Abstract
Various oxides are used to stabilize zirconium oxide (ZrO2), but their superior hardness causes wear of the machining tool. Calcia-doped zirconia has been studied but reports on properties suitable for dental application are lacking. Therefore, this study aimed to fabricate and characterize zirconia stabilized by calcium oxide (CaO) derived from cockle shells and compare it with zirconia stabilized by commercial CaO, sintered at different temperatures. In this study, 176 pressed pellets of zirconia mixed with CaO either derived from cockle shells or commercial CaO were sintered between 1200 and 1500 °C to produce calcia-doped zirconia. Characterizations were made with SEM and XRD. Specimens were subjected to density, compressive and flexural strength, and Vickers hardness testing. Data were analyzed using the independent t-test and one-way ANOVA. XRD revealed the zirconia was stabilized into tetragonal and cubic phases (Ca-SZ). Ca-SZ cockle shells (CS) and Ca-SZ commercial (CC) have average particle sizes of 267 nm and 272 nm, respectively, with similar surface roughness. At 1400 °C sintering temperature, flexural strengths were 1165 and 1152 MPa, compressive strengths were 4914 and 4913 MPa, and Vickers hardness were 977 and 960 MPa for Ca-SZ(CS) and Ca-SZ(CC), respectively. Both Ca-SZ materials showed no significant difference in most properties (p < 0.05) when sintered at different temperatures. The fully sintered Ca-SZ is less hard compared to the ceria-stabilized tetragonal zirconia polycrystal (Ce-TZP) available on the market. Thus, Ca-SZ may be used as an alternative to the current zirconia available on the market for dental application.
Highlights
Zirconia-based ceramics have been used as dental implants [1] in addition to framework underneath the brittle veneering porcelain in the fabrication of fixed dental prostheses, such asAppl
The zirconia was successfully stabilized with nano-calcium oxide (CaO) derived from cockle shells and from commercial source into tetragonal and cubic phases
The zirconia was successfully stabilized with nano-CaO derived from cockle shells and from commercial source into tetragonal and cubic phase (Ca-SZ) using a physical mixing technique
Summary
Zirconia-based ceramics have been used as dental implants [1] in addition to framework underneath the brittle veneering porcelain in the fabrication of fixed dental prostheses, such asAppl. Zirconia-based ceramics have been used as dental implants [1] in addition to framework underneath the brittle veneering porcelain in the fabrication of fixed dental prostheses, such as. Sci. 2020, 10, 5751 crowns and bridges [2]. As the aesthetic properties of zirconia-based ceramics improve, they have been used to construct the whole crown and bridge works in combination with computer-aided design/computer-aided manufacturing (CAD/CAM) [3]. Pure zirconia has three polymorphic forms at atmospheric pressure: monoclinic from room temperature until 1170 ◦ C, tetragonal (1170–2370 ◦ C) and cubic (2370–2680 ◦ C) [4]. Pure zirconia encounters a setback whereby upon cooling of the polymorphs, large volume change occurs, which would result in the cracking of the brittle products. The zirconia crystals in their tetragonal or cubic shape at room temperature remain stable. Zirconia-containing ceramic systems currently used in dentistry are yttrium cation-doped tetragonal zirconium polycrystals (3Y-TZP), magnesium cation-doped partially stabilized zirconium (Mg-PSZ), zirconium-toughened alumina (ZTA) and ceria-stabilized zirconia-alumia (CeTZP/A) [3,7,8]
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