Digital workflow: In vitro accuracy of 3D printed casts generated from complete-arch digital implant scans

Statement of problem. Data on the accuracy of printed casts from complete-arch digital implant scans are lacking. Purpose. The purpose of this in vitro study was to compare the 3D accuracy of printed casts from a complete-arch digital implant intraoral scan with stone casts from conventional impressions. Material and methods. An edentulous mandibular cast with 4 multiunit abutments with adequate anteroposterior spread was used as the master cast. Digital scans (n=25) were made by using a white light intraoral scanner (IOS). The generated standard tessellation language (STL) data sets were imported into a computer-assisted design (CAD) software program to generate complete-arch implant casts through 3D printing technology. The 25 printed casts and the mandibular master cast were further digitized by using a laboratory reference scanner (Activity 880; Smart Optics). These STL data sets were superimposed on the digitized master cast in a metrology software program (Geomagic Control X) for virtual analysis. The root mean square (RMS) error and the average offset were measured. Results. When compared with the master cast, the printed casts had a mean +/- standard deviation RMS error of 59 +/- 16 mu m (95% CI: 53, 66). The maximum RMS error reached 98 mu m. The average offsets were all negative, with a significant difference compared with zero (P<.001). Conclusions. The implant 3D deviations of the printed casts from complete-arch digital scans had statistically significant differences compared with those of the master cast but may still be within the acceptable range for clinical application.