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Future Dental Journal of Egypt

Abstract

Objectives: To evaluate the effect of different surface treatments; plasma treatment, silica coating using plasma technology and sandblasting, on bond strength, surface roughness and microscopic structure of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP) after thermo-cycling. Matrials and methods: One hundred discs (n ¼ 100) of yttria-stabilized tetragonal zirconia were prepared from (Y-TZP) ceramic blocks using MAD/MAM milling technology, and were divided into four equal groups (n ¼ 25) according to the type of surface treatment. Group (1): control (no surface treatment). Group (2): zirconia discs were sandblasted by alumina particles. Group (3): zirconia discs treated by plasma technology to produce surface roughness. Group (4): zirconia discs coated by silica using plasma technology. Samples of each group were subdivided into four subgroups according to different analytical techniques. Subgroup (A): (n ¼ 10) subjected to testing of bond strength of zirconia discs to adhesive resin cement after thermo-cycling. Subgroup (B): (n ¼ 5), to evaluate the microscopic changes of zirconia discs by scanning electron microscope (SEM). Subgroup(C): (n ¼ 5) to evaluate the crystal structure and phase transformation of YZ ceramic by X-ray diffraction (XRD). Subgroup (D): (n ¼ 5) to measure three dimensional surface roughness of YZ ceramic by optical interference microscope. Results: Statistical analysis of shear bond strength by ANOVA revealed the presence of no statistically significant difference between group (3) and (4); both showed the statistically significantly highest mean shear bond strength values. Group (2) showed statistically significantly lower mean values followed by group (1). SEM showed that the topographic pattern differed by different surface treatments of samples. XRD revealed that; group (1) showed the statistically significantly highest mean % of zirconium oxide (Tetragonal phase). Group (2) showed the statistically significantly lowest mean % of Zirconium oxide (Tetragonal phase) and highest mean % of Boehmite and Zirconium oxide (Anorthic phase); Group (3) and (4) showed the statistically significantly highest mean % of Zirconium oxide (Monoclinic phase) and low % of zirconium oxide (Tetragonal phase). 3D- optical surface roughness showed that group (3) and (4) had highest mean (Ra) values. Group (2) showed statistically significantly lower mean values. Group (1) showed the statistically significantly lowest mean (Ra) values. Conclusions: (1) Surface treatments of Y-TZP ceramic together with MDP primer and silane-coupling agent application improve the bond strength to resin cement. (2) Plasma-Silica coating and plasmaoxygen treatment, both are valuable methods that improve the bond strength of resin cement to YTZP ceramic. (3) Silica coating by plasma technology provides durable bond strength and can be a promising alternative pretreatment before silane application to enhance bonding with zirconia ceramic. (4) Tetragonal-monoclinic phase transformation had occurred in Y-TZP samples received both types of plasma treatment.

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