Fluoride excretion of adults living in border regions with either water or salt fluoridation.

The canton of Basel-Stadt was the only canton in Switzerland which introduced drinking water fluoridation (DWF) at 1 ppm (mg/l). All other cantons have relied on fluoridated domestic salt at 250 ppm F as the main vehicle for basic fluoride exposure. It has been suggested that persons living and working in the DWF areas or persons commuting to the DWF areas may be exposed to higher than optimal doses of fluoride. The objective of this present study was to determine the urinary fluoride excretion of adults living and or working in neighboring areas of either salt or water fluoridation. In this study, 24-hour urine was collected from 69 healthy subjects and tested for fluoride concentration. The mean fluoride concentration for all participants was 0.55 +/- 0.25 ppm (mg/l) ranging from 1.14 to 0.09 ppm. The mean fluoride excretion was 0.95 +/- 0.47 mg F/d ranging from 0.18 to 2.12 mg F/d. The 33 subjects living in a DWF region showed a mean urine fluoride concentration of 0.64 +/- 0.24 ppm (mg/l) and a mean fluoride excretion of 1.14 +/- 0.48 mg F/d. Those 36 subjects living in a region without DWF showed a mean urine fluoride concentration of 0.47 +/- 0.24 ppm (mg/l) and a mean fluoride excretion of 0.78 +/- 0.40 mg F/d. A significant difference between the two means of the groups living in regions with or without DWF was detected when the Mann-Whitney statistical test was applied (p < 0.005). The combined intake of fluoridated drinking water and fluoridated table salt in the sub-group of 11 subjects who commuted showed an overall increase in fluoride urine concentration. The measured values, however, were not significantly different from the other sub-groups.

Corrosion at the marginal gap of implant-supported suprastructures and implant failure.

PURPOSE: Late failure, which occurs after successful osseointegration, is usually attributed to prosthodontic determinants. Corrosion of metallic suprastructures and incorrectly handled materials are often primary causes of late implant failure. In this study, 6 implants whose failure was related to suprastructure metal corrosion and adjacent bone were investigated. MATERIALS AND METHODS: Six implants as well as their suprastructures were analyzed for surface corrosion using light and scanning microscopy. Metal alloys and soldering compounds were analyzed using energy-dispersive x-ray analysis. Bone adhering to the implants was removed and analyzed for metal content using atom absorption spectroscopy. RESULTS: Extensive corrosion lesions and areas of oxidation were detected on all 6 of the implants and inner crown surfaces. Bone tissue collected from 5 of the implants showed higher contents of metal ions in comparison to physiologic baseline values detected in healthy bone. DISCUSSION: In spite of the high gold content of the suprastructure, corrosion occurred. Bonding oxides necessary for the process of fusing porcelain to gold will initiate corrosion. Apparently, once corrosion is initiated it rapidly progresses at the gap crevices, and toxic metal ions are released. These toxic ions diffuse into the peri-implant bone, causing bone structure breakdown and hastening osseodisintegration. CONCLUSION: Biocompatible metals, alloys, and ceramics should be used for implant-supported suprastructures. It is also essential that gaps between the implant and its suprastructure be avoided by cementing the suprastructure or sealing the gap.