Development of Translucent Zirconia for Dental Crown Applications (original) (raw)
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Research Square (Research Square), 2021
Translucent zirconia represents a favourite material for monolithic ceramic dental restorations. However, materials approaches employed so far to improve the translucency of zirconia ceramics are accompanied by a significant decline in strength. Thus, we aimed to develop dental 3Y-TZP ceramics that can provide excellent strength and, simultaneously, enhanced translucency. In this investigation, machinable tetragonal zirconia ceramics based on fine mesostructured zirconia particles stabilized with 3 mol% of yttria and prepared by the gelcasting processing method were developed. Properties of sintered samples were characterised, namely: shrinkage, density, structure, surface roughness, hardness, biaxial strength, and total forward transmittance. Zirconia ceramics with an average biaxial strength of 1184 MPa and a total forward transmittance of 46.7% for a 0.5 mm thick sample at a wavelength of 600 nm were obtained. These ceramics exhibited homogeneous structure with grains sizes up to 620 nm and purely tetragonal phase composition. The developed ceramics provided a favourable combination of high translucency comparable even with the mixed cubic/tetragonal structure of a common 4Y-TZP, and very high strength that is achievable only in the pure tetragonal 3Y-TZP.
Jurnal Teknologi, 2016
This study aims to investigate the effect of sintering temperature on the translucency of yttria-stabilized zirconia (YSZ) for dental crown applications. YSZ suspension was treated by colloidal processing and 24 h of sedimentation to eliminate agglomerates and aggregates. The green bodies of YSZ were then shaped into pellets through slip casting. These bodies were sintered into a final shape at 1450 degrees C-1650 degrees C. The densities of the specimens were measured using Archimedes method. Light transmission of the YSZ specimen was also evaluated using a spectrophotometer with an integrating sphere. Morphological analysis was conducted with field-emission scanning electron microscopy. Results showed that sintering temperature significantly influenced the density, light transmission, and microstructure of YSZ. High sintering temperatures produced YSZ with a compact and homogeneous microstructure and a high density. Furthermore, the low light scattering effect on the porosity-free microstructure yielded light transmission as high as 37% in YSZ sintered at 1650 degrees C. The optimal sintering temperature was found to be 1600 degrees C, at which 34% light transmission was generated. In conclusion, high sintering temperatures improved the translucency of YSZ. This effect was attributed to effective densification of grains and elimination of pores at high temperatures, thereby alleviating the light scattering effect of the pores. At the optimal temperature, YSZ with high density and translucency and a compact microstructure was formed.
Ceramics International, 2018
The achievement of a high esthetic value in polycrystalline yttria-stabilized tetragonal zirconia (Y-TZP)-based dental restorations is hindered by the low translucency of Y-TZP. Thus, this study investigated the effects of processing method and sintering temperature on the translucency of Y-TZP for dental applications. Wet (slip casting) and dry (cold isostatic pressing) processing methods were used. Y-TZP specimens were fabricated by applying the processing methods and sintering at different temperatures (1450-1650°C). The mechanical, morphological, and optical properties of the Y-TZP specimens were examined and compared. The specimens were benchmarked with a commercial Y-TZP, namely, Cercon ©. Results showed that wet processing produced higher mechanical properties and translucency than dry processing. This finding can be mainly attributed to the higher capability of wet processing than dry processing in alleviating the agglomeration in Y-TZP. Among the several specimens that were tested, the slip-casted Y-TZP that was sintered at 1600°C showed the optimum mechanical properties (99.5% density and 12.7 GPa hardness) and translucency (35% light transmission) for dental applications. Furthermore, the light transmission achieved in this study was approximately three times higher than that of the commercial Y-TZP (13%), thereby indicating a potential alternative to replace the commercial Y-TZP. Highly translucent Y-TZP with excellent mechanical properties was developed in this study through wet processing with a sintering temperature of 1600°C. The developed Y-TZP can be an alternative to commercial products to produce a highly esthetic dental restoration.
World Academy of Science, Engineering and Technology, International Journal of Medical, Health, Biomedical, Bioengineering and Pharmaceutical Engineering, 2017
The ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) has been used as a dental biomaterial for several decades. The strength and toughness of this material can be accounted for by its toughening mechanisms, which include transformation toughening, crack deflection, zone shielding, contact shielding, and crack bridging. Prevention of crack propagation is of critical importance in high-fatigue situations, such as those encountered in mastication and para-function. However, the poor translucence of Y-TZP in polycrystalline form is such that it may not meet the aesthetic requirements due to its white/grey appearance. To improve the optical properties of Y-TZP, more detailed study of the optical properties is required; in particular, precise evaluation of the refractive index, absorption coefficient, and scattering coefficient are necessary. The measurement of the optical parameters has been based on the assumption that light scattered from biological media is isotropically distributed over all angles. In fact, the optical behavior of real biological materials depends on the angular scattering of light due to the anisotropic nature of the materials. The purpose of the present work is to evaluate the optical properties (including color, opacity/translucence, scattering, and fluorescence) of zirconia dental ceramics and their control through modification of the chemical composition, phase composition, and surface microstructure.
Sintering Strategies for Dental Zirconia Ceramics: Slow Versus Rapid.
Purpose of Review Advances in zirconia ceramics have expanded their application in dentistry, necessitating faster delivery of zirconia-based restorations. With the introduction of high translucency grades of zirconia ceramics, the rapid sintering strategies that aim to reduce processing times can have a central impact on clinically relevant properties. The present review has surveyed the available literature evaluating the properties of rapidly sintered dental zirconia ceramics. Recent Findings Recent studies emphasize the evolution of sintering protocols for zirconia ceramics, especially highlighting differences between conventional sintering (CS) and rapid methods like speed (SS) and high-speed sintering (HSS). These modern rapid sintering techniques transform the microstructure of zirconia ceramics, impacting its translucency, flexural strength, and aging resistance. These properties exhibit variability based on zirconia type and chosen sintering process, with HSS showing particular promise. Summary Rapid sintering protocols offer efficient alternatives to traditional zirconia ceramic processing, with benefits in cost and time. Despite the recent findings, discrepancies persist within zirconia generations, calling for further standardization and investigation.
ZIRCONIA-BASED CERAMICS FOR DENTAL APPLICATIONS
4th INTERNATIONAL CONGRESS OF MULTIDISCIPLINARY STUDIES IN MEDICAL SCIENCES, 2022
Dental ceramics have excellent aesthetic quality and reproduce the appearance of natural teeth. In addition, they are biocompatible, chemically stable, have high hardness, good fracture toughness, excellent wear resistance, and long-term color stability. There are several ceramic materials available for applications in dental prostheses, and fracture toughness is the most critical property. Zirconia stabilized with yttria (3Y-TZP) stands out due to its better fracture toughness than all available ceramics for dental prostheses application. The increase in zirconia toughness is due to the tetragonal to monoclinic phase transformation induced by stress. The transformation is accompanied by a 4-5% volume increase, resulting in compressive stresses. The compressive stresses around the monoclinic ZrO2 grains reduce the tensile stress field ahead in the crack tip and decrease or eventually stop crack propagation. However, zirconia may undergo hydrothermal degradation named “low-temperature degradation” (LTD) in the presence of water. LTD is a phenomenon of slow aging that starts on the surface of the material when in contact with water, and that induces a change in the metastable crystalline structure of zirconia. Various characteristics of the oral environment such as mechanical stress, temperature, and humidity improve LTD. Another physical property of zirconia that highlights its use in dentistry is translucency. This optical property places it among the most suitable materials for aesthetic prostheses. In the present work, the main properties of 3Y-TZP zirconia used in unitary and multiple prostheses are analyzed.
Comparative study of physical properties of zirconia based dental ceramics
The aim of this project was to evaluate and compare the mechanical properties of commercial yttria partially stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics, which have generated interest in restorative dentistry because of their high strength and high resistance to fracture. Mechanical properties of three commercial Y-TZP ceramics (Lava™, Cercon® and Invizion™) were investigated including the biaxial flexural strength, hardness, fatigue, and subcritical crack growth. Crown shaped specimens (Kavo Everest ZS-blanks with IPS e.max® Ceram and IPS e.max® Zirpress) were submitted to the fatigue followed by biaxial flexural strength test. The microstructure was analysed using AFM, and elemental analysis and fracture pattern were analysed via SEM. Additionally, stress induced ransformation toughening was studied using Vickers indentation (load 20-50 kg) and Raman spectroscopy. The phase transformation was also analysed on fracture surfaces of specimens that failed after bia...
Zirconia a Modern Ceramic Material in Dentistry - a Systematic Review
Among the dental ceramics, zirconia has emerged as a resourceful and promising material because of its biological, mechanical and optical properties, which has certainly accelerated its routine use in CAD/CAM technology for different types of prosthetic treatment. The zirconia systems currently available for use in dentistry include ceramics with a 90% or higher content zirconium dioxide, which is the yttrium, stabilized tetragonal Zirconia (Y-TZP) and glass infiltrated ceramics with 35% partially stabilized zirconia. Zirconia based restorations are quite versatile and can be used for crowns, bridges, implant abutments and fixtures and as post materials. This article reviews the unique property of zirconia and its wide application in dentistry, with more emphasis on prosthetic uses. Keywords: Zirconia, Esthetics, Restorations, Mechanical properties.
Nanostructured Zirconia-Based Ceramics and Composites in Dentistry: A State-of-the-Art Review
Nanomaterials
The objective of this paper is to review the current knowledge on the development of nanostructured zirconia-based ceramics and composites suitable for application in dentistry. Isi Web of Science, Science Direct, Scientific.net databases, and Google were searched electronically for the period of 1980 to the present, matching the keywords “nano” with the keywords: “Zirconia, ZrO2, Y-TZP, and dental, dentistry”. A total of 74 papers were found, with the majority coming from Asia, indicating a more active scientific interest on the topic in this geographic area, followed by Europe, South America, and North America. The research shows, even though the scientific activity on nanostructured ceramics was intense in the last fifteen years, the development of fully dense zirconia-based nanoceramics is yet at an initial stage, most of all from the point of view of the clinical applications. It has been demonstrated that nanostructured ceramics can show improved properties because of the redu...