who had had a dental graft performed by Dr. Cserepfalvi in the USA, I have personally used homografts consisting of the introduction of a tooth germ in the place of a tooth with the hope that it will continue to develop.

Humans↗
PubMed2001

TNF signaling via the ligand-receptor pair ectodysplasin and edar controls the function of epithelial signaling centers and is regulated by Wnt and activin during tooth organogenesis.

Ectodermal dysplasia syndromes affect the development of several organs, including hair, teeth, and glands. The recent cloning of two genes responsible for these syndromes has led to the identification of a novel TNF family ligand, ectodysplasin, and TNF receptor, edar. This has indicated a developmental regulatory role for TNFs for the first time. Our in situ hybridization analysis of the expression of ectodysplasin (encoded by the Tabby gene) and edar (encoded by the downless gene) during mouse tooth morphogenesis showed that they are expressed in complementary patterns exclusively in ectodermal tissue layer. Edar was expressed reiteratively in signaling centers regulating key steps in morphogenesis. The analysis of the effects of eight signaling molecules in the TGFbeta, FGF, Hh, Wnt, and EGF families in tooth explant cultures revealed that the expression of edar was induced by activinbetaA, whereas Wnt6 induced ectodysplasin expression. Moreover, ectodysplasin expression was downregulated in branchial arch epithelium and in tooth germs of Lef1 mutant mice, suggesting that signaling by ectodysplasin is regulated by LEF-1-mediated Wnt signals. The analysis of the signaling centers in tooth germs of Tabby mice (ectodysplasin null mutants) indicated that in the absence of ectodysplasin the signaling centers were small. However, no downstream targets of ectodysplasin signaling were identified among several genes expressed in the signaling centers. We conclude that ectodysplasin functions as a planar signal between ectodermal compartments and regulates the function, but not the induction, of epithelial signaling centers. This TNF signaling is tightly associated with epithelial-mesenchymal interactions and with other signaling pathways regulating organogenesis. We suggest that activin signaling from mesenchyme induces the expression of the TNF receptor edar in the epithelial signaling centers, thus making them responsive to Wnt-induced ectodysplasin from the nearby ectoderm. This is the first demonstration of integration of the Wnt, activin, and TNF signaling pathways.

Activins↗
PubMed1996

Numerous members of the Sox family of HMG box-containing genes are expressed in developing mouse teeth.

We used RT-PCR to detect the expression in mouse molar and incisor tooth germs of 14 of the 19 known members of the Sox family of HMG box-containing transcription factors. These sequences fell into all 6 of the main subdivisions of the Sox family. In general, the relative transcript abundance of the different Sox genes is similar between molar and incisor tooth germs, although 3 low-abundance transcripts were found in only a single tooth type. The expression of Sox genes during tooth development has not been reported previously and further experiments will be required to determine their role in this process.

Animals↗
PubMed1986

On nerves and teeth in the lower jaw of the cichlid Tilapia mariae.

The anatomy of the teeth and tooth-related nerves in the lower jaw was examined in the cichlid Tilapia mariae. This was done in order to establish a basis for studies on dental neuroplasticity in a polyphyodont vertebrate. The region of interest was explored in specimens fixed by glutaraldehyde perfusion, and by using X-ray photography, maceration, scanning electron microscopy, gross dissection, and light microscopic examination of serial sections. The results show that the lower jaw carries some 60-65 functional teeth. In addition, numerous replacement teeth and tooth germs in various stages of development are located in a cavity in the dentary bone. Numerous nerve bundles are present in immediate relation to the dental follicles of tooth germs. Unerupted teeth do not contain light-microscopically discernible pulpal axons, but the pulps of functional teeth contain myelinated axons. Both perifollicular and pulpal nerve bundles derive from a nerve plexus, which is formed by branches from r. mandibularis trigemini. This nerve is easily accessible to experimental manipulation, where it courses through the adductor mandibulae muscular complex. Thus, the lower jaw of T. mariae seems to represent a suitable system for the study of tooth-nerve interactions in a polyphyodont species.

Animals↗
PubMed1977

A longitudinal radiographic study of the mineralization of 2nd premolars.

Odontogenesis of the 2nd premolar begins in the majority of cases at the age of 3-3 1/2 years, although this period can vary more widely than that for other permanent teeth. For this reason, aplasia of this group of teeth cannot be diagnosed as early and with the same degree of certainty. A group of 104 children aged 3-7 years in whom one or more tooth germs mesial to the 1st permanent molar were not visible in the various age groups was reexamined radiographically in the region where they apparently lacked the development of tooth germs. The second examination took place 16-24 months after the first, and a comparison was made of the two examinations. The study confirms that the 2nd premolar can be very late in developing and that the chance of this being so is greater in the maxilla than in the mandible.

Bicuspid↗
PubMed2005

Developmental appearance of dentin matrix protein 1 during the early dentinogenesis in rat molars as identified by high-resolution immunocytochemistry.

Dentin matrix protein 1 (DMP 1) is an acidic phosphoprotein that has been postulated to play an important role in mineralized tissue formation. We have examined rat molar tooth germs by applying a high-resolution immunocytochemical approach with the purpose to identify the temporal and spatial localization of DMP 1 at the onset of dentinogenesis. Upper molar tooth germs of 2- to 3-day-old Wistar rats were fixed in a cacodylate-buffered 0.1% glutaraldehyde + 4% formaldehyde fixative, left unosmicated and embedded in LR White resin. The sections were incubated with a polyclonal DMP 1 antibody for postembedding colloidal gold immunolabeling and examined in a Jeol 1010 transmission electron microscope. The earliest localization of DMP 1 was in the Golgi region as well as in the nucleus of differentiating odontoblasts. When mineralization spread from matrix vesicles to the surrounding matrix, DMP 1 was extracellularly detected around the mineralizing globules. In the regions of fully mineralized mantle dentin, it was present in the mineralized regions, mainly around the peritubular dentin. The appearance of DMP 1 during early dentinogenesis implies a direct role for this protein in both odontoblast differentiation and matrix mineralization.

Animals↗