A.S. Hallsworth

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

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.

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.

Mineral and Magnesium Distribution within the Approximal Carious Lesion of Dental Enamel

The chemical changes taking place in enamel during carious attack have been studied by analysing the histologically defined zones of the small approximal lesion. Sam- pies of altered enamel were dissected from each zone and compared with sound enamel from adjacent control areas. Enamel from the primary translucent zone, the area of the lesion presumed to be least affected by caries, contained about 1.2% by volume less mineral and about 12% by weight less magnesium than the adjacent, apparently sound enamel. The translucent zone, therefore, appeared to result from demineralisation, associated with a preferential loss of magnesium-rich mineral.

Volume distribution and concentration of protein, mineral and water in developing bovine enamel

The percentage volume of enamel occupied by mineral, matrix protein and water was determined at each of four stages. Protein decreased throughout development from 20 to 30 per cent to a minimum of 2-3 per cent in mature tissue. Mineral content remained fairly consistent during secretion (15-20%) rising to 70-80 per cent in mature enamel. Water content rose from varying levels to 60-70 per cent at the secretion/maturation boundary decreasing to about 20 per cent in mature enamel. The loss of protein and subsequent delay in the onset of mineral increment resulted in tissue porosity. The duration of this hydrated, porous stage may determine susceptibility of the tissue to, for example, fluoride ion.

Distribution of Magnesium in Mature Human Enamel

The distribution of magnesium has been determined in the enamel of permanent human teeth. The concentrations increased from the surface towards the interior. The gradients were not smooth, pockets of relatively high magnesium concentration frequently occurred around the dentinal cornua and in the region of fissures. The distribution patterns obtained suggested a correlation between magnesium concentration and low density enamel and possibly between magnesium and protein concentration.

Arrest and Control of Carious Lesions: A Study Based on Preliminary Experiments with Resorcinol-Formaldehyde Resin

An experimental investigation has been made into the possibilities of retarding the progress of carious attack by infiltrating cariostatic material into enamel lesions. The problems associated with this kind of procedure are discussed against the background of experimental observations made using a formulation based on a resorcinol-formaldehyde resin.

A Microbiological Study of Early Caries of Approximal Surfaces in Schoolchildren

A cross-sectional epidemiological study has been undertaken to relate the bacterial composition of approximal dental plaque with the earliest stages of caries development in schoolchildren. Small samples of plaque were removed from multiple sites around the contact areas of 42 premolars extracted for orthodontic reasons from 29 schoolchildren (mean age = 13.5 yr). Caries diagnosis was based on polarized light microscopy and contact microradiography of thin sections cut through the sample sites. Fifty-seven percent of sites (37l60) showed histological evidence of demineralization. Both the isolation frequency and the mean percentage viable count of mutans streptococci and Actinomyces viscosus were higher at sites with early caries, although mutans streptococci could not be detected at 37% of sites with early caries. At these latter sites, the proportions of Veillonella were markedly reduced. Lactobacilli were rarely isolated and were never recovered from caries-free surfaces. Analysis of the data shows that the relationship between plaque bacteria and enamel is neither merely passive nor indifferent, and that particular stages of lesion formation may be associated with different combinations of bacteria.

Effect of Surface Zone Deproteinisation on the Access of Mineral Ions into Subsurface Carious Lesions of Human Enamel

It has been proposed that the so-called intact surface zone of carious lesions of enamel could restrict the ingress of mineral ions and hinder remineralisation. The present study was intended to determine the role of organic (proteinaceous) material in restricting the movement of mineral ions into carious lesions in vitro. Natural carious lesion surfaces were divided into two halves. The experimental half was de-proteinised using hypochlorite, the control half remained untreated. The whole tooth was exposed to 45Ca in solution, and 45Ca uptake into experimental and control tissue was measured by image analysis of autoradiographs prepared from lesion sections. The results indicated that uptake was improved by removal of organic material.