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 μm (95% CI: 53, 66). The maximum RMS error reached 98 μm. 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.