Trueness of merging partial arch scans using different intraoral scanners for diagnostic casts: A proof of concept.

Objective
To evaluate whether digitizing dentate partial arch casts with intraoral scanners (IOSs) achieves trueness comparable to casts from irreversible hydrocolloid complete arch impressions.Methods
Maxillary and mandibular dentate typodonts were digitized with an industrial-grade scanner to generate master STL files. Five irreversible hydrocolloid partial arch impressions of the right and left quadrants and anterior region, and five complete arch impressions were made and poured in stone (Control, C). Each partial arch cast was scanned with two IOSs (CEREC Primescan [PS] and TRIOS 3 [TS]), while complete arch stone casts were digitized with the industrial scanner. The master files and all scan files were imported into a metrology-grade analysis software program to evaluate surface deviations (μm), linear distances between canine cusp tips and second molar distal marginal ridges (μm), and intermolar width deviations (μm). The data were analyzed using generalized linear model analysis (α = 0.05).Results
The interaction between main factors affected the surface deviations, while the dental arch affected the intermolar width deviations (P ≤ 0.040). PS-mandible had the highest surface deviations (P ≤ 0.047), except for TS-mandible (P > 0.050). TS-mandible had higher surface deviations than C-maxilla and C-mandible (P ≤ 0.032). Maxillary intermolar width deviations were higher than mandibular (P = 0.043).Conclusions
Conventional mandibular impressions had higher surface trueness than partial arch cast scans. When PS was used, maxillary partial arch cast scans had higher trueness than mandibular. Mandibular impressions had higher intermolar width trueness. Nevertheless, all measured deviations can be considered clinically acceptable according to previously reported ranges.Clinical Significance
When maxillary and mandibular impressions are needed in restricted mouth opening situations, tested intraoral scanners can be considered to scan partial arch casts to subsequently virtually merge them to obtain the arch's impression.