Cost-effectiveness of removing amalgam from dental wastewater.

Mercury in the form of amalgam is commonly introduced into dental wastewater as a result of amalgam placements and removals. Dental wastewater is primarily discharged to municipal sewers that convey industrial and residential wastewater to publicly owned treatment works (POTWs) for treatment prior to discharge to surface waters. In some localities, the sewage sludge generated by POTWs from the treatment of wastewater is incinerated, resulting in the emission of mercury to the atmosphere. Some of the mercury emitted from the incinerators is deposited locally or regionally and will enter surface waters. An assessment was conducted of the use of mercury in amalgam in California and the discharge of that mercury from dental facilities to surface waters via the effluent from POTWs and air emissions from sewage sludge incinerators (SSIs). The annual use of mercury in amalgam placements conducted in California was estimated to be approximately 2.5 tons. The annual discharge of mercury in the form of amalgam from dental facilities to POTWs as a result of amalgam placements and removals was estimated as approximately one ton. The discharge of mercury to surface waters in California via POTW effluents and SSI emissions was estimated to total approximately 163 pounds. A cost-effectiveness analysis determined that the annual cost to the California dental industry to reduce mercury discharges to surface waters through the use of amalgam separators would range from 130,000 dollars to 280,000 dollars per pound.

Wastage of a silicone impression material in a general practice setting: a comparison between hand and automixing methods.

A practice-based, randomised, controlled trial has been undertaken to investigate the wastage of impression material when recording full arch one-stage, polyvinyl siloxane impressions using four techniques: putty and automix light viscosity material, putty and automix regular viscosity material, putty and tubed light viscosity material, and putty and tubed regular viscosity material. A total of 100 maxillary impressions, comprising 25 recorded using each of the four techniques, were obtained according to a predetermined scheme for randomisation. All material wasted in dispensing, mixing and applying each impression was determined by repeated weighing. Statistical comparisons of the mean weights of material wasted for each type of impression revealed that significantly (P < 0.01) less wastage occurred with the automix techniques. It is concluded that automix impression techniques may, in more extensive studies, be found to be more cost effective than tubed impression material techniques when recording impressions of the type investigated.

An investigation of the disposal of hazardous wastes from New Zealand dental practices.

A national survey was conducted to investigate current procedures in New Zealand dental practices for disposal of clinical waste. A questionnaire was sent out to all dental practices in New Zealand, and non-returns were followed up by two further mailings. From three mailings 767 useable questionnaires were returned (71.3% of those sent out, 79.0% of those potentially valid). Responses indicated that 56.4% of dental practices disposed of bloody swabs into the waste paper bin, and 24.4% disposed of contaminated sharp items into the general household refuse collection. Qualitative interviews with dental practitioners revealed a lack of concern about disposal of contaminated waste into the general waste. The existence of legislation governing waste disposal was not sufficient to motivate many practitioners to comply with guidelines. In some areas there was no specialised waste disposal service available, but some dentists had rejected a specialised service on the grounds of cost or inconvenience. Substantial efforts were made to salvage amalgam waste to be sold for scrap.