Pubic Health Briiefs ences might thus be related to biases specific to the study designs.The small risk associated with coffee consumption might be explained by residual confounding. If caffeine were a causal agent, we would have suffered loss of power from lack of information on other caffeine intake. However, nutrition survey data show total caffeine intake and coffee consumption to be highly correlated (r = .98) in Quebec women (Health and Welfare Canada, personal communication). Evidence of an association between caffeine consumption and early fetal loss has been reported,15 but no such association has been reported, so far aswe are aware, with spontaneous abortion.If the observed associations were causal, cigarettes accounted for about 11% of all spontaneous abortions (40% in women who smoked 20 or more cigarettes per day), alcohol consumption for about 5% (45% in women drinking 3 or more drinks per day) and coffee for about 2% (16% in women drinking 10 cups per day).

T Th he e e ep pi id de em mi io ol lo og gy y o of f m me es so ot th he el li io om ma a i in n h hi is st to or ri ic ca al l c co on nt te ex xt tThe epidemiology of mesothelioma in historical context. J.C. McDonald, A.D. McDonald. ©ERS Journals Ltd 1996. ABSTRACT: Primary malignant mesothelial tumours were recognized by pathologists before asbestiform minerals (chrysotile, crocidolite and amosite) were mined commercially. The discovery, 40 yrs ago, of a causal link with crocidolite and the wide-ranging epidemiological studies which followed are the subject of this review.Early case-control and descriptive surveys, supplemented by cohort studies in insulation workers and chrysotile miners, quickly demonstrated major occupational and geographical differences, with high risk in naval dockyard areas and in the heating trades. In the 1980s, reliable cohort surveys showed that in mining and in the manufacture of asbestos products the mesothelioma risk was much higher when exposure included crocidolite or amosite than chrysotile alone. However, qualitative and quantitative information on exposure was too often inadequate for this evidence to be conclusive. Well-controlled lung fibre analyses have reduced these deficiencies and demonstrated the probable implications of the greater biopersistence of amphibole fibres. Chrysotile for industrial use often contains low concentrations of fibrous tremolite, which may well explain the few cases of mesothelioma associated with this type of asbestos.Progress in this field has been much retarded by controversy, for which the 20 year gap between the availability of reliable estimates of risk for the mining of chrysotile and that for crocidolite or amosite may have been largely responsible.

No abstract

We analyzed data from a survey of occupational factors and pregnancy outcome to examine the effects of cigarette, alcohol, and coffee consumption on pregnancy outcome. Clear and statistically significant associations were found between cigarette and alcohol consumption and spontaneous abortion. There was a weaker but statistically significant association with coffee consumption: If the associations were casual, 11% of the spontaneous abortions could be attributed to smoking, 5% to alcohol, and 2% to coffee.

The use of virtual reality (VR) in the training of operative dentistry is a recent innovation and little research has been published on its efficacy compared to conventional training methods. Two groups of dental students, with no experience in operative dentistry, were trained solely by either VR or conventional training in the preparation of conventional class 1 cavities. The subjects all used the same operative armamentarium and phantom heads, and were allocated the same duration of practice periods. At the completion of these training periods, both groups produced two class 1 cavities on the lower left first molar, which were subsequently coded and blindly scored for the traditional assessment criteria of outline form, retention form, smoothness, cavity depth and cavity margin angulation. An ordinal score of 0-3 or 0-4 was assigned for each assessment criterion: the higher the score, the worse the evaluation. After initial independent scoring, the two examiners discussed any notable differences until an agreed score was reached. Once the codes were broken, non-parametric analyses were performed on the data. Wilcoxon Tests for the semiquantitative scores indicated significant differences between the VR and conventional training groups for outline form, depth and smoothness but not for retention or cavity margin angulation at P < 0.05 level, with the VR group receiving the higher, i.e. worse, scores. Cavity margin angulation approached significance with a P-value of 0.0536. The results indicated that VR-based skills acquisition is unsuitable for use as the sole method of feedback and evaluation for novice students.

Ascertainment, through 7,400 pathologists, of all fatal malignant mesothelial tumors in Canada (1960-75) and the U.S.A. (1972) gave a total of 668 cases (272 in 1972). In Canada, the annual number of male cases rose from about 17 in 1966 to 25 in 1972 but the number of female cases remained fairly steady at a much lower level. The annual incidence in North America in 1972 was estimated at 2.8 per million males and 0.7 per million females aged 15 years and over. Occupational histories were obtained "blind" for 480 of the 557 cases through 1972, and their matched controls; relative risks were as follows: insulation work, 46.0 asbestos production and manufacture, 6.1, heating trades (other than insulation) 4.4. For nearly half the male cases and for about 5% of female cases, the tumor could be attributed to occupational exposure to asbestos, of which a fifth were in shipyards. No indication was found of other possible causes (including man-made mineral fibers, tobacco smoking, or residence near zeolite deposits). Four subjects were men who had been employed in Quebec chrysotile mines and 3 were children of employees, but no other subject had lived in the mining area. The findings remain consistent with a much greater mesothelioma-producing potential for crocidolite and amosite than for chrysotile; however, further studies of factory workers exposed to chrysotile only are needed to confirm this. Mineral fiber analysis of lung tissue from patients and controls is in progress.

No abstract

The use of virtual reality (VR) in the training of operative dentistry is a recent innovation and little research has been published on its efficacy compared to conventional training methods. To evaluate possible benefits, junior undergraduate dental students were randomly assigned to one of three groups: group 1 as taught by conventional means only; group 2 as trained by conventional means combined with VR repetition and reinforcement (with access to a human instructor for operative advice); and group 3 as trained by conventional means combined with VR repetition and reinforcement, but without instructor evaluation/advice, which was only supplied via the VR-associated software. At the end of the research period, all groups executed two class 1 preparations that were evaluated blindly by 'expert' trainers, under traditional criteria (outline, retention, smoothness, depth, wall angulation and cavity margin index). Analyses of resulting scores indicated a lack of significant differences between the three groups except for scores for the category of 'outline form', for group 2, which produced significantly lower (i.e. better) scores than the conventionally trained group. A statistical comparison between scores from two 'expert' examiners indicated lack of agreement, despite identical written and visual criteria being used for evaluation by both. Both examiners, however, generally showed similar trends in evaluation. An anonymous questionnaire suggested that students recognized the benefits of VR training (e.g. ready access to assessment, error identification and how they can be corrected), but the majority felt that it would not replace conventional training methods (95%), although participants recognized the potential for development of VR systems in dentistry. The most common reasons cited for the preference of conventional training were excessive critical feedback (55%), lack of personal contact (50%) and technical hardware difficulties (20%) associated with VR-based training.