Caries prevalence in the permanent dentition of a mediaeval population from the south-west of Scotland.

The prevalence, distribution and location of dental caries were studied in the permanent dentition of skeletons from a large mediaeval cemetery, where successive phases of use could be distinguished. The main phases dated from 1240 AD to 1440 AD. During this 200-year period, caries prevalence showed a statistically significant linear trend to increase. There was an increase in caries prevalence with increasing age from age band 20-25 through 26-35 to 36-45, and this trend was statistically significant in all phase groups but one. The teeth attacked by caries were chiefly molars, followed by premolars, with a low rate of attack in incisors and canines. The differences in caries prevalence between these major tooth classes were significant. Juveniles and adults presented different patterns of carious attack on tooth surfaces, occlusal surfaces being most frequently affected in juveniles, and approximal surfaces in adults. The overall caries prevalence in the mediaeval population of Whithorn was 6.4% of the teeth present, a figure similar to those published for other Scottish mediaeval groups, but lower than the caries prevalence in an English mediaeval group.

Caries prevalence in the deciduous dentition of a mediaeval population from the south-west of Scotland.

The prevalence, distribution and location of dental caries were studied in the deciduous dentition of 185 skeletons aged between 6 months and 13 years from a large, mostly mediaeval, cemetery, where successive phases of use could be distinguished. The main phases dated from 1240 to 1440 AD. During this period, no consistent trend or pattern of caries was identified, but there was a significantly higher caries prevalence in the age band 6-12.9 years than in the age band 0.1-5.9 years. The caries prevalence in the juveniles from the earlier Northumbrian, or Anglo-Saxon, phase of the cemetery was higher than in any mediaeval phase group, with mostly approximal surfaces affected. In the mediaeval population, first deciduous molars generally showed lower caries prevalence than second deciduous molars, significantly lower for the older age band, and maxillary molars consistently showed lower levels than mandibular molars. The highest caries rate, shown by mandibular second molars in the older age band, was 7.9%. In deciduous molars, the occlusal surface was most frequently affected by caries, whereas in the permanent molars of the same population the approximal surfaces had shown the highest level of attack. The overall caries prevalence in deciduous teeth in the mediaeval population of Whithorn was 2.3% of the teeth present, lower than the levels found in previous Scottish and English population groups, including a small assemblage of children from the Scottish sites of Elcho, Southwick and Kirkhill.

Computer morphing of scanning electron micrographs: an adjunct to embryology teaching.

Traditional embryology courses demand considerable expenditure of time and effort from students to master the spatial awareness skills necessary to create three-dimensional mental images from two-dimensional serial sections. Then students must imagine a movie sequence of the changes which take place during normal development. Further steps are required to relate this information to the clinical situation. As more medical and dental schools move towards problem-based curricula, more efficient methods of improving understanding of embryology are needed. The development of many organs can be studied using scanning electron micrographs of embryos at different ages. These high quality images are more easily interpreted by our students than histological sections and the understanding achieved more readily applied to clinical problems. Still more beneficial would be the provision of moving images showing the actual changes happening. We decided to use computer morphing techniques to prepare movie sequences showing development of the face and plate. For each, four scanning electron micrographs of appropriately-sized sheep embryo heads were taken at the same magnification and orientation to use as start and end points of morphing sequences. After using retouching techniques to colour the separate processes, further sequences were prepared. The discipline of maintaining the same magnification throughout and the possibility of directly observing changes between stages revealed some surprising growth patterns. This technique is adaptable to any area of biological development where pre- and post-illustrations are available. Animations can be presented on computer or on video and incorporated into programs. Student feedback has been very favourable.

Acid hydrolases in HeLa cells: comparison of methods for light microscopy.

To distinguish lysosome populations of HeLa cells, acid phosphatase, beta-glucuronidase, arylsulfatase and esterase were demonstrated using various substrates and couplers with different fixations, pHs and inhibitors. The substrates chosen were for acid phosphatase, naphthol AS-BI phosphate with fast red violet LB at pH 4.6; for beta-glucuronidase, naphthol AS-BI beta-D-glucuronide with fast red violet LB at pH 4.4; for arylsulfatase, p-nitrocatechol sulfate, with lead as the capturing ion, at pH 4.8 and 5.6; and for esterase, naphthol AS-D acetate with fast blue BB at pH 6.5. In the azo-dye methods, the coupling was always simultaneous and results were satisfactory with unfixed cells. For optimal demonstration of arylsulfatase, cells were fixed in glutaraldehyde in 0.1 M cacodylate buffer pH 7.2, 2% for 24 hr or 6.25% for 2 hr, and washed for 1-9 days in 0.1 M veronal acetate buffer pH 7.2, 7.5% with respect to sucrose. Two groups of lysosomes were distinguished. One comprised small bodies, probably primary lysosomes, which lay in a cluster near the nucleus. They had quite stable membranes and were mostly acid phosphatase-positive. They sometimes contained beta-glucuronidase or esterase, but rarely arylsulfatase. The other group included all the acid hydrolase-positive bodies scattered throughout the rest of the cytoplasm. They were mostly larger, with more labile membranes, and contained beta-glucuronidase, esterase or arylsulfatase, but rarely acid phosphatase.

Retention of preclinical knowledge by clinical students.

To form a sound foundation for clinical subjects, oral biology must be taught in such a way that information gained early in the dental course is remembered when required in the clinical years. Knowledge retention was assessed by having students answer 20 sets of five multiple answer, multiple choice items after one term's study of oral biology and the same test after a lapse of 20 months with no intervening teaching in the subject. An analysis of the results obtained in these tests is presented and the scores are compared with performance in other oral biology examinations. Performance in the professional examination was most highly correlated with the examination closest to it in time, although this was a practical examination and was considered to be measuring different skills.