Use of a scanning laser three-dimensional digitizer to evaluate dimensional accuracy of dental impression materials.

A steel die was machined to represent a dental arch with teeth prepared for complete crowns. Impressions and casts were made from the die, and critical dimensions were measured by two methods--one using micrometers and the other a scanning laser three-dimensional (3-D) digitizer. The digitizer recorded measurements were more precise than the micrometer's and virtually eliminated operator error because the acquisition of data was automatic. The digitizer could also be useful for high-precision analyses of the dimensional accuracy of dental impression materials, but the cost and complexity of the instrument makes it less desirable for low-precision work.     

RELATIONSHIP OF COMBINATIONS OF AIDS COUNSELLING AND TESTING TO SAFER SEX AND CONDOM USE IN HOMOSEXUAL MEN

In a cross-sectional survey of 172 homosexual men in a city of one million inhabitants, questions were asked on testing for AIDS and counselling history, sexual practices, prophylactic behaviours, condom use and associations with the gay subculture along with other background variables. Respondents were divided into four groups: those who had had both HIV testing and safer sex counselling, those who had only had testing, those who had only had counselling, and those who had had neither. All but 4 per cent of respondents had heard of safer sex. Results showed that increase in comdom use for both oral and anal sex, and stopping prior to ejaculation were associated with the combined testing and counselling group, and occurred significantly more often than the counselling only and no intervention groups. The testing only group fell midway between the counselling plus testing and the counselling only, and no intervention groups. A scale constructed by summing the four measures of safer sex showed that testing only, and counselling and testing combined were significantly superior in terms of safer sex practices than the counselling and no intervention groups. Correlates of being given a condom at point of testing included increased insertive anal intercourse and stopping before ejaculation as well as increased condom use during anal intercourse. These findings suggest that provision of free condoms in a context of professional and peer support may enhance condom usage during behaviours known to transmit HIV. While these data may be interpreted with caution with regard to causality, they do imply (in the absence of evidence that such behaviours characterise individuals who present for HIV-related interventions) that some interventions or combinations of interventions are significantly more effective than others.     

A model of sterile vesicoureteric reflux in the sheep

Eighteen Coopworth ewe lambs were divided into three groups based on the initial cystourethrogram and cystometry findings at 5 – 7 weeks of age: group 1, 6 lambs with spontaneous low-pressure bilateral vesicoureteric reflux (VUR) on bladder filling were used to study the natural history of reflux; group 2, 5 lambs with no VUR detected were used to establish an experimental model of bilateral VUR using an unroofing surgical procedure; group 3, 7 lambs with spontaneous VUR detected during micturition had the same surgical procedure to increase the degree of VUR. All three animal groups were followed for 4 – 10 months. Spontaneous VUR was demonstrated in 13 of 18 lambs (25/36 ureters). The presence and severity of spontaneously occurring reflux in group 1 lambs diminished with increasing age. VUR was created successfully in group 2 and increased in degree in group 3 animals. The only significant histological finding in all three animal groups with grades II and III VUR was distal renal tubular dilatation. The sheep is a useful and readily available animal for studying VUR. During 4 – 10 months of follow-up, sterile reflux without bladder outflow obstruction resulted in distal renal tubular dilatation, but no renal parenchymal damage. Received April 17, 1997; received in revised form August 5, 1997; accepted August 21, 1997