Evaluation of the Accuracy and Time Efficiency of Different Intraoral Scanners for Direct Digital Post Space Scan

Abstract

ABSTRACT

Statement of problem. IOSs are commonly used in dental practices. However, limited research compares the accuracy of scanning posts and core restorations using different IOSs with conventional impression techniques. This gap in research makes it harder for dentists to choose the best scanner for post-and-core procedures, particularly in more complicated cases or cases with multiple teeth requiring post and core. Limited studies investigated the accuracy of IOSs using CEREC Primescan (Dentsply Sirona) and iTero 5D Element (Align Technology, Inc). No studies investigated the accuracy of IOSs using TRIOS 6 (3shape) for direct digital custom post scan compared to conventional impressions. Additionally, no studies have evaluated the time efficiency of IOSs compared to the conventional impression for post and core fabrication.

Purpose. The purpose of this in vitro study was to evaluate the trueness and precision of 3 IOSs (TRIOS 6, 3Shape; iTero 5D Element, Align Technology; and CEREC Primescan, Dentsply Sirona) for the direct digital scanning of a 10-mm post space, to compare them with a conventional polyvinyl siloxane (PVS) impression, and to compare the time efficiency of the digital and conventional techniques

Materials and Methods:

Six extracted human maxillary anterior teeth (2 central incisors, 2 lateral incisors, and 2 canines) were obtained under an approved Rutgers institutional review board protocol. The experimental tooth (a maxillary central incisor) received standardized endodontic treatment and a 10-mm post space preparation; all teeth were mounted in a typodont to simulate the clinical arch, with the remaining teeth serving as adjacent teeth. A micro-computed tomography (micro-CT) scan (SkyScan 1272) of the experimental tooth served as the reference (master) standard tessellation language (STL) file. The experimental tooth was scanned 15 times with each of the 3 IOSs (groups T, I, and P; 45 STL files), and 15 conventional PVS impressions were made with digitally designed, 3D-printed sectional custom trays (with vertical seating stops, seated under a standardized static load) and digitized with a desktop scanner (AutoScan-DS-EX Pro 3D; Shining 3D) to provide 15 STL files (60 experimental files total). All files were imported into a

metrology software program (Geomagic Control X; 3D Systems) and superimposed onto the reference by an initial alignment followed by a best-fit aligtment to the stable external tooth surfaces, with the post space excluded from the alignment. The root mean square (RMS) deviation was recorded over the captured post-space surface, and the maximum capture depth was recorded in millimeters and as a percentage of the 10-mm preparation. Trueness was defined as the mean RMS deviation from the reference, and precision as the standard deviation of the RMS values within each group. Scanning and impression times were recorded with a stopwatch. Data were analyzed by using the Welch ANOVA with the Games-Howell post hoc test (trueness and time) and the Kruskal-Wallis test with the Bonferroni correction (capture depth) (α=.05).

Results:

Significant differences were found among the groups in trueness, capture depth, and time (P<.001). The Primescan group recorded the highest trueness (lowest RMS, 23.1 µm). The Primescan and conventional (PVS) groups captured essentially the full post-space depth (100% and 98.5%), whereas the TRIOS 6 and iTero 5D groups captured only approximately 64.5%. The Primescan group required the least time and the iTero 5D group the most.

Conclusions:

Only the Primescan and the conventional PVS impression captured the full 10-mm post-space depth, whereas the TRIOS 6 and iTero 5D recorded approximately 64.5%. All groups showed low RMS deviations (below 30 µm), indicating that capture depth, rather than surface accuracy, distinguished the scanners.