Reliability of Different Bending Test Methods for Dental Press Ceramics.

Daisuke Miura,Yoshiki Ishida,Harumi Aoki,Akikazu Shinya,Taira Miyasaka

doi:10.3390/ma13225162

Daisuke Miura, Yoshiki Ishida + Show 3 more

Open Access

https://doi.org/10.3390/ma13225162

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Abstract

Objective: This study investigates the reliability of different flexural tests such as three-point-bending, four-point bending, and biaxial tests, in strengthening the dental pressed ceramics (DPCs) frequently used in clinical applications. Methods: The correlations between the three types of bending tests for DPCs were investigated. Plate-shaped specimens for the three-point and four-point bending tests and a disc-shaped specimen for the biaxial bending test were prepared. Each bending test was conducted using a universal testing machine. Results: The results for six DPCs showed that the flexural strength in descending order were the three-point flexural strength, biaxial flexural strength, and four-point flexural strength, respectively. Then, a regression analysis showed a strong correlation between each of the three test methods, with the combination of four-point and biaxial flexural strength showing the highest values. The biaxial flexural strength was not significantly different in the Weibull coefficient (m) compared to the other tests, with the narrowest range considering the 95% interval. The biaxial bending test was found to be suitable for materials with small plastic deformation from the yield point to the breaking point, such as DPCs.

Highlights

In recent years, ceramics have been widely used to fabricate crown restorations due to the increasing demand for aesthetic properties, mechanical strength, and biocompatibility [1,2]
All-ceramic crowns are fabricated via the refractory model, casting, computer-aided design/computer-aided manufacturing (CAD/CAM), and press mould techniques
Our results showed that the biaxial flexural test shall be a potentially effective method in various bending tests to measure the flexural strength on dental pressed ceramics (DPCs), as reliable as the four-point bending test

Summary

Introduction

Ceramics have been widely used to fabricate crown restorations due to the increasing demand for aesthetic properties, mechanical strength, and biocompatibility [1,2]. All-ceramic crowns are fabricated via the refractory model, casting, computer-aided design/computer-aided manufacturing (CAD/CAM), and press mould techniques. In the refractory model technique, crowns were fabricated via the building and baking method on the refractory casts made from duplicate impressions. The technique required expert skills and a long working time [3]. The casting technique has high strength and good optical properties owing to the crystallizing process after casting. This technique has some disadvantages such as crystallization inhomogeneity, casting porosity, and producing a rounded casting instead of metal casting due to the high sensitivity of ceramics to the temperature of the casting mould [4]

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Conclusion