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금속-도재관의 제작에 이용되는 치과용 저융도재의 이축굽힘강도 평가
소정모,최운재 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.2
This study was performed to evaluate the biaxial flexure strength of dental metal-bonding porcelains. Three kinds of commercially available low-fusing porcelains of Ceramco (CC), Vintage (VT) and Omega 900 (ON) and three kinds of ultra low-fusing porcelains of Carmen (CM), Carrara (CR) and finess (FN) were selected as experimental materials. Disc specimens were prepared to the final dimensions of 12㎜ in diameter and 1㎜ in thickness. Specimens were polished sequentially from #800 to #2000 emery papers, and the final surface finishing on the tensile side was received an additional polishing sequence through 0.3㎛ alumina paste. The biaxial flexure test was conducted using the ball-on-three-ball method at a crosshead speed of 0.5mm/min. The highest Weibull modulus value of 17.5 was observed in the VT group and the lowest value of 8.7 was observed in the ON group. However, the highest characteristic strength value of 107.0 MPa was observed in the ON group and the lowest value of 54.1 MPa was observed in the CM group. The highest biaxial flexure strength value of 101.4 MPa was obtained in the ON group and the lowest value of 54.1 MPa was obtained in the CM group. Results of Tukey test showed that an overall significant difference was indicated except the CM and CR and the FN and VT groups (p<0.05). The fracture surfaces showed that the cracks were propagated into the conical shape from the maximum tensile stress region. The higher the fracture strength values are, the rougher the fracture surface becomes. There was no significant relation between strength and porosity in fracture surfaces.
치과보철물 제작시 Sprue 부착 형태가 주조성에 미치는 영향
최운재,소정모,Choi, Un-Jea,So, Jung-Mo 대한치과기공학회 2002 대한치과기공학회지 Vol.23 No.2
The purpose of this study was to evaluate the influence of sprue joint form on castability in dental prosthetics. The researcher carried out experimental study according to the type was divided by sprue joint form. Therefore type A was made thicken than sprue diameter of type B and type C was made it conversely. The results were as follows: 1. In the order of castability, type C(87.8%) was first and then type A(87.0%) and type B(79.2%) was last. However there was no significant difference statistically. 2. If reservior was located at the correct position and in sufficient size, internal shrinkage porosity in the casting bodies were not generated in the type of all. 3. At the reservoir, internal shrinkage porosity was generated first in type A, followed by type Band type C in the order named. Although it gives no impact on casting body, porosity seems to appear the least when it's produced in the form of type C.
김동환,배태성,소정모 대한치과기재학회 2001 대한치과재료학회지 Vol.28 No.2
This study was performed to evaluate the effect of aging in water at 37℃ on the toothbrush abrasion of compomers. One resin-modified glass-ionomer material of Improved Fuji Ⅱ LC(FL) and three compomers of Compoglass(CG), Dyract AP(DR) and F2000(FT) were used. Sector form specimens were fabricated with split teflon mold having the inner and outer diameter of 10㎜ and 30㎜, respectively. Sample paste was filled in teflon mold and a mylar strip was placed on the surface to remove the excess material by pressing glass plate. The tip of the activator light was placed on the upper surface of the specimen, which was cured for 40 seconds. All samples were divided into two groups and they were immersed in distilled water at 37℃ for 10 and 100 days. Specimens were polished sequentially with 400 to 2,000 emery paper using a rotary grinder under water spray, and the final surface finishing was achieved with a 1□m diamond paste. Toothbrush abrasion test was conducted under a load of 2.0N and the abraded surfaces were examined with profilometer(Form Talysurf, Rank Taylor Hobson Co, England) and SEM(X-650, Hitachi Co, Japan) after 50,000 cycles. The abrasion resistance of resin-modified glass-ionomer material, Improved Fuji Ⅱ LC, was statistically lower than that of compomers (p<0.05). A significant decrease in abrasion resistance occurred in the 100 day-aged groups (p<0.01). SEM observation of compomers (p<0.05). A significant decrease in abrasion resistance because of the protrusion and missing of filler particles due to the selective removal of matrix resin. It was found that in vitrc resistance to toothbrush-dentifrice abrasion of compomers was accelerated with aging in water.