الفهرس | Only 14 pages are availabe for public view |
Abstract The introduction of yttrium partially stabilized tetragonal zirconia polycrystal (Y-TZP) to the dental field opened the design and application limits of all-ceramic restorations with greater confidence and success rates. With its superior mechanical properties, three or four-unit fixed partial dentures (FPDs) are no longer the safe limit for the construction of core veneered all ceramic restorations. Establishing a strong and stable bond with Zirconia has proven to be difficult, as the material is acid resistant and does not respond to common etching and silanation procedures used with other glass containing ceramic materials which react to silane coupling agents. As Zirconia is relatively opaque and monochromatic in colour, a layer of veneering ceramic is built on to provide the restoration with the required esthetics. Low-temperature degradation (LTD) has been associated with several 3Y-TZP-based biomaterials. The bond between veneering ceramic and Zirconia framework is currently the subject of comprehensive investigations. Thus the purpose of this study is to investigate the effect of a new method of surface treatment of Zirconia on its bond strength with the ceramic veneering ceramics with different veneering techniques and with and without s-LTD aging. A total of 144 microbars were prepared. Each 36 have received a different surface treatment namely: no treatment (control), Air Abrasion with 110μm aluminum oxide particles (Al2O3), Silica infiltration with silicate compound and heat, and acid etch with a mixed solution of HF and HNO3.Then each 36 were further divided into three groups each 12 received different veneering technique Layering, Sintering CAD on technique and Adhering CAD on technique. Then each 12 microbar were divided into two groups were one group didn’t receive any treatment and the other groups were aged using s-LTD aging in an autoclave at 134ºC for 6 hours. The bars were attached to a specially designed attachment and tested in the universal testing machine (LLOYD). The load required for fracture of each specimen was recorded in MPa. Data were presented as mean and standard deviation (SD) values, a regression model using threeway Analysis of Variance (ANOVA) was used in testing significance for the effect of surface treatment, veneering technique, aging and their interactions on mean micro-tensile bond strength. Tukey’s post-hoc test was used for pair-wise comparison between the groups when ANOVA test is significant. Fractured microbars viewed under digital microscope with magnification 40X and type of failure was specified recorded as number and percentage in each subgroup. The results of this study revealed that that surface treatment, veneering technique, aging and the interaction between the three variables had a statistically significant effect on mean micro-tensile bond strength. Air abrasion showed statistically significant same mean micro-tensile bond strength as that of Control, Silica infiltration higher than control whereas acid etched lower than control. Sintering CAD-on showed statistically significant higher mean micro-tensile bond strength than both Layering and Adhering CAD-on veneering technique. Aging showed statistically significant higher mean micro-tensile bond strength than Without Aging. |