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Nanostructured Ceramics for Health
Published in Debasish Sarkar, Nanostructured Ceramics, 2018
In recent years, 3Y-TZP ceramics has gained importance as restorative materials due to its good mechanical and tribological properties. Mechanical properties include high strength and toughness with good biocompatibility and esthetic properties are major concern for the development of dental ceramics. 3Y-TZP is less stable to spontaneous t → m transformation in presence of micron grain matrix, where in fact the smaller grain size (<0.2 µm) restricts the spontaneous transformation rate and improves high toughness and mechanical properties [8,9]. Guazzato et al. demonstrate that equiaxed (0.2–0.5 µm) sintered 3Y-TZP has a better microstructure and enhanced mechanical properties for bioimplant applications [10]. In convention, the hardness is inversely proportional to grain size, but fracture toughness depends on transformation toughening phenomenon of grain size, which is mostly controlled by yttria content or sintering atmosphere. Thus, integration of these properties favors the development of zirconia bioceramics with having nanostructured matrix and tetragonal phase.
Sintering behavior and mechanical properties of machinable zirconia/mica composites
Published in Journal of Asian Ceramic Societies, 2019
Seiichi Taruta, Issei Yamaguchi, Tomohiko Yamakami, Tomohiro Yamaguchi
Zirconia ceramics, particularly tetragonal zirconia polycrystalline (TZP) stabilized with 3 mol% yttria, have excellent mechanical properties (i.e. high strength, fracture toughness and wear resistance), chemical durability, biocompatibility and aesthetics [1–14]. They are therefore the most promising materials for metal-free dental restorations; however, they also have some issues. Low-temperature degradation (LTD), or “aging”, is well-known as the main issue for the long-term reliability of zirconia ceramics [5–7,9,11,12,14–18]. Aging is the slow transformation of zirconia crystals from the tetragonal phase to the much more stable monoclinic phase in the absence of mechanical stress. This causes surface roughening and micro-cracking [5,7,17] and exposes zirconia-based dental restorations to the risk of spontaneous catastrophic failure [10,11]. Zirconia-based dental restorations with layers of ceramic veneer added to improve their translucency or aesthetics increase the risk of chipping because of the compatibility of zirconia and ceramic veneers [1,2,4,5,8,9,11,12,14,18]. In order to provide higher restorative quality, a highly precise occlusal fit (i.e. high dimensional accuracy) is required [7,12,13]. As one of the issues to zirconia-based dental restorations, however, zirconia ceramics have much lower machinability, which is regarded as a key mechanical property for precise fitting [7,12], although the precision of zirconia-based dental restorations is dependent on various factors [12,13].
Study on grinding of pre-sintered zirconia using diamond wheel
Published in Materials and Manufacturing Processes, 2018
P. Suya Prem Anand, N. Arunachalam, L. Vijayaraghavan
Zirconia has been predominantly used in the current years due to its excellent material properties as compared to other ceramic materials. It has been used in the structural applications such as manufacturing industry, biocompatible implants (Y-TZP), automotive components, and refractories.[1,2] To meet these structural demands, zirconia-based ceramic is added with yttrium oxide to attain high strength and fracture toughness. The oxide that has been added to pure zirconia controls the stress developed during the phase transformation, which arrests the crack propagation (transformation toughening) and simultaneously retains the hardness.[3] This transformation toughening mechanism enhances the strength of these materials compared to other ceramics due to its high degree of crack resistance.[4,5]
Fracture load of colored and non-colored high translucent zirconia three-unit fixed dental prosthesis frameworks
Published in Acta Biomaterialia Odontologica Scandinavica, 2018
Deyar Jallal Hadi Mahmood, Michael Braian, Abdul-Salam Khan, Armin Shabaz, Christel Larsson
Yttrium-oxide stabilized tetragonal zirconia polycrystals (Y-TZP), often referred to as zirconia, is considered a reliable material for dental restorations such as crowns and fixed dental prostheses (FDPs) [1,2]. The unique transformation toughening properties of Y-TZP give the material excellent mechanical properties, and it was introduced as a stronger and tougher material compared to previous ceramic alternatives [3]. Zirconia has not been used as long as the gold standard, metal ceramics, so there is not yet enough data for long-term comparisons, but several trials present predictable and comparable five-year survival results [1,2,4]. Despite the excellent mechanical properties of zirconia as a core material, superficial chip-off fractures in the veneering porcelain have been reported as a common issue and it is the primary reason for clinical failure of veneered zirconia [1,2,4]. With recent material developments, such as improved translucency and coloring options, there is a possibility today, to make monolithic zirconia restorations without the need for veneering porcelain to cover its previous original opaque, white appearance [5–7]. With monolithic restorations, the risk of veneer fractures is eliminated.