Abstract
This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) dental ceramics: two conventional (Lava Frame and IPS ZirCad) and one with high-translucency (Lava Plus). Plates obtained from sintered blocks of each ceramic were divided into four groups: AS (as-sintered); 30 (air-abrasion with 30 mm Si-coated Al2O3 particles); 50 (air-abrasion with 50 mm Al2O3 particles) and 150 (air-abrasion with 150 mm Al2O3 particles). After the treatments, the plates were submitted to X-ray diffractometry; 3-D profilometry and SEM/EDS. The AS surfaces were composed of Zr and t phases. All treatments produced t®m phase transformation in the ceramics. The diameter of air-abrasion particles influenced the roughness (150>50>30>AS) and the topography. SEM analysis showed that the three treatments produced groove-shaped microretentions on the ceramic surfaces, which increased with the diameter of air-abrasion particles. EDS showed a decrease in Zr content along with the emergence of O and Al elements after air-abrasion. Presence of Si was also detected on the plates air-abraded with 30 mm Si-coated Al2O3 particles. It was concluded that irrespective of the type and diameter of the particles, air-abrasion produced t®m phase transformation, increased the roughness and changed the elemental composition of the three Y-TZP dental ceramics. Lava Plus also behaved similarly to the conventional Y-TZP ceramics, indicating that this high translucency ceramic could be more suitable to build monolithic ceramic restorations in the aesthetic restorative dentistry field.
Highlights
Due to their excellent mechanical properties, Y-TZP dental ceramics are among the most widely used framework materials in the field of restorative dentistry
In addition to the mechanical properties, the favorable optical behavior allows this ceramic material to be used as a framework for all types of ceramic restorations, e.g., total crowns, onlays and fixed prosthodontic appliances as well
Y-TZP dental ceramics are composed by a metastable tetragonal phase (t), retained at room temperature by careful control of grain size (
Summary
Due to their excellent mechanical properties, Y-TZP dental ceramics are among the most widely used framework materials in the field of restorative dentistry. A tetragonal-monoclinic (t→m) phase transformation takes place at the crack tips under applied stresses, which is accompanied by a volume expansion of about 3–5% [2] This stress-induced t→m phase transformation leads to the development of internal compressive stresses that oppose crack propagation, creating a toughening mechanism that increases the crack propagation strength of the material [3,4]. The absence of silica in their structure renders Y-TZP ceramic materials not susceptible to hydrofluoric acid etching To overcome this limitation, approaches such as air-abrasion, treatment with gas plasma, silica coating, use of phosphate monomers and fusing glass beads have been suggested to modify the Y-TZP ceramic surfaces in order to achieve strong and reliable bond strengths with the resin cements [5,6]
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