J.A. Weatherell

Variations in the composition of developing rat incisor enamel

The developing enamel of rat incisors was dissected into a series of samples extending from the newly-formed partially-mineralised matrix to the mature enamel. Chemical analysis showed that, on a dry weight basis, the tissue achieved the composition of mature enamel well before the completion of mineral uptake. The enamel at this stage was porous and relatively soft. As more mineral was acquired, its hardness increased. Throughout the developing region, the Ca:P ratio remained fairly constant, but the CO2:P and Mg:P ratios both decreased due, apparently, to dilution by an influx of relatively CO2- and Mg-free mineral.

Amino acid composition, distribution and origin of “tuft” protein in human and bovine dental enamel

Abstract Protein with a composition resembling that of the “tuft” protein, previously described only in the enamel of mature human molars, has been isolated from different types of mature permanent and deciduous human and bovine teeth. A protein fraction not dissimilar from tuft protein in composition has also been obtained from developing enamel.

Matrix and Mineral Changes in Developing Enamel

An investigation of the changes taking place in the enamel and the enamel organ during enamel development has been carried out by analyzing small samples of tissue dissected from developing incisors of rat and bovine incisors. Observations showed that the synthesis of the enamel matrix and its subsequent loss were associated chiefly with a change in the major matrix components. This consisted of a selective loss of amelogenin components prior to secondary mineralization. Before this loss, some increase in the proportion of smaller molecular weight components suggested the possibility of limited breakdown. Even at the earliest stages examined, significant concentration of mineral ions was present. This increased steeply after most of the organic matrix had been removed. The Ca/P ratio of this mineral was constant throughout development. The concentration of minor inorganic ions (F, Mg and CO3) decreased as the tissue developed and a tendency was observed for certain ions (F, 32PO4) to penetrate and concentrate in the enamel, apparently as a consequence of the lost matrix being replaced by water, just prior to the steep increase in mineral content of the tissue.

Changes in the Fluoride Concentration of the Labial Enamel Surface with Age

Using a recently developed micro-procedure, small samples of enamel, dissolved from the labial or buccal surfaces of permanent anterior teeth, were analysed to establish the pattern of fluoride distri

Micro-Sampling by Abrasion

An attempt has been made to develop a technique for the serial sampling of porous enamel, mesenchymal tissues, ectopic mineral deposits, developing tissues and other material not amenable to the estab

Variation in Composition of Dental Enamel Within Thin Ground Tooth Sections

Recently developed micro-sampling and micro-analytical techniques have been used to determine the distribution of calcium, phosphorus and protein in individual enamel sections. Absolute values for calcium, phosphorus and protein were variable (30–40% calcium, 13–23% phosphorus and 0.002–0.015 mol amino acids/100 µg enamel), but consistent patterns of distribution were revealed in the tissue. The average values for calcium (37.5%), phosphorus (17.5%) and Ca:P ratio (2.1) agreed with those quoted in the literature. The volume of tissue occupied by the mineral and the significance of the composition patterns with respect to enamel formation and caries are discussed.

Four Chemically Distinct Stages in Developing Enamel from Bovine Incisor Teeth

Chemical analysis and the appearance of developing enamel from deciduous bovine incisors have distinguished four stages during the process of development: (1) secretion of soft, translucent, partially

Changes in Amino-Acid Composition of Developing Rat Incisor Enamel

SummaryThe amino-acid composition and total “protein” content of enamel particles dissected serially from the developing enamel of rat incisors have been determined. Changes in protein content and amino-acid composition occurred throughout all stages of development. The most obvious alterations occurred in the vicinity of a white opaque band. Here, protein was lost most rapidly and considerable changes in amino-acid composition occurred.

Loss of Carbonate during the First Stages of Enamel Caries

The changes in carbonate concentration of enamel associated with the first visible stages of carious attack have been investigated. Samples of translucent-zone enamel and adjacent samples of sound ena

The effect of tooth wear on the distribution of fluoride in the enamel surface of human teeth

Abstract Distribution curves, describing the change in fluoride concentration from the surface to the interior of enamel, were determined in different regions of the tooth surface in a large number of permanent human anterior teeth of different ages and types, from districts with and without fluoride in the water supply. The distribution curves varied considerably from place to place in the tooth surface, often being shallow towards the biting edge of the tooth and steeper in cervical and approximal regions. These differences in the shape of the curves seemed largely attributable to wear. There was also a variation in the curves with age and type of tooth. The lost fluoride was not apparently restored by post-eruptive uptake, even in teeth from a district where the fluoride concentration of the water supply was relatively high.