Microstructural and crystallographic surface changes after grinding zirconia‐based dental ceramics

Abstract

The purpose of this study was to evaluate microstructural and crystallographic phase changes after grinding 3Y-TZP dental ceramics. Ceramic blanks were sintered according to manufacturer's recommendations and divided into four groups: (A) as-sintered control, (B) diamond-ground manually under water, (C) ground and polished, and (D) ground and annealed at 1000 degrees C for 1 h. Bulk specimens were analyzed by X-ray diffraction to characterize the crystalline phases. The microstructure was investigated by SEM. XRD analyses showed that the control group and the group that was ground and annealed contained only tetragonal zirconia. However, after grinding or after grinding followed by polishing, rhombohedral zirconia and strained tetragonal zirconia were present, without any detectable amount of monoclinic zirconia. Annealing led to the disappearance of both residual lattice strain and the rhombohedral phase. The microstructure of the ground and polished specimens was characterized by significant residual surface damage associated with grain pullout to a depth of about 20 microm. This type of damage could have an impact on the long-term fatigue behavior of 3Y-TZP.

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

“…However, other studies 38) have verified that grinding without irrigation would favor the zirconia through a reverse phase transformation (m→t), due to the localized generated heat, and that the t phase could increase the flexural resistance of the zirconia 28) . In this study it was observed that grinding, irrespectively of DG or WG, promoted a reverse phase transformation (m→t) when compared with the control group, with WG group being responsible for the greater transformation of monoclinic grains into tetragonal (Tables 1 and 2). SEM images (Figs.…”

“…X-ray diffraction has been often used to quantify the crystalline zirconia phases; however some inconsistent results regarding the peaks of tetragonal, cubic and monoclinic phases have been continuously referred and compared among papers [26][27][28][29] . In this study, the presintered specimens showed tetragonal and monoclinic phases in an amount allowed by the ISO 13356 30) .…”

“…In this study, the presintered specimens showed tetragonal and monoclinic phases in an amount allowed by the ISO 13356 30) . After sintering, the tetragonal phase was the main crystalline phase, but cubic phase was also identified 27,28) . Its formation could be explained due to the temperature and sintering cycle used (1,500 o C for 8 h) that favors its formation.…”

“…However, this phase is not always reported, mostly because of the overlap of the main planes of the cubic phase in relation to tetragonal 28) . The main peak of the cubic phase plane (111) at 30.11º (2θ) overlaps with the (011) at 30.22º (2θ) of the tetragonal phase; thus it is not possible to distinguish them depending on the instrumental broadening of the equipment.…”

Experimental investigation on the surface and subsurface damages characteristics and formation mechanisms in ultra-precision grinding of SiC

“…As a consequence, tremendous efforts have been made to investigate material removal mechanism and the corresponding surface and subsurface damages during grinding of difficult-to-machine material such as alumina [8], silicon nitride [9][10][11][12], zirconia [13], glasses [14,15], and particulate reinforced titanium matrix composites [16,17]. Specific to silicon carbide ceramics, Agarwal et al [18] conducted a high machining rate grinding experiments to study the surface/ subsurface damage formation and material removal mechanism.…”