Y-TZP zirconia regeneration firing: Microstructural and crystallographic changes after grinding

Abstract

This study evaluated microstructural and crystallographic phase changes after grinding (G) and regeneration firing/anneling (R) of Y-TZP ceramics. Thirty five bars (Lava TM and Ice Zirkon) were divided: Y-TZP pre-sintered, control (C), regeneration firing (R), dry grinding (DG), dry grinding+regeneration firing (DGR), wet grinding (WG) and wet grinding+regeneration firing (WGR). Grinding was conducted using a diamond bur and annealing at 1,000°C. The microstructure was analyzed by SEM and the crystalline phases by X-ray diffraction (XRD). XRD showed that pre-sintered specimens contained tetragonal and monoclinic phases, while groups C and R showed tetragonal, cubic and monoclinic phases. After grinding, the cubic phase was eliminated in all groups. Annealing (DGR and WGR) resulted in only tetragonal phase. SEM showed semi-circular cracks after grinding and homogenization of particles after annealing. After grinding, surfaces show tetragonal and monoclinic phases and R can be assumed to be necessary prior to porcelain layering when grinding is performed.

The impact of laser scanning on zirconia coating and shear bond strength using veneer ceramic material

“…This property of zirconia provided satisfactory SBS values without showing phase transformation from t-m. However, other studies have reported phase transformation from t-m during grinding and sandblasting 31,32) . The conflicting results may be contributed to the different methodologies followed by the present and previous studies.…”

Toughening of highly translucent zirconia by monoclinic ZrO₂ and SiO₂ particle coating

“…In general, it is known that temperatures above 1,000°C are sufficient for grazing of zirconia ceramics (850-950°C 18) ). This glazing also contributes to the re-crystallization of zirconia surface 19,20) . Thus, our hypothesis was that adjustment of the glazing (coating) material can improve the mechanical properties of PSZ through the re-crystallization process.…”

Efeito de diferentes protocolos de desgaste nas características superficiais e comportamento mecânico da zircônia (Y-TZP)

“…Alguns autores têm relatado que o desgaste pode causar transformação da fase tetragonal para fase monoclínica (Ho et al, 2009;Karakoca & Yilmaz, 2009;Maerten et al, 2013;Subasi et al, 2014;Gungor et al, 2015;Coldea et al, 2015;Lee et al, 2016;Ramos et al, 2016;Pereira et al, 2016A;Pereira et al, 2016B;Hatanaka et al, 2016;Ryan et al, 2017;Guilardi et al, 2017), enquanto outros não observam a presença desta fase após o desgaste (Kosmac, 2004;Denry & Holloway, 2006;Curtis et al, 2006;Amaral et al, 2013;Strasberg et al, 2014;Chun et al, 2017).…”

“…A presença de conteúdo cristalino na fase cúbica foi identificado por alguns autores quando a temperatura de sinterização foi de 1400°C a 1600°C (Scott, 1975;Ruiz & Readey, 1996;Matsui et al, 2003;Chevalier et al, 2004;Polli et al, 2016;Ryan et al, 2017) e após o desgaste (Curtis et al, 2006) devido ao estresse gerado durante este procedimento (Hasegawa et al, 1985). Entretanto, a presença desta fase não é muito relatada na literatura, porque pode haver sobreposição entre os planos da fase cúbica em relação a tetragonal, dificultando sua identificação (Denry & Holloway, 2006).…”

“…As propriedades da zircônia podem ser modificadas na presença desta fase, pois são altamente influenciadas pelo volume das fases cristalinas e a fase cúbica possui duas vezes o volume da fase tetragonal (Ryan et al, 2017). Como consequência da presença desta fase, pode haver má distribuição dos íons de ítrio (Matsui et al, 2003;Chevalier et al, 2004) e a zircônia pode ficar mais susceptível ao processo de degradação à baixas temperaturas (Chevalier et al, 2004).…”