Effect of distance between the abutment and the adjacent teeth on intraoral scanning: An in vitro study.

STATEMENT OF PROBLEM: The introduction of intraoral scanners has increased the use of digital technology in dental procedures. However, data on the accuracy of abutment scans according to the distance between the adjacent tooth and the abutment are lacking.

PURPOSE: The purpose of this in vitro study was to compare the 3D accuracy of abutment scans according to the distance between the adjacent tooth and the abutment.

MATERIAL AND METHODS: A right maxillary first molar was removed and scanned with an industrial 3D scanner, and the image was extracted as a standard tessellation language (STL) file. Six virtual models with 1-mm, 1.5-mm, 2-mm, 2.5-mm, 3-mm, and 3.5-mm spacing between abutment teeth and adjacent teeth were fabricated with an industrial computer-aided design (CAD) software program. Then, 6 master models were fabricated with a 3D printer and copied into dental gypsum. The replicated models (reference models) were scanned 20 times with an intraoral scanner (CS3600); the resulting model was referred to as the CAD test model. The adjacent teeth of the reference models were deleted, and the models were scanned with a laboratory scanner; the resulting model was referred to as the CAD reference model. The CAD reference model was used to measure the scan accuracy in 4 directions (buccal, lingual, mesial, and distal) and 4 areas (occlusal, angle, axial, and margin) by using 3D inspection software. The Friedman nonparametric test (α=.05) was used for comparison, and post hoc testing was performed by using the Mann-Whitney U-test and Bonferroni correction method (direction and area variables; α=.0008, distance variable; α=.0003).

RESULTS: The buccal, lingual, mesial, and distal directions of the abutment were significantly different according to distance (P<.001). The margin, axial, angle, and occlusal regions of the abutment were also significantly different according to distance (P<.001).

CONCLUSIONS: The distance between the abutment teeth and adjacent teeth affected the accuracy of the abutment scan. In intraoral scanning, when the distance between the abutment teeth and the adjacent teeth is more than 1.5 mm, the scan error does not increase, and more accurate scan data can be obtained.