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Open AccessArticle

Modeling of the Influence of Chemical Composition, Sintering Temperature, Density, and Thickness in the Light Transmittance of Four Zirconia Dental Prostheses

1
Instituto Militar de Engenharia, Materials Science Department, Praça General Tibúrcio, 80, Praia Vermelha, Rio de Janeiro, RJ 22290-270, Brazil
2
Faculdade de Tecnologia, Universidade Estadual do Rio de Janeiro, Rod. Presidente Dutra, km 298, Polo Industrial, Resende, RJ 27537-000, Brazil
*
Author to whom correspondence should be addressed.
Materials 2019, 12(16), 2529; https://doi.org/10.3390/ma12162529
Received: 18 June 2019 / Revised: 31 July 2019 / Accepted: 6 August 2019 / Published: 8 August 2019
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Abstract

Research has increasingly been conducted to improve the toughness and aesthetics of zirconium oxide (zirconia) used in prosthetic dentistry. However, the balance between better mechanical properties and greater translucency, to ensure aesthetic requirements, is still a challenge in the development of a novel zirconia for dentistry applications. This study evaluated the transmittance of visible light for four types of pre-sintered zirconia blocks used in dentistry (3Y-SBE, Zpex, Zpex-4, and Zpex-Smile). The objective is to analyze the simultaneous influence of sintering temperature, in the range of 1450–1560 °C, as well as the chemical composition (%Y2O3), density, and thickness (1.0, 1.3, 1.6, and 2.0 mm) in the zirconia’s transmittance. To evaluate the interactive influence of these variables, a statistical learning model based on gradient boosting is applied. The results showed that the effect of the sintering temperature has an optimal (maximum transmittance) point. Increasing the temperature beyond this point reduces the transmittance of the material for all types of zirconia. Moreover, the optimal transmittance point is affected by the chemical composition of each type of zirconia. In addition, the results showed that the transmittance of all types of zirconia had an inverse relationship with the density, zirconia Zpex-Smile being the most sensitive to this parameter. Furthermore, the transmittance of 3Y-SBE, Zpex, and Zpex-4 decreases approximately linearly with the specimen thickness, whereas zirconia Zpex-Smile has a sublinear decrease, which is expected due to the optical isotropy of the cubic phase. View Full-Text
Keywords: zirconia; transmittance; translucency; prosthetic dentistry zirconia; transmittance; translucency; prosthetic dentistry
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Fonseca, Y.R.; Elias, C.N.; Monteiro, S.N.; dos Santos, H.E.S.; dos Santos, C. Modeling of the Influence of Chemical Composition, Sintering Temperature, Density, and Thickness in the Light Transmittance of Four Zirconia Dental Prostheses. Materials 2019, 12, 2529.

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