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

Abstract

The purpose of this study was to measure and correlate the fitness and trueness of a 3-unit fixed dental prosthesis (FDP) fabricated using two digital workflows. The 3-unit FDPs were fabricated using two digital workflows (N = 15). The digital workflows were divided into chairside (closed type) and in-lab (open type) groups. The scanning, computer-aided design (CAD), and computer-aided manufacturing (CAM) processes were conducted with 3shape E1 scanner, exocad CAD software, and DDS EZIS HM, respectively, in the in-lab group; and with CEREC omnicam intraoral scanner, CEREC CAD software, and CEREC MC XL, respectively, in the chairside group. The fitness of the fabricated 3-unit FDPs was evaluated by scanning the silicone replica of the cement space and analyzing the thickness of the silicone replica in the three-dimensional (3D) inspection software (Geomagic control X). The trueness of the milling unit was analyzed by 3D analysis of the CAD reference model, which is the design file of the 3-unit FDP, and the CAD test model, which is the scanned file of the 3-unit FDP. In the statistical analysis, comparison of the two groups was conducted by Mann–Whitney U test, and the correlation between the fitness and trueness was conducted by Pearson correlation test (α = 0.05). The marginal and internal fit were significantly lower in the in-lab group at all measurement positions (p < 0.001). The trueness of the milling unit was significantly higher in the in-lab group compared to the chairside group (p < 0.001). There was a positive correlation between the trueness and internal fit (correlation coefficient = 0.621) in the in-lab group (p = 0.013). The use of appropriate equipment in an in-lab (open type) digital workflow enables a better fabrication of 3-unit FDPs than a chairside (closed type) digital workflow, and poor trueness on the inner surface of the crown adversely affects the internal fit.

Effects of Trueness and Surface Microhardness on the Fitness of Ceramic Crowns

“…The introduction of intraoral scanners and their combination with dental computer-aided design and computer-aided manufacturing (CAD/CAM) systems has enabled the chairside production of prostheses [1][2][3][4]. As such CAD/CAM systems do not require a working model to be fabricated, prostheses are produced rapidly, which reduces the patient treatment time [1][2][3].…”

“…As such CAD/CAM systems do not require a working model to be fabricated, prostheses are produced rapidly, which reduces the patient treatment time [1][2][3]. Lithium disilicate ceramics are widely used for dental prostheses because they are aesthetic materials with a short sintering time [4,5]. Four-axial milling units are also preferred to minimize patient treatment time [4][5][6][7][8].…”

“…Lithium disilicate ceramics are widely used for dental prostheses because they are aesthetic materials with a short sintering time [4,5]. Four-axial milling units are also preferred to minimize patient treatment time [4][5][6][7][8]. Crowns fabricated from lithium disilicate materials have shown a high survival rate [6].…”

“…When using dental CAD/CAM systems, it is important to evaluate the consistency between the designed crown and the fabricated crown [4,5,9,10]. Low consistency may affect the marginal and internal fit of a prosthesis [4,9,10].…”

“…When using dental CAD/CAM systems, it is important to evaluate the consistency between the designed crown and the fabricated crown [4,5,9,10]. Low consistency may affect the marginal and internal fit of a prosthesis [4,9,10]. Trueness indicates the similarity of the prosthesis designed first in CAD software (CAD reference model) with the fabricated prosthesis (CAD test model) [4,9,10].…”