High resolution electron microscopy of enamel crystals in cases of human dental fluorosis.

Surface enamel from human subjects with dental fluorosis was studied by means of high-resolution transmission electron microscopy. Immediately below the relatively highly mineralized outermost surface enamel layer was an extensive hypomineralized area. The highly mineralized layer was composed of many large elongated hexagonal crystals and extremely small hexagonal crystals. Frequently the small crystals were attached to the periphery of the large crystals. In the hypomineralized area, large crystals were sparsely arranged; and a few small crystals were seen. Some large crystals showed either perforated centers or defects on their peripheries. These findings suggest that the hypomineralized area undergoes caries-like changes in terms of crystal dissolution and that the highly mineralized surface layer is either formed or modified by remineralization.

Establishment of a large collection of extracted teeth for research.

A collection of over 14,000 teeth extracted at the Prince Philip Dental Hospital since 1982 has been organized and catalogued on a computerized database management system. The computer catalogue provides, for each tooth in the collection, information on the age and sex of the patient, and the date of extraction and condition of the tooth. The catalogue can be searched according to any combination of the descriptive variables in the database record. Researchers, including visiting scientists, can borrow teeth from the central "tooth library" on a temporary or permanent basis. Further information on particular teeth (e.g. patient's medical and dental histories, dental radiographs) can be obtained from patients' charts. Establishment of this collection has greatly facilitated the work of researchers in clinical dentistry, dental anatomy, and dental anthropology.

Observations on the preparation of sections of dental hard and soft tissues without conventional embedding procedures.

Inexpensive thin copper discs loaded with diamonds embedded in small slits around the periphery, may be used to cut sections from unembedded tooth samples without disrupting the cellular and extracellular components intimately associated with hard tissue interfaces. The tissue may be unfixed, fixed or cut using fixation or dye solutions as the lubricant. The use of these discs therefore opens up new avenues of histochemical investigation of hard tissue unrestricted by those artefacts associated with conventional or traditional methods of preparation.

A method of matching skulls with photographic portraits using landmarks and measurements of the dentition.

A method of matching and identifying skulls to family snapshots or passport photographs is described. The technique depends on the recovery of teeth, particularly the maxillary anterior teeth, with the skull and the availability of an antemortem photograph showing those teeth. Measurements of the anterior dentition of unidentified skulls are used to determine the magnification factor necessary for the preparation of life-sized transparencies of photographs. Superimposition of dental landmarks in these transparencies leads to correlation of further cranial features, thus enabling a successful positive identification. Suggestions are made for a system of identification based on assessment of visible features of the dentition.

Comments on the porosity of human tooth enamel.

The porous nature of surface and sub-surface enamel undergoing the final stages of maturation has been observed on unerupted, partly-erupted, and fully-erupted human teeth, using polarized light microscopy, microradiography, and scanning electron microscopy. Maturation deficiency of developmental origin can be distinguished from early carious lesions with polarized light by the absence of a well-circumscribed "dark" zone.

Preparation of an experimental low-fluoride diet from single-cell organisms for rats and mice.

1. A method for producing a standard low-fluoride diet from a green alga and yeast is described. Chlorella pyrenoidosa was grown in a culture medium prepared with distilled water and analytical grade chemical salts. The spent culture medium from the alga culture was reclaimed and replenished with salts and sucrose for the production of yeast, Saccharomyces cerevisiae. 2. The single-cell organisms were separated by centrifugation from their culture media and the dried cells were blended with sucrose, maize oil, cellulose and a salt mix to produce diet pellets for rats and mice. 3. The diet was readily accepted as food by rats and mice and it was found to contain 100-300 micrograms fluoride/kg dry weight. Two generations of rats and four generations of mice were bred on this diet. 4. The use of hydroxyapatite to reduce the fluoride content of the chemical used in the production of the alga and yeast biomass was investigated. Diet pellets prepared with this biomass contained 45-60 micrograms fluoride/kg dry weight.

Matrix--mineral relationships in enamel tissues.

A personal view of vertebrate enamels and their matrix-mineral relationships is given by first considering enamel types and speculating on the nature, distribution, formation and role of enamel protein. Not all the work consulted is mentioned in the text. The additional works are, however, included in the list of references.

On the relationship between tetracycline and the incremental lines in dentine.

Ground and decalcified sections of human, goat and pig teeth were examined using polarized and ultraviolet fluorescence microscopy, microradiography and electron microscopy. The experimental animals were given doses of tetracycline within the range 3-150 mg/kg. After the low doses there was no evidence of any disturbance of mineralization or of structural organization in either the goat or the pig. After the higher doses, however, the tetracycline lines usually corresponded with a disturbance of structural organization and often with a disturbance of mineralization as well. In the human cases, the tetracycline lines sometimes corresponded with a disturbance of mineralization or of structural organization. However, our evidence suggests that the disturbances in the structure or mineralization of the dentine in the human subjects were not caused by the tetracycline. It was concluded that, provided the dose is kept low (3-31 mg/kg) tetracycline can be used as a reliable non-toxic marker in growth studies and is also used in the study of mineral deposition.