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

• Main Authors: Kunhee Lee, Keunbada Son, Kyu-bok Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Applied Sciences
• Subjects: trueness; marginal and internal fit; surface microhardness; ceramic; dentistry
• Online Access: https://www.mdpi.com/2076-3417/10/5/1858

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.