Effect of different arch widths on the accuracy of three intraoral scanners

Abstract

Purpose: The purpose of this study was to compare the accuracy of three intraoral scanner (IOS) systems with three different dental arch widths.

Materials and methods: Three dental models with different intermolar widths (small, medium, and large) were attached to metal bars of different lengths (30, 40, and 50 mm). The bars were measured with a coordinate measuring machine and used as references. Three IOSs were compared: TRIOS 3 (TRI), True Definition (TD), and Dental Wings (DW). The relative length and angular deviation of both ends of the metal bars from the scan data set (n = 15) were calculated and analyzed.

Results: Comparing among scanners in terms of trueness, the relative length deviation of DW in the small (1.28%) and medium (1.08%) arches were significantly higher than TRI (0.46% and 0.48%) and TD (0.33% and 0.18%). The angular deviation of DW in the small (1.75°) and medium (1.83°) arches were also significantly greater than TRI (0.63° and 0.40°) and TD (0.55° and 0.89°). Comparing within scanner, the large arch of DW showed better accuracy than other arch sizes (P < .05). On the other hand, the larger arch of TD presented a greater tendency of angular deviation in terms of trueness. No significant differences were found in terms of trueness between the arch widths of TRI group.

Conclusion: The different widths of the dental arches can affect the accuracy of some intraoral scanners in full arch scan.

Keywords: Accuracy; Arch size; Arch width; Digital impression; Intraoral scanner.

© 2021 The Korean Academy of Prosthodontics.

Figures

Fig. 1. The metal bar with the positions of points A, point B, vector ν1, vector ν2, and three sizes of dental models (small, medium, and large) attached with the different lengths of the metal bars (30, 40, and 50 mm).

Fig. 2. Different scan patterns of the three scanners: TRI = TRIOS 3; DW = Dental Wings, TD = True Definition.

Fig. 3. (A) Nine planes (plane 1–9) were created with the best fit algorithm to the metal bar surfaces. (B) Three points (point 1–3) originated from the intersection of the three different planes, and the horizontal plane from these points was set to be parallel to the XY-axis, line 1 from point 1 to point 3 was set to the X-axis. (C) The coordinate of point 1 was set as the origin, and two points (A, B) were created from the intersection of the three different planes. (D) Lines A and B were created from two different planes to obtain the two vectors (ν1, ν2) in the same direction.

Fig. 4. (A) The box plots present the relative length deviation of trueness (RDT). (B) The relative length deviation of precision (RDP) of the three scanners (TRI = TRIOS 3; TD = True Definition; DW = Dental Wings) in three different arch widths.

Fig. 5. (A) The box plots present the angular deviation in terms of trueness (αIOS). (B) The angle deviation in terms of precision (αP) of the three scanners (TRI = TRIOS 3; TD = True Definition; DW = Dental Wings) in three different arch widths.