J Adv Prosthodont.  2013 Nov;5(4):485-493. 10.4047/jap.2013.5.4.485.

Bond strength of veneer ceramic and zirconia cores with different surface modifications after microwave sintering

• Saka M
• Yuzugullu

• KMID: 2176543
• DOI: http://doi.org/10.4047/jap.2013.5.4.485

Abstract

PURPOSE
To evaluate the effects of surface treatments on shear bond strength (SBS) between microwave and conventionally sintered zirconia core/veneers.
MATERIALS AND METHODS
96 disc shaped Noritake Alliance zirconia specimens were fabricated using YenaDent CAM unit and were divided in 2 groups with respect to microwave or conventional methods (n=48/group). Surface roughness (Ra) evaluation was made with a profilometer on randomly selected microwave (n=10) and conventionally sintered (n=10) cores. Specimens were then assessed into 4 subgroups according to surface treatments applied (n=12/group). Groups for microwave (M) and conventionally (C) sintered core specimens were as follows; M(C),C(C): untreated (control group), M1,C1:Al2O3 sandblasting, M2,C2:liner, M3,C3:Al2O3 sandblasting followed by liner. Veneer ceramic was fired on zirconia cores and specimens were thermocycled (6000 cycles between 5degrees-55degrees C). All specimens were subjected to SBS test using a universal testing machine at 0.5 mm/min, failure were evaluated under an optical microscope. Data were statistically analyzed using Shapiro Wilk, Levene, Post-hoc Tukey HSD and Student's t tests, Two-Way-Variance-Analysis and One-Way-Variance-Analysis (alpha=.05).
RESULTS
Conventionally sintered specimens (1.06 +/- 0.32 microm) showed rougher surfaces compared to microwave sintered ones (0.76 +/- 0.32 microm)(P=.046), however, no correlation was found between SBS and surface roughness (r=-0.109, P=.658). The statistical comparison of the shear bond strengths of C3 and C1 group (P=.015); C(C) and M(C) group (P=.004) and C3 and M3 group presented statistically higher (P=.005) values. While adhesive failure was not seen in any of the groups, cohesive and combined patterns were seen in all groups.
CONCLUSION
Based on the results of this in-vitro study, Al2O3-sandblasting followed by liner application on conventionally sintered zirconia cores may be preferred to enhance bond strength.

Keyword

Microwave sintered zirconia; Shear bond strength; Al2O3 sandblasting; Liner; Optical microscope; Chipping

MeSH Terms

Adhesives
Ceramics*
Collodion
Fires
Methods
Microwaves*
Zirconium
Adhesives
Ceramics
Collodion
Zirconium

Figure

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  Fig. 1 Veneer ceramic fabrication using a specially designed split mold.

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  Fig. 2 Shear bond strength testing using a semicircular blade attached to the universal testing machine.

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  Fig. 3 Comparison of shear bond strength values (MPa) of specimens.

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  Fig. 4 Microstructure of (A) conventionally and (B) microwave sintered zirconia cores (×20,000).

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  Fig. 5 Scanning electron microscopy of fracture surfaces of conventionally sintered zirconia and veneer ceramic specimens (A) Combined fracture pattern, (B) Cohesive fracture pattern.

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  Fig. 6 Scanning electron microscopy of fracture surfaces of microwave sintered zirconia and veneer ceramic specimens (A) Combined fracture pattern, (B) Cohesive fracture pattern.

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