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PubMed1977

[Study of a non-collagen protein fraction of dentin during minerlization].

A protein fraction of mineralizing porcine dentine was analysed after E.D.T.A. demineralization. This fraction of heterogeneous composition had a high content of phosphorus. Its acid character, deductible from the amino acid analysis, was confirmed by electrophoresis. After Sephadex gel filtration, five fractions were obtained. They could be characterized by amino acid analysis and phosphorus dosage. Two fractions contained phosphorus and were very rich in aspartic acid and serine. The three other fractions were characterized by their very high content of glycine.

Amino Acids↗
PubMedDate not supplied

[Mineralization and structure of enamel (a study using scanning electron microscopy and X-ray micro-analysis of the lower incisor of the albino rat)].

In order to know the morphostructural changes that occurs in the enamel during the mineralization and to study the rod tridimensional orientation, the author has examined the literature concerning these subjects comparing it to the results of his researches realized by S.E.M. and Rx-microprobe-analysis. It has been demonstrated that three phases can be distinguished during the mineralization: "fibrillation phase", "rod density phase", "interrod density phase". The fibrillation phase begins in the middle of the ameloblastic secretion phase, ends 8 mm from the cervical ansa and is characterized by the unmasking of the matrix subunits and chemically by the disappearance of the sulphur. The rod density phase occurs in the area included between 8 and 14 mm from the cervical ansa, that is in the ameloblastic modulation phase, and is characterized by the aggregation of the intraprismatic subunits and by the calcium increase. The interrod density phase that occurs during the ameloblastic pigmentation phase, is characterized by the aggregation of the interprismatic subunits and by the presence of the iron in the most superficial enamel layers. The rod orientation in the space has been studied during the second phase of the mineralization suice the intraprismatic subunits join while the interprismatic ones remain in the fibrillation phase; besides the author has compared the results of these studies to the morphology of the external opening of the honeycomb pits. In such a way it has been demonstrated that the rod originates from the dentine-enamel junction forming a 60 degree angle that opens in the cuspidalmesial or cuspidal-lateral direction. In the outer enamel layer the rod loses its mesial or lateral inclination and bends further towards the cusp delimiting a 30 degree angle; finally it bends outward and as a sharpend that is ortogonal to the enamel external surface. It is eventually discussed how this model of rod reconstruction is fit to convert the tangential forces that develop during the mastication into compression forces.

Amelogenesis↗
PubMedDate not supplied

[Characteristics of the enamel mineralization of the intact permanent teeth in children 6 to 14 years old].

The composition of enamel from the first permanent lower molars was studied intravitally in 140 somatically asymptomatic children with intact teeth. The contents of Ca, P and molar Ca/P ratio were determined. At the age of 10, 13 and 14 years Ca levels were higher as related to 10, 13 and 14 for cuspid and to 13 and 14 years for paracervical specimen. After 10 years, cuspid Ca content was higher than cervical. At the age of 10 to 14 cuspid P content was reduced. Age-related increase in molar Ca/P ratio was also found. The values attained those characteristic of adult intact enamel at cuspid by the age of 9, and at cervix by 12 years. The data suggest that cuspid enamel matures earlier than pericervical one.

Adolescent↗
PubMed1978

Physiological recalcification of carious dentin.

In order to confirm the ability of physiological recalcification of the human carious dentin, the first layer of carious dentin was removed from the symmetric cavities of bilateral pairs of human teeth, disclosing it by 0.5% basic fuchsin-propylene glycol solution staining. One of the pair teeth was immediately extracted and the other was left in the mouth after filling the cavity with polycarboxylate cement. The Ca content and hardness of the remaining second layer immediately and three months after the operation were compared by an electron probe microanalyzer and microhardness tester. They increased markedly after three months returning to the normal level from inside, proving physiological recalcification. A similar experiment was performed by using bilateral pairs of dog teeth with cavities having artificially decalcified dentin floor. After removing the fuchsin-stainable first layer, one of the pair was immediately extracted and the other was left in the mouth for three months after exposing or filling the cavity with various cements. As the Ca content was compared, a marked recalcification of the second layer of softened dentin was observed after three months returning to the normal level from the inside. The effect of different cavity treatment was slight.

Animals↗
PubMed1979

SnF2 treatment of enamel, hydroxyapatite or brushite at 37 degrees C and 50 degrees C: an infra-red investigation.

The effect of 4% SnF2 on brushite, hydroxyapatite and powdered bovine enamel applied for short, 15 or 30 minute, periods was investigated using infra-red spectroscopy. It was found that brushite was converted into a fluoridated hydroxyapatite, a reaction which was both time and temperature dependent. The reactions of hydroxyapatite and powdered enamel with SnF2 were similar. There was a drop in the OH- peak intesities. X-ray diffraction analysis of these samples showed that F- ions occupied mainly OH positions in the hydroxyapatite lattice structure. In all reactions an increase in temperature from 37 degrees C to 50 degrees C increased the reaction speed by at least a factor 2. The most probable result of in vivi SnF2 application on sound enamel is the formation of a fluoridated hydroxyapatite together wity stannous complexes and amorphous CaF2. In demineralized areas some of the brushite is converted into a fluoridated hydroxyapatite as is some of the remaining hydroxyapatite. In the more protected area of an enamel lesion these reactions may well continue for some time after the topical fluoride application; Sn2F3PO4 may also therefore be formed.

Animals↗