Assessing the toxicity of chemically fractionated Hamilton Harbour (Lake Ontario) sediment using selected aquatic organisms

Studies of the sediments of Hamilton Harbour, Lake Ontario, Canada, have shown variable degrees of pollution with a large number of organic and inorganic pollutants. Three areas in the Harbour – Windemere Basin, Cootes Paradise and Randle Reef – exhibited particularly high levels of contaminants, with concomitant impacts on benthic organisms. Sediment samples examined in this study were taken from a site in Randle Reef in Hamilton Harbour and a station (LE 23) in Lake Erie used as a reference sample. The samples were subjected to chemical fractionation to remove organic contaminants, with one fraction being used as total extract, and another aliquot being subjected to silica gel fractionation to give four fractions. Each fraction was chemically analysed and an aliquot used for bioassays following exchange with dimethylsulfoxide. Standard biotests were performed with Daphnia magna, Hyalella azteca, Pimephales promelas (fathead minnows) and Selenastrum capricornutum. Results from direct sediment contact bioassays indicated that sediment from Randle Reef is highly toxic, whereas the Lake Erie sample had no observable impacts. Total extract when added at 1% to the bioassays replicated the solid phase with acute toxicity for Randle Reef, and no effect on Lake Erie. For the silica gel fractionation, Fraction 1 (F1) showed similar toxicity as the total extract, even at low additions, whereas F2–4 gave variable and inconclusive results. F1 eluted with hexane contained the non-polar fractions, predominantly the polyaromatic hydrocarbons, and these compounds are the most likely causative agents for the highly acute toxicity observed in the sediment of Randle Reef

Replacement of teeth exhibiting periapical pathology by immediate implants: a prospective, controlled clinical trial

OBJECTIVES: The aim of the present study was to test whether or not immediate implantation leads to more biological complications, when performed at extraction sockets of teeth exhibiting periapical pathology compared with teeth not exhibiting periapical pathology. MATERIALS AND METHODS: In 17 consecutively admitted patients, immediate implant placement was planned in order to replace single teeth exhibiting periapical pathology (test group). These teeth demonstrated pain, periapical radiolucency, fistula, suppuration or a combination of these findings. Another 17 consecutively admitted patients in need of single tooth replacement in the absence of periapical pathology served as the control group. Implant placement and accompanying bone regeneration were performed according to standard clinical procedures. Implants were loaded after a healing period of 3 months. Clinical and radiographical parameters were assessed at the time of implant placement (baseline) and at 12 months thereafter. RESULTS: Out of the 34 patients, four test and one control patient had to be withdrawn from the study due to the inability to obtain primary implant stability. The residual 29 implants revealed a survival rate of 100% 1 year after placement. Clinical and radiographical differences between 12 months and baseline comparing test and control groups showed no statistical significances for any of the parameters assessed. Within test and control groups there was a statistically significant loss of vertical bone height at the adjacent teeth (mesial test=0.4+/-0.6 mm, control=0.4+/-0.5 mm; distal test=0.3+/-0.2 mm, control=0.7+/-0.8 mm) as well as at the implant site (mesial test=1.9+/-1.4 mm, control=1.8+/-1.1 mm; distal test=1.7+/-1.4 mm, control=1.6+/-1.1 mm) and of buccal keratinized mucosa (test=-2.2+/-1.2 mm; control=-1.3+/-1.6 mm) between baseline and 12 months. During the first 13 weeks of healing, two sites of the test and one site of the control group showed signs of infection, which required intervention. Neither the incident of early exit nor of signs of infection was statistically significantly different between the test and the control group (Mann-Whitney U test). CONCLUSION: It is concluded that for those implants where primary stability was achieved, the immediate implant placement performed at extraction sockets exhibiting periapical pathology did not lead to an increased rate of complications and rendered an equally favorable type of tissue integration of the implants in both groups. Implant placement into such sites can, therefore, be successfully performed