الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 103 |  |  |
| | | from | 103 | | |
Abstract
The purpose of this study was to evaluate the effect of different surface treatments om microtensile bond strength and color stability hybrid ceramic repaired with composite .
Fifty samples were prepared from commercially available nano ceramic hybrid CAD /CAM blocks (Grandio blocs) using precision cutting diamond saw to form two types of samples : group I, micro bars for micro tensile bond strength testing (twenty five microbars) and grouop II, slices for color stability testing (twenty five slices). Then specimens from each group were divided to five sub-groups(five specimens each) according to the surface treatment used: first subgroup: diamond bur abrasion, second subgroup diamond and silane:, third subgroup: sandblasting, forth subgroup: sandblasting+ silane and fifth subgroup: silane coupling agent.
Dual cure resin cement was applied to the specimens , then composite was built up and photoactivated to form ceramic-composite complex. Specimens from each subgroup were subjected to 5000 cycles inside the thermocycling machine.
The microbars was subjected to microtensile bond strength test using universal testing machine (5ST, Tunius Olsen, England).
Reflective spectrophtometer (X-Rite,model RM200QC ,Neu-Isenburg, Germany) was used to determine the color of the ceramic-composite slices specimens in CIELAB system. The color changes ΔE of the specimens were calculated using the following formula: he average values were calculated.
ΔE*=[(L*1−L*0)2+(a*1−a*0)2+(b*1−b*0)2]1/2.
Color measurmrents were made before surface treatments, after surface treatments and composite repair, and after thermocycling.
Data were collected, tubulated and statistically analyzed with the following conclusion:
Within the limitations of this study, it was found that; -
1- Surface treatment with sandblasting and silane application increased the microtensile bond strength significally.
2- Surface treatment with diamond bur had good color stability.
3- Silane application without surface treatment decreased the microtensile bond strength and color stability .
4- addition to color parameters and composition of ceramics, their surface treatment also affected the optical properties of restorations
5- Thermocycling affected the color stability negatively.