Accuracy comparisons of intraoral scanning, stereophotogrammetry, and reverse scanning techniques

Evidence regarding the accuracy of reverse scanning, which has been developed as an alternative to intraoral scanning, is lacking.

The purpose of this study was to compare the accuracy of intraoral scanning and reverse scanning methods using a single scanner and a stereophotogrammetry system for complete arch implant recording under in vitro conditions.

A total of 45 recordings were made from an edentulous maxillary definitive cast with 6 multi-unit abutments using 3 different digital recording techniques (intraoral scanning, reverse scanning, and stereophotogrammetry) (n=15). Intraoral and reverse scanning were carried out using an intraoral scanner (Primescan; Dentsply Sirona), while stereophotogrammetry was performed with Oxo Core (Oxo Technology). The definitive cast was also scanned with a desktop optical scanner (inEos X5; Dentsply Sirona) to obtain the reference model. Linear and angular accuracy, comprising trueness and precision, were evaluated using a reverse-engineering software program (Geomagic Control X; 3D Systems). Trueness was calculated as the deviation from the reference model, and precision was defined as the deviation of repeated measurements from the group mean. Linear trueness was analyzed with the Kruskal-Wallis test and Dunn post hoc comparisons, and angular trueness was assessed using Welch ANOVA and Tamhane T2 post hoc testing. Precision was evaluated with the Kruskal-Wallis test. The significance level was set at α=.05.

Significant differences were observed for linear trueness (P=.003), with reverse scanning exhibiting the highest trueness (39.1 µm), followed by intraoral scanning (69.7 µm) and stereophotogrammetry (102.8 µm). Angular trueness also differed significantly (P<.001), with intraoral scanning showing the highest trueness (0.12 ±0.07 degrees) and reverse scanning the lowest (0.67 ±0.16 degrees). Precision did not differ significantly for either linear or angular measurements (P=.082 and P=.058, respectively).

Reverse scanning demonstrated the highest linear trueness but the lowest angular trueness among the tested techniques. Although all methods showed clinically acceptable linear accuracy, the angular accuracy of reverse scanning exceeded the clinically acceptable threshold, indicating that its clinical applicability may be limited.