Published online Jul 31, 2009.
https://doi.org/10.4047/jkap.2009.47.3.312
A study on the shear bond strengths of veneering ceramics to the colored zirconia core
Abstract
Statement of problem
Delamination of veneering porcelain from underlying ceramic substructures has been reported for zirconia-ceramic restorations. Colored zirconia cores for esthetics have been reported that their bond strength with veneered porcelain is weaker compared to white zirconia cores.
Purpose
This study aimed to investigate the shear bond strength by manufacturing the veneering porcelain on the colored zirconia core, using the layering technique and heat-pressing technique, and to evaluate the clinical stability by comparing the result of this with that of conventional metal ceramic system.
Material and methods
A Metal ceramic (MC) system was tested as a control group. The tested systems were Katana zirconia with CZR (ZB) and Katana Zirconia with NobelRondo Press (ZP). Thirty specimens, 10 for each system and control, were fabricated. Specimen disks, 3 mm high and 12 mm diameter, were fabricated with the lost-wax technique (MC) and the CAD-CAM (ZB and ZP). MC and ZB specimens were prepared using opaque and dentin veneering ceramics, veneered, 3 mm high and 2.8 mm in diameter, over the cores. ZP specimens were prepared using heat pressing ingots, 3 mm high and 2.8mm in diameter. The shear bond strength test was performed in a Shear bond test machine. Load was applied at a cross-head speed of 0.50 mm/min until failure. Mean shear bond strengths (MPa) were analyzed with the One-way ANOVA. After the shear bond test, fracture surfaces were examined by SEM.
Results
The mean shear bond strengths (SD) in MPa were MC control 29.14 (2.26); ZB 29.48 (2.30); and ZP 29.51 (2.32). The shear bond strengths of the tested systems were not significantly different (P > .05). All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.
Conclusion
1. The shear bond strengths of the tested groups were not significantly different from the control group (P > .05). 2. There was no significant different between the layering technique and the heat pressing technique in the veneering methods on the colored zirconia core. 3. All groups presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.
Fig. 1
Fabricated specimens. A: MC, B: ZB, C: ZP
Fig. 2
Shear bond test machine (Simple Tensile Tester Model No. RB312 PETI, R&B Inc., Daejeon, Korea).
Fig. 3
SEM photographs of MC group after shear bond strength test (× 20). They presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.
Fig. 4
SEM photographs of ZB group after shear bond strength test (× 20). They presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.
Fig. 5
SEM photographs of ZP group after shear bond strength test (× 20). They presented cohesive and adhesive failures, and showed predominance of cohesive failures in ceramic veneers.
Fig. 6
SEM photographs of the interfaces for A: MC, B: ZB, C: ZP after shear bond strength test (× 400).
Table I
List of materials
Table II
Firing schedule of Cerabien and CZR ceramic veneers
Table III
Firing schedule of zirconia cores
Table IV
Press program of NobelRondo Press veneer
Table V
Mean values and SDs of the shear bond strength (MPa)
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