• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.415-424
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• 2013

Purpose: This study is to present a standard value for clinical crown angulation and inclination required in laboratory process and see if the value can be used for actual laboratory process. Methods: In order to find out a standard value for clinical crown angulation and inclination, this study made a study model of normal occlusion of 21 females in twenties. The clinical crown angulation and inclination of both six-maxillary and six-mandibular anterior teeth are measured by Set-up Model Checker. From the measured value above, the mean and standard deviation of the twelve teeth are obtained, and then the mean of the teeth between right and left side is calculated. Results: Each clinical crown angulation of maxillary central incisor, lateral incisor, and canine is like this; $1.0^{\circ}{\pm}1.3^{\circ}$, $3.0^{\circ}{\pm}1.3^{\circ}$, and $5.0^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.6^{\circ}{\pm}1.1^{\circ}$, $1.5^{\circ}{\pm}1.1^{\circ}$, and $4.1^{\circ}{\pm}1.1^{\circ}$. Each clinical crown inclination of maxillary central incisor, lateral incisor, and canine is like this; $6.1^{\circ}{\pm}1.8^{\circ}$, $4.5^{\circ}{\pm}1.9^{\circ}$, and $-6.2^{\circ}{\pm}1.4^{\circ}$. In case of mandibular, each degree is like this; $0.3^{\circ}{\pm}1.5^{\circ}$, $0.3^{\circ}{\pm}1.8^{\circ}$, and $-7.5^{\circ}{\pm}1.8^{\circ}$. Conclusion: As the result, the mean value for clinical crown angulation and inclination can be referred to actual laboratory process. However, the mean value is different from those of the precedent study and an unsatisfied one for adopting the standard value.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.9-17
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• 2005

The use of titanium alloys as biomaterials is increasing due to their superior biocompatibility and enhanced corrosion resistance compared to conventional stainless steels and cobalt-based alloys. Ti-6Al-4V ($\alpha+\beta$type) alloy instead of pure titanium ($\alpha$type) is being widely used as biomaterials has some characteristics such as high fatigue strength, tensile strength and corrosion resistance. But it has been reported recently that the vanadium element expresses cytotoxicity and the aluminium element is related with dementia of Alzheimer type and neurotoxicity. In order to overcome their detrimental effects, $\beta$-phase stabilizer Nb was chosen in the present study. This paper was described the influence of phase changes of Ti-Nb alloys on mechanical properties. Ti-3wt.%Nb($\alpha$type),Ti-20wt.%Nb($\alpha+\beta$type) and Ti-40wt.%Nb($\beta$type) alloys were melted by vacuum arc furnace. The specimens were homogenized at 1050$^{\circ}C$ for 24hr and were then hot rolled to 50% reduction. Each alloys were solution heat treated at $\beta$ zone and $\alpha+\beta$ zone after homogenization and then were aged. The mechanical properties of Ti alloys were analysed by hardness test, tensile test, elongation test and SEM test. The results can be summarized as follows: 1) The higher hardness value of $\alpha+\beta$type alloy was obtained compared to the, $\alpha,\beta$type alloys. 2) The aged treated showed better hardness compared to the solution heat treated, homogenized. 3) In the case of solution and aging treatment at $\beta$region, the $\alpha+\beta$type alloy showed the most highest tensile strength and $\beta$type alloy showed the best elongation.

• Journal of Technologic Dentistry
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• v.23 no.1
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• pp.9-19
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• 2001

Microstructure and phase transformation of Ti-Ni-Cu alloy powders produced by using attrition milling method were studied. Mixed powders of Ti-(50-X)Ni-XCu ($X=0{\sim}20$ at%) in composition range were mechanically alloyed for maximum 20 hours by using SUS 1/4" ball in argon atmosphere. Ball to powder ratio was 50: 1 and impeller speed was 350rpm. Mechanically alloyed with attrition millimg method. powder was heat treated at the temperature up to $850^{\circ}C$ for 1 hour in the $10^{-6}$ torr vacuum. Ti-Ni-Cu alloy powders have been fabricated by attrition milling method. and then phase transformation behaviours and microstructual properties of the alloy powders were investigated to assist in improving the the high damping capacity of Ti-Ni-Cu shape memory alloy powders. The results obtained are as follows: 1. After heat treating of fully mechanically alloyed powder at $850^{\circ}C$ for 1hour. most of the B2 and B 19' phases was formed and $TiNi_3$ were coexisted. 2. The B 19' martensite were formed in Ti-Ni-Cu alloy powders whose Cu-content is less than 5a/o. where as the B19 martensite in those whose Cu-content is more than 10at%. 3. The powders of as-milled Ti-Ni-Cu alloys whose Cu-contents is less than 5at% are amorphous. whereas those of as-milled Ti-Ni-Cu alloys whose Cu-content is more than 10at% are crystalline. This means that Cu addition tends to suppress amorphization of Ti-Ni alloy powders.

• Journal of Technologic Dentistry
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• v.36 no.4
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• pp.247-253
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• 2014

Purpose: The aim of this study was to evaluate the effect of colored zirconia with different coloring liquids. Methods: Total 30 specimens were prepared. Specimens were classified into 6 groups: IPS e.max Ceram(P), Uncolored zirconia(C), VITA In-Ceram$^{(R)}$2000 YZ LL1(L), Zirkonzahn coloring liquid(Z), Wieland coloring liquid(W), and Kuwotech coloring liquid(K). Four different types of zirconia coloring liquid, VITA In-Ceram$^{(R)}$ 2000 YZ LL1(VITA Zahnfabrik, Germany), Zirkonzahn coloring liquid(Zirkonzahn, Italy), Wieland coloring liquid(Wieland, Germany), Kuwotech coloring liquid(Kuwotech, Korea) were used to fabricate colored zirconia by using infiltrating method and then completely sintered. The color of the all specimens was measured using the spectrophotometer(CM-2600d, Konica Minolta, Japan) and expressed in terms of the 3-coordinated values(CIE $L^*a^*b^*$). Color differences were calculated using the equation $${\Delta}E^*=[({\Delta}L^*)^2+({\Delta}a^*)^2+({\Delta}b^*)^2]^{1/2}$$. Results: $L^*a^*b^*$ values of the colored zirconia were affected by the coloring liquids. The uncolored zirconia(C) group showed the highest $L^*$ value and zirkonzahn coloring liquid(Z) group showed the lowest $L^*$ value. Zirkonzahn coloring liquid(Z) showed the highest $a^*$ value and VITA In-Ceram 2000 YZ LL1(L) group showed the highest $b^*$ value. Generally, the color difference(${\Delta}E^*$) in all groups showed higher than 3.7 except between IPS e.max Ceram(P) and wieland coloring liquid(W) group. Conclusion: Within the limitations of this study, various coloring liquids influenced the $L^*$, $a^*$, and $b^*$ values of colored zirconia. IPS e.max Ceram(P) and wieland coloring liquid(W) group did not show clinically perceiving color difference.

• The Journal of the Convergence on Culture Technology
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• v.4 no.4
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• pp.181-186
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• 2018

The purpose of this study is to provide students with basic information about the stress of the national examination and the stress of the students who have difficulties in school life and the development of counseling and education program for satisfactory academic life. The survey of the 213 students of dental hygiene departments in Chungcheong, Gyungsang region was carried out. As a result of SPSS 3.0 analysis, the index of happiness Satisfaction was the highest points. Happiness index showed statistically significant difference in gender, personality, friendship, academic achievement, pocket money satisfaction, and health status. There was statistically significant difference between the major and the major in satisfaction, personality, friendship, motivation, and power status, and happiness index and major satisfaction were statistically significant.

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.129-134
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• 2012

Purpose: This study was conducted to investigate the colors of zirconia and veneered ceramics according to the build-up method of veneer porcelain. Methods: The samples were divided into three groups: a group for which a liner was applied to the zirconia surface and dentine coating was built up and burned (Cz1), a group for which the dentine coating was directly built up and burned (Cz2), and a group for which the samples were wash-burned with dentine coating and a dentine coating was built up and burned again (Cz3). The the colors were measured with a Spectrophoto-meter. Results: The average $L^*$ value of the Cz3 group was the highest among the groups at $59.1{\pm}0.5$ (P<0.05), followed by Cz2 at $57.5{\pm}0.8$ and Cz1 at $56.6{\pm}1.3$. The $a^*$ value of Cz3 was negative at $-0.0{\pm}0.0$ and the $a^*$ values of Cz2 and Cz1 were positive at $0.2{\pm}0.1$ and $0.4{\pm}0.0$, respectively (P<0.05). The $b^*$ of Cz1 was the highest at $11.2{\pm}0.6$, followed by Cz3 at $10.8{\pm}0.5$ and Cz2 at $10.5{\pm}0.8$ (P<0.05). Conclusion: Compared to other experimental groups, the Cz3 groups showed the brightest colors with high brightness and relatively low green and yellow levels.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.17 no.2
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• pp.11-17
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• 2011

Background: To evaluate the influences of Eye movement program applied to elderly people on static balance. Methods: The subjects consisted of fourteen elderly people. The subjects were divided into two group. The control group (n=7) received no exercise and/or stimulation. The Eye movement program training (E/P) group (n=7) performed balance training using word card and batom. E/P group were accomplished during 4weeks (5 day/week, 60 min/day). All tests were completed before and after experiment. The static balance ability was measured by normal standing when eye open and close on good balance system, respectively. For each case, the experimental data were obtained in 3 item; mean X speed, mean Y speed and velocity moment. Results: The result of this study were as follows: 1. In E/P group, the statistically significants were shown on only mean Y speed in the case of normal standing when eye open (p<.05), but the statistically significants were not shown on mean X, Y speed and velocity moment in the case of normal standing when eye close (p>.05). 2. In control group, the statistically significants were not shown on all posture (p>.05). 3. There was a statistically significant difference on the mean Y speed and velocity moment in the case of normal standing when eye open between control group and E/P group (p<.05). Conclusions: The above results revealed that balance training using Eye movement program were partly effective for improving the static balance ability.

• Journal of radiological science and technology
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• v.23 no.2
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• pp.43-54
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• 2000

This paper will present the result of research which was done with 201 places on the actual condition of using dental diagnostic radiography unit and the protection of radiography. The purpose of this paper is to comprehend the actual condition of using dental x-ray unit and to protect when they do radiation work. Moreover this paper was completed to prepare basic materials that could be helpful to reduce the exposure from radiation. This paper obtains the following result. 1. On radiation photographing work in the dentist office, 50.3% of dental hygienists treat this job, and 19.2% of assistants, 10.8% of dentists, 5.6% of radiolotechnologists and 4.2% others performed this job. 2. The case that radiation worker is educated about diagnostic radiography safety supervision has been shown 14.4% and uneducated case has been shown 78.1%. 3. The result about the actual condition of using the oral diagnostic radiation per day was that a number of film which take photograph again (less than 1 exposure) was 40.3%. Normal photographing($1{\sim}10$ exposure) was 85.1% which is the highest percentage. Using the bitewing film and occlusal film was 7.0%, and 12.4% respectively. The percent that they use cephalo film and panoramic film was 16.4% 29.8% respectively. 4. Dental intra diagnostic radiography unit made in $1996{\sim}2000$ was 24.9% and the one made in $1991{\sim}1995$ was 19.9%, in $1986{\sim}1990$ was 19.9%, in 1985 was 9.5% according to the answer. On kVp, they use 60 kVp mostly(61.7%) and On mA, they use 10 mA with the highest percent(66.7%). On the dental extra diagnostic radiography units which are used for doing the extra oral radiography, the one made in $1996{\sim}2000$ was 13.4%, in $1991{\sim}1995$ was 9.5%, in $1985{\sim}1990$ was 2.0% according to the answer. They use $71{\sim}80\;kVp$ with 10.9% and $60{\sim}75\;kVP$ with 9.5%. They use less than 10 mA with 19.4% and $11{\sim}15\;mA$ with 2.5%. $16{\sim}20\;mA$ with 1.5%. But the case they exactly do not know how much mA they use or they do not have any mA was 76.6%. 5. General characteristics and the part of protection through the protective equipment by operator are completed with 89.1%. They have shown the similar difference in the relationship with age(p<0.001), experience(p<0.05) and in-patient(p<0.05). 6. When they take photographs of radiation with general quality, how far they keep the proper distance from the cone is as follows, Keeping safe distance is 12.9% according to the answer with the low percent. This result is similar with the difference related in experience(p<0.05) and work(p<0.05), the area of working(p<0.05) and in-patient(p<0.05). 7. The answer about the question-if they hold the tube head when they take photographs with general characteristics is as follows. The answer that they never hold the tube head and cone occupies 62.7% with the highest percent. It is shown the similar difference with age(p<0.05). 8. According to the study that they put on dosimeter with general characteristics is as follows. 64.7% has never put on the dosimester with the highest percent. 33.8% showed similar differences with experience(p<0.05), work(p<0.001), the area of work(p<0.005)and in-patient(p<0.001).

• Journal of Technologic Dentistry
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• v.21 no.1
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• pp.27-41
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• 1999

The Ag-Pd-Cu alloys containing a small amount of Au is commonly used for dental purposes, because this alloy cheaper than Au-base alloys for clinical use. However, the most important characteristic of this alloy is age-hardenability, which is not exhibited by other Ag-base dental alloys. The specimens used were Ag-30Pd-10Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electric furnace and centrifugal casting machine in Ar atmosphere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at 350-$550^{\circ}C$ Age-hardening characteristic of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of hardness testing, X-ray diffraction and electron microscope observations, electrical resistance, differential scanning calorimetric, energy dispersed spectra and electron probe microanalysis. Principal results are as follows ; Maximum hardening occured in two co-phases of ${\alpha}_2$ + PdCu In stage II, decomposition of the $\alpha$ solid solution to a PdCu ordered phase($L1_o$ type) and an Ag-rich ${\alpha}_2$ phase occurred and a discontinuous precipitation occurred at the grain boundary. From the electron microscope study, it was concluded that the cause of age-hardening in this alloy is the precipitation of the PdCu redered phase, which has AuCu I type face-centered tetragonal structure. Precipitation procedure was ${\alpha}{\to}{\alpha}_1+PdCu{\to}{\alpha}_2+PdCu$ at Pd/Cu = 3 Pd element of Ag-Pd-Cu alloy is more effective dental alloy on anti-corrosion and is suitable to isothermal ageing at $450^{\circ}C$.

• Journal of Technologic Dentistry
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• v.28 no.2
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• pp.355-366
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• 2006

The purpose of this study was to determine if repeated casting has a detrimental effect on the corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis, vickers hardness test, SEM, EDX and corrosion test were performed to determine the effects of recasting on chemical composition, microstructure, physical property, castability and corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed that major crystal phase contained nickel-chrome compounds, Nickel carbide and Chrome carbide. Microstructure analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed recasting has no effect on microstructure. EDX analysis results indicated the percentage of the main component nickel(Ni) in the specimens of the VeraBond showed a tendency to increase with recasting, but those of other components Carbon(C) showed a tendency to decrease with recasting, Chrome(Cr), Silicon(Si), Aluminium(Al) and molybdenum(Mo) showed no changes in the percentage. The percentage of the main component nickel(Ni) in the specimens of the Rexillium V showed a tendency to increase with recasting, but those of other components silicon(Si), carbon(C) and molybdenum(Mo) showed a tendency to decrease with recasting, chrome(Cr) and aluminium(Al) showed no changes in the percentage. The vickers hardness results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The castability results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The cast and recast specimens of the VeraBond and the Rexillium V showed no differences in the corrosion resistance. The results indicate that the VeraBond and the Rexillium V can be safely recast.