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Biomedical subjects

J A Weatherell

Publications and source records attributed to J A Weatherell.

At least 19 recordsLinked to original sources
PubMed1992

The thickness of the sound and periodontally diseased human cementum.

Cementum of teeth previously analysed for fluoride was re-examined in order to determine whether or not periodontal disease had affected the thickness of the tissue. In the periodontally diseased teeth the cementum was thinner than normal in the middle region of the root. The apical cementum, however, was significantly thicker in periodontally diseased than in the sound teeth of subjects over 60 yr old. This may account for the higher total fluoride levels previously reported in the apical cementum of these same teeth.

Adult↗
PubMed1992

Influence of occlusion on the fluoride distribution in rat molar cementum.

This study was undertaken to examine the influence of occlusion on the fluoride distribution in cementum following an experiment in which the occlusion in rats was locally altered by extracting the upper left molar. These and control rats with normal occlusion were given water containing 0 or 100 ppm fluoride for 12 weeks. The fluoride distributions in cementum from both first lower molars of the same animal were compared. The fluoride concentrations had increased throughout the tissue as a result of increased fluoride administration, irrespective of any changes in occlusion. They were, as usual, generally highest at or near the cementum surface and decrease towards the interior of the tissue. Where there had been a change in occlusion, the thickness of cementum was less than that of the contralateral tooth, but, despite this, the fluoride profiles in contralateral teeth were similar in both experimental and control rats. In the experimental rats, on the other hand, the total fluoride tended to be lower, and the mean fluoride tended to be higher in left molars without antagonists. These findings were never seen in the control rats. It was concluded that the alteration in occlusion influenced the fluoride distribution in the cementum through its effect on the rate of cementum formation.

Animals↗
PubMed1992

Determination of volumes of fluid in the mouth by fluoride dilution.

A dilution technique, with fluoride as a marker, has been developed to measure the volume of saliva and other fluids in the mouth. Immediately after swallowing, a small amount of fluoride solution is placed in the mouth, mixed with the oral fluids, and expelled from the mouth. The fluoride concentration of the expelled oral fluid is measured and the volume of fluid in the mouth at the time of spitting calculated from the fluoride dilution. Mean values of 0.75 +/- (SD) 0.28 ml for males and 0.72 +/- (SD) 0.16 ml for females were recorded. The accuracy of the volume determination is about +/- 0.10 ml in vivo. This technique has provided a convenient and rapid means of determining saliva volumes. It could also be used to determine rates of secretion and may prove useful in the clinic for assessing a patient's salivary competence.

Adult↗
PubMed1991

Distribution of fluoride across human primary enamel.

The distribution of fluoride was described in detail from the incisal to the cervical region in 10 pairs of primary lower central incisors. Fluoride analyses were done on the right incisors; optical microscopic studies were done on the left. The distribution data obtained from fluoride analyses of the right incisors were superimposed on micrographs of sections through the left incisors. An abrasive microsampling technique (Weatherell et al., 1985) was used to determine the fluoride concentration and distribution. Fluoride concentration was the highest at the enamel surface and decreased from there to the interior. The fluoride distribution did not level off to an even plateau in the enamel interior, as suggested by earlier studies. Apart from the high concentration in the surface region, the fluoride levels in prenatal and postnatal enamel were rather similar. The fluoride concentration tended to be low at the neonatal line.

Child↗
PubMed1991

Distribution of fluoride in the cementum of human deciduous canines.

This study was undertaken to determine the fluoride distribution in human deciduous cementum. Ten pairs of sound deciduous canines, extracted from children aged 6-9 years, were examined. The teeth were sectioned, and specimens of cementum were removed from the buccal or lingual aspect of the sections. Samples were removed sequentially by abrasion, from the cementum surface to the cementum-dentine junction, and their fluoride content determined as described earlier. The concentrations of fluoride were highest at or near the cementum surface and decreased towards the interior of the tissue. Concentrations and patterns of fluoride distribution were characteristic of the individual subjects. The distribution patterns of fluoride in the contralateral teeth from the same subject were also fairly similar.

Child↗
PubMed1979

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.

Amelogenesis↗
PubMed1977

Changes in amino-acid composition of developing rat incisor enamel.

The 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.

Amino Acids↗
PubMed1975

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 C02- and Mg-free mineral.

Amelogenesis↗