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Statement of problem Creating a rough surface for bonding with airborne-particle abrasion with alumina may damage the surface of zirconia. Other treatment methods for creating a bonding surface without causing damage require investigation. Purpose The purpose of this in vitro study was to find ways of treating the zirconia surface without causing flaws, debris, pits, microcracks, or tetragonal to monoclinic phase transformation. Material and methods Yttria-stabilized tetragonal zirconia polycrystal ( Y-TZP) ceramic surfaces were treated with gas plasma, argon-ion bombardment, 150-μm abrasive zirconia particles, and abrasive 150-μm alumina particles; untreated surfaces were used as the control group. X-ray diffraction (XRD) and confocal Raman spectroscopy were used to study the phase transformation. The roughness of specimens was measured with a confocal 3D laser scanning microscope. Modification of surface topography was analyzed with field emission scanning electron microscopy ( FESEM ), and the flexural strength was measured with a universal testing machine. Statistical analyses were performed with 1-way ANOVA, followed by comparison of means with the Tukey honest significant difference test. The standard deviation was calculated with descriptive statistics. Results The sintered Y-TZP ceramic used in this study showed 2 phases, tetragonal and cubic. Specimens abraded with 150-μm alumina particles showed a higher monoclinic volume fraction (V mXRD =8.68%) and roughness (R a =0.91μm) than specimens abraded with 150-μm zirconia particles (V mXRD =1.22%, R a =0.08μm). One-way ANOVA indicated a significance difference in roughness among groups ( P <.01). No phase transformation was observed in specimens treated with argon-ion bombardment or plasma. According to the Raman results, the volume fraction of the monoclinic phase for the specimens treated with airborne-particle abrasion depended on the distance from the ceramic surfaces and decreased with the increase in this distance. A slightly higher flexural strength was observed for untreated specimens (1009 MPa), followed by specimens treated with gas plasma (1000 MPa) and those airborne-particle abraded with 150-μm zirconia particles (967 MPa). The flexural strength of other specimens was lower (940 MPa for specimens abraded with 150-μm alumina particles and 916 MPa for specimens subjected to argon-ion bombardment). One-way ANOVA analysis indicated no significant difference in flexural strengths among all groups ( P >.2). FESEM measurements showed that airborne-particle abrading Y-TZP surfaces with 150-μm alumina particles caused more damage to this area than the other methods. Conclusions Y-TZP ceramic surfaces treated with zirconia particles, argon-ion bombardment, and gas plasma were damaged less in comparison with surfaces abraded with alumina particles. [ABSTRACT FROM AUTHOR]

Objectives Purpose of this in vitro study was to evaluate the effect of surface modifications on the tensile bond strength between zirconia ceramic and resin. Methods Zirconia ceramic surfaces were treated with 150-μm abrasive alumina particles, 150-μm abrasive zirconia particles, argon-ion bombardment, gas plasma, and piranha solution (H 2 SO 4 :H 2 O 2 = 3:1). In addition, slip casting surfaces were examined. Untreated surfaces were used as the control group. Tensile bond strengths (TBS) were measured after water storage for 3 days or 150 days with additional 37,500 thermal cycling for artificial aging. Statistical analyses were performed with 1-way and 3-way ANOVA , followed by comparison of means with the Tukey HSD test. Results After storage in distilled water for three days at 37 °C, the highest mean tensile bond strengths (TBS) were observed for zirconia ceramic surfaces abraded with 150-μm abrasive alumina particles (TBS AAP = 37.3 MPa, TBS CAAP = 40.4 MPa), and 150-μm abrasive zirconia particles (TBS AZP = 34.8 MPa, TBS CAZP = 35.8 MPa). Also a high TBS was observed for specimens treated with argon-ion bombardment (TBS BAI = 37.8 MPa). After 150 days of storage, specimens abraded with 150-μm abrasive alumina particles and 150-μm abrasive zirconia particles revealed high TBS (TBS AAP = 37.6 MPa, TBS CAAP = 33.0 MPa, TBS AZP = 22.1 MPa and TBS CAZP = 22.8 MPa). A high TBS was observed also for specimens prepared with slip casting (TBS SC = 30.0 MPa). A decrease of TBS was observed for control specimens (TBS UNT = 12.5 MPa, TBS CUNT = 9.0 MPa), specimens treated with argon-ion bombardment (TBS BAI = 10.3 MPa) and gas plasma (TBS GP = 11.0 MPa). A decrease of TBS was observed also for specimens treated with piranha solution (TBS PS = 3.9 MPa, TBS CPS = 4.1 MPa). A significant difference in TBS after three days storage was observed for specimens treated with different methods ( p < 0.001). Thermal cycling significantly reduced TBS for all groups ( p < 0.001) excluding groups: AAP( p > 0.05), CAAP( p > 0.05) and SC( p > 0.05). However, the failure patterns of debonded specimens prepared with 150-μm abrasive zirconia particles were 96.7% cohesive. Conclusion Treatment of zirconia ceramic surfaces with abrasive zirconia particles is a promising method to increase the tensile bond strength without significant damage of the ceramic surface itself. An alternative promising method is slip casting. [ABSTRACT FROM AUTHOR]

Abstract: Excessive synchronisation of basal ganglia activity at frequencies &#60;30Hz is a hallmark of the parkinsonian state, and may contribute to bradykinesia. Accordingly, we electrically stimulated chronically implanted subthalamic macroelectrodes in 10 Parkinson''s disease patients, after overnight withdrawal of anti-parkinsonian medication. We compared the effects of stimulation at 0, 5, 10, 15, 20, 25, 30, and ca. 130Hz by measuring kinesia time (KT) in a tapping task. Although the effects of direct stimulation were small, frequency–response curves demonstrated local peaks at 5–10Hz and at 20–25Hz, superimposed upon an overall tendency for KT to reduce with increasing stimulation frequency. This is consistent with the hypothesis that spontaneous activities in these bands might promote bradykinesia. [Copyright &y& Elsevier]