Alan T. Richards

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It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the(More)
OBJECTIVE To demonstrate the usefulness of a survival-time regression model for the analysis of data from two 3-year trials of the caries-preventive effect of sugar-substituted chewing gums and fluoride toothpaste, carried out among 892 Lithuanian children. METHODS A caries onset was defined as a transition from sound to carious and a caries recovery was(More)
The aim of the investigation was to measure the effect of fluoride on vertebral trabecular bone compressive strength and to correlate this with fluoride-induced changes in bone density. This correlation would express changes in the quality of bone during fluoride treatment. Pigs were used in the experiment because their trabecular bone structure and(More)
Metastasis into a thyroid neoplasm-tumor-to-tumor metastasis-is exceedingly rare. We describe the 28th documented case of a tumor metastatic to a thyroid neoplasm and review the literature on tumor-to-tumor metastasis involving a thyroid neoplasm as recipient. All cases showed a recipient thyroid neoplasm with an abrupt transition to a morphologically(More)
The present study was undertaken to estimate bio-availability and biological half-life of fluoride and accumulation of fluoride in bone in the domestic pig. Eight animals receiving 2 mg F-/kg b.w. per day from age 8 to 14 months were compared with eight controls. Plasma fluoride concentrations just prior to the daily oral dose were measured at regular(More)
Plasma fluoride concentrations were studied in 11 pigs following single oral or intravenous doses of fluoride. The results showed a less-than-20% bioavailability of fluoride when administered with calcium-rich food. Pharmacokinetic analyses showed that the plasma half-life varied from 0.6 to 1.4 h, depending on diet and route of fluoride administration.(More)
Low gastric acid output leads to hypergastrinaemia, which results in the stimulation of dormant enterochromaffin-like cells in the gastric mucosa; these can progress to carcinoid tumours. A patient is described with this syndrome. Reduction in gastrin levels by antrectomy resulted in regression of the carcinoids.
The aim of this study was to test whether dental fluorosis can be produced by administration of chronic doses of fluoride during only the post-secretory stage of enamel mineralization. Eight control and eight experimental pigs matched by weight and litter were fed a low-fluoride diet (less than 0.05 mg F-/kg b.w. daily) from weaning to slaughter at 14(More)
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.
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(More)