Abstract
The purpose of this study was to evaluate the accuracy of intraoral scanners in 10 abutments (five premolars and five molars) obtained in a dental clinic and to analyze the impacts of the volume and area of abutments on scanning accuracy. Abutment casts were scanned five times with a 3D contact scanner (DS10; Renishaw plc). The five scan files were lined up and then merged, and one high-resolution computer-aided design reference model (CRM) was obtained. To obtain a computer-aided design test model (CTM), three types of intraoral scanners (CS3600 (Carestream Dental), i500 (Medit), and EZIS PO (DDS)) and one type of laboratory scanner (E1; 3Shape) were employed. Using 3D analysis software (Geomagic control X; 3D Systems), the accuracy of the scanners was evaluated, including optimal overlap by optimal alignment. The conformity of the overlapped data was calculated by the root mean square (RMS) value, using the 3D compare function for evaluation. As for statistical analysis, testing was conducted, using one-way and two-way ANOVA and the Tukey HSD test (α = 0.05) for the comparison of the groups. To analyze the correlations of the volume and area of the abutments with accuracy, Pearson’s correlation analysis was conducted (α = 0.00625). Both premolar and molar abutments showed a lower RMS value on the laboratory scanner than on the intraoral scanners, and the RMS value was lower in premolars than in molars (p < 0.001). In the intraoral scanner group, CS3600 showed the best accuracy (p < 0.001). There were significant positive correlations for the volume and area of the abutments with accuracy (p < 0.001). The type, volume, and area of the clinically applicable abutments may affect the accuracy of intraoral scanners; however, the scanners used in the present study showed a clinically acceptable accuracy range, regardless of the type of abutment.
Highlights
Breaking from the conventional dental workflow, which is dependent on the operator’s experience, digital dental workflows have been made possible by the introduction of dental computer-aided design and computer-aided manufacturing (CAD/CAM) [1,2,3]
If it is difficult to use an intraoral scanner in a given dental clinic due to various oral conditions, a digital workflow is possible through partially digital workflows [9,10,11]
It is necessary to obtain a CAD test model (CTM), using an intraoral scanner, and to obtain a CAD reference model (CRM), using an industrial optical scanner or contact scanner with a high level accuracy so that it can be used as a standard [16,17]
Summary
Breaking from the conventional dental workflow, which is dependent on the operator’s experience, digital dental workflows have been made possible by the introduction of dental computer-aided design and computer-aided manufacturing (CAD/CAM) [1,2,3]. From a partially digital workflow that involved the process of obtaining a virtual cast through taking an oral impression, working model production, and use of a laboratory scanner [4], the use of intraoral scanners made fully digital dental workflows possible [5]. Intraoral scanners have the advantage of being able to obtain virtual casts directly from the patient’s mouth without any additional work process, which is an essential element of a chairside CAD/CAM system [6,7]. If it is difficult to use an intraoral scanner in a given dental clinic due to various oral conditions, a digital workflow is possible through partially digital workflows (the process of obtaining a virtual cast by taking an oral impression, producing a working model, and using a laboratory scanner) [9,10,11]. Previous studies have noted that if the scanning accuracy of virtual casts exceeds 100 μm, the final restoration in the maxilla and mandible may fit incorrectly, and an allowable range for a scanning accuracy of less than 100 μm has been suggested based on the acceptable cement space for the fixed prostheses [24,25,26]
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