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Updated: Apr 3, 2026
Measuring the Complete-arch Distortion of an Optical Dental Impression
Published on: May 30, 2019
Accuracy of scanning using photogrammetry and reverse scan for complete arch implant-supported prostheses: An in
Dalia Mohammed Farid1, Dina Essam Bahig2, Rami Maher Sadek Ghali3
1Lecturer of Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, Egyptian-Russian University, Cairo, Egypt.
Statement Of Problem:
Intraoral scanning of complete arch implant-supported prostheses is still unpredictable. Accurate capture of implant positions in complete arch prostheses is crucial for obtaining passive fit as well as long-term prosthetic success. While photogrammetry offers high accuracy and efficiency, the reverse scan technique has emerged as a suitable cost-effective alternative to the regular procedure.
Purpose:
The present in vitro investigation aimed to evaluate the dimensional accuracy, specifically trueness and precision, of the reverse scan technique and intraoral photogrammetry in capturing positions of complete arch implants.
Material And Methods:
The present investigation was based on a participant with a prosthesis made using the conventional open tray impression technique and a 3-dimensional (3D) printed cast produced by digitizing the definitive stone cast from the open tray impression. The interim implant-supported prosthesis was milled to replicate the original design that was delivered to the participant. The digital files were 1 reference scan (derived from the cast made using the conventional open tray impression technique), 10 reverse scans, and 10 intraoral photogrammetry scans. By using metrology and a 3D inspection software program (Geomagic Control X; 3D systems), the reference digital definitive cast model standard tessellation language (STL) file was considered a reference for comparing all subsequent trueness measurements; for the precision comparisons, the STL files were analyzed using pairwise comparisons within each group with a total of 45 comparisons per group. The superimposition between the scans using initial alignment was followed by the best-fit algorithm where the part used as a reference for accuracy 3D comparisons was the abutment part. The final measurement of deviation was reported in root mean square, whereas the measurements were recorded in millimeters. Comparisons between groups were performed using independent t tests (α=.05), and the results were expressed as mean values with corresponding standard deviations (SDs).
Results:
Regarding trueness, the deviation measured with photogrammetry was significantly lower (56.49 ±1.52 µm) than that of the reverse scan technique (94.21 ±2.49 µm) (P<.001) indicating higher trueness. In contrast, when measuring precision, the deviation recorded with the reverse scan technique was significantly lower (3.21 ±0.22 µm) than that of the intraoral photogrammetry technique (4.20 ±0.38 µm) (P<.001).
Conclusions:
Intraoral photogrammetry is a promising alternative scanning technique for complete arch implant-supported prostheses providing higher dimensional accuracy in terms of trueness when compared with the reverse scanning method. Reverse scanning is a reliable fully digital method offering greater precision than intraoral photogrammetry.
