The Distribution of Magnesium in Developing Rat Incisor Dentin

Abstract

Previous studies have shown that rat incisor dentin contains a considerable amount of magnesium that is distributed heterogeneously. The cementum-related dentin, especially its incisal portion, is richest in magnesium. It was the purpose of the present study to investigate the changes that occur in the magnesium content during dentin maturation.Cross-sections were prepared from rat incisors at the apical, middle, and incisal levels. By means of an electron microprobe, tracings were made of the Ca-, Mg-, and P-signal frequencies. Comparison of corresponding dentin layers within and between the cross-sections showed that the Mg/P molar ratio was always higher in the cementum-related dentin (CRD) than in the enamel-related dentin (ERD) and increased from the apex toward the incisal edge. Especially in the incisal crosssection, an increase in Mg/P was found from the older (peripheral) toward the younger (central) dentin layers. As the Mg/P ratio varied from 0.07 to 0.33, the Ca/P ratio was found to fluctuate from 1.48 to 1.15. The two ratios appeared to be highly correlated (r = -0.97; p<0.001), suggesting that Mg replaces Ca and is bound to phosphate. overdose of Nembutal injected intracardially. Their lower right jaws were dissected out and stored frozen. Cross-sectional slices (1 mm in thickness) of the incisors, together with the surrounding tissues, were prepared at an apical, middle, and incisal level (Fig. 1) by use of a Microslice 2 MR (Metals Research Ltd., Cambridge, England) with a diamond saw blade under constant water cooling. After removal of the surrounding bone, the cross-sections of the incisors were dehydrated through a graded series of ethanol and propyleneoxide and embedded in epoxy resin (Epon LX112, Ladd), which was polymerized at 60°C. All specimens were embedded simultaneously in the same piece of epoxy resin, in such a way that the slices obtained from one tooth were next to each other. The incisal aspect of each slice was then serially polished with silicon carbide abrasive paper (nos. 240 to 600), followed by a 0.03-,um aluminum oxide micropolisher.Electron microprobe analysis. -After the slices were coated with a carbon layer in a Balzer BEA 250 evaporator, the specimens were subjected to electron microprobe analysis in a JEOL Superprobe 733 (10 kV, 10 WxA, beam area 1 1Lm2, ten s per J Dent Res 70(3): 187-191, March, 1991

Dental Phenotype in Jalili Syndrome Due to a c.1312 dupC Homozygous Mutation in the CNNM4 Gene

“…This could be interpreted to suggest that in the odontoblasts which also express CNNM4 [1,4], the defect of the protein impairs the transport of Mg into the tissue. As Mg of the dentin mineral is believed to compete with Ca and to be bound to phosphate [15], the observed slightly increased Ca content would also appear to agree with this assumption.…”

XRMA and ToF-SIMS Analysis of Normal and Hypomineralized Enamel

“…The inductive analysis also showed that Mg was the most important element for discrimination of hypomineralized from normal enamel. Animal studies have shown that increased levels of Mg in enamel at late developmental stages may delay mineralization, resulting in poorly crystallized enamel (Spencer et al, 1989;Steinfort et al, 1991). Normal enamel shows consistent gradients similar to that seen for Na, whereas MIH enamel shows inconsistent trends.…”

Role of genetic background in determining phenotypic severity throughout postnatal development and at peak bone mass in Col1a2 deficient mice (oim)

“…Oim/+ tibias of both strains are intermediate to Wt and oim/oim in both fluoride levels and biomechanical integrity. Magnesium, thought to inhibit crystal formation by competing with calcium and blocking the active crystal growth sites [49,50], also demonstrated a negative association with bone strength and energy to failure. Fratzl et al demonstrated that oim/oim cortical bone has thinner and less well aligned crystals, contributing to the reduced strength of the bone [51].…”