Estimation of angulation of Brånemark titanium fixtures from radiographic thread images.

Identity of film positioning and of X-ray beam angulation is essential for valid comparisons of marginal bone height around osseointegrated implants. The purpose of the present study was to analyze the possibilities of estimating fixture angulation in relation to film plane from the threads of Brånemark fixtures. 10 observers compared 62 images of fixtures with angulations ranging from 0 degrees to +/- 15 degrees with a set of reference radiographs. Out of 620 recordings, 29% were right, and 71% differed by greater than or equal to 1 degree. The observers distinguished with great accuracy between negative and positive angulations. 81% of the recordings differed by 2 degrees or less. It is concluded that the threads of Brånemark fixtures are helpful in controlling the identity of serial radiographs of implants. The test circumstances were ideal compared to clinical cases, and it is possible that accuracy will be less in patient cases.