Correlated physicochemical and age changes in embryonic bovine enamel

Abstract

Whole enamel scrapings from unerupted teeth of embryonic calves have been separated into fractions of varying density by stepwise centrifugation in bromoform-toluene mixtures of increasing specific gravity. Partition of enamel in this manner yields individual fractions of increasing mineral phase age and maturation. Whole scrapings and isolated fractions of the fetal bovine enamel were examined by X-ray powder diffraction, scanning electron microscopy, and atomic absorption and infrared spectroscopy to determine time-related changes in the physiochemical nature of the constituent mineral phase particles. These analyses showed poorly crystalline hydroxyapatite (HA) as the only detectable solid phase of calcium phosphate present in all fractions, its degree of crystallinity increasing with increasing density. Molar Ca/P ratios and magnesium content were highest in lowest density fractions. Carbonate vibration bands at 875 and 1420-1450 cm-1, common to mineralized tissue, were observed in intermediate and higher density fractions and in whole unfractionated enamel. Another carbonate band at approximately 705 cm-1, unusual to vertebrate calcified tissue, was detected in low density fractions and disappeared rapidly with increasing enamel maturation. Its precise relation with the enamel mineral phase has not been determined.

Single Bovine Enamel Particles Examined by Electron Optics

“…Analyses of bulk bovine enamel fractions prepared by density gradient centrifugation have been made previously by x-ray diffraction, scanning electron microscopy, atomic absorption, and infrared spectroscopy (Landis and Navarro, 1983). Rather than examining bulk properties, the present studies have investigated single mineral particles or their small clusters from the same samples.…”

“…Tissues and procedural descriptions have been reported previously (Landis and Navarro, 1983). In summary, enamel was obtained by scraping unerupted mandibular and maxillary incisors and molars removed from 53 fresh, frozen bovine fetuses approximately 30 to 150 days old in utero.…”

“…Lowest-density fractions yielded highest molar Ca/P ratios and magnesium content on chemical analysis, and all fractions contained carbonate determined by infrared spectroscopy. It was suggested that carbonate may be related to the relatively higher Ca/P molar ratios observed in lower-density enamel fractions, but its precise relationship to the enamel mineral phase could not be elaborated (Landis and Navarro, 1983).…”

“…Whole enamel scrapings from unerupted teeth of embryonic calves have recently been separated by density (p) gradient centrifugation in organic solvents to provide relatively homogeneous fractions representing progressive stages of mineral phase maturation (Landis and Navarro, 1983). The mineral fractions obtained were examined by bulk analysis methods: All fractions (1.6 < p < 2.4 g/cm3) contained poorly crystalline hydroxyapatite as the only solid phase of calcium phosphate detectable on x-ray powder diffraction.…”

Aqueous density fractionation of mineralizing tissues: An efficient method applied to the preparation of enamel fractions suitable for crystal and protein studies

“…However, despite the recognized relationship between the organic and the inorganic parts in calcifying tissues, there are few concomitant studies of both sides of the question. This is probably the consequence of the lack of an appropriate methodology suitable for both mineral and organic matrix studies.Protein changes associated with increasing rain- [13,21,22]. This method involves the use of mixtures of organic solvents unsuitable for protein studies, and the complete removal of water from the tissue.…”