Trueness and precision of scanning abutment impressions and stone models according to dental CAD/CAM evaluation standards

Abstract

PURPOSEThe purpose of the present study was to compare scanning trueness and precision between an abutment impression and a stone model according to dental computer-aided design/computer-aided manufacturing (CAD/CAM) evaluation standards.MATERIALS AND METHODSTo evaluate trueness, the abutment impression and stone model were scanned to obtain the first 3-dimensional (3-D) stereolithography (STL) file. Next, the abutment impression or stone model was removed from the scanner and re-fixed on the table; scanning was then repeated so that 11 files were obtained for each scan type. To evaluate precision, the abutment impression or stone model was scanned to obtain the first 3-D STL file. Without moving it, scanning was performed 10 more times, so that 11 files were obtained for each scan type. By superimposing the first scanned STL file onto the other STL files one by one, 10 color-difference maps and reports were obtained; i.e., 10 experimental scans per type. The independent t-test was used to compare root mean square (RMS) data between the groups (α=.05).RESULTSThe RMS±SD values of scanning trueness of the abutment impression and stone model were 22.4±4.4 and 17.4±3.5 µm, respectively (P<.012). The RMS±SD values of scanning precision of the abutment impression and stone model were 16.4±2.9 and 14.6±1.6 µm, respectively (P=.108).CONCLUSIONThere was a significant difference in scanning trueness between the abutment impression and stone model, as evaluated according to dental CAD/CAM standards. However, all scans showed high trueness and precision.

Effect of rinsing time on the accuracy of interim crowns fabricated by digital light processing: An in vitro study

“…The duplicated epoxy die was scanned with a dental laboratory scanner (Identica Hybrid, Medit, Seoul, South Korea) to fabricate a virtual study die, 24 and the scanned images were saved in Standard Triangulated Language (STL) file formats to create a virtual study die. The blue light LED-based scanner used in this study has high accuracy in scanning impressions and abutments, and is widely used to analyze accuracy.…”

“…Previous accuracy evaluation was performed linearly using digital calipers, and recent advances in dental scanners and 3D superimposition software have made it possible to measure accuracies of a wide variety of surfaces. 5 16 17 22 23 24 25 26 27 28 Accuracy is classified into trueness and precision. Trueness refers to the degree of agreement between the virtually designed dental restoration and the specimen, while precision indicates the degree of agreement within the specimens.…”

Influence of inlay preparation design on the trueness of different impression techniques

“…In this study, all dataset obtained from different impression techniques were loaded into a recognized worldwide (3D) superimposition (reverse-engineering) software, where they were superimposed on the reference model, to evaluate trueness. (31,40) The idea relies on calculating the square difference between a number of points (x, y, z axis) when two different scans were superimposed onto each other; then, the sum of these squares was divided by the number of points, and the square root of this value was considered the root mean square (RMS).This is probably a more precise value than an arithmetic mean because the difference between each data point is represented by a positive (expansion) value and a negative (contraction) value, and viewed on the color map as red and blue colors, respectively. (22) With regard to trueness for the 6 degrees axial wall divergence, the impression scan had the best results (0.0701μm), followed by the cast scan (0.0727μm), 3Shape Trios (0.0889μm) and Omnicam (0.0921μm).…”

“…For the trueness measurement, color difference maps and reports (n=80) were obtained by superimposing the digital data sets of the scans from the two IOS onto the reference model, then (3D) deviation analysis was performed with the best-fit algorithm method (30) to evaluate and visualize the positive (expansion) and negative (contraction) discrepancies (in micrometers) on a color coded image of the superimposition (Fig.2). By using this method, for each superimposition, the root mean square (RMS) of the amount of deviation at each measurement point was recorded using the equation below : ( 31) The data collected was checked for normal distribution and analyzed using two-way analysis of variance (ANOVA), followed by Tukey's HSD test (SPSS v20, Chicago, IL, USA) at a significance level of P ≤ 0.05.…”

A Comparative Study of the Fitness and Trueness of a Three-Unit Fixed Dental Prosthesis Fabricated Using Two Digital Workflows

“…With the introduction of the computer-aided design and computer-aided manufacturing (CAD-CAM) system, fixed dental prostheses (FDP) can be produced using a digital workflow through three-dimensional (3D) data acquisition, CAD, and CAM processing, as opposed to the conventional workflow involving a manual process using the lost wax technique [1][2][3]. Prior to the introduction of intraoral scanners, the digital workflow was used to fabricate a gypsum model through impression-taking in the patient's mouth, and to obtain a virtual model using a desktop optical scanner [2,4].…”