Fig 1.
The overall experimental workflow in this study.
Two devices were used in this experimental study to obtain digital models: an intraoral scanner (black line) and CBCT (red line).
Fig 2.
Cone-beam computed tomography (CBCT) scanning.
(a) CBCT apparatus (RAYSCAN α+) and (b) a polyvinylsiloxane impression fixed on a customized chin rest provided by the manufacturer for scanning.
Fig 3.
Conversion from the DICOM format to STL files using customized conversion software.
(a) DICOM file loading, (b) negative data, (c) selection of the positive range, and (d) conversion to a positive format.
Fig 4.
Flow chart of the conversion process.
Fig 5.
Expectation-maximization (EM) algorithm using Gaussian mixtures for auto-thresholding of the polyvinylsiloxane (PVS) impression.
(a) The threshold of PVS impressions found using the EM algorithm, (b) the raw data of computed tomography values before using the EM algorithm.
Fig 6.
(a) Scanned with an intraoral optical scanner (CS 3600), (b) saved in the STL format.
Fig 7.
Three-dimensional deviations between the comparison and reference STL files using GeoMagic software.
Fig 8.
Computer-aided design for the interim crown.
Fig 9.
Fabricated interim crown with a photopolymer using a digital light-processing 3D printer.
Fig 10.
Two-dimensional replica method.
(a) Filled with light-body impression materials and seated together with the stone models, (b) 50 N of pressure was applied for 5 minutes using static load equipment, (c) the pressure was removed from the stone models after polymerization, (d) cylinder-shaped molds were filled with putty, (e) the specimen was created, (f) the specimen was sectioned buccolingually and mesiodistally at the midline.
Fig 11.
Schematic representation of the measurement points in a cross-section of a specimen.
MA: marginal area; AA: axial area; AOA: axio-occlusal angle; OA: occlusal area.
Fig 12.
Measurement of marginal and internal gaps using a digital microscope (magnification ×100).
Table 1.
The root-mean-square values of the IOS-scanned and CBCT-scanned digital models (μm).
Fig 13.
Comparison of the marginal gap and internal gap between mesiodistal and buccolingual surfaces.
MD: mesiodistal; BL: buccolingual; MA: marginal area; AA: axial area; AOA: axio-occlusal angle; OA: occlusal area. P-values were obtained using the Mann-Whitney U test.
Fig 14.
Comparison of the marginal and internal gap according to the measurement area.
MA: marginal area; AA: axial area; AOA: axio-occlusal angle; OA: occlusal area. * p<0.05; ** p<0.01; *** p<0.001 P-values were obtained using the Mann-Whitney U test.
Table 2.
Descriptive statistical analysis of marginal and internal gaps (μm).