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Photogrammetry and Conventional Impressions for Recording Implant Positions: A Comparative Laboratory Study

2005; Wiley; Volume: 7; Issue: 1 Linguagem: Inglês

10.1111/j.1708-8208.2005.tb00046.x

1708-8208

Anders Örtorp, Torsten Jemt, Tomas Bäck,

Anatomy and Medical Technology

ABSTRACT Background: The development of digitized techniques for manufacturing implant frameworks has made possible alternative "impression" techniques for recording implant positions. Purpose: The objective of the present study was to test the precision and accuracy of a three-dimensional photogrammetric technique to record implant positions in vitro and to compare casts made with this technique with conventional casts fabricated with two conventional impression techniques. Materials and Methods: Twenty casts were fabricated from 10 polyether (Impregum™, ESPE Dental AG, Seefeld, Germany) impressions and 10 plaster (Kühns Abdrucksgips, Ernst Hirnischs GmbH, Goslar, Germany) impressions of one master model. The casts were measured in a coordinate measuring machine (Zeiss Prismo VAST, Oberkochen, Germany) and compared with the master model. Six separate three-dimensional photographs of the master model were taken with a special camera. After the photographs were measured with an analytic plotter, results were analyzed and compared to the coordinates of the original model and casts. Results: A systematic pattern of distortion in the x-axis was found for the two impression techniques. Expansion of the implant arch at the terminal implants (p < .01) averaged 22 μm and 94 |im on photographs and plaster casts, respectively. Polyether casts contracted an average of 52 μm when compared with the master (p < .01). In absolute figures, photogrammetry and the polyether technique reproduced the x-axis and three-dimensional parameters more accurately than the plaster technique did when cylinder center point distortion was compared (p < .05 to p < .001). However, angular cylinder distortion in absolute figures was greater with the photographic technique than with either of the impression techniques (p < .05-p < .001). Conclusion: Photogrammetry is a valid option for recording implant positions and has a precision comparable to that of conventional impression techniques. At present, however, it is limited to framework fabrication techniques that are based on digital platforms.