Effect of Different Surface Treatments on the Bond Strength of Lithium Disilicate Ceramic to the Zirconia Core.
OBJECTIVE
The aim of this study was to evaluate the effect of different surface treatments [sandblasting, Erbium:Yttrium-Aluminium-Garnet (Er:YAG), and femtosecond lasers] on the shear bond strength (SBS) of the CAD-on technique.


BACKGROUND
Although demand for all-ceramic restorations has increased, chipping remains one of the major problems for zirconia-based restorations.


METHODS
Forty yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) zirconia plates (IPS e.max ZirCAD, Ivoclar Vivadent) were cut, sintered (12.4 × 11.4 × 3 mm) and divided into four groups according to the surface treatments (n = 10): a control group with no surface treatment (Group C), sandblasting with 50 μm Al2O3 (Group S), Er:YAG laser irradiation (Group E), and femtosecond laser irradiation (Group F). Also, 40 cylindrical (5 mm diameter, 2 mm height) lithium disilicate (IPS e.max CAD) veneer ceramics were cut and fused to all zirconia cores by a glass-fusion ceramic and crystallized according to the CAD-on technique. Specimens were subjected to shear force using a universal testing machine. The load was applied at a crosshead speed of 0.5 mm/min until failure. Mean SBS (MPa) were analyzed with one way ANOVA (p < 0.05). The failed specimens were examined under a stereomicroscope at ×20 to classify the mode of failure.


RESULTS
The highest SBS was observed in Group F (36 ± 3.31 MPa), followed by Group S (33.03 ± 5.05 MPa), and Group C (32.52 ± 10.15 MPa). The lowest SBS was observed in Group E (31.02 ± 4.96 MPa), but no significant differences were found between the control and surface treated groups (p = 0.377). All the specimens showed a mixed type of failure.


CONCLUSIONS
Femtosecond laser application increased the bond strength between zirconia-veneer specimens. However, the novel CAD-on technique with no surface treatment also showed high bonding strength. Thus, this technique could prevent ceramic chipping without additional surface treatments.
1 Faculty of Dentistry, Department of Prosthodontics, Selcuk University , Konya, Turkey .
Tuba
T
Yilmaz-Savas
1 Faculty of Dentistry, Department of Prosthodontics, Selcuk University , Konya, Turkey .
Necla
N
Demir
1 Faculty of Dentistry, Department of Prosthodontics, Selcuk University , Konya, Turkey .
A Nilgun
AN
Ozturk
2 Faculty of Science, Department of Physics, Selcuk University , Konya, Turkey .
Hamdi Sukur
HS
Kilic
D020906:Air Abrasion, Dental; D002516:Ceramics / Q000737:chemistry*; D001840:Dental Bonding; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D006801:Humans; D053844:Lasers, Solid-State; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D033081:Shear Strength; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry*
C493120:lithia disilicate; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide