Earticle

Purpose: This study examined the corrosion level by alloy type and pH, and used the corrosion levels as the dental health data. The study utilized one Ni-Cr alloy for the full and removable partial denture metal frameworks and two Ni-Cr alloys for porcelain-fused-to-metal crown, among the non-beryllium dental casting non-precious Ni-Cr alloys. Methods: The alloy specimens were manufactured in 10 and stored in the corrosive solution(pH 2.2-4.4) in the electrical water bath(37 ) for seven days. Afterwards, the metal ions were quantitatively analyzed using the ICP. Results: Of the three metal alloys, Bellabond-Plus alloy and SOLIBOND N alloy, with 22% or higher chrome chemical contents, had higher corrosion resistance than Jdium-100 alloy with 20% chrome chemical content. In all three alloys, the corrosion of Ni was highest, and metal ion corrosion was higher in the pH 2.2 corrosive solution. Conclusion: Although Ni-Cr alloy was not very corrosive, a Ni-allergic patient should not have Ni-Cr alloy prosthesis. The Ni-Cr alloy for porcelain-fused-to-metal crown should be designed for the dental porcelain to cover the whole crown.

Purpose: The age-hardening mechanism of an Au-Ag-Cu-Pt-Zn alloy for crown and bridge fabrication was investigated by means of hardness test, X-ray diffraction study and field emission scanning electron microscopic observation. Methods: Before hardness testing, the specimens were solution treated and then were rapidly quenched into ice brine, and were subsequently aged isothermally at 400-450℃ for various periods of time in a molten salt bath and then quenched into ice brain. Hardness measurements were made using a Vickers microhardness tester. The specimens were examined at 15 kV using a field emission scanning electron microscope. Results: By the isothermal aging of the solution-treated specimen at 450℃, the hardness increased rapidly in the early stage of aging process and reached a maximum hardness value. After that, the hardness decreased slowly with prolonged aging. However, the relatively high hardness value was obtained even with 20,000 min aging. By aging the solution-treated specimen, the f.c.c. Au-Ag-rich a0 phase was transformed into the Au-Ag-rich a1 phase and the AuCuⅠ ordered phase. Conclusion: The hardness increase in the early stage of aging process was attributed to the formation of lattice strains by the precipitation of the Cu-rich phase and then subsequent ordering into the AuCuⅠ-type phase. The decrease in hardness in the later stage of aging process was due to the release of coherency strains by the coarsening of tweed structure in the grain interior and by the growth and coarsening of the lamellar structure in the grain boundary. The increase of inter-lamellar space contributed slightly to the softening compared to the growth of lamellar structure toward the grain interior.

Purpose: The aim of this study measured and compared the marginal and internal fit of metal cores with two base metal alloy (Ni-Cr alloy(non-beryllium), Co-Cr alloy). Methods: Maxillary right first molar abutment fabricated by titanium was prepared for this study. Impressions(10ea) were made from titanium model, and study models were poured with improved dental stone. Wax cores of twenty were prepared for burn-out and casting. Ten wax cores cast Ni-Cr alloy(non-Be), and finally ten cast Co-Cr alloy. Marginal and internal fit of cores was evaluated using silicone replica technique and digital microscope(x160). The data were statistically analyzed with the independent samples t-test ( <.05). Results: Mean(standard deviation, SD) marginal and internal fit total size of Ni-Cr alloy(non-Be) group was 73.3(14.4) and of Co-Cr alloy group 65.6(17.4) . The marginal and internal fit total size of Ni-Cr alloy group(non-Be) was statistically significantly greater than that of Co-Cr alloy group (P=.004). Conclusion: Co-Cr alloy cores in this study had a better marginal fit than Ni-Cr alloy(non-Be) cores.

Purpose: The aim of this study was to analysis the composition on the centrifugal casting and the oxide on the casting temperature. Methods: The nickel based alloy were used in this study. Wax pattern specimens (10*10*2) were invested with phosphate-bonded investment in metal rings, the liquid/powder ratio and overall burn-out schedules for these investments were followed in accordance with the manufacturer’s instructions. After casting, the alloy specimens were evaluated as regards composition(EPMA). The casting temperatures were as follows: 1400℃ and 1700℃. The quantitative analysis of oxides were scanning electron microscope(SEM), energy dispersive spectroscopy(EDS) and line scanning. Results: Nearer the injection lines showed that there is a large amount of nickel. Quantitative of oxides of Ni-Cr alloy cast from 1400℃ is lager than Ni-Cr alloy cast from 1700℃ Conclusion: Casting when using a centrifugal casting machine centrifugal force affects the composition of the alloy. The higher the temperature, the amount of oxide that is generated many.

Purpose: The aim of study was to compare the dimensional stability of digitized dental stone replica using different color of gypsum materials using a white light scanner with three- dimensional software. Methods: A master model(500B-1, Nissin dental product, Japan) with the prepared lower full arch tooth was used. Several type stones(white, yellow, green) were used for 30 stone casts(10 casts each) duplicated a master model of mandible. The master model and the replicas were digitized with the non -contacting white light scanner to create 3-dimensional digital models. The linear distance between the reference points were measured and analyzed on the Delcam Copycad (Delcam plc, UK) 3D graphic software. One-way analysis of variance(ANOVA) combined with a Tukey multiple-range test were used to analysis the data( =0.05). Results: There were considerable differences in mean values between gypsum materials within each color(white, yellow, green), and this difference was statistically significant, p=0.001. Conclusion: Digitization of dental materials on optical scanner was affected by color. Three different color of gypsum materials showed clinically acceptable accuracies of full arch digital model produced by them. Besides, these results will have to be confirmed in further clinical studies.

Purpose: The goal of this study is to investigate the correlation of orthodontic treatment with self-esteem and how orthodontic treatment has an effect on university student’s self-esteems by investigating and analyzing the difference in self-esteem of each general characteristic and the difference in self-esteem according to the existence or nonexistence of malocclusion and orthodontic treatment for adult university students. Methods: This study conduced a survey for 420 university students including dental related department, department of health and department of non-dental health in two universities located in Taegu, Gyeongbuk-do province from May 15, 2012 to May 30, 2012, and in 420 questionnaires of the investigated 420 target students, total 400(95.2%) questionnaires except for the questionnaires with falsely or erroneous responses were used for study analysis. Results: In the relations of general characteristic with self-esteem, for self-esteem by each gender, male student showed higher, for self-esteem by residential area, the university student residing at metropolitan area showed higher, for self-esteem by financial status, high class and middle class students in home financial status showed higher, for self-esteem by face shape, the student with triangular face shape showed higher, and in the relation of self-esteem with orthodontic treatment, the university student who is getting orthodontic treatment showed higher self-esteem statistically significantly. Conclusion: For gender, male university student, for residential area, the university student residing at metropolitan area, the high class university student in financial status, the university student with triangular face shape, and the university student who is getting orthodontic treatment showed statistically significantly higher self-esteem.

Purpose: This study was survey on future job vision and its pride (self-esteem) of dental technicians. It also investigates the future vision on their major of job (denture) and its awareness to improve the work environment and enhance their satisfaction towards job and duties. Methods: In order to research job and its duty satisfaction of dental technicians who mainly work at denture part, certified questionnaire was modified and upgraded for its use. Collected documents were used by ‘Window SAS 8.0 Program’ for analysis. The significance of the test related to the items and its standards has been decided for p<0.05. To find out the differences between choices when choosing career and the duty satisfaction, t-test, one-way ANOVA and two-way ANOVA have been used. Results: Following research findings show: 1. There was high self-esteem towards the job as dental technicians but low in future job vision. 2. It has been found that if satisfaction on their job (dental technician) is high then also their satisfaction on its duty (denture part) is high. 3. The factors that affects mostly on duty satisfaction of denture part are ‘the contribution on improving oral cavity of people’( =0.33118), ‘The possibility of growth of person’s job choices’( =0.30035) and ‘person’s satisfaction on choosing job’( =0.16069). 4. If there is an increase level on the contribution of improving people’s oral cavity, the possibility of growth of person’s job choices and the person’s satisfaction on choosing job, then there is also high growth in denture part’s duty satisfaction. 5. It has been found that if there are more employment histories of denture part, the duty satisfaction of denture part were also high. On the other hand, the more employment history of dental technicians get, the duty satisfaction of their denture part was low. Conclusion: Following research results show that there is high self-esteem towards the job as dental technicians but the vision towards future was low. This shows that there is no bright future on dental technology. Therefore, it is important that not only to improve the work environment and pay rise on dental technologists but also to satisfy them. Various program developments and continuous research are needed to increase satisfaction.

Purpose: This study is conducted to evaluate the job stressors for dental technicians in Ulsan city. Methods: The Korean standard job stressors assessment tool developed by Korea Occupational Safety and Health Agency (KOSHA) was used to compare the survey result with Korean reference value. The questionnaire on the social, demographic and job characteristics of dental technicians was also used to find the factors affecting to job stressors by using multiple linear regression analysis. Results: A total of 155 questionnaire was collected from 2010 to 2011. Among the eight fields of stressors, the physical environment (men 50.0, women; 58.3) and job demands (men 57.1, women 57.1) were higher than the median value of the Korean Workers. By multiple linear regression analysis, the significant factors to the physical environment were the satisfaction degree of indoor odor, number of employee, duty and working hours. In terms of the job demand, duty, working hours, age, and the satisfaction to the efficiency of space utilization were significantly associated to the score of job demand. Conclusion: Based on these results, it is necessary to manage appropriate workload, control indoor odor and design an efficient work space for prevention of job stress of dental technicians.

Purpose: The purpose of this study is to investigate the improvement measure of dental technician practical examination. Methods: A survey was performed on 111 dental technicians who were self-written questionnaire. The results were analyzed by SPSS 12.0. The collected data was analyzed by frequency and chi-square test. Results: Questions most necessary work tools with the articulator was the highest with 55.9%, Electric wax carver(16.2%), heating clear(14.4%), CAD/CAM program(9.0%) was in the order. The need for additional practical test in response to actions included maxillary and mandibular comments occlusal work that you have to wax up the highest rate of 63.8%. Items most in need of improvement was strengthen of clinically oriented(48.0%), separation of written and practical(14.6%), control the degree of difficulty(11.4%) were the next order. Conclusion: Based on the results of this study, the current dental technician did not show major problems in the practical test. However, clinicians should be strengthened mainly. To do this, the use of the articulator is essential.

Purpose: The purpose of this study was to examine the recognition of dental technician's about including denture into the coverage of the national health insurance. Methods: This study carried out self-administered questionnaire survey from June 10, 2012 to June 20 by having research subjects as 230 dental technician. Except 22 copies with incomplete response, 208 copies were used as the materials of final analysis. Results: The recognition of dental technician on the national health insurance of denture was 48%, but there was a low recognition on the details. The rates of dental technician who approved of the inclusion of denture into the coverage of the health insurance respectively stood at 59%. Conclusion: The coverage of the health insurance should be extended to dental medicine in a manner to satisfy dental technicians, dental service providers and receivers. Also, further studies for the extending coverage of the details are needed.

Purpose: In order to validate empirically the theoretical model of this study subjects, who were limited in Andong gun, Youngyang gun, Uiseong gun, Bonghwa gun, Chilgok gun, Cheongsong gun according to residence-specified distribution and over aged 65, were focused to the elderly in rural areas with geographical characteristics where they have difficulties in accessibility of dental facilities and dental care. Methods: The collected data were analyzed by the SPSS 19.0 program. First, the frequency analysis was performed for each independent variable and the dependent variable.Second, reliability analysis and correlation analysis were conducted for daily living skills and Biomedical Vigilance. Third, multivariate analysis was performed in terms of and the post-administration management.Fourth, multiple regression analysis was performed to identify the factors affecting the post-management of dentures and the period of using dentures. Results: By results of the multiple regression analysis, the elder the subjects are( = 0.03), the lower their income activities are( = -0.18), the smaller their monthly allowances are( = -0.16), the worse their daily activity skills are( = -0.12), the more they were mounted their dentures by an unlicensed contractor( = 0.07), and the more they cost to their dentures( = 0.14), the longer the period of use dentures are. And the beneficiaries of Basic Livelihood Security( = -0.14) who got free denture business are shorten the period of using dentures. According to multiple regression analysis for post management of dentures, the independent variables like the health education( = 0.24), smoking( = -0.18), periodic oral examination( = 0.13), dentures mounted by an unlicensed contractor( = -0.13) are shown statistically significant results. In that study subjects are taking part in health education and non-smokers, they are likely to have more chances to post management for their dentures like periodic oral examination. However the subjects who were weared their denture by an unlicensed contractor get less chance to post management for their dentures. Conclusion: As the elderly who want to wear denture are increasing due to the denture insurance for the elderly, the need for oral health education for the elderly is an urgent request, especially continuos education for the way of use their dentures and follow-up management for the elderly who were already mounted their dentures. And also, the need for more systematic researches is requested for securing objective data.

Purpose: This study was to investigate oral hygiene knowledge and the actual condition of oral care for the students in the public health and non-public health Departments. Methods: The survey sample consisted of 262 randomly selected students. 197 of them are public health-related students and 65 are non-public health-related students. The questionnaires used in this study consisted of 4 items for general information, oral health status of 2 items, 5 items for Oral hygiene knowledge and actual condition of oral care of 5 items. Collected data were analyzed by Frequency Analysis t-test and Crosstabs using SPSS(Statistical Package for Social Sciences) Win 19.0 statistics program. Results: Regarding general characteristics of the subjects, there were 53.8% of first-year student, 26.0% of secondyear student and 20.2% of third-year student among 52.3% of males and 47.7% of females. The subjects received less than “100,000” won(13.0%), “100,000-190,000” won (5.0%), “200,000-290,000” won(30.9%), “300,000-390,000” won (33.2%) and more than “400,000” won(17.9%) a month for an allowance. The subjects had ‘none’ (44.3%), ‘1’(6.5%), ‘2’(12.6%), ‘3’(5.0%), ‘4’(5.3%), ‘more than’ 5(0.8%) of dental caries and ‘do not know’ were 25.6%. The numbers of dental prosthetics were ‘no’ (35.5%), ‘1’(13.7%), ‘2’(17.2%), ‘3’(10.3%), ‘4’(11.5%), and ‘more than 5’(11.8%). The public health students(84.8%) had a higher positive response rate than the non-public health students(66.2%). The public health students(80.2%) had a higher negative response rate than the non-public health students(78.5%) in the result of onset of gum disease pain awareness. The non- public health students(65.5%) had a higher negative response rate than the public health students(68.3%)) in the result of heredity of gum disease. The t-test showed that public health-related department students(M=8.264, SD=0.821) had more knowledge about oral hygiene than non-public health-related department students(M=8.015, SD=1.082). ‘do not use’ in the oral care products except toothpaste and toothbrush showed that public health-related department students(60.4%) use the products more than non-public health- related department students(66.2%). Conclusion: In this study, public health- related department students had higher oral hygiene knowledge and actual condition of oral care compared to non-public health-related students, but low in practical action. Due to the lower level of dental care products use in non-public health-related department, a continuous oral care education program is required.

Purpose: The purpose of this study is analyzing how much students of dental technology possess core competencies and cognition between dental technicians and students. Methods: The subjects of this study were dental technicians, dental technology students and a self-administered structured questionnaire survey wax conducted for 428 selected people. Collected data were analyzed using SPSS Win 20.0 statistics program and analysis techniques include the frequency, t-test, One-way ANOVA. Results: The results of the survey are as follows. The cognition of key competency according to the gender in the students showed differences in interpersonal ability, information ability and the requirement of key competency according to the gender in the students showed differences in speaking ability, listening ability, problem solving ability. The cognition of key competency according to the grade in the students showed difference in speaking ability, listening ability and the requirement of key competency according to the grade in the students showed difference in comprehension of organization ability. The speaking ability is the lowest in the cognition of key competency according to the gender, grade, experience of clinical training in the students and the skill ability is the highest in the requirement of key competency according to the gender, experience of clinical training in the students. The cognition of key competency according to the career in the dental technicians showed difference in problem solving ability, self-regulation and self-development ability, skill ability and the requirement of key competency according to the career in the dental technicians showed difference in writing ability. The cognition of key competency according to the educational background in the dental technicians showed difference in comprehension of organization ability. The foreign language ability is the lowest in the cognition of key competency according to the career, job in the dental technicians and the skill ability is the highest and the math ability is th lowest in the requirement of key competency according to the career, place of employment in the dental technician. Conclusion: This study can be used as basic data for dental technology that are available not only to field-oriented disciplines but also to overall higher education fields which aim to strengthen key competency.

Purpose: The purpose of this study was to investigate the stress distribution of the surrounding tissues according to 3 proximal plate types of the RPI clasp. Methods: The removeable partial denture which mandibular right and left second premolars and mandibular molars were lost was attached to a three dimensional photo elastic epoxy resin model. Then 120N of vertical load was applied. After 3-dimensional photoelastic stress analysis was used to record the isochromatic fringe patterns. Results: Kratochvil type guiding plane exhibited little uniform stress distribution on load center and alveolar ridge, but higher stress concentration on buccal surface of second premolar. Krol type guiding plane exhibited the stress concentration on the front of load center and relatively higher stress concentration on buccal surface of first premolar. However, this type had no effect on canine. Researcher type guiding plane showed the stress concentration on second premolar and molar, but the little stress distribution on first premolar. Conclusion: In all types, excessive stress concentration was appeared and three types were not significant different.