Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tooth Germ”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources
PubMed1996

Dendritic cells: a novel cellular component of the rat incisor enamel organ appearing in the late stages of enamel maturation.

Immunocompetent cells in the enamel organ of rat incisors were examined immunohistochemically using OX6, ED1, and ED2 monoclonal antibodies known to recognize the Class II MHC molecules, a monocyte-macrophage lineage, and residential macrophages, respectively. The OX6 immunopositive cells (MHC cells) were located exclusively in the enamel maturation zone. MHC cells increased in number in the incisal direction and occasionally extended cytoplasmic processes deep into the ameloblast layer. Migration of MHC cells in the ameloblast layer were also encountered. MHC cells lacked phagolysosomes and could be distinguished from typical macrophages. ED2 immunopositive cells were not seen in the enamel organ. ED1 positive cells displayed identical localization to MHC cells except that some appeared in the transitional zone. MHC cells could not be seen in the enamel organ of rat molar tooth germs. Our data confirmed the presence of a large population of "dendritic" immunocompetent cells in the enamel organ of rat incisors and characterized the ultrastructural features of these cells. Biological significance of the immunocompetent cells in the enamel organ during amelogenesis needs to be clarified.

Amelogenesis↗
PubMed2002

Tissue engineering of complex tooth structures on biodegradable polymer scaffolds.

Tooth loss due to periodontal disease, dental caries, trauma, or a variety of genetic disorders continues to affect most adults adversely at some time in their lives. A biological tooth substitute that could replace lost teeth would provide a vital alternative to currently available clinical treatments. To pursue this goal, we dissociated porcine third molar tooth buds into single-cell suspensions and seeded them onto biodegradable polymers. After growing in rat hosts for 20 to 30 weeks, recognizable tooth structures formed that contained dentin, odontoblasts, a well-defined pulp chamber, putative Hertwig's root sheath epithelia, putative cementoblasts, and a morphologically correct enamel organ containing fully formed enamel. Our results demonstrate the first successful generation of tooth crowns from dissociated tooth tissues that contain both dentin and enamel, and suggest the presence of epithelial and mesenchymal dental stem cells in porcine third molar tissues.

Absorbable Implants↗
PubMed2005

Runx2 (Cbfa1) inhibits Shh signaling in the lower but not upper molars of mouse embryos and prevents the budding of putative successional teeth.

Heterozygous mutations in the RUNX2 (CBFA1) gene cause cleidocranial dysplasia, characterized by multiple supernumerary teeth. This suggests that Runx2 inhibits successional tooth formation. However, in Runx2 knockout mice, molar development arrests at the late bud stage, and lower molars are more severely affected than upper ones. We have proposed that compensation by Runx3 may be involved. We compared the molar phenotypes of Runx2/Runx3 double-knockouts with those of Runx2 knockouts, but found no indication of such compensation. Shh and its mediators Ptc1, Ptc2, and Gli1 were down-regulated only in the lower but not the upper molars of Runx2 and Runx2/Runx3 knockouts. Interestingly, in front of the mutant upper molar, a prominent epithelial bud protruded lingually with active Shh signaling. Similar buds were also present in Runx2 heterozygotes, and they may represent the extension of dental lamina for successional teeth. The results suggest that Runx2 prevents the formation of Shh-expressing buds for successional teeth.

Animals↗
PubMed1990

Heterogeneity of distribution pattern at the electron microscopic level of heparan sulfate in various basement membranes.

Using the high-iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining technique and enzymatic digestion, we investigated the ultrastructural distribution pattern of heparan sulfate side chains of heparan sulfate proteoglycan (HSPG) in various basement membranes (nerve, capillary, oral epithelial, muscle, and dental basement membranes). Four different distribution patterns of stain deposits were identified as heparan sulfate on the basis of enzymatic degradation by heparitinase. In some basement membranes associated with tooth germs and oral epithelium, HID-TCH-SP stain deposits were regularly located at both sides of the lamina densa, but few were observed in the lamina densa itself. In nerve, muscle, and capillary basement membranes, the stain deposits were localized at the external side of the lamina densa adjacent to the underlying connective tissue, but were not found in the laminae lucida and densa. In the internal basal lamina of junctional epithelium of gingiva, the stain deposits were detected mainly in the lamina lucida region. Finally, in some dental and oral epithelial basement membranes, the stain deposits were randomly distributed throughout both laminae lucida and densa. Thus, the present study demonstrated distinct differences in heparan sulfate distribution pattern among various basement membranes, suggesting their architectural heterogeneity.

Animals↗
PubMed2005

Effect of connective tissue growth factor (CCN2/CTGF) on proliferation and differentiation of mouse periodontal ligament-derived cells.

BACKGROUND: CCN2/CTGF is known to be involved in tooth germ development and periodontal tissue remodeling, as well as in mesenchymal tissue development and regeneration. In this present study, we investigated the roles of CCN2/CTGF in the proliferation and differentiation of periodontal ligament cells (murine periodontal ligament-derived cell line: MPL) in vitro. RESULTS: In cell cultures of MPL, the mRNA expression of the CCN2/CTGF gene was stronger in sparse cultures than in confluent ones and was significantly enhanced by TGF-beta. The addition of recombinant CCN2/CTGF (rCCN2) to MPL cultures stimulated DNA synthesis and cell growth in a dose-dependent manner. Moreover, rCCN2 addition also enhanced the mRNA expression of alkaline phosphatase (ALPase), type I collagen, and periostin, the latter of which is considered to be a specific marker of the periosteum and periodontium; whereas it showed little effect on the mRNA expression of typical osteoblastic markers, e.g., osteopontin and osteocalcin. Finally, rCCN2/CTGF also stimulated ALPase activity and collagen synthesis. CONCLUSION: These results taken together suggest important roles of CCN2/CTGF in the development and regeneration of periodontal tissue including the periodontal ligament.

Journal Article↗
PubMed1999

Pleiotropic features of syndromic craniosynostoses correlate with differential expression of fibroblast growth factor receptors 1 and 2 during human craniofacial development.

Mutations in FGFR1, -2, and -3 are linked to five human craniosynostosis syndromes. In addition to premature fusion of cranial sutures, nonskeletal manifestations in skin, and teeth together with CNS abnormalities, reflect widespread effects of these mutations. To understand this pleiotropy, we have assessed craniofacial FGFR1 and -2 expression in the human embryo from 6 wk postfertilization. We found that both genes are expressed in sheets of condensed mesenchyme before overt chondrogenic differentiation and that distinct patterns of expression are established by 8 wk. Thus, FGFR2(BEK) is expressed evenly throughout developing cartilage and bone, whereas FGFR1 transcripts predominate in perichondria and periostea. Complementary patterns of FGFR1 and FGFR2(BEK and KGFR) expression are also observed in the enamel epithelium and papilla mesenchyme of the tooth germ, at a stage when morphogenetic tissue interactions ensue. Both genes are expressed in the cortical layer of the brain, but expression levels vary significantly within the choroid plexus and wall of the fourth ventricle. Similarly, tissue-specific differences in receptor expression are found in both the skin and salivary glands. These expression data are consistent with the pleiotropic manifestations of syndromic craniosynostoses and provide the basis for a new paradigm to explain the associated CNS problems.

Case-Control Studies↗
PubMed1994

Ameloblastic fibro-odontoma in the mandibular incisor of a cow.

Odontogenic neoplasm was found in the mandibular incisor area of a 3-year-old Japanese black ox. Macroscopically, the cut surface was white and firm with streaks of hard tissue. Histologically, the tumor was composed of enamel organ structures with odontogenic hard tissue in fibromatous areas. It was diagnosed as ameloblastic fibro-odontoma. The absence of the 4th permanent incisor confirmed by radiography and microscopic examination strongly suggests that this tumor has been originated from the tooth germ tissues of the permanent left 4th incisor.

Animals↗
PubMed2005

Perlecan, a basement membrane-type heparan sulfate proteoglycan, in the enamel organ: its intraepithelial localization in the stellate reticulum.

The localization and biosynthesis of perlecan, a basement membrane-type heparan sulfate proteoglycan, were studied in developing tooth germs by using murine molars in neonatal and postnatal stages and primary cultured cells of the enamel organ and dental papilla to demonstrate the role of perlecan in normal odontogenesis. Perlecan was immunolocalized mainly in the intercellular spaces of the enamel organ as well as in the dental papilla/pulp or in the dental follicle. By in situ hybridization, mRNA signals for perlecan core protein were intensely demonstrated in the cytoplasm of stellate reticulum cells and in dental papilla/pulp cells, including odontoblasts and fibroblastic cells in the dental follicle. Furthermore, the in vitro biosyntheses of perlecan core protein by the enamel organ and dental papilla/pulp cells were confirmed by immunofluorescence, immunoprecipitation, and reverse transcriptase-polymerase chain reaction. The results indicate that perlecan is synthesized by the dental epithelial cells and is accumulated in their intercellular spaces to form the characteristic stellate reticulum, whose function is still unknown.

Animals↗
PubMed2006

Immunohistochemical localization of alpha-Smooth muscle actin during rat molar tooth development.

The dental follicle contains mesenchymal cells that differentiate into osteoblasts, cementoblasts, and fibroblasts. However, the characteristics of these mesenchymal cells are still unknown. alpha-Smooth muscle actin (alpha-SMA) is known to localize in stem cells and precursor cells of various tissues. In the present study, to characterize the undifferentiated cells in the dental follicle, immunohistochemical localization of alpha-SMA was examined during rat molar tooth development. Rat mandibles were collected at embryonic days (E) 15-20 and postnatal days (P) 7-28. Immunohistochemical stainings for alpha-SMA, periostin, Runt-related transcription factor-2 (Runx2), tissue nonspecific alkaline phosphatase (TNAP), and bone sialoprotein (BSP) were carried out using paraffin-embedded sections. alpha-SMA localization was hardly detected in the bud and cap stages. At the early bell stage, alpha-SMA-positive cells were visible in the dental follicle around the cervical loop. At the late bell to early root formation stage (P14), these cells were detected throughout the dental follicle, but they were confined to the apical root area at P28. Double immunostaining for alpha-SMA and periostin demonstrated that alpha-SMA-positive cells localized to the outer side of periostin-positive area. Runx2-positive cells were visible in the alpha-SMA-positive region. TNAP-positive cells in the dental follicle localized nearer to alveolar bone than Runx2-positive cells. BSP was detected in osteoblasts as well as in alveolar bone matrix. These results demonstrate that alpha-SMA-positive cells localize on the alveolar bone side of the dental follicle and may play a role in alveolar bone formation.

Actins↗
PubMed1984

Enamel hypoplasia in permanent teeth induced by periodontal ligament anesthesia of primary teeth.

Periodontal ligament anesthesia was applied to 16 primary teeth in jaw quadrants of two monkeys. The teeth in the contralateral positions were not injected and the permanent teeth in this area served as controls. The animals were killed after 22 months when the permanent incisors began to erupt. In total, enamel hypoplasia or hypomineralization (or both) was noticed in 15 permanent teeth in the experimental quadrants but in none of the controls. The results strongly emphasized that periodontal ligament anesthesia should be used with great care on primary teeth close to developing permanent teeth.

Anesthesia, Dental↗
PubMed2000

The adult unoperated cleft patient: absence of maxillary teeth outside the cleft area.

OBJECTIVE: The purpose of this study was to investigate the possible absence of teeth in the postcanine region of the upper jaw of the unoperated adult cleft patient. METHOD: The study was performed on 266 dental casts of fully unoperated adult cleft patients. The patients were divided into four groups according to the type of the cleft: unilateral cleft lip and alveolus, unilateral cleft lip and palate, bilateral cleft lip and alveolus, and bilateral cleft lip and palate. RESULTS: No absence of permanent teeth in the canine and postcanine area of the upper jaw could be found. CONCLUSION: The results are in contradiction with the established hypothesis that absence of teeth outside the cleft area of the maxilla is due to an unknown congenital factor. On the contrary, the findings support the hypothesis that surgery for the closure of the hard palate in early childhood is the most important etiological factor for the absence of teeth outside the cleft area in the early operated cleft patient. The superficial position of the tooth germs (at the time of the palatal surgery), especially those of the premolars, supports this hypothesis.

Adolescent↗
PubMed1992

Three-dimensional changes in direction and interrelationships among enamel prisms in the dog tooth.

This study describes the three-dimensional features of enamel prisms and their arrangement in dog teeth. Tangential semithin sections of demineralized tooth germ were serially cut from the enamel surface to the enamel-dentin junction. Straight rows of enamel prisms parallel or perpendicular to the meridian were selected at the enamel-dentin junction; these prisms were reconstructed from micrographs with a personal computer. Near the enamel-dentin junction, the arrangement of enamel prisms appeared regular. Viewed from the enamel surface, the cut-ends of the enamel prisms that were parallel to the meridian at the enamel-dentin junction appeared as a sine curve, with 16 enamel prisms forming one period. The enamel prisms in a row perpendicular to the meridian were parallel to each other and deflected to the left or right from the enamel-dentin junction. Away from the enamel-dentin junction, the periodicity of the prisms gradually disappeared. The sine curve formed by the cut-ends of prisms in a row parallel to the meridian became irregular, and prisms in rows perpendicular to the meridian crossed each other. The semithin sections showed belt-like zones arranged perpendicular to the meridian. Each belt-like zone consisted of enamel prisms oriented in the same direction, those in neighboring zones being oriented in opposite directions. The disappearance of the regular arrangement of prisms was related to changes in their location in the belt-like zones.

Animals↗