Shear Bond Strength of Zirconia All-Ceramics at the Core-Veneer Interface

Objectives:  Limited data exists regarding shear bond strength of zirconia copings and veneering porcelains in all-ceramic crown systems.  This study evaluated the strength of the bond at the core-veneer interface utilizing several contemporary zirconia and porcelain systems.

Methods:  Zirconia copings were milled using KaVo-Everest and 3M-ESPE Lava systems.  Porcelains (Lava-Ceram, Ceramco-PFZ, Nobel-Rondo, and GC-Initial Zr) were applied following manufacturer's instructions.  Ceramo-metal (Mowrey 52-SF and Jensen-Creation) and titanium (Everest-Ti and GC Initial Ti) copings served as controls.  Strength for all 10 groups (n=10) was measured with an Electroforce-3300 at 0.5 mm/min until failure.  Shear bond strength (MPa) was calculated: load(N)/area(mm²).  Data was analyzed using ANOVA and Tukey HSD, p<0.05.

Results:  Two-way ANOVA indicated significant differences for substructure and porcelain type (p<0.0001) but no significant interaction when combining both factors (p=0.1097).  The post hoc test determined significant difference for the PFM control group, with no significance among other substructures.  The test also indicated significantly higher shear bond strength for Jensen porcelain compared to all others, while Ceramco-PFZ was also significantly higher than the remaining groups.

Group	Mean Shear Bond Strength (MPa)	Group Comparisons
Gold—Jensen	21.70±8.15	A
Everest—Ceramco	14.87±4.83	B
Lava—Ceramco	14.07±4.35	B
Lava—GC Initial Zr	12.82±2.25	C
Lava—Nobel-Rondo	10.38±2.83	C
Everest—Lava-Ceram	9.44±3.21	C
Lava—Lava-Ceram	8.72±3.14	C
Everest—GC Initial Zr	8.37±2.63	C
Titanium—GC Initial Ti	7.71±3.05	C
Everest—Nobel-Rondo	7.55±2.44	C

Means with same letter not significantly different, p>0.05.

Conclusion:  Shear bond strength of all zirconia-porcelain systems tested were significantly weaker than the PFM control.  However, among zirconia substructures, Ceramco-PFZ porcelain was significantly stronger than all other porcelain types.  Further investigations regarding alternative surface treatments and cyclical loading are required.

Supported by NIH/NIDCR T32 DEO14678-05, KaVo-America, 3M-ESPE, Nobel-Biocare, Dentsply-Ceramco, and University of Iowa College of Dentistry.