Photogrammetric Full-Arch Implant Impressions: A Litterature Review

     Making conventional impressions to obtain definitive casts that are used to fabricate full arch implant-supported prostheses can be technique sensitive and time consuming. Recording the accurate implant position and orientation is essential for proper seating and achieving a passive fit that would ensure long-term stability of the implant-supported prosthesis. (Jemt 2012)

    After the evolution of digital dentistry, intraoral scanners have been used for impression procedures, including those with multiple implants. However, it has been shown that the reliability of intraoral scanners is still questionable, especially in fully edentulous cases. (Papaspyridakos 2016)

    Therefore, a new impression technique called stereophotogrammetry, has been introduced in 1994, by Jemt and Lie, to overcome the challenges faced with the conventional and intraoral scanning techniques. 

    What is the photogrammetric impression technique? Can we use it as an alternative to the conventional and digital intraoral scanning methods?

    This technique was first applied for implant recording in 2005 and has shown to reduce chair-side time during impression making, the possible errors associated with it and increase patient’s comfort during this procedure.

    What makes this technique special is that it obtains impressions of multiple implant positions and orientations using a stereo camera that recognizes target points on custom scan bodies attached to the implants and automatically captures 350 images in less than 2 minutes with a margin error of 10 microns.
    The stereo camera should be held at a 15 to 30 cm distance from the patient’s mouth and at an angle of 45º to the scan bodies. The stereo camera then automatically registers the geometrical properties of the custom scan bodies and their interrelated spatial position in a photographic image that could be then converted into an STL file.

    Several authors have investigated the accuracy of this method and compared it to the conventional as well as the intraoral scanning methods, however the conclusions were controversial.