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Title: 0872 - Additional Heat Treatment of Alumina-blasted Highly Translucent Partially Stabilized Zirconia

Authors:

Keiichi Yoshida (Presenter)
Nagasaki University Hospital

Hao Yu, Nagasaki University
Takashi Sawase, Nagasaki University

Abstract:

Objectives: This study assessed the influence of alumina-blasting and additional heat treatment on the flexural strength and crystallographic phase of highly translucent partially stabilized zirconia (PSZ, Aadva NT, GC).

Methods: High-translucency PSZ bars were milled and sintered according to the manufacturer’s recommendations. Specimens were alumina-blasted with 50 μm alumina at 0.1, 0.15, 0.2, or 0.3 MPa (AB), and a subsequent additional heat treatment at 1,000°C for 15 min (HT) was carried out. A 3-point flexural strength test was performed with the alumina-blasted surface subjected to tensile forces at a span length of 20 mm (n = 10). The crystalline phase of zirconia was analyzed by X-ray diffraction (XRD). Means ± SDs of flexural strength and crystalline phase content are listed in the table. The flexural strength data were analyzed by one-way ANOVA and the same lowercase superscript letters were not significantly different by Tukey-Kramer tests (p > 0.05).

Results: The flexural strengths of alumina-blasted zirconia at four blasting pressures were significantly lower than those of non-alumina-blasted zirconia. However, additional heat treatment of alumina-blasted specimens showed significantly higher flexural strength than that of alumina-blasted specimens at each pressure. Alumina-blasted zirconia specimens at any air pressures showed cubic, tetragonal, and rhombohedral phases by XRD. As the blasting pressure increased, the content of the rhombohedral phase also increased, in particular when the pressure was at 0.2 and 0.3 MPa. In contrast, by additional heat treatment, the rhombohedral phase disappeared to transform reversely to the original cubic phase, while the contents of cubic and tetragonal phases increased and became higher than that of alumina-blasted specimens.

Conclusions: These results suggest that additional heat treatment after alumina-blasting in highly translucent PSZ is necessary to recover the flexural strength of non-alumina-blasted specimens by approximately from 75 to 90% and to disappear the rhombohedral phase.

Table(s):

Group of Treatment Flexural Strength (MPa) Crystalline Phase Content (%)
Cubic Tetragonal Rhombohedral
None 637.5 ± 72.7f 50 45 5
0.1 MPa AB 431.6 ± 35.1b,c 50 45 5
0.1 MPa AB + HT 569.1 ± 66.0e 52 48 0
0.15 MPa AB 376.5 ± 22.2a,b 50 44 6
0.15 MPa AB + HT 514.7 ± 55.0d,e 52 48 0
0.2 MPa AB 352.6 ± 19.6a 43 38 19
0.2 MPa AB + HT 476.8 ± 44.8c,d 52 48 0
0.3 MPa AB 366.6 ± 26.6a,b 42 38 20
0.3 MPa AB + HT 479.8 ± 49.6c,d 51 49 0

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None

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