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

Abstract

This study aims to evaluate the fitness, surface microhardness, and trueness of crowns fabricated from three types of dental ceramic blocks (HASS Rosetta, IPS e.max CAD, and VITA Suprinity) and analyze the correlations between them. A crown was first designed in computer-aided design (CAD) software. To create a crown designed model (CDM), the design file was extracted from the CAD software, and a lithium disilicate block was processed from the file with a milling machine. To create a crown scanned model (CSM), the inside of the fabricated crown was digitized using a contact scanner. Using three-dimensional (3D) inspection software (Geomagic Control X; 3D Systems), the CDM and CSM were then superimposed, and their 3D trueness was analyzed. To measure the surface microhardness of the blocks, the specimens were polished and subjected to the Vickers hardness test. The fitness of the fabricated crowns was evaluated by applying a modified silicone replica technique. Pearson correlation analysis was performed to assess the correlations between trueness, surface microhardness, and fitness. In addition, the significance of differences between the three types of dental ceramic blocks was analyzed using one-way analysis of variance (ANOVA). Significant differences in the trueness, surface microhardness, and marginal fit were observed between ceramic blocks of different types. There were also positive correlations between trueness, surface microhardness, marginal fit, and internal fit. While the marginal fit of crowns fabricated from each of the three types of ceramic blocks was in the clinically permitted range (<120 µm), there were differences in the trueness and surface microhardness, depending on the type of block. However, crowns fabricated from each of the three materials have surface microhardness that is clinically applicable.

Effect of Tooth Types on the Accuracy of Dental 3D Scanners: An In Vitro Study

“…There were some limitations to the present study. Previous studies have reported that the type of scanner can affect the marginal and internal fit of the prosthesis [43][44][45][46][47]. Depending on the results of the present in vitro study, there were few displacements of scanning in the desktop scanners, so further studies that consider the clinical environment are needed for the intraoral scanner.…”

Marginal and Internal Fit of Ceramic Restorations Fabricated Using Digital Scanning and Conventional Impressions: A Clinical Study

“…The correlations were divided as per the size of the Pearson correlation coefficient (PCC), as reported previously [ 33 ]. The results of the correlation analysis among the variables were explained through the following criteria by the previous studies [ 14 , 16 , 33 ]: perfect (PCC = +1 or −1), strong (PCC = +0.7–+0.9 or −0.7–−0.9), moderate (PCC = +0.4–+0.6 or −0.4–−0.6), and weak (PCC = +0.1–+0.3 or −0.1–−0.3) (α = 0.05).…”

“…An intraoral scanner is an essential tool in chairside computer-aided design and computer-aided manufacturing (CAD/CAM) system because it allows the acquisition of a virtual cast directly from the patient’s oral cavity without the need for any additional work process [ 11 , 12 , 13 , 14 , 15 ]. In the dental clinic, where quick fabrication is necessary, lithium disilicate ceramic material is preferred because it takes less milling time and less crystallization time [ 16 ]. The lithium disilicate ceramic crown is superior to a zirconia crown in terms of better aesthetics, faster fabrication, and easier post-processing process [ 17 , 18 ].…”

“…The accuracy of the impression obtained from the patient’s oral cavity is important for the fabrication of a well-fitting prosthesis [ 13 , 14 , 15 , 16 ]. The deformation of the impression may lead to poor marginal and internal fit of the prostheses along with inaccurate working cast fabrication [ 13 , 14 ].…”

“…This may cause issues, such as plaque deposits in the oral cavity, secondary caries, cement dissolution, and periodontal disease [ 13 ]. Furthermore, the poor internal fit may cause loss of the retention force of the prostheses and lower fracture resistance [ 14 , 16 ]. In general, it is judged that the clinically allowable marginal fit of the fixed prostheses is 100–120 µm [ 17 , 18 , 19 , 20 ].…”