The purpose of this study was to evaluate the accuracy on posterior teeth of full arch digital impression in
different scanning sequences on fully dentate and partial edentulism by two intraoral scanners (TRIOS® and 3MTM
True Definition). Two dental models were prepared: fully dentate and partial edentulism of maxillary right second
premolar and maxillary right first molar. Full arch scans started from right to left were compared with the reverse
direction (n=10). Only digital data on maxillary right first premolar and maxillary right second molar from STL files
were superimposed within group to evaluate precision and superimposed with the reference scan (high accurate
scanner) to evaluate trueness using Geomagic Qualify 2013. Kruskal-Wallis test was implemented to compute precision
(α=0.05) and the results showed that precision of all groups were not different. Three-way ANOVA was used to analyze
trueness (α=0.05) and the results showed that TRIOS® had significantly lower mean deviation (12.86 ± 3.81μm)than
3MTM True Definition (15.03 ± 4.17 μm) (p=0.013). TRIOS® scanned on fully dentate model had significantly higher mean
deviation (14.71 ± 3.91 μm) than partial edentulous model (11.01 ± 2.71 μm) (p=0.003). No statistically significant
difference between scanning sequences was observed. In conclusion, intraoral scanner, scanning sequence and partial
edentulism did not affect the precision. TRIOS® had better trueness than 3MTM True Definition. Partial edentulous
model scanned with TRIOS® was found to have higher trueness than fully dentate model. No matter whether the full arch
scanning started from any quadrant, it did not affect the trueness on the posterior data when considered in ashort span.