J Adv Prosthodont.  2014 Jun;6(3):151-156. 10.4047/jap.2014.6.3.151.

Tensile strength of bilayered ceramics and corresponding glass veneers

• Anunmana C
• Champirat
• Jirajariyavej B

• KMID: 2118224
• DOI: http://doi.org/10.4047/jap.2014.6.3.151

Abstract

PURPOSE
To investigate the microtensile bond strength between two all-ceramic systems; lithium disilicate glass ceramic and zirconia core ceramics bonded with their corresponding glass veneers.
MATERIALS AND METHODS
Blocks of core ceramics (IPS e.max(R) Press and Lava(TM) Frame) were fabricated and veneered with their corresponding glass veneers. The bilayered blocks were cut into microbars; 8 mm in length and 1 mm2 in cross-sectional area (n = 30/group). Additionally, monolithic microbars of these two veneers (IPS e.max(R) Ceram and Lava(TM) Ceram; n = 30/group) were also prepared. The obtained microbars were tested in tension until fracture, and the fracture surfaces of the microbars were examined with fluorescent black light and scanning electron microscope (SEM) to identify the mode of failure. One-way ANOVA and the Dunnett's T3 test were performed to determine significant differences of the mean microtensile bond strength at a significance level of 0.05.
RESULTS
The mean microtensile bond strength of IPS e.max(R) Press/IPS e.max(R) Ceram (43.40 +/- 5.51 MPa) was significantly greater than that of Lava(TM) Frame/Lava(TM) Ceram (31.71 +/- 7.03 MPa)(P<.001). Fluorescent black light and SEM analysis showed that most of the tested microbars failed cohesively in the veneer layer. Furthermore, the bond strength of Lava(TM) Frame/Lava(TM) Ceram was comparable to the tensile strength of monolithic glass veneer of Lava(TM) Ceram, while the bond strength of bilayered IPS e.max(R) Press/IPS e.max(R) Ceram was significantly greater than tensile strength of monolithic IPS e.max(R) Ceram.
CONCLUSION
Because fracture site occurred mostly in the glass veneer and most failures were away from the interfacial zone, microtensile bond test may not be a suitable test for bonding integrity. Fracture mechanics approach such as fracture toughness of the interface may be more appropriate to represent the bonding quality between two materials.

Keyword

Zirconia; Lithium disilicate; Microtensile; Glass-ceramic; Bond strength; Ceramic

MeSH Terms

Ceramics*
Glass*
Lithium
Mechanics
Tensile Strength*
Ceramics
Lithium

Figure

• 

  Fig. 1 Schematics of fractured microbar of IPS e.max® Press/ IPS e.max® Ceram under fluorescent black light shows difference in appearance between the core and veneering materials. The veneer appears brighter (right), whereas the core is darker. The failure pattern is classified as cohesive failure.

• 

  Fig. 2 Schematics of fractured microbar of Lava™ Frame/ Lava™ Ceram under fluorescent black light shows similar appearance as IPS e.max® microbars. Zirconia cores appear darker (left), and failure modes are classified as (A) cohesive failure (B) interfacial failure.

• 

  Fig. 3 SEM micrographs of fracture surface of Lava™ Frame/ Lava™ Ceram. The fracture pattern is classified as interfacial, which was found less than 10% of the tested specimens as the fracture originated in the zirconia core material at the interfacial zone. (A) the surface of veneer with exposed core material (arrows) at core side (at 85x magnification), (B) veneer side (at 90x magnification).

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