Future Opportunities in Zirconia Applications in Dentistry:Functionally Graded Concept. Review (original) (raw)
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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.
Zirconia based dental ceramics: structure, mechanical properties, biocompatibility and applications
Zirconia (ZrO 2) based dental ceramics have been considered to be advantageous materials with adequate mechanical properties for the manufacturing of medical devices. Due to its very high compression strength of 2000 MPa, ZrO 2 can resist differing mechanical environments. During the crack propagation on the application of stress on the surface of ZrO 2 , a crystalline modification diminishes the propagation of cracks. In addition, zirconia's biocompatibility has been studied in vivo, leading to the observation of no adverse response upon the insertion of ZrO 2 samples into the bone or muscle. In vitro experimentation has exhibited the absence of mutations and good viability of cells cultured on this material leading to the use of ZrO 2 in the manufacturing of hip head prostheses. The mechanical properties of zirconia fixed partial dentures (FPDs) have proven to be superior to other ceramic/composite restorations and hence leading to their significant applications in implant supported rehabilitations. Recent developments were focused on the synthesis of zirconia based dental materials. More recently, zirconia has been introduced in prosthetic dentistry for the fabrication of crowns and fixed partial dentures in combination with computer aided design/computer aided manufacturing (CAD/CAM) techniques. This systematic review covers the results of past as well as recent scientific studies on the properties of zirconia based ceramics such as their specific compositions, microstructures, mechanical strength, biocompatibility and other applications in dentistry.
Modern processing technologies of all-ceramic dental crowns with various zirconia frameworks
2016
CAD/CAM (computer aided design/computer aided manufacturing) processing or zirconia frameworks and overpressing of the veneer are modern methods available to achieve all-ceramic bilayered crowns. Besides materials strength, other factors affect restorations’ clinical longevity, such as prosthesis design and technological steps. The aim of the study is to display alternative modern technologies for the fabrication of all-ceramic molar crowns with various zirconia frameworks. The individual processing procedures could cause structural flaws. The structural flaws may be located in the framework, at the veneer–core interface, at the surface, in the bulk of the veneering material, and lead to stress concentration as well as act as fracture initiation sites. An innovative modality for the improvement of all-ceramic restorations in the posterior areas might be the possibility to use glass ceramics as veneering material for zirconia cores and to adjust framework designs. Individual processi...
Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations
International Journal of Dentistry, 2013
Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out.Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests.Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers.Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the materia...
Fixed partial dentures (FPDs) can be manufactured from metal, metal-ceramic, or ceramic materials. 1 Ceramic systems can be used in FPD production in the posterior region, providing excellent esthetics, biocompatibility, and high fracture strength. 2 Yttria partially stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics have become popular with their high mechanical properties and can be veneered with feldspathic porcelain to improve esthetics. 3 However, the feldspathic porcelain is susceptible to delamination and chipping. 4,5 Therefore, monolithic zirconia restorations with altered composition and microstructure have been introduced to improve the optical properties without significantly affecting the mechanical properties, expanding their clinical indications. 6-8 Zirconia has been reported to have flexural or bending strength values between 900 and 1200 MPa and resistance to fracture values of approximately 9 to 10 MPa. 9,10 In addition, in vitro studies have indicated that monolithic zirconia crowns have sufficient fracture strength in the molar region, even if the crown thickness is reduced to 0.5 mm. 11 This minimal preparation preserves tooth tissue and increases crown retention. 12 Polished zirconia has also been reported to result in less wear on the antagonists than glazed zirconia. 13 a
The bending stress distribution in bilayered and graded zirconia-based dental ceramics
Ceramics International, 2016
The purpose of this study was to evaluate the biaxial flexural stresses in classic bilayered and in graded zirconia-feldspathic porcelain composites. A finite element method and an analytical model were used to simulate the piston-on-ring test and to predict the biaxial stress distributions across the thickness of the bilayer and graded zirconia-feldspathic porcelain discs. An axisymmetric model and a flexure formula of Hsueh et al. were used in the FEM and analytical analysis, respectively. Four porcelain thicknesses were tested in the bilayered discs. In graded discs, continuous and stepwise transitions from the bottom zirconia layer to the top porcelain layer were studied. The resulting stresses across the thickness, measured along the central axis of the disc, for the bilayered and graded discs were compared. In bilayered discs, the maximum tensile stress decreased while the stress mismatch (at the interface) increased with the porcelain layer thickness. The optimized balance between both variables is achieved for a porcelain thickness ratio in the range of 0.30-0.35. In graded discs, the highest tensile stresses were registered for porcelain rich interlayers (p=0.25) whereas the zirconia rich ones (p=8) yield the lowest tensile stresses. In addition, the maximum stresses in a graded structure can be tailored by altering compositional gradients. A decrease in maximum stresses with increasing values of p (a scaling exponent in the power law function) was observed. Our findings showed a good agreement between the analytical and simulated models, particularly in the tensile region of the disc. Graded zirconia-feldspathic porcelain composites exhibited a more favourable stress distribution relative to conventional bilayered systems. This fact can significantly impact the clinical performance of zirconiafeldspathic porcelain prostheses, namely reducing the fracture incidence of zirconia and the chipping and delamination of porcelain.
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.
Dental ceramics: a review of new materials and processing methods
Brazilian oral research, 2017
The evolution of computerized systems for the production of dental restorations associated to the development of novel microstructures for ceramic materials has caused an important change in the clinical workflow for dentists and technicians, as well as in the treatment options offered to patients. New microstructures have also been developed by the industry in order to offer ceramic and composite materials with optimized properties, i.e., good mechanical properties, appropriate wear behavior and acceptable aesthetic characteristics. The objective of this literature review is to discuss the main advantages and disadvantages of the new ceramic systems and processing methods. The manuscript is divided in five parts: I) monolithic zirconia restorations; II) multilayered dental prostheses; III) new glass-ceramics; IV) polymer infiltrated ceramics; and V) novel processing technologies. Dental ceramics and processing technologies have evolved significantly in the past ten years, with most...
Ceramics
For fixed dentures, new generations of zirconia with diverse characteristics and design choices are of significant interest. Although in vitro studies and finite element analysis (FEA) studies have been published, comprehension of various new methods of material testing and analysis remains insufficient. Young’s modulus and Poisson’s ratio of the desired materials must be available for investigators to validate FEA investigations that are accompanied by mechanical testing. The aim of this narrative review was to find recent FEA studies that report these values for newly developed commercial CAD/CAM zirconia restorative materials and compile them in a data list. A PubMed search was performed (English articles; 2018–2023; keywords: FEA, finite element, zirconia). Full-text articles (157) were examined, including studies (36) reporting the commercial materials’ names, Young’s modulus, and Poisson’s ratio. Only 21 studies had the source of their values referenced. A list of the material...
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...