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At least 37 records · Page 2Linked to original sources
PubMed1987

Ultrastructure of in-vitro recovery of mineralization capacity of fluorotic enamel matrix in hamster tooth germs pre-exposed to fluoride in organ culture during the secretory phase of amelogenesis.

The recovery of mineralization capacity of fluorotic enamel matrix was investigated in 3-day-old hamster first molar tooth germs already pre-exposed in organ culture to 10 parts/10(6) F- for 24 h during the secretory phase. The germs were then cultured for another 24 h in a fresh medium without F-. The unmineralized fluorotic enamel matrix secreted in vitro eventually mineralized in the absence of F- but the orientation of the crystals compared to those in the fluorotic enamel was disturbed, especially in the younger regions of the enamel nearest cervical-loop in which the underlaying fluorotic enamel was most hypermineralized; but least disturbed in the more mature parts of the enamel organ in which the fluorotic enamel was less hypermineralized. The subsequent culture in F(-)-free medium did not abolish or reduce the degree of hypermineralization induced by F- treatment during the initial 24 h of culture. It seems that in vitro the inhibitory effect of F- on enamel matrix mineralization during the secretory phase is completely reversible when the ion is removed from the matrix environment, i.e. F(-)-induced synthesis and secretion of defective enamel matrix is not the cause of the lack of matrix mineralization. The F(-)-induced hypermineralization seems to be irreversible.

Amelogenesis↗
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

A histological study of the chronology of initial mineralization in the human deciduous dentition.

Accurate dating of initial mineralization in the dentition was derived from fetuses aged according to the maternal history, assessment of gestational age by obstetricians, paediatricians and pathologists, histological evaluation of their cerebellar and renal development, and accurate measurements of crown-rump length, skull circumference, brain and body weight. Serial sections of the jaws of 121 fetuses ranging from 10 to 26 weeks post-menstrual age first showed mineralized dentine in the deciduous central incisor at 15-19 weeks, in the lateral incisor at 16-21 weeks, in the canine at 19-22 weeks, in the deciduous first molar at 16-19 weeks and in the second molar at 20-22 weeks. These age ranges differ from those for initial mineralization common in textbooks, particularly for the molars.

Cuspid↗
PubMed1988

The appearance of matrix vesicles and mineralization during tooth development in three teleost fishes with well-developed enameloid and orthodentine.

Ultra-thin resin sections of tooth bearing parts from three species were examined by electron microscopy. During enameloid matrix formation, matrix vesicles (MV) and fine aggregations of crystal-like structures probably derived from the MV were found in the enameloid matrix. In enameloid, however, no additional mineralization occurred along the collagen fibrils until mineralization had begun initially at the junction between the enameloid and orthodentine areas. Advance of mineralization along collagen fibrils was inhibited in the enameloid area before initial mineralization despite the presence of MV. Many MV were observed at the initial mineralization site; they appeared in the predentine during odontogenesis after the initial mineralization and were still visible during the stage of basal dentine formation. The odontoblasts continued to produce MV from the early stage of enameloid matrix formation until the late stage of basal dentine formation. However, despite their long appearance, MV are probably involved directly with the mineralization only when the initial mineralization starts.

Animals↗
PubMed1991

Amelogenin post-secretory processing during biomineralization in the postnatal mouse molar tooth.

The primary structures, molecular genetics and biosynthesis of the amelogenin protein of the developing tooth are established, but knowledge of their subsequent post-secretory processing and its relation to enamel biomineralization is fragmentary. Preparations of tooth matrix proteins were isolated from molars (M1) of mice from birth to 15 days and analysed by SDS-PAGE and immunochemical methods. Amelogenin proteins, isolated and partially purified by HPLC, were characterized by amino acid analysis and SDS-PAGE. At birth a 26 kDa amelogenin was present that during subsequent developmental stages generated a series of 20-25 kDa amelogenins differing in apparent size by approximately 1 kDa. Amino acid analyses showed that all these amelogenins have amino-terminal TRAP sequences; analyses for both glycosylation and phosphorylation were negative. It is suggested that these post-secretory amelogenins are generated by a sequence of specific carboxy-terminal cleavages, and that the observed post-secretory processing of amelogenin is functionally linked to the structure of the enamel matrix and the control of crystallite development.

Age Factors↗
PubMed1990

Apical closure of mature molar roots with the use of calcium hydroxide.

Calcium hydroxide may induce apical root closure in affected mature teeth as well as in immature teeth. Once an apical hard tissue barrier is formed, a permanent root canal filling can be safely condensed. Two cases are described in which calcium hydroxide induced apical root closure in mature molar teeth where the apical constriction was lost because of chronic inflammatory process.

Adult↗