In vitro comparison of the accuracy (precision and trueness) of eight dental scanners for dental bridge scanning

Fariborz Vafaee; Mahsa Mohajeri; Naser Mohammad Gholi Mezerji; Marouf Ebrahim Zadeh

. 2021 Oct 21;18:84.

In vitro comparison of the accuracy (precision and trueness) of eight dental scanners for dental bridge scanning

Fariborz Vafaee ¹, Mahsa Mohajeri ^2,^✉, Naser Mohammad Gholi Mezerji ³, Marouf Ebrahim Zadeh ⁴

PMCID: PMC8554480 PMID: 34760075

Abstract

Background:

Dental scanners play a critical role in computer-aided design/computer-aided manufacturing technology. This study aimed to compare the accuracy (precision and trueness) of eight dental scanners for dental bridge scanning.

Materials and Methods:

In this in-vitro experimental study, a typodont model with a missing maxillary right first molar was prepared for a 3-unit fixed partial denture. Each scanner (Sirona inEos inLab, Sirona X5, Dentium, Imes icore 350I I3D, Amann Girrbach map 100, 3Shape D100, 3Shape E3) performed seven scans of the typodont, and the data were analyzed using 3D-Tool software. The abutment length, abutment width, arch length, and interdental distance were measured. To assess the accuracy of each scanner, trueness was evaluated by superimposing the scanned data on true values obtained by the 3shape Triosscanner as the reference. Precision was evaluated by superimposing a pair of data sets obtained from the same scanner. Precision and trueness of the scanners were compared using the one-way ANOVA followed by the post-hoc Tukey's HSD test and one-sample t-test (P<0.05 was considerer significant).

Results:

The precision of scanners ranged from 14 μm (3Shape Trios) to 45 μm (Imes icore 350i), whereas the trueness ranged from 38 μm (3Shape d700) to 71 μm (Sirona X5).

Conclusion:

The reported trueness values for 3Shape Trios, Sirona inEos inLab, Sirona x5, Dentium, Imes icore350i, Amann Girrbach, 3Shape d700, and 3Shape e3 were 63, 45, 71, 67, 70, 53, 38, and 42 μm, respectively, whereas the precision values were 14, 29, 44, 34, 45, 44, 30 and 28 μm, respectively.

Key Words: Accuracy, dental scanner, precision, trueness

INTRODUCTION

Nowadays, computer-aided design/computer-aided manufacturing (CAD/CAM) technology is becoming increasingly popular due to fewer clinical sessions, leading to higher patient comfort.[1,2,3] This technology has been popular since the 1980s and is currently used to manufacture a wide range of dental prostheses such as fixed partial dentures, removable partial frameworks, maxillofacial prostheses, and complete dentures.[4,5,6] The processing chain of CAD/CAM technology consists of three different steps, namely scanning, designing, and manufacturing of the prosthesis, which can be milled or 3D-printed using different types of materials.[7]

There are two types of scanners based on the method of fabrication of CAD/CAM crowns: intraoral scanners which directly scan the dental arch and extraoral scanners, scanning either the dental impressions or the laboratory-fabricated casts. Intraoral scanners mainly use the tenets of active triangulation, confocal microscopy, and wave-front sampling. The output of these scanners can be divided into two subgroups of camera image impressions and video image impressions.[4,8,9,10,11] Extraoral scanners are divided into three subgroups, namely laser, structured light, and contact scanners.[4] Laser and light scanners produce scans faster and are not influenced by the density of the object. Despite this advantage, these types of scanners are affected by the optical properties of the object being scanned such as shininess of the surface and brightness. Contact scanners use a contact probe touching a cast, which is highly accurate but can potentially damage the scanned surface. The slow scanning speed of this group of scanners is another drawback of this type of scanners.[1,4,12,13,14]

Enhancement of accuracy is among the most important goals of digital dentistry, and computer-aided technology can decrease discrepancies which occur during the conventional method of impression making and crown fabrication.[15,16,17,18] According to different technologies of intraoral and extraoral scanners, different companies produce different types of scanners. There is inconsistent information about the accuracy of crowns made with these systems. Accuracy of scanners consists of precision (how close the repeated measurements are to each other), trueness (how far the measurements are aberrant from the actual dimensions), and marginal adaptation.[15,19,20,21]

The purpose of this study was to compare the accuracy (precision and trueness) of eight dental scanners for dental bridge scanning. The null hypothesis was assumed for this investigation was that there would be no differences between different dental scanners with regard to accuracy.

MATERIALS AND METHODS

This in-vitro experimental study compared the accuracy (precision and trueness) of eight dental scanners. The accuracy of Sirona inEos inLab (Dentsply Sirona, USA), Sirona X5 (Dentsply Sirona, USA), Dentium Rainbow™ (Dentium, Korea), imes icore 350I I3D (imes-icore, Germany), Amann Girrbach map 100 (Amann Girrbach, Austria), 3Shape D100 (3shape, Denmark), and 3Shape E3 (3shape, Denmark) was evaluated, and data of each scanner were compared with the data received from the 3shape Trios intraoral scanner (3shape, Denmark) as the reference.

A typodont model (Hossbm, Iran) with a missing maxillary right first molar was prepared for a 3-unit fixed partial denture by a prosthodontist according to the principles of Rosenstiel et al.[7] Next, three points were created on the surface of the prepared tooth as reference points. Each scanner performed seven scans of the typodont, and the obtained data were analyzed using 3D-tool software (3D-Tool GmbH and Co., KG, Germany). The abutment length, abutment width, arch length, and interdental distance were measured, as shown in Figure 1. In order to compare the trueness, the prepared typodont was first scanned with 3shape Trios scanner as the reference. This true value was then compared with the measurements made by each scanner. Then, precision was determined based on the differences in values obtained by repeated measurements by each scanner.

3D-Tool software and the measurement sequence: (a) Images of abutment with reference points on its surfaces scanned with ATOS scanner. (b) Selecting the measure markup item. (c) Selecting the vortex item. (d) Marking the deepest point on reference area. (e) Measuring the exact distance between the two selected points.

The collected data were analyzed using the SPSS software version 19.0 (IBM company, Armonk, New York, USA). Precision and trueness were compared among different scanners using one-way ANOVA followed by the post-hoc Tukey's honestly significant difference test and one-sample t-test (P <0.05 was considerer significant).

RESULTS

The mean and standard deviation of arch length [Table 1], crown width of tooth #14 [Table 2], crown width of tooth #16 [Table 3], interdental distance [Table 4], crown length of tooth #14 [Table 5], and crown length of tooth #16 [Table 6] were compared using the one-way ANOVA [Table 7].