THE INFLUENCE OF ABUTMENT ANGULATION ON STRAINS AND STRESSES ALONG THE IMPLANT BONE INTERFACE - COMPARISON BETWEEN 2 EXPERIMENTAL-TECHNIQUES/

Statement of problem. Preangled abutments produce different stress dis tribution compared to straight abutments. Purpose. The objectives of t his study were to (1) test the hypothesis that preangled abutments pro duce different stress distribution than straight abutments by using st rain gauges attached to implants embedded ill a medium simulating bent : to determine strain distribution along the implant/bone interface; ( 2) test this hypothesis by photoelastic method; and (3) compare the: t wo experimental techniques. Materials and methods. Five Integral Omnil oc cylindrical implants 13 x 4 mm were polished to remove the hydroxya patite coating, then six linear miniature strain gauges vr ere attache d, three on each side of the implant's surface. Two similar implants w ere embedded in a photoelastic material. Three abutments, straight, 15 degrees, and 25 degrees, were connected to each implant; strain versu s applied compressive forces were recorded. Strain response to force p arameter was defined as the slope of the strain-force curve. Isochroma tic fringe patterns were also recorded. Results. The strain gauge meas urements showed higher, threefold and 4.4 fold, compressive strain con centration in the coronal zone of the implant when 15-degree and 25-de gree angulated abutments were used, respectively, compared with the st raight abutment; whereas the photoelastic method showed an increase of only 11% in fringe order. Tensile strains were also measured From the coronal contralateral position on the implant, where photoelastic mod els did not show a change in stress type. Conclusions. Data obtained f rom strain gauges bonded to implants embedded in a medium can represen t a precise simulation of the clinical condition when analyzing stress distribution along the implant/bone interface. Photoelasticity provid es different information and therefore should be regarded as a complem entary method.