الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The improvement of translucency of zirconia without significantly losing their fracture resistance led to increasing its indications for minimally invasive esthetic restorations, thus it is of a great interest to examine the adhesive potentials of the material by the use of shear bond strength test of UTML zirconia to enamel after performing different surface treatment modalities, with examination of their effect on the changes in the surface topography, and translucency properties, these were in-line with the clinical trial for evaluation of the clinical performance of ultra- translucent zirconia veneers.
For the in-vitro studies, thirty- six ultra-translucent zirconia discs were divided into three groups (n=12): Control: as-sintered discs, Sandblasted discs: by 110μm Al2O3 particles, for 10 sec at a pressure of 2.5 bar from a distance of 10mm, and Etched discs: by placement of UTML zirconia discs in Zircos-E etching solution for thirty minutes in ultra-sonic cleaner. Two randomly selected specimens from each group were examined for surface roughness and remaining 10 discs from each group were bonded to enamel surfaces of human central incisors for SBS test. The translucency evaluation was done for 10 rectangular ultra-translucent zirconia specimens using a reflection spectrophotometer before and after application of surface treatments. For the clinical trial, ultra-translucent zirconia anterior veneers (of 0.5mm thickness) for two central incisors of fifteen patients were treated by either sandblasting or etching and were followed up immediately after cementation and at regular follow up visits at 3, 6, 9, 12, 15 and 18 months using the modified California Dental Association (CDA)/Ryge criteria regarding the color match, zirconia surface, marginal discoloration, and marginal integrity.
Concerning the clinical trial, all veneers from both groups showed a color match with 100% score (A), and zirconia surface smoothness with 100% score (A) at the baseline evaluation and up to 18 months, while both the marginal integrity and marginal discoloration showed 100% score (A) at the baseline evaluation that was changed into (93.3% score A and 6.7% score B) for the sandblasted veneers and (86.7% score A and 13.3% score B) for the etched veneers, thus, all veneers were considered as successful after 18 months of clinical service
Concerning the shear bond strength results, the sandblasted and the etched discs specimens had a significantly higher shear bond strength results than the as-sintered disc specimens, while, there was insignificant difference between the sandblasted and etched disc specimens.
Concerning the surface examinationresults, the control specimens showed the interconnected grain structure with the lowest surface roughness, the sandblasted specimens showed a uniform existence of superficial irregularities with small surface flaws all over the examined area, while the etched specimens showed a gross discontinuity of the grain structure accompanied with different degrees of rough textures and porosities of variable depths.
Concerning the translucency parameter and contrast ratio, after performing the surface treatments, our results showed that, the TP of both the sandblasted and the etched specimens decreased with a lower TP value for the etched specimens, there was a significant difference between the two groups after performing the surface treatment and they showed also a significant different with a lower translucency for each group in comparison to its initial condition. The CR of both groups increased but there was no significant difference between both of them, while they showed a higher contrast ratio for each group in comparison to its initial condition that showed a significant difference.
Ultra- translucent zirconia could be selected for the minimally invasive aesthetic restorations using adequate surface treatments with a resultant optimal bonding and satisfactory aesthetics.