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

Daehee Jang,Kyu-Bok Lee,Keunbada Son

doi:10.3390/app9142778

Daehee Jang, Kyu-Bok Lee + Show 1 more

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https://doi.org/10.3390/app9142778

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Journal: Applied Sciences	Publication Date: Jul 10, 2019
Citations: 19	License type: CC BY 4.0

Affiliation: Kyungpook National University

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.

Highlights

With the introduction of the computer-aided design and computer-aided manufacturing (CAD–CAM) system, fixed dental prostheses (FDP) can be produced using a digital workflow through three-dimensional (3D) data acquisition, CAD, and CAM processing, as opposed to the conventional workflow involving a manual process using the lost wax technique [1,2,3]
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
Two mill burs were used in the four-axial milling unit for both the chairside and in-lab groups, and our findings show that the milling unit influences the trueness

Summary

Introduction

With the introduction of the computer-aided design and computer-aided manufacturing (CAD–CAM) system, fixed dental prostheses (FDP) can be produced using a digital workflow through three-dimensional (3D) data acquisition, CAD, and CAM processing, as opposed to the conventional workflow involving a manual process using the lost wax technique [1,2,3]. Prior to the introduction of intraoral scanners, the digital workflow was used to fabricate a gypsum model through impression-taking in the patient’s mouth, and to obtain a virtual model using a desktop optical scanner [2,4]. Sci. 2019, 9, 2778 hand, the intraoral scanner can acquire a virtual model through direct optical scanning of the patient’s mouth. The introduction and development of intraoral scanners have led to a significant increase in the demand for digital workflows [5,6,7]

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