A Study on the Accuracy of Adaptive Error Detection between Implant Body and Impression Coping Using Digital X-Ray

Implants demand the taking of more accurate impressions than those required for the preparation of prostheses for dentulous jaws. The recent advent of technologies such as computer-aided design and computer-aided manufacturing has enabled frames to be produced as a single unit ; impressions thus have a major effect on the accuracy of superstructures, and it is essential that they are taken accurately. We carried out an X-ray study to investigate errors arising when implant impressions are taken, with the objective of obtaining highly accurate impressions for the production of implant prostheses. To investigate the conditions under which errors are overlooked when X-rays are used to check the accuracy of impressions, we made impressions of implants with 10-100 μm thick celluloid strips inserted between the impression coping and the fixture and of implants without this artificial gap, and scanned these impressions at angles ranging from 0°-25° to the horizontal with respect to the platform. A digital X-ray scanner was used with either a charge-coupled device (CCD) or an imaging plate (IP). The X-rays obtained were randomized and reviewed by multiple dentists, who assessed whether or not a gap was present. Visualization limits were better for the CCD than the IP. When scanning was performed at an angle, the proportion of reviewers recognizing the presence of a gap on IP images started to change when the angle exceeded 5°, and the proportion of those overlooking the presence of a gap increased at angles exceeding 10°. On CCD images, the proportion began to change when the angle exceeded 10°, but while the scanning angle was within 15° there was no major change in the proportion of reviewers who overlooked the presence of a gap. When using X-rays to check the fit of the impression coping in the process of taking implant impressions, an indicator or similar method should be used to ensure that the scanning angle is properly oriented horizontally with respect to the platform.