Abstract
This in vitro study aims to synthesize a glass-ceramic reinforced by yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP) and to characterize it structurally, physically and mechanically, comparing with two commercially available glass ceramics: lithium disilicate (IPS e.max CAD®, Ivoclar Vivadent, Leichstein) and zirconium oxide reinforced lithium silicate (Celtra Duo®, Dentsply). For this purpose, a nanoscaled Y-TZP powder will be obtained and mixed with a Tetraethylorthosilicate (TEOS) additive in the proportion 30/70 vol%, added to solvent, binder and deflocculant. In a previously lubricated metallic device with the dimensions proposed by ISO 6872 (4mm width X 2mm thickness X 14mm length), 5g of the mixture will be inserted and subjected to cold uniaxial pressing at 80 MPa. Then blocks for CAD/CAM C14 HTA1 IPS e.max CAD® and Celtra Duo® will be cut with diamond disc (245 rpm, under refrigeration) in bars of 4mm width X 2mm thickness X 14mm length. The groups will be composed by 10 bars of each material, being VEY (experimental glass-ceramic enhanced with Y-TZP nanoparticles), VCD (glass-ceramic Celtra Duo®) and VMAX (glass-ceramic IPS e.max CAD®). Initially, these bars will be submitted to evaluation of their optical properties on white and black backgrounds, which will allow the calculation of the material's contrast ratio and translucency parameter. Afterwards, these same bars will be subjected to 3-point bending test using a metal device under a 5000 N load cell at a constant speed of 0.5 mm/min attached to an Emic DL 500 universal testing machine and with the aid of an automation program Tesc® 2.0. The qualitative fractographic analysis of the fractured specimens will be performed using a DinoLite AM313T digital stereomicroscope, where 5 specimens from each group will be submitted to scanning electron microscopy (SEM) analysis. The obtained data will be organized and, if they present normal distribution, will be submitted to ANOVA and complemented with Tukey test; If there is a non-normal distribution, will be submitted to Kruskal-Wallis and Dunn non-parametric tests. For all cases, the level of significance will be set at 5% (p <0.05%). (AU)
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