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Biomedical subjects

J A Weatherell

Publications and source records attributed to J A Weatherell.

At least 37 records · Page 2Linked to original sources
PubMed1989

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 (37/60) 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.

Adolescent↗
PubMed1989

Potential benefits of toothpaste advertising on dental health.

This paper considers the effect of advertising on the sales of various brands of toothpaste. It has attempted to investigate the relationship between the level of sales of a brand and those of its competitors. Econometric estimations of the demand-function for toothpaste have been made and the authors have tried to determine the interrelationships between advertisement and toothpaste sales. The findings cast doubt upon the efficiency of the present system of competitive advertisement and suggest a possible alternative approach to the marketing of toothpaste which could increase sales and, at the same time, beneficially influence dental health.

Advertising↗
PubMed1988

Site-specific differences in human dental plaque pH after sucrose rinsing.

The object was to find out whether site-specific variations of pH might correlate with those of oral clearance as indicated by past studies using fluoride, sucrose and glucose as markers. Eleven subjects with 24 h growth of dental plaque rinsed the mouth with a 10% solution of sucrose. The pH of plaque, harvested from the labial or buccal cervical and approximal regions of certain teeth or groups of teeth, was then measured. The results confirmed previous reports that plaque pH varies from site to site in the mouth; the pattern observed was similar in each of the subjects. In the anterior part of the mouth, concentrations of hydrogen ion were invariably higher in plaque from the upper than from the lower surfaces of the teeth. The reverse pattern was found in the posterior part. This site-specific pattern was similar to that of oral clearance, as indicated by comparison with known values for glucose concentrations, a finding consistent with the view that site-specific pattern of plaque pH may reflect or at least be influenced by such differential clearance patterns.

Adolescent↗
PubMed1988

Distribution of fluoride in the enamel of rat incisors examined by an abrasive microsampling technique.

This study was undertaken to reveal detailed changes in fluoride distribution at different developmental stages of upper incisor enamel under various fluoride administration regimes. Four groups of Wistar rats received water containing 0, 25, 50 and 100 parts/10(6) fluoride respectively for 10 weeks. Five different enamel specimens were removed from the developing enamel, excluding the matrix-formation stage. Fluoride distribution in each specimen was analysed from the surface to the enamel-dentine junction using an abrasive microsampling technique. Fluoride concentration was invariably highest at the surface and decreased sharply towards the interior at every site in both control and experimental groups. The concentration throughout the tissue increased with fluoride intake at each stage of development. The fluoride-gradient curves were similar at each of the different sites of tooth development. However, the fluoride concentration of the enamel interior was significantly higher at early maturation than at the other four sites.

Animals↗
PubMed1988

The dissolution rate of enamel in acid in developing rat incisors.

This study was undertaken to determine the changes in this dissolution rate at different developmental stages after different fluoride dietary regimes. Four groups of Wistar rats received water with 0, 25, 50 and 100 parts/10(6) fluoride respectively for 10 weeks. Six exposed windows of 2 mm2 were prepared on the enamel surface of the upper incisors, corresponding to six different developmental stages. The acid-dissolution rates were determined at each window by using 1.4 M sodium acetate-hydrochloric acid buffer (pH 2.3). The rate of enamel dissolution was highest in the matrix-formation stage and dropped sharply in a step-wise fashion towards the stages of secondary mineralization and iron deposition. The dissolution rate in the maturation stage decreased significantly with increasing intake of fluoride. However, in the pigmented enamel, the opposite occurred. The iron pigmentation or the porosity in this region of fluorosed enamel might be responsible for the change in the dissolution rate of the pigmented enamel.

Animals↗
PubMed1988

Fluoride distribution and histological structure of human cementum.

Thirty-one teeth taken post-mortem from 10 subjects aged from 40 to 66 years were studied. A close relationship was found between fluoride (F) distribution and histological structure. Although, as in all mineralized tissues, F concentrations tended to be highest towards the external surface, individual patterns of F distribution also seemed to reflect the histological pattern, especially the distribution of cellular or acellular cementum. In general, F concentrations were high in acellular and low in cellular cementum.

Adult↗
PubMed1988

Availability of fluoride at different sites in the buccal sulcus.

After rinsing with a fluoride solution, the amounts of fluoride taken up by small pieces of dentine placed strategically about the mouth varied considerably from site to site in the oral cavity. The pattern of fluoride availability in this subject's mouth was in line with previous findings about fluoride distribution in his labial sulcus. The present results therefore suggest by analogy that considerable variations in fluoride clearance and concentration must exist throughout the oral cavity. These previous studies of fluoride clearance from the labial sulcus also showed that there are marked differences between individuals. The present findings, emerging from a study of 1 subject, therefore imply a need for more information about the variations in the availability, concentration and clearance of fluoride and, by extrapolation, of other substances throughout the mouths of different individuals.

Absorption↗
PubMed1988

Patterns of fluoride distribution on the surface of a tooth fragment after clinical treatment with fluoride gel.

This paper describes site-to-site variations in fluoride concentration in the surface region of a tooth fragment sent from a patient who, following radiation therapy, had been repeatedly treated with fluoride gel. The fluoride content of the tooth surface was determined with the intention of establishing the extent to which the treatment had enhanced the fluoride content of the tooth surface. The work illustrates the difficulties in the choice of a suitable sampling site and the importance of adopting a suitable sampling technique. It highlights, once again, some of the problems encountered in attempting to interpret analytical data about fluoride levels in tooth surfaces.

Dental Enamel↗
PubMed1988

Mineral and protein concentrations in enamel of the developing permanent porcine dentition.

Calcium, phosphorus and protein analyses have been performed on developing permanent enamel from the mandibular dentition of the domestic pig. The pattern of mineralization and protein loss was similar from tooth to tooth and similar to teeth from other species. Comparison of different teeth at the same developmental stages (secretion--stage 1, transition--stage 2 and maturation - stage 3) revealed remarkably similar concentrations of calcium, phosphorus, and protein regardless of tooth type. These data were similar to those from other deciduous dentitions, except that maturing/mature tissue in the pig seemed less well mineralized.

Age Factors↗
PubMed1988

Maturation in developing permanent porcine enamel.

Mineral content per tissue volume was investigated in developing permanent porcine enamel and contrasted with weight-related data. Levels of mineralization were correlated directly with the histological appearance of the overlying enamel organ. Magnesium concentrations were measured at different stages of enamel development. Mineral levels rose from approximately 30% per volume of tissue during the secretory stage to approximately 60% in mature tissue. This is much lower than final mineral levels in enamel of other species. Enamel containing low mineral levels was adjacent to tall secretory ameloblasts which had reduced in height by approximately 50% at a point corresponding to the beginning of the maturation stage. Magnesium concentrations remained relatively constant throughout the secretory stage, at 0.2% Mg by weight. These rose by 3-4 times in the enamel of the maturation stage. The low levels of mineralization in the mature porcine enamel did not appear to be due to enamel pathology, and the possibility of porcine teeth erupting in an immature, partially porous condition is discussed.

Ameloblasts↗
PubMed1987

Distribution of fluoride across human dental enamel, dentine and cementum.

This was determined across the entire width of sections from 20 mandibular premolars, containing enamel, coronal dentine, root dentine and cementum. An abrasive technique was used to sample all three dental tissues in a single experiment. In the profiles of fluoride distribution, fluoride concentration was thus precisely related to the position of the tissue sample. There was a marked increase in the fluoride content of coronal and root dentine, at least until the age of about 50 years. There had been uptake of fluoride by the root dentine and cementum throughout the life of the tooth. There was no evidence of any change in the fluoride content of enamel with age.

Adult↗
PubMed1987

The distribution pattern of fluoride concentrations in human cementum.

The distribution of fluoride across human cementum has been determined on 59 individual teeth taken post mortem from five subjects aged 30, 43, 54, 66 and 70 years. Eight teeth of different types were examined from each of the five subjects together with a further 19 teeth from the 54-year-old, making a total of 27 teeth from this subject. As in a previous study, F concentrations were generally higher towards the surface of the cementum, but there were considerable variations between F gradients. The teeth from each subject seemed to comprise a family of profiles, characteristic of the individual.

Adult↗
PubMed1987

Developmental stages in permanent porcine enamel.

Developing permanent teeth of different ages were obtained from Danish Landrace pigs. Visibly distinct zones on their enamel surfaces were shown to correspond to changes in chemical composition previously reported for other species. The time of appearance, rate of progress and duration of each stage was determined for each tooth type.

Animals↗
PubMed1986

Distribution and retention of salivary fluoride from a sodium fluoride tablet following various intra-oral dissolution methods.

The distribution and retention of salivary fluoride were investigated according to the following intra-oral dissolution methods of a sodium fluoride tablet: active chewing/swishing, active sucking/swishing, and passive dissolution in the maxillary and mandibular labial vestibule. The results suggested that the oral cavity was somewhat compartmentalized, in that homogeneous distribution of a dissolved fluoride tablet did not occur throughout the mouth, but rather each site sampled was influenced by various rates of clearance and retention. Tablet chewing may have an advantage over tablet sucking in terms of salivary fluoride retention, and there was a tendency for fluoride to be preferentially retained in the maxillary labial vestibule following swishing. The passive tablet dissolution methods resulted in a less homogeneous distribution of fluoride. Although the fluoride retention values for passive dissolution were impressively superior to either active dissolution method, the alarmingly high salivary fluoride concentrations (4000 ppm F) recorded at the passive dissolution sites should discourage its use until the potential cytotoxicity of this approach is thoroughly investigated.

Administration, Oral↗
PubMed1985

Distribution of fluoride in human cementum.

Fluoride and phosphorus concentrations were determined in layers of cementum and dentine serially-abraded from the root surface, passing through the cementum-dentine junction and into the underlying dentine, using silicon carbide-impregnated film. The concentrations of F in the cementum mineral were variable but consistently maximal at or near to the external surface of the root and tending to fall towards the interior and across the cementum-dentine junction into the underlying dentine. The F content in the cementum tended to increase with age.

Adolescent↗