Trueness comparison of various intraoral scanners and hybrid workflow for ceramic restoration.

Background: The scanned abutment file for the digital design of restorations can be either obtained directly using the intraoral scanner (IOS) or scanning the impression or the working model with the extraoral scanner (EOS). The trueness of the scanned file pertains to its effect on the accuracy of the restoration.

Objective: This study aimed to compare the trueness of scan files from different intraoral scanners (IOSs) and the hybrid workflow using the E3 extraoral scanner (EOS) for ceramic restoration.

Methodology: The model of the mandibular right first molar was prepared for the ceramic crown, and it was scanned with the EOS in reference Standard Tessellation Language (STL) file format. The following seven experimental groups were investigated. The IOSs-iTero Element 5D (IT), Trios 4 (TF), Medit i700 (MI), Primescan (PM), Virtuo Vivo (VV)-were directly scanned on the prepared model. The silicone impression of the prepared model was scanned with EOS (IS). The working model poured from the impression was scanned with the EOS (WS). The test STL file was trimmed and superimposed on the reference STL file for the trueness assessment using Geomagic Control X. The point deviation at the surface and margin of each group were compared. The mean deviation was calculated and statistically analyzed with One-way ANOVA (α=0.05). The minimum and maximum deviation of each area were also recorded.

Results: Compared with the other groups, the impression scan group had a significantly greatest deviation (p<0.05) in surface (37.65±1.14 µm), margin (63.57±5.85 µm) and overall (50.61±3.28 µm). The WS group showed significantly greater deviation (p<0.05) in surface (23.93±1.20 µm), margin (46.18±2.00 µm) and overall (35.05±1.16 µm) than the IOS groups. In some IOS groups, the deviation was also significantly different (p<0.05).

Conclusion: The IOS is recommended for obtaining the scanned file due to its lesser deviation when compared to the hybrid workflow. While statistical differences exist among IOSs, the clinical relevance of these differences appears minimal. If the IOS does not exist, scanning the working model is preferred over scanning impressions directly. However, further clinical validation studies are necessary to confirm this finding.