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주규지,신재우,동경래,임창선,정운관,김영재 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.9
Reducing the exposure dose from a periapical X-ray machine is an important aim in dentalradiography. Although the radiation exposure dose is generally low, any radiation exposure isharmful to the human body. Therefore, this study developed a method that reduces the exposuredose significantly compared to that encountered in a normal procedure, but still produces an imagewith a similar resolution. The correlation between the image resolution and the exposure dose ofthe proposed method was examined with increasing distance between the dosimeter and the X-raytube. The results were compared with those obtained from the existing radiography method. Whenperiapical radiography was performed once according to the recommendations of the InternationalCommission on Radiological Protection (ICRP), the measured skin surface dose was low at 7 mGyor below. In contrast, the skin surface dose measured using the proposed method was only 1.57mGy, showing a five-fold reduction. These results suggest that further decreases in dose might beachieved using the proposed method.
치과 도재용착용 Ni-Cr 합금의 열처리에 따른 결합력 연구
주규지,신재우,조홍규 대한치과기공학회 2016 대한치과기공학회지 Vol.39 No.2
Purpose: This study was to evaluate the shear bond strength of ceramic fused to Ni-Cr alloy(Alophaloy) by heat treatment. Methods: The specimens were divided into 5 groups according to heat treatment conditions prior to porcelain application. Eighteen specimens from each group were subjected to the shear load a universal testing machine using a 0.1㎜/min cross-head speed and two specimens from each group were observed with SEM and EDX line profile. Results: The observation of the oxide film on the metal surface by SEM photograph showed a coarsening with an increasing degassing hold time. The diffusion of metal oxide was observed farther from the opaque layer in the heat treated specimen than no heat treated specimen. The shear bond strength measured highest to A5(55.23MPa) in the 10min holding group and measured lowest from A1(24.38MPa) in the no heat treated group, and there was a significant difference(p<0.05). Conclusion: The shear bond strength of Ni-Cr alloy improved in the heat treatment compared to the no heat treatment specimen.
치과주조용 Ti-Zr-(Cu)계 합금의 경도 및 미세조직
주규지 대한치과기공학회 2005 대한치과기공학회지 Vol.27 No.1
Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded SiO2 investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature phase and low temperature phase and also the inclusion of the eutectoid structure( Ti+Ti2Cu). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti- 13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.
인산염계 SiO2 주형재와 치과주조용 Ti-Zr-(Cu)계 합금의 계면반응
주규지 대한치과기공학회 2005 대한치과기공학회지 Vol.27 No.1
Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. To investigate the surface reaction layers produced by the reaction with mold materials and the influence of the reaction layers on the hardness of castings, A phosphate bonded SiO2 base investment was used as mold material, and microstructure observation and hardness test were performed. The surface reaction layers of Ti-13%Zr and Ti-13%Zr-5%Cu alloys were thinner than that of CP Ti had a clearly multiple structure. A difference of the hardness between surface and inner of the Ti-13%Zr and Ti-13%Zr-5%Cu alloys became less than that of CP Ti. From the results, it was found that the Ti-Zr-(Cu) based alloys were possible to cast with SiO2 base investment without the great changes of mechanical properties of the castings.
지르코니아 세라믹의 Glass-infiltration에 의한 2축 굽힘강도에 관한 연구
주규지,정종현,송경우 대한치과기공학회 2008 대한치과기공학회지 Vol.30 No.1
This study was to evaluate the biaxial flexural strength of zirconia ceramics after glass-infiltration on zirconia core. The zirconia specimens were made with diameter-15mm, thickness-0.6mm using zirconia block which divided into 1) sintered group, 2) heat - treated group, 3) Glass - infiltrated group and experimented fracture strength by each 10 specimens in experimental group. The biaxial flexural test was performed at crosshead speed of 0.1ßÆ min. The experiment result average fracture strength was shown 541.0ßÁ in sintered group and glass-infiltrated group as 662.2ßÁ river of 22.4% rise appear. Weibull coefficient sintered group is 3.462 and glass-infiltrated group improved believability about fracture strength from melting permeation processing of glass by 4.716.
치과 도재용착용 Ni-Cr 합금의 열처리에 따른 결합력 연구
주규지,신재우,조홍규 대한치과기공학회 2016 대한치과기공학회지 Vol.38 No.2
Purpose: This study was to evaluate the shear bond strength of ceramic fused to Ni-Cr alloy(Alophaloy) by heat treatment. Methods: The specimens were divided into 5 groups according to heat treatment conditions prior to porcelain application. Eighteen specimens from each group were subjected to the shear load a universal testing machine using a 0.1㎜/min cross-head speed and two specimens from each group were observed with SEM and EDX line profile. Results: The observation of the oxide film on the metal surface by SEM photograph showed a coarsening with an increasing degassing hold time. The diffusion of metal oxide was observed farther from the opaque layer in the heat treated specimen than no heat treated specimen. The shear bond strength measured highest to A5(55.23MPa) in the 10min holding group and measured lowest from A1(24.38MPa) in the no heat treated group, and there was a significant difference(p<0.05). Conclusion: The shear bond strength of Ni-Cr alloy improved in the heat treatment compared to the no heat treatment specimen.
Fracture of Self-Expandable Metal Stent during Endoscopic Removal in Benign Biliary Stricture
주규래,백창렬,정우철,이강문,양진모 대한소화기내시경학회 2013 Clinical Endoscopy Vol.46 No.1
The endoscopic insertion of the self-expandable metal stent (SEMS) in benign biliary stricture has become an alternative to surgery. Fracture or migration of SEMS can occur rarely as complications. We report a case of fracture of SEMS during endoscopic retrieval in patients with chronic pancreatitis. In this case, broken stent was successfully removed with endoscopic ballooning of bile duct and with a snare device.
저온열화에 따른 치과용 지르코니아의 전자현미경 관찰 연구
이정환,주규지,안재석,Lee, Jung-Hwan,Joo, Kyu-Ji,Ahn, Jae-Seok 대한치과기공학회 2011 대한치과기공학회지 Vol.33 No.1
Purpose: Thy yttria tetragonal zirconia polycrystalline(Y-TZP) is a good structural ceramic for dental restoration. But it have a problem that delamination of veneering ceramic from the Y-TZP core materials. The problem generally occur at the interface, thus this study was conducted to evaluate the interface of Y-TZP using scanning electron microscopy(SEM). Methods: To investigate this aspect, high-resolution SEM observations were made of polished and etched (HF content gel) cross-sections of the interface area. Dry and moist veneering porcelain powders were built up on the zirconia base. Results: The extent of this surface faceting is dependent upon the moisture content of the porcelain powder and the firing temperature. More moisture and higher final heating temperature accelerates the observed faceting of the Y-TZP grains at the interface to the veneering ceramic. Conclusion: These changes of the Y-TZP grains indicate that destabilization of the tetragonal phase of zirconia occurs at the interface during veneering with ceramic. It may result in a reduction of the stability of the zirconia and interface.