Radiographic verification of implant abutment seating

Statement of problem. It is possible to incorrectly seat an abutment on an external hex implant. Purpose. This study investigated the theoretical and practical limits of radiographic verification of the complete seating of implant abutments on external hex implants. Material and methods. A positioning device that could accurately place the film and/or tube head in any vertical relation desired relative to the implant and abutment was fabricated. For all records, a standard abutment was secured to the implant in both a fully seated position (closed) and with the abutment turned approximately 30 degrees and seated atop the implant external hex (open). Digital radiographs were made with the tube head fixed perpendicular to the implant and the film angled at 0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 degrees. The film was then positioned parallel to the implant and the tube head was angled at 0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 degrees. An image of each position was shown to 36 dentists and they were asked if the image was diagnostic for determining the status of the implant/abutment interface. Results. The data were analyzed with a computer statistics program. The group with the tube head changed was analyzed with the Cochran's Q test and revealed a statistically significant ( p < 0.0001) change in the diagnostic value of radiographs beginning at 20 degrees. The group with the film angle changed was analyzed with a Pearson chi-square and showed no statistical difference ( p = 0.394) for the diagnostic value of any of the film angles. Conclusion. Maintaining the tube head to less than 20 degrees from perpendicular to the long axis of the implant resulted in a diagnostic radiograph, regardless of the angle of the film. (J Prosthet Dent 1998;79:298-303.)