The influence of lifelong exposure to environmental fluoride on bone quality in humans

grantor: University of TorontoThe objective of this study was to determine if lifelong exposure to environmental sources of fluoride (including fluoridated water) had an effect on bone quality in humans. Ninety-two femoral heads were obtained from individuals undergoing total hip arthroplasty in regions with and without fluoridated water (Toronto and Montreal, respectively), so that the donors would have had a wide range of fluoride exposure. As the samples were obtained at surgery, the femoral heads were affected by osteoarthritis (75), osteoporosis (9) and other diseases. The fluoride content of cancellous bone was assessed by instrumental neutron activation analysis. A number of contributors to bone quality were assessed. The compressive and torsional mechanical properties were measured for cancellous cores excised from the centre of the femoral head. The architecture was assessed by image analysis of an x-ray of a 5 mm thick coronal section of the femoral head, as well as of histological sections taken from the superior (weightbearing) and the inferior (nonweightbearing) surface of the femoral head. The degree of mineralization was measured using backscattered electron imaging and microhardness, again at the superior and the inferior surface. Femoral heads from Toronto donors had a greater mean fluoride content than those from Montreal donors (1033 ± 438 ppm vs. 643 ± 220 ppm). However, the fluoride content of the Toronto donors ranged approximately twelve-fold (192-2264 ppm) and entirely contained the range of Montreal donors. Therefore, fluoridated water exposure is not the only determinant of fluoride content. The logarithm of the bone fluoride content increased with age. No substantive effect of fluoride, independent of age, was observed for the mechanical properties. Similarly, at the inferior surface, the architecture was affected by age but not by fluoride incorporation but the degree of mineralization was not affected by either. However, the degree of mineralization (measured by both backscattered electron imaging and microhardness) at the superior surface increased linearly with the fluoride content. As osteoarthritis results in a reduced degree of mineralization at the superior surface, this suggests that the presence of fluoride (which increases the degree of mineralization in osteoarthritis-affected bone) may aid in preventing this loss.Ph.D

Persistence, engagement, and migration in engineering programs

Records from the Multiple-Institution Database for Investigating Engineering Longitudinal Development indicate that engineering students are typical of students in other majors with respect to: persistence in major; persistence by gender and ethnicity; racial/ethnic distribution; and grade distribution. Data from the National Survey of Student Engagement show that this similarity extends to engagement outcomes including course challenge, feculty interaction, satisfaction with institution, and overall satisfaction. Engineering differs from other majors most notahly by a dearth of female students and a low rate of migration into the major. Noting the similarity of students of engineering and other majors with respect to persistence and engagement, we propose that engagement is a precursor to persistence. We explore this hypothesis using data from the Academic Pathways Study of the Center for the Advancement of Engineering Education. Further exploration reveals that although persistence and engagement do not vaiy as much as expected by discipline, there is significant institutional variation, and we assert a need to address persistence and engagement at the institutional level and throughout higher education. Finally, our findings highlight the potendal of making the study of engineering more attractive to qualified students. Our findings suggest that a two-pronged approach holds the greatest potential for increasing the number of students graduating with engineering degrees; identify programming that retains the students who come to college committed to an engineering major, and develop programming and policies that allow other students to migrate in. There is already considerable discourse on persistence, so our findings suggest that more research focus is needed on the pathways into engineering, including pathways from other majors