Accuracy Of Full-Arch Scanning With Intra-Oral Scanners

Methods:  A master metal maxillary jaw with fiduciary marked abutments located at tooth position equivalent measurement points of:  A=#2, B=#4, C=#7, D=#10, E=#13, F=#15, was designed and CNC milled.  A laboratory scanner D810 (3Shape, Copenhagen, Danmark) was used to scan the master jaw and the system’s software used to produce an STL file to act as the reference study model. The master jaw was scanned 5 times with the D810 and scannings analyzed to determine the accuracy of the system. Then two powderless systems were used to perform IOS scans of the master jaw 5 times: 1) Trios color IOS (3Shape), 2) NEVO Scanner (E4D, Richardson, TX). System files were converted to STL format and exported for analysis. Convince™  Software (3Shape) is an industrial system allowing  inspection of IOS 3D scan data against the master jaw STL lab scanner reference files. Deviations from the master model reference point A were calculated in x,y,z dimensions around the arch at the abutments.

Results: The mean (sd) variance (um) of Lab Scanner was A-B=+5(2), A-C=+7(3), A-D=+11(4), A-F=+19(4), @F/z-axis=+4(1). Mean (sd) deviations (um) of IOS were:   TRI:A-B=-60(8), A-C=-74(6), A-D=-21(5), A-F=+43(8), @F/z-axis=+17(2).   E4D: A-B=-35(5), A-C=+59(9), A-D=-31(5), A-F=+645(76), @F/z-axis=+18(1).

Conclusions:  Under conditions of this preliminary in vitro study the Trios scan expanded the arch medio-laterally (M-L) and moderately contracted anterior-posteriorly (A-P). The E4D scan greatly expanded the arch M-L and moderately in A-P dimensions. Both systems slightly increased the z-axis (height). Future work will scan master jaw with coordinate measuring machine generating a master STL file for comparison.