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News Bulletin : ADA News Bulletin November 2010
34 NOVEMBER 2010 done decades ago. Dental mercury was stored in the wooden dispenser. Mercury was squeezed up from below by rotating the top bit clockwise, and into the small cup at the top. When the operator had judged the amount of mercury to be sufficient, he tipped it into a 'mercury balance', and one of the weights was moved outwards until a balance was achieved. Now the operator noted, from the scale, the weight of the mercury. The other balance weight was then moved out to a little less than the mercury value, the amount depending on the alloy type and the degree of plasticity the dentist wanted. A little less than the mercury value was usual. Now the amalgam alloy (a milled powder, spherical particles, or anything in between) was added to achieve balance, and the powder and mercury tipped into a small mortar. A pestle was now used to 'triturate' the mix until it formed a blob. The assistant then gathered the blob and expressed any excess mercury using a small piece of Chamois leather or a gauze swab, and 'mulled' the mix by squeezing and rubbing the blob. The dentist then 'plugged' the cavity with this mix, scraping and carving any excess from the restoration surface. Before we knew how dangerous mercury vapour can be,† some dentists or chair side assistants would 'mull' the blob in the palm of the hand, and squeeze out the excess mercury between finger and thumb. This is not a good idea. The excess mercury finished up in the sink or on the carpet, leading to a high concentration of mercury vapour in many dental surgeries. Encapsulated mercury/ alloy mix and a mechanical amalgamator eliminated these potential dangers, and also the deleterious effects of the salt and moisture content of a sweaty palm on the set amalgam restoration. Dentistry has progressed a long way in just a few decades. Soon, improved composite technology, adhesive techniques and materials, plus perhaps new materials such as graphene may make amalgams obsolete, after 150+ years. clinical hints †The Mad Hatter in Alice in Wonderland was mad because he used mercury salts to 'felt' the fibres when making hats (see also Minamata disease). Honorary Clinical Associate Professor, Barrie R D Gillings, 121 Bannockburn Road, turramurra 2074. Phone: 02 9144 3787; Fax: 02 9440 9159; e-mail: email@example.com Scared of running out of medical oxygen? www.airliquidehealthcare.com.au Changes to Australian Standards (AS2473.3) for medical oxygen mean that you will need to upgrade your oxygen regulators and your manifold system by the following dates: • SA/WA/NT Quarter 1 2010 • QLD August 2010 • NSW/ACT February 2011 • VIC/TAS June 2011 Call us now on 1300 36 02 02 and enquire about our solutions. Integrated oxygen cylinders PRESENCETM Low maintenance oxygen regulators NOVA 40 Audit of medical oxygen systems and gas installation Relative Analgesia MATRX nitrous oxide sedation systems
ADA News Bulletin October 2010
ADA News Bulletin December 2010