Improvement of marginal integrity around Titanium Alloy and Yttrium-Stabilized Zirconia dental implant abutments
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Objectives : The aim of this in vitro study was to evaluate the effect of cleaning protocols on gingival fibroblasts' viability and attachment around surrogate abutments of Titanium Alloy (Ti6Al4V) and Yttrium-Stabilized Zirconia (e-Max ZirCAD) specimens. Methods : The specimens (10x25x2 mm each) were divided into three groups (n=5/group). The groups were  finished and polished followed by ultrasonic cleaning in water for 5 minutes,  finished and polished followed by ultrasonic cleaning in 95% isopropanol for 5 minutes, and  finished and polished, followed by ultrasonic cleaning in 95% isopropanol for 5 minutes, then subjected to radio-frequency glow discharge treatment (RFGDT) for 3 minutes. Representative specimens' surfaces were characterized at each preparative step by critical surface tension (CST) determination, multiple attenuated internal reflection infrared spectroscopy (MAIR-IR), scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDS), and profilometry. Tissue culture polystyrene was the comparative and control surface. After cell culture with gingival fibroblasts, MTT tests were done to determine viability of cells attached to the specimens (2 materials, 3 test groups each, polystyrene controls). Light microscopy was used to inspect for cell shapes, densities and degrees of spreading on the test specimens faces, and in the culture well bottoms adjacent to removed test specimens. Results : Data showed the higher surface energy RFGDT Titanium Alloy specimens were superior to the water-cleaned and alcohol-cleaned specimens in terms of having higher MTT activity per gingival fibroblast cell. It was found that more spreading of the cells on the GDT Titanium Alloy specimens occurred than on the water-cleaned specimens. For Yttrium-Stabilized Zirconia specimens, there were not statistically significant differences among the three different cleaning protocols, in terms of MTT activity per attached gingival fibroblast cell or cell spreading. Conclusion : It is concluded that the examined cleaning protocols (water-cleaning, alcohol-cleaning, and RFGDT) do differently affect the Titanium Alloy specimens, but they do not so strongly influence the Zirconia. The best results from the present study provide support for the hypothesis that glow-discharge-treatment can stimulate cellular activity and cell spreading. The glow-discharge-process is quick, inexpensive and easy to manipulate. Therefore, it is suggested that the plasma glow-discharge-treatment may operate as an effective clinical technique for cleaning and beneficially increasing the surface energies of Titanium Alloy dental implant abutments before use in the oral cavity. Pilot clinical trials are recommended.