국소의치 부연결장치의 주조방법에 따른 결함특성

Abstract

Co-Cr and Ni-Cr alloys have been used for partial denture frameworks. These alloys are required for high tensile strength and a good corrosion resistance in the mouth atmosphere. Corrosion resistance depend on casting defects, casting methode and casting alloy composition of casting alloys. Eespecially casting defects of partial denture frameworks are mainly shrinkage porosity, inclusions, micro-crack, particles from investment and dendritic structure. In order to investigate defect characteristics of minor connector for partial denture. Three casting alloys (PDS : 63Co - 27Cr - 5.5Mo, Ticonium : 63Ni-16Cr, Wironit : 63Co - 30Cr- 5Mo) were prepared for fabricating partial denture frameworks with various casting methods : centrifugal casting(Kerr,USA), high frequency induction casting(Jelenko Eagle,USA), vacuum pressure casting(Bego,Germany). The casting temperature was 1380℃ (PDS and Ticonium) and 1420℃(Wironit). The casting morphologies were analyzed using FE-SEM, EDX, and OM. The detection of casting defects was carried out using radiographic tester(Smart2000E, Denmark) with various exposure time, tube current(4.5㎃) and voltage(80Kvp). These results are as follows : 1. Dendritic structure showed in the case of PDS and Wironit alloy, and Columnar structure appeared in Ticonium alloy. 2. The α-Co and ε-Co phase formed in the matrix of PDS and Wironit alloy. The Ni2Cr phase found in the matrix of Ticonium alloy. 3. Hardness and fracture strength values of PDS and Wironit alloy showed higher than that of Ticonium alloy. Therefore hardness and fracture strength were improved in the order of centrifugal casting, high frequency induction casting, and vacuum pressure casting method. It was concluded that the defects of minor connector for partial denture were improved in the order of centrifugal casting, high frequency induction casting, and vacuum pressure casting method.