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RISS 인기검색어
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- 저자 : H. Ralph Rawls (검색결과 3 건)
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치과용 갈륨합금의 조성변화가 부식 및 기계적특성에 미치는 영향
박영준,이용렬,이도재,Norling, Berry K,Rawls, H Ralph 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.2
This study was performed to evaluate the effects of compositional variations of dental gallium alloys on their corrosion and mechanical behaviors. 60Ag-28Sn-12Cu wt% (ST group) was prepare by atomization. ST-Pd and ST-Pt groups were prepared by substituting part of tin (Sn) with Pd (2 wt%) and Pt (0.05 wt%), respectively. Low-and high-copper amalgam alloys (LCA and HCA) were also prepared by atomization method for comparison. Alloy powders of each group were mixed with liquid gallium alloy that was composed of 61.98Ga-24.99In-12.98Sn-0.05Bi wt%. Specimens were made according to ADA specification no. 1. Corrosion behavior was evaluated by potentiodynamic anodic polarization test together with X-ray diffractometry (XRD), and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). 24 hour-compressive strengths and dimensional changes were measured. Following results were obtained. ST-Pd group showed most anodic behavior with the corrosion potential (E□) of-707 mV (vs. SCE), which is a significant shift in the noble direction from the -883 mV(vs.SCE) of the ST group (p<0.05). Among the specimens of St-Pd group, one specimen even had an E□ of -580 mV showing pronounced improvement in corrosion resistance. LCA group showed the worst corrosion resistance, having E□ of -896 mV. Set specimens had multi-phase microstructures consisting of Ag9In4, CuGa₂, □-Sn, Ag□₂Ga₂□, AG₄Sn and Cu3Sn, and all the groups showed similar XRD patterns. Ag9In4 was the main reaction matrix phase showing strongest XRD peak. CuGa2 phase surrounded the unreacted powder particles. A mixture of light Ag9In4 phase and a dark gray Ga42.3-Cu17.1-Ag16.8-Bi0.2 wt% solid solution appeared in the intergranular layer. ST-Pd group required the shortest mixing time. The intensity of the Ag4Sn peak of unreacted powder was lower and peak intensity of Ag□Ga₂□ phase, which is more corrosion resistant, was higher when compared to that of ST group. Sn(Cu)-Cl corrosion products having various morphologies were formed on corroded specimen surfaces. ST-Pd group had lesser deposition of corrosion product compared to other groups. LCA group specimens corroded more than HCA group specimens. 27-hour ST-Pd group showed highest value compared to those of other groups (p<0.05). HCA group showed higher compressive strength compared to that of LCA group. 24-hour setting expansions were ST-Pd*****(0.24%)<<LCH(0.43%)<ST-Pt(0.51%) <ST(0.56%)<<HCA(1.33). ST-Pd group showed significantly lower setting expansion (p<0.014). HCA group having 28 wt% Cu in alloy powder showed 1.33% setting expansion value which is significantly higher than those of other groups (p<0.01). In summary, substituting 2 wt% palladium for 2 wt% tin in the alloy powder improved the corrosion resistance and compressive strength, and reduced the degree of setting expansion. High-copper content induced excessive setting expansion. This finding indicates that there is still room for further improvement of the corrosion resistance and mechanical properties of dental gallium alloys through composition modification. With furher research, there is still a possibility for gallium alloy to become a successful substitute for dental amalgam.
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