Capturing complete arch implant positions in two partial photogrammetry scans: Does it impact the accuracy of complete arch implant scans?

Statement Of Problem: Extraoral photogrammetry (PG) systems can record implant positions in 1 scan or in 2 scans that are then merged. However, the accuracy of implant positions recorded in 2 partial photogrammetry scans is unknown.

Purpose: The purpose of this in vitro study was to compare the accuracy of complete arch implant scans recorded in 1 or 2 scans by using 3 extraoral PG systems.

Material And Methods: An edentulous cast with 6 implant abutment analogs (MultiUnit Abutment Plus Replica) was digitized (T710). Two groups were developed depending on the number of scans recorded to capture the 6 implant positions: 1 or 2 scans (n=30). Additionally, 3 subgroups were created based on the PG used: Icam4D, Grammee, OxoFit. In the 1-scan group, the corresponding markers of each system were placed on the implant abutment analogs of the cast. On each specimen, a scan was recorded to capture the 6 implant positions. In the 2-scan group, the corresponding markers of each system were hand tightened on the implant abutment analogs located on the right and left first molars and right and left lateral incisors. The first PG scan was obtained to capture these 4 implant positions. Afterwards, the markers of the right and left lateral incisors were removed and hand tightened on the implant abutment analogs positioned on the right and left first premolars. Lastly, the second PG scan was obtained to capture these 4 implant positions. In the ICam4D and Grammee subgroups, the partial scans were merged by the PG software program. In the OxoFit subgroup, the partial PG scans were merged by using a program (DentalCAD). Linear and angular measurements among the implants were completed on the digitized cast and used to compare the discrepancies with the same measurements acquired on each specimen. Two-way ANOVA and Tukey tests were used to analyze the trueness data. The Levene test was used to analyze the precision values (α=.05).

Results: Linear trueness differences were found among the groups (P=.048) and subgroups (P<.001). The 1-scan group achieved the best linear trueness (P=.048). The Icam4D obtained the best linear trueness. Linear precision differences were found among subgroups (P=.018). Icam4D had the best linear precision. Angular trueness differences were found among the groups (P=.022) and subgroups (P<.001) with a significant group×subgroup interaction (P<.001). The 1-scan group obtained better angular trueness than the 2-scan group. The Icam4D and OxoFit obtained the best angular trueness. Angular precision discrepancies were found among the groups (P<.001) and subgroups (P<.001) tested. The 1-scan group had the best angular precision. The Icam4D and OxoFit obtained the best angular precision.

Conclusions: The number of scans and extraoral PG system impacted the implant position's accuracy of complete arch implant scans. The discrepancies measured involved 13 µm of mean linear trueness, 9 µm of mean linear precision, 0.145 degrees of mean angular trueness, and 0.053 degrees of mean angular precision among the subgroups tested. The impact of these statistically significant differences may not be clinically relevant.