الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The new cubic ultra-translucent (UT) zirconia was introduced IN 2015. It can be used in laminate veneers and ultra-thin laminate veneers, construction of single crown, three unit fixed partial denture, onlays and screw retained superstructure on implant. The flexural strength of UT zirconia is 550 MPa.
Resin bonding to Zirconia ceramic is challenging. Unlike Glass ceramics hydrofluoric acid etching and silanization techniques have been ineffective for zirconia- resin bonding. Zirconia is a polycrystalline structure devoid of any glass component and therefore they are categorized as non etchable ceramics.
This study was conducted to investigate the effect of adhesive promoter type (Zirconia primer and universal bonding agent), resin cement type (conventional and phosphate containing resin cement) on bond strength of ultra-translucent zirconia to resin cement.
42 Ultra translucent zirconia plates with dimensions (10mm width×5mm length×2mm thickness) were prepared from slicing Bruxizer anterior block using a diamond disc fixed on Isomet 4000microsaw. The discs were finished by using silicon carbide paper400 grit. All the samples were sintered in the sintering machine.
All the samples were sandblasted by 50 µm .alumina particles with pressure 2.5bar at 10cm distance from the surface for 20seconds at 90º.
The samples were divided into 3 main groups according to primer type. Each main group was subdivided into 2 subgroups according to resin cement type.
One sample from each group was examined for the surface topography before bonding to resin cement. This was done using scanning electron microscope and elemental surface composition examination through the energy dispersive X ray (EDX).
Small transparent polyvinyl tubes (catheter) with diameter 4mm, 3mm height and 2mm thickness were cut and placed in the center of all samples and bonded to zirconia plates using a bonding agent and cured with light emitting diode of high intensity for 10seconds.
For the samples which received Z-PRIME PLUS, it was added in 2 coats with applying air free oil/water syringe for10seconds for each coat. Then the resin cement was added as before and according to group sampling.
For the samples which received (ALL BOND UNIVERSAL) ,it was added in 2 coats as the first coat was added and then air free oil/ water syringe was used for 10seconds and the second coat was applied and light cured for 10seconds. Then the resin cement was added as before and according to group sampling.
For all groups half of the samples were bonded to conventional composite resin cement (DUO LINK). The other half of the samples were bonded phosphate containing resin cement (TheraCem).The resin cement was added through the tube by its dispensing tip till filling of the tube. The excess cement was removed by a microbrush. Then the resin cement was light cured for 20seconds.
A pencil was used to draw a circle around each tube to define the area of bonding at the microscopic examination after shear bond strength test.
Using a sharp scalpel blade number15 the tubes were cut and removed to get a resin cement cylinder.
All the samples were stored in a special closed container containing distilled water at 37 ºc for 1 week in incubator.
Each zirconia plate with its resin cylinder was fixed to the lower compartment of a universal testing machine by screws with 5KN load and data were taken down by computer software.
A compression mode of force at a cross head speed of 0.5mm/min was applied to all the samples up to failure using a universal testing machine.
The loads were changed to MPa dividing maximum failure load (N) by the bonding area (mm2) .ALL the samples were investigated to arbitrate the mode of failure by using a digital microscope.
The results of this study showed that: the SEM of the surface of sandblasted ultra-translucent zirconia with alumina particles revealed a highly rough surface with irregularities was detected. The shape of crystals changed due to phase transformation. For the surface of sandblasted zirconia coated with Z –PRIME: wider black spaces are shown the shape of crystals are not defined. For the surface of zirconia coated with universal bonding agent: tiny pores were detected with fine black lines.
The EDX analysis showed: for the untreated surface the highest peak was detected for zirconia element also low peak for oxygen and carbon elements. For sandblasted ultra-translucent zirconia a peak of alumina was noticed after sandblasting with alumina. For sandblasted zirconia coated with Z –PRIME a peak of phosphate and carbon were noticed after application of Z-PRIME. For zirconia coated with universal bonding agent a peak of carbon, oxygen and phosphorus were detected.
Z-PRIME with conventional composite resin cement represented higher statistically significant shear bond strength value (19.58 Mpa) than no applied primer with phosphate containing resin cement on sandblasted sintered zirconia. (15.88MPa).
Z-PRIME with phosphate containing resin cement represented higher statistically significant shear bond strength value (15.36 MPa) than no applied primer with conventional composite resin cement on sandblasted sintered zirconia.(14.53 MPa)
ALL BOND UNIVERSAL with phosphate containing resin cement represented higher statistically significant shear bond strength value (12.56 MPa) than applied ALL BOND UNIVERSAL with conventional composite resin cement on sandblasted sintered zirconia.(11.98 MPa).
Z-PRIME with conventional composite resin cement represented the highest statistically significant shear bond strength value (19.58 MPa) of all the remaining groups.
After deboning the images of digital microscope revealed that the mode of failure in the control group was adhesive as there was not any resin remnant left on the zirconia disc. For the samples coated with z-prime, universal bonding with both (DUO LINK) resin cement and (TheraCem) resin cement showed a mixed failure as the surface is partially covered with the resin cement.