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PubMedDate not supplied

[Autotransplantation of tooth germs].

During the routine orthodontic examination of a 8-year-4-month old female, it was found that the upper right canine and premolars were missing. The anamnesis revealed that their buds had been surgically removed after a trauma when she was 6 years old. The lower incisors were slightly crowded. Since the age of the patient would not permit a fixed prosthetic restoration in the next few years, it was decided to attempt an autogeneic transplant of the lower first premolars to replace the upper right canine and premolars too.

Bicuspid↗
PubMed1986

Characteristics of mineralization of rat molar tooth germs in organ culture.

The behaviour of first (M1) and second (M2) upper molars of 3-day-old rats was compared histologically and by measuring several variables (dry and ash weight, Ca, P and Mg content) on cultured teeth and contralateral control teeth (not cultured). New information was gained by additional computations and calculating correlation coefficients between the variables of the control and cultured molars separately and combined. The M2 seems to perform better in culture than the M1. The M2 model revealed possibilities for further standardization.

Animals↗
PubMed2004

[Enamelin transcriptional expression in developing postnatal rat tooth germ].

OBJECTIVE: To observe the transcriptional expression of enamelin in developing postnatal rat first mandibular molar germs, for further studies of functions of enamelin in enamel development and mineralization. METHODS: Tissue slices of first mandibular molar germ of rat 1, 3, 7, 10, 14 days after birth were prepared. The enamelin mRNA expression was identified by in situ hybridization. RESULTS: Enamelin mRNA was observed in both ameloblast and odontoblast in 1-10 day old rat postnatal first mandibular molar germs. Enamelin mRNA appeared very weakly at 1st day, and increased through 3rd day, reached the maximum at 7th day, and reduced at 10th day and became negative at 14th day postnatally; while the expression of enamelin mRNA in odontoblast maintained lower from 1st to 10th day and negative at 14th day postnatally. CONCLUSION: Enamelin gene transcriptional expression lasts from preameloblast to maturation ameloblast, which suggests that enamelin may participate in the development of enamel and mantle dentin.

Ameloblasts↗
PubMed1990

Ultrastructural visualisation of proteoglycans in early unmineralised dentine of rat tooth germs stained with cuprolinic blue.

The ultrastructural distribution and localisation of proteoglycans (PGs) of early developing rat dentine were examined using cuprolinic blue in a critical electrolyte concentration procedure. Results show that the cuprolinic blue method produces images of higher morphological quality than other cationic dyes. PGs appeared as ribbon-like electron-opaque precipitates of various sizes, ranging between 1.4 and 0.2 microns in length, distributed throughout the matrix and in close association with well preserved matrix vesicles and collagen fibrils. Matrix vesicles revealed tightly packed PG filaments which appeared to be attached to their membrane. It is possible that the close association of PG filaments with matrix vesicles and collagen indicates that PGs are related to the process of mineralisation of dentine.

Animals↗
PubMed1979

Frozen ultrathin-sections for x-ray microanalysis of rat tooth germs.

In order to detect the precise location and pathways of calcium in the ameloblastic layer with EM and EDX, frozen ultrathin-sections, potassium pyroantimonate (PPA) method and 45Ca-autoradiography (A.R) were employed. A population of dense granules containing Ca and P was mainly observed within the nuclei and mitochondria of the frozen-sectioned ameloblasts, whereas PPA-reaction was seen not only within them but in ER, Golgi vesicles and intercellular spaces. No granules were found at the enamel matrix by both methods, but peaks for Ca and P were distinct. Silver grains of 45Ca-A.R were located in nuclei, mitochondria. Golgi complex and intercellular spaces. These results indicate that calcium can transport across the ameloblastic layer through two main pathways, extracellular and transcellular.

Ameloblasts↗
PubMed1986

The differences in calcium distribution pattern between preodontoblasts and preameloblasts in developing rat molar tooth germs.

Ultrastructural localization of calcium in preodontoblasts and preameloblasts was investigated using the potassium pyroantimonate technique, and it was confirmed that there were clear differences in calcium distribution pattern between preodontoblasts and preameloblasts. In preodontoblasts, pyroantimonate reaction products were mainly observed in the Golgi region, lateral intercellular spaces, and secretory granules, especially in the distal portion of cell body; however, few were found in mitochondria and on the plasma membrane. In preameloblasts, on the other hand, the precipitates were located in mitochondria, nuclei, and on the inner face of the plasma membrane; however, few reaction products were observed in the intercellular spaces, lysosomelike granules, secretory granules, and stippled materials. Granular reaction product approximately 20-40 nm in diameter adhered preferentially to the growing end of needlelike crystals in the initial enamel matrix.

Ameloblasts↗
PubMed1987

Effect of alkaline-phosphatase inhibition by 1-p-bromotetramisole on the formation of trichloroacetic acid-[32P]-insoluble phosphate from inorganic [32P]-phosphate and [32P]-pyrophosphate in non-mineralizing and mineralizing hamster molar tooth-germs in vitro.

In culture, 1-p-bromotetramisole (pBTM), a specific inhibitor of alkaline phosphatase, significantly inhibited the formation of trichloroacetic acid (TCA)-insoluble [32P]-phosphate from inorganic [32P]-phosphate in the proliferating non-mineralizing second (M2) maxillary molar germs but had no effect in the actively mineralizing first (M1) germs. Addition of 10(-5) M inorganic pyrophosphate in the culture medium with a [32P]-phosphate label increased the inhibition of the formation of TCA-insoluble [32P]-phosphate in the M2. pBTM almost completely inhibited the formation of TCA-insoluble [32P]-phosphate from inorganic [32P]-pyrophosphate in the non-mineralizing M2. In the actively mineralizing M1, the compound significantly inhibited but did not abolish the formation of TCA-insoluble phosphate. These results confirm earlier biochemical findings that alkaline phosphatase possesses a pyrophosphatase activity probably related to the turnover of phosphorylated macromolecules necessary for cell differentiation and proliferation.

Alkaline Phosphatase↗
PubMed1987

Immunohistochemical localization of type IV collagen in mouse tooth germ: an ultrastructural study.

Localization of type IV collagen was analyzed at the ultrastructural level in mouse embryonic molars by using a preembedding technique. Cryostat sections were incubated with type IV collagen antibody and then treated with the peroxidase-antiperoxidase complex. This antibody was visualized at the epithelio-mesenchymal interface. Labeling was intense and uniformly distributed throughout the basement membrane. However, it was mainly restricted to the lamina densa. No immunostaining was detectable in the lamina lucida but it was crossed by fine filaments that appeared as projections from the lamina densa to the epithelial cell plasma membrane. At the mesenchymal aspect of the basement membrane, projections of labeled material extended from the lamina densa in the underlying dental mesenchyme. At the presecretory stage of odontoblasts, these projections were in close connection with mesenchymal cell processes.

Animals↗
PubMed1990

Evolution of cytokeratin expression in developing human tooth germ.

Cytokeratin expression by the developing human enamel organ between the 10th and the 23rd gestational week was studied by indirect immunofluorescence microscopy technique using a panel of 15 monoclonal antibodies. The results showed that five antibodies (RKSE 60, Kk 8-60, EE 21-6, 6B10 and 1 C-7) were never reactive, that five antibodies (RCK 102, 42.39.13.1, Ks 19 and Pan 1-8) were always positive and that five antibodies (KB 37, RPN 11-62, Ks 13.1, Ks 8-12 and Ks 18.174) obtained or increased their positivity between weeks 12 and 13. It was concluded that a switch in cytokeratin expression occurred around the 12th-13th weeks. No further important change could be noticed after this period. So it is suggested that final cell differentiation was initiated at weeks 12-13.

Amelogenesis↗
PubMed1983

Glycosaminoglycans in embryonic mouse tooth germs. A histochemical analysis.

Glycosaminoglycans (GAG) were localized in embryonic mouse molars by Alcian-blue staining in a critical-electrolyte-concentration (CEC) method (Scott and Dorling, 1965). Sulfated GAG were distinguished from hyaluronate (HA) by combining the binding specificity of Alcian blue and substrate specificity of GAG-lytic enzymes. The stratum reticulum was found to contain a small amount of HA, but no chondroitin sulfate (CS). The amount of HA decreased gradually during odontogenesis. No GAG were detected in the outer and inner dental epithelia. The basement membrane and the predentine were intensely stained, and shown to be rich in HA and CS. The preodontoblastic layer contained small amounts of HA and CS. These decreased progressively during odontogenesis. No GAG was found at the odontoblastic layer. The lower dental papilla contained a constant amount of HA (the major component) and CS.

Animals↗
PubMed1987

Ultrastructural observations on the intraodontoblastic collagen fibrils of the mouse tooth germs.

We examined electron-microscopically and histochemically the ultrastructural features of the intraodontoblastic collagen fibrils of the mouse. These collagen fibrils were most common in secreting odontoblasts (pre-odontoblasts) of the maturating stages. In such cells they were most numerous at the peripheral zone of the Golgi apparatus, and were sometimes seen in odontoblastic processes. Intraodontoblastic collagen fibrils also had morphological variations including a banded structure enclosed by limiting membranes of vacuoles, fusion with primary lysosomes, and an electron-dense material covering with a structure that was not banded. Study of acid phosphatase activity showed that these structural changes were caused by the degradation of intraodontoblastic collagen fibrils by lysosomes. The results of studies of the permeation of lanthanum nitrate and the alkaline phosphatase reaction showed that these collagen fibrils were separate from the extracellular matrix and that there was no phagocytosis of the odontoblasts.

Acid Phosphatase↗
PubMed1986

Scanning electron microscopy of the extracellular matrices of rat molar tooth germs in organ culture in vitro.

Second upper molars from 3-day postnatal rats were cultured for 2 weeks and compared with in-vivo specimens from 7-day postnatal rats. Several preparatory techniques were applied to expose the extracellular matrices, the three-dimensional structure of which were examined by SEM. The combination of phosphate-buffered saline and ultrasonics as preparation for the observation of the enamel, hypochlorite treatment to study the predentine, the freeze-fracture technique for the dentinal tubules and oxygen-plasma-ashing for the mineralization front of dentine gave best results. Enamel formed in vitro was prismatic similar to in vivo. The fissures were devoid of enamel and the enamel-free areas at the cusp tips were larger than in vivo. In the cervical area in vitro, the enamel stopped abruptly instead of gradually decreasing. The predentine and the dentine were normal in structure.

Animals↗
PubMed1982

Formation of tight junctions in differentiating and secretory ameloblasts of rat molar tooth germs.

Forty newborn rats were perfused with Karnovsky fixative and the tight junctions in differentiating and secretory ameloblasts were examined by conventional electron microscopy and freeze-fracture replications. Pre-ameloblasts were divided into types I, II and III based on morphology. Initial indications of tight-junction formation appeared as linear aggregations of particles in type II. The apparent tight junctional strands were observed in type III and in secretory ameloblasts. Though the junctional strands were numerous and long, no complete barrier between pre-ameloblasts at their distal ends was present. Complete zonular tight junctions were first observed at the distal ends of secretory ameloblasts; at this stage, proximal tight junctions incompletely sealed the paracellular spaces around the ameloblasts. Throughout their formative processes, the tight junctional strands were engaged in forming gap junctions. The structural features of tight junctions were considered to be closely associated with the cytodifferentiation of ameloblasts and permeability in the ameloblast layer.

Ameloblasts↗
PubMed1987

Heterogeneity of amelogenin mRNA in the bovine tooth germ.

The amelogenins are a complex mixture of hydrophobic proteins that are the major organic component of developing enamel. To study the molecular mechanisms underlying the heterogeneity of the amelogenins we isolated cDNA clones encoding these proteins. The clones were definitively identified by hybrid-selected translation experiments and by comparison of the DNA sequence with the protein-derived amino acid sequence. Southern hybridization of bovine genomic DNA indicated that amelogenin is a single copy gene. However, Northern hybridization experiments distinctly showed two major species of mRNA, each of which were sufficiently large enough to encode the highest known molecular weight species of amelogenin proteins. Furthermore, immunoprecipitation of hybrid-selected translation products using isolated amelogenin cDNA showed multiple, translated protein products. These data are supportive of a differential mRNA processing mechanism involved in generating a heterogeneous family of amelogenin matrix proteins from a single gene.

Ameloblasts↗
PubMed1983

Ultrastructural and cytochemical studies of resorptive and digestive functions of secretory ameloblasts in kitten tooth germs.

Ultrastructural and cytochemical studies of kitten secretory ameloblasts were made in order to clarify their functions in the resorption and digestion of extracellular organic materials. The secretory ameloblast had triangular Tomes' processes whose profile was divided into type 1 and type 2 faces. Type 1 face was associated with tubular structures, coated pits, coated vesicles, and irregularly shaped vesicles presumably representing phagosomes. Freeze-fracture replicas clearly showed the presence of large, particle-rich depressions and small depressions on the cell membrane P face in the type 1 face of the Tomes' process. Exocytosis of secretory granules was seldom observed. In both thin sections and replicas, the type 2 face possessed cell membrane microinvaginations. From the supranuclear region to a zone near the Tomes' process, many dense bodies, multivesicular bodies, and vacuoles were present; and many of them showed intense acid phosphatase reactions. Reaction products of acid phosphatase were demonstrated in the Golgi apparatus, GERL, and the lateral cell membrane. These results suggest that kitten secretory ameloblasts resorb and digest extracellular organic materials.

Absorption↗
PubMed1993

[Chemical and traumatic irritation of a canine premolar tooth germ].

The arrest of a premolar bud was observed in an animal experiment that was designed to study the influence of endodontic treatment in dogs' temporary teeth on the eruption of their permanent successors. A chemical irritation was induced by the burst of ZOE (zinc oxide and eugenol) into the dental follicle. Moreover, a mechanical trauma on the temporary molar was promoted by the dog's biting on its cage metallic bars. The devitalization effects were studied in thick undecalcified ground sections which were subjected to microradiographic analysis, to UV light microscopy in order to detect the fluorescent indicators of calcification, and finally to methylene blue staining. The arrest of the bud development was noted in fluorescent microscopic examination. Cellular cementum was formed on the pulpal surface of the dentine, while cementum, chondroid tissue, woven bone and lamellar bone developed in the pulpal tissue. These observations advise caution during root canal therapy of temporary teeth, especially those that are exposed to mechanical trauma. Such as the upper incisors.

Animals↗
PubMed1982

Ultrastructure of odontoblasts in kitten tooth germs as revealed by freeze-fracture.

Fifteen kittens were perfused with 2.5 per cent glutaraldehyde or modified Karnovsky fixative. Distribution and structural features of the three kinds of intercellular junctions; gap junctions, macular tight junctions and desmosome-like junctions were clarified by correlated observations using thin sections and freeze-fracture replicas. Distal junctional complexes of the odontoblasts were composed of both gap and macular tight junctions and sealed extracellular spaces incompletely, because of the poor sealing capacities of macular tight junctions. Therefore, there was no predentine-pulp barrier in the odontoblast layer. Except for the junctional complex, no tight junction was observed in the odontoblasts. Gap junctions and desmosome-like junctions were found between adjacent odontoblasts and between odontoblasts and neighbouring pulp cells. Gap junctions were similar to those of many other tissues but the desmosome-like junctions were different from mature desmosomes in the epithelial cells and showed immature features. Each intercellular junction of odontoblasts is considered to form a site of intercellular communication and cell-to-cell attachment.

Animals↗
PubMed1983

Fine structure of secretory ameloblasts in kitten tooth germs, with special regard to intercellular junctions as revealed by freeze-fracture.

Using both thin sectioning and freeze-fracture replication, junctional complexes at both proximal and distal ends of the cells consisted of tight junctions in close association with gap junctions and desmosomes. The tight junctions generally consisted of smooth, continuous rows of particles on the P-face and corresponding patterns of shallow grooves on the E-face of cell membranes. Though sealing of paracellular spaces around the ameloblasts in the proximal junctional complex was incomplete, there was complete sealing around the ameloblasts and well-developed meshwork structures of tight junctions in distal junctional complexes. Discontinuous and free-ending strands of tight junctions were frequent in junctional complexes, suggesting that ameloblast distal junctional complexes serve, not only as a barrier to high molecular passive substances through the ameloblast layer, but also as a channel for ions and low-molecular substances. Ameloblasts were firmly connected with stratum intermedium cells by desmosomes and gap junctions. The gap junctions on ameloblast basal and lateral surfaces probably function in intercellular transfer of ions and low-molecular substances between the stratum intermedium and ameloblasts and in control of ameloblast cytodifferentiation.

Ameloblasts↗