DESCRIPTION: Recent epidemiological evidence suggests higher fracture incidence in communities with fluoridated water. It is conceivable that an increase in fractures may be due to a decrease in bone strength caused by chronic fluoride exposure. Pilot data from rats shows that fluoride reduces bone strength more dramatically in older animals. Thus, bone fluoride accumulation may lead to increased fracture risk in older animals. There is also evidence that fluoride incorporation into the skeleton is altered by dietary changes, especially changes in calcium intake.In this application, the Principal Investigator proposes to measure mechanical and material properties of fluorotic bone from femurs and vertebrae of normal and physiologically challenged rats. Bone specimens will be obtained from Dr. Ann Dunipace of the Oral Health Research Institute at Indiana University, who is Principal Investigator of a grant entitled "Effects of fluoride in medically compromised animals". The Principal Investigator proposes to work in collaboration with Dr. Dunipace and test bone specimens from rats maintained under conditions of aging, diabetes, chronic renal failure and nutritional deficiencies. The hypothesis to be tested is that fluoride accumulation in the bone mineral leads to progressively decreased mechanical properties. It is expected that age and diet will alter the severity of the fluoride effect on bone strength. Bones from diabetic rats or rats with chronic renal failure are expected to accumulate more fluoride in their skeletons,resulting in greater bone strength deficit. It is also hypothesized that fluoride ion distribution in the bone mineral will have a direct effect on the mineralization and elasticity of the bone matrix.