الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
The purpose of this in-vitro study was to evaluate the Color stability, surface roughness and marginal integrity of endodontically treated teeth restored with CAD/CAM Ceramill® comp and Cerasmart endocrowns after two bleaching protocols (At-home and in-office) after thermo-mechanical aging.
A total of 32 mandibular first molar teeth were used in this study. The teeth were divided into two main groups according to the type of the endocrowns material used and two subgroups according to the bleaching protocol.
group 1: Endodontically treated teeth restored with Cerasmart endocrowns (16 samples).
Subgroup (a): At-Home bleaching Opalescence PF 20% (8 samples).
Subgroup (b):In-Office bleaching Opalescence Boost PF 40% (8 samples).
group 2: Endodontically treated teeth restored with Ceramill comp endocrowns (16 samples).
Subgroup (a): At-Home bleaching Opalescence PF 20% (8 samples).
Subgroup (b):In-Office bleaching Opalescence Boost PF 40% (8 samples).
Teeth were mounted in epoxy resin blocks during endocrowns preparation and during testing procedure
A specially designed centralizing device was constructed to allow accurate placement of teeth in the epoxy resin blocks.
Teeth were endodontically treated, prepared with butt joint design to receive the endocrowns restoration.
Teeth were scanned with Cerec omnicam and Cerec software was used to design the restorations. CEREC MC XL machine was used to mill all the restorations.
Samples were then sub-divided according to their bleaching protocol either at-home or in-office and cemented using RelyX ultimate clicker resin cement using a standardized loading device.
All samples were subjected to thermo-mechanical aging to simulate one year using the chewing simulator to resemble the oral cavity conditions.
After Thermocycling and mechanical fatigue, All specimens (n=32) were measured to obtain baseline data in terms of:
A) Colour using X-Rite Spectrophotometer.
B) Surface Roughness using Environmental Scanning Electron Microscope (ESEM) and Optical Stereomicroscope.
C) Vertical marginal gap using Stereomicroscope.
Bleaching procedure was then applied to all samples, each according to its subgroup.
The 3 outcomes were measured again after the bleaching procedure to determine and detect the effect of bleaching.
Then the data obtained were collected, tabulated and then subjected to statistical analysis.
The following results were obtained:
1- Regardless of the bleaching agent concentration, both CAD/CAM materials tested showed a significant increase in ΔE values above the clinically acceptable value (ΔE=3.7), color changes were perceivable by non-skilled persons and thus considered not clinically acceptable.
Afterbleaching with Carbamide peroxide, there was no statistically significant difference between the two CAD/CAM types.
After bleaching with Hydrogen peroxide, Ceramill showed statistically significantly lower mean (ΔE) than Cerasmart.
2- Concerning surface roughness, the results showed that CAD/CAM type, bleaching agent, time and the interaction between variables had no statistically significant effect on mean surface roughness (Ra). However, qualitative assessment using SEM micrographs revealed slight change in surface morphology.
3- Concerning marginal fit, both Cerasmart and Ceramill material groups recorded higher marginal gap mean values after bleaching regardless of bleaching agent type or concentration yet, they all lied within the clinically acceptable range (<120µm).