Abstract
Introduction: The Y-TZP zirconia used for prosthetic infrastructure, in some clinical situations, can be exposed to the oral environment. In these situations, a polished surface without changes is extremely important. Objective: The aim of this study was to evaluate the mean roughness (Ra) and Vickers hardness of Y-TZP zirconia (Lava™) after simulating ten years of brushing. Material and method: Thirty-six Y-TZP bar-shaped specimens (20mm X 4mm X 1.2mm) were divided into three groups: storage in distilled water (DW, n=12, control); brushing with distilled water (BDW, n=12) and brushing with distilled water and fluoride toothpaste (BFT, n=12). Brushing was performed using a brushing machine with a soft-bristled toothbrush, simulating 10 years of brushing (878.400 cycles, 100gf). The mean roughness (Ra in μm) and Vickers hardness (VHN) of all specimens were measured twice: before and after the experimental treatment, in profilometer and microhardness tester (500gf, 30 seconds), respectively. Data were analyzed using the two-way ANOVA test (α = 0.05). Result: The interaction between groups was not significant for roughness (p = 0.701) nor for hardness (p = 0.928). The final averages for Ra (μm) were equal to: DW - 0.63; BDW - 0.64; and, BFT - 0.68. The final averages for Vickers hardness (VHN) were: DW - 1301.16; BDW - 1316.60; and, BFT - 1299.58. Conclusion: It was concluded that the brushing with distilled or fluoridated toothpaste was not able to change the roughness and hardness of Y-TZP zirconia used in this study.
Highlights
The Y-TZP zirconia used for prosthetic infrastructure, in some clinical situations, can be exposed to the oral environment
Y-TZP zirconia has been used as the framework of all-ceramic crowns and fixed partial dentures, implants, abutments and brackets[2,3,4]
Various authors have designed studies of the surface roughness and hardness of Y-TZP zirconia[5,7,8,9,10,11,12,20]. These studies have attracted attention because of the degradation process to which zirconia is subject when exposed to the oral environment and, in particular, when it is without veneering porcelain
Summary
The Y-TZP zirconia used for prosthetic infrastructure, in some clinical situations, can be exposed to the oral environment. Objective: The aim of this study was to evaluate the mean roughness (Ra) and Vickers hardness of Y-TZP zirconia (LavaTM) after simulating ten years of brushing. Conclusion: It was concluded that the brushing with distilled or fluoridated toothpaste was not able to change the roughness and hardness of Y-TZP zirconia used in this study. Zirconia is a polymorph material that occurs in three phases: monoclinic (M) (from room temperature up to 1170°C), tetragonal (T) (1170°C to 2370°C) and cubic (C) (above 2370°C)[1,2]. It exhibits better performance in the tetragonal form[3]. Studart et al.[4] demonstrated that Y-TZP zirconia is considered the most suitable material to resist high stress on posterior all-ceramic bridges, being suitable for the manufacture of frameworks having up to five elements
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