J Adv Prosthodont.  2013 Feb;5(1):36-43. 10.4047/jap.2013.5.1.36.

Comparison of two fracture toughness testing methods using a glass-infiltrated and a zirconia dental ceramic

• Triwatana
• Srinuan P
• Suputtamongkol K

• KMID: 2284770
• DOI: http://doi.org/10.4047/jap.2013.5.1.36

Abstract

PURPOSE
The objective of this study was to compare the fracture toughness (KIc) obtained from the single edge V-notched beam (SEVNB) and the fractographic analysis (FTA) of a glass-infiltrated and a zirconia ceramic.
MATERIALS AND METHODS
For each material, ten bar-shaped specimens were prepared for the SEVNB method (3 mm x 4 mm x 25 mm) and the FTA method (2 mm x 4 mm x 25 mm). The starter V-notch was prepared as the fracture initiating flaw for the SEVNB method. A Vickers indentation load of 49 N was used to create a controlled surface flaw on each FTA specimen. All specimens were loaded to fracture using a universal testing machine at a crosshead speed of 0.5-1 mm/min. The independent-samples t-test was used for the statistical analysis of the KIc values at alpha=0.05.
RESULTS
The mean KIc of zirconia ceramic obtained from SEVNB method (5.4 +/- 1.6 MPa.m1/2) was comparable to that obtained from FTA method (6.3 +/- 1.6 MPa.m1/2). The mean KIc of glass-infiltrated ceramic obtained from SEVNB method (4.1 +/- 0.6 MPa.m1/2) was significantly lower than that obtained from FTA method (5.1 +/- 0.7 MPa.m1/2).
CONCLUSION
The mean KIc of the glass-infiltrated and zirconia ceramics obtained from the SEVNB method were lower than those obtained from FTA method even they were not significantly different for the zirconia material. The differences in the KIc values could be a result of the differences in the characteristics of fracture initiating flaws of these two methods.

Keyword

Fracture toughness; Dental ceramics; Zirconia

MeSH Terms

Ceramics
Collodion
Zirconium
Ceramics
Collodion
Zirconium

Figure

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  Fig. 1 A: The special plaster mold filled with the slip mixture ready for sintering, B: Specimens after firing (upper) and after glass infiltrated (lower).

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  Fig. 2 The schematic diagram of the depth of V-notch measured on the fracture surface of a SEVNB specimen.12

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  Fig. 3 Schematic diagram of the critical flaw size: a the crack depth; 2b the crack width.16

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  Fig. 4 The microstructural features of the zirconia-based at magnification of 10,000× (A), and glass-infiltrated dental ceramic at magnification of 1,200× (B).

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  Fig. 5 The V-notch prepared on zirconia-based (A) and glass-infiltrated (B) dental ceramics in SEVNB at magnification of 50×.

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  Fig. 6 The uniform V-notch on the fracture surface of zirconia-based (A) and glass-infiltrated (B) dental ceramics obtained from the SEVNB method (black arrow) at magnification of 30×.

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  Fig. 7 A Vickers indentation with corner cracks on the surface of a Y-TZP specimen (A). A semicircular crack caused from a Vickers indentation and observed on the fracture surface on a Y-TZP specimen (B). The white arrow indicated the Vickers indentation.

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  Fig. 8 The semicircular crack on the fracture surface of Y-TZP (A) and ICZ (B) specimens at 160× magnification. The crack size was outlined by the black arrows.

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