ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Publications Copernicus
Articles | Volume II-5
28 May 2014
 | 28 May 2014

Photogrammetric determination of discrepancies between actual and planned position of dental implants

G. Forlani and F. Rivara

Keywords: Medicine, Photogrammetry, Close range, Measurement, Accuracy, Simulation

Abstract. The paper describes the design and testing of a photogrammetric measurement protocol set up to determine the discrepancies between the planned and actual position of computer-guided template-based dental implants. Two moulds with the implants positioned in pre- and post- intervention are produced and separately imaged with a highly redundant block of convergent images; the model with the implants is positioned on a steel frame with control points and with suitable targets attached. The theoretical accuracy of the system is better than 20 micrometers and 0.3–0.4° respectively for positions of implants and directions of implant axes. In order to compare positions and angles between the planned and actual position of an implant, coordinates and axes directions are brought to a common reference system with a Helmert transformation. A procedure for comparison of positions and directions to identify out-of-tolerance discrepancies is presented; a numerical simulation study shows the effectiveness of the procedure in identifying the implants with significant discrepancies between pre- and post- intervention.