The Stress & Strain Analysis in Implant Dentistry. The face of Dentistry has changed forever with the introduction of reliable dental implants, manufactured from pure titanium. These are surgically positioned to ensure that the material fuses correctly with the jawbone. Thereafter, these dental implants act as artificial tooth roots or alternatively can be used as anchors to retain dentures. When natural teeth are lost, the accompanying bone can also be affected through resorption. In many cases, loss of bone support can lead to problems with implant placement. It is sometimes necessary for the Dental Surgeon to insert implant fixtures in a less than ideal location and attach angled components to align them in a more appropriate position. Unfortunately, the use of abutments and excessive cantilevers may lead to forces generated in the bone which exceed the “physiological limit”. As part of a Masters Thesis, Dr John Murray and Mr John Kelleway of the Eastman Dental Institute in London, conducted an in vitro analysis using photoelastic coatings and strain gauges, supplied by Measurements Group UK Limited. It was considered that Measurements Group’s PhotoStress® System would be the most effective method of analysing and visually evaluating the stress affecting the anterior region of a maxilla. The incorporation of strain gauges on the model surface, prior to coating, allowed corroboration of the data acquired. A test rig was designed to retain an anatomically correct model of a jawbone, constructed in acrylic resin and incorporating three dental implants positioned in a conventional, “axially loaded” manner. Three additional implants were also placed, these being sited at varying angles to the load applied. All implants were extended by use of abutments (components extending from the implant head to the interior of the artificial tooth). The use of angled abutments facilitated ideal tooth position from differing implant situations. Identical load was applied to each tooth in turn via a jig incorporating a lever arm assembly, enabling a weighted platform to be raised and lowered. It was possible to draw conclusions regarding ideal and compromised implant positions. Test results showed that implants used in conjunction with angled abutments did not cause undue stress or potential problems for those patients who had previously suffered from dental bone loss and that, indeed, they can continue to smile! ____________________________________________ For more information, please contact:- Anton Chitty Measurements Group UK Ltd. Stroudley Road, Basingstoke RG24 8FW. UK Tel: +44(0) 1256-462131 Fax: +44(0) 1256-471441 July 2000

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