• 대한치과기공학회지
• /
• 제26권1호
• /
• pp.41-48
• /
• 2004

Ti-20%Zr(-5%Cr) alloys not containing harmful Al and V were newly designed in order to reveal their possibility for dental casting and melted in an arc melting and casting furnace under Ar atmosphere. The corrosion resistance was studied by anodic polarization test. From the observation of anodic polarization behavior, it was found that the corrosion resistance was markedly increased by the addition of Cr. The corrosion resistance of Ti-20%Zr-5%Cr alloy was superior to that in Ti-6%Al-4%V alloy but almost similar to that in CP Ti using in market place today.

• 대한치과기공학회지
• /
• 제25권1호
• /
• pp.81-87
• /
• 2003

Ti-20%Zr-X%Cr(X=0,5) based alloys not containing hamful Al and V were newly designed in order to reveal their possibility for dental casting alloys, and melted in argon-arc casting machine. The mechanical properties were evaluated by using universal testing machine. The tensile strength and %elongaton of the alloys markedly increased with Cr content. The Ti-20%Zr-5%Cr alloy showed a similar tendency with Ti-6%Al-4%V alloy in tensile strength, but surpassed in %elongation. From these results, it was concluded that new alloys for successful dental casting materials should be designed as Ti-Zr-Cr based alloys.

• 대한치과기공학회지
• /
• 제24권1호
• /
• pp.51-63
• /
• 2002

The purpose of this study was to be of use for getting rid of job stress from dental technicians, by examining how much they were stressed out at work place as one of the professional medical personnels. The subjects in this study were 255 selected dental technicians who were working in the region of Taegu. The one-on-one interview was conducted from March 1 to 30, 2001, with structured questionnaire. The questionnaire sued in this study included 19 question items about the general characteristics and 29 items regarding job stress. The job stress was categorized into seven subareas based on earlier studies and considering the job situations of dental technicians: heavy workload, job conflicts, improper treatment, role and job knowledge, human relations, physical environment and personal matters. The job stress extent was measured on five-point Likert scale that is widely used in social science: one point for no stress, two for little stress, three for so-so, four for a little stress, and five for severe stress. Therefore, a higher point means a severer job stress. The reliability of the questionnaire turned out very good with Cronbach a = 0.9272. The findings of this study were as follows: 1. The general characteristics of the dental technicians investigated could be described as below: (1) By gender, 80.4% of the dental technicians were male, and 50.2%, the largest percentage, were in their 20s, followed by those in their 30s, those in their 40s, and those in their 50s in the order named. (2) The most common work place was dental technician shop(92.5%), followed by dental technology room in dental hospital or clinic and in general hospital in the order named. The primary duties were coating materials work(30.6%), followed by sculpture, grinding, partial and full denture and orthodontics in the order named. 2. The most larges (1) The most largest motivation to be a dental technician was its being a professional(33.7%), followed by the advice from others, their own aptitude, and good economic treatment in the order named. 3. Their job stress could be explained as below: (1) Their collective job stress average was 3.96$^{\circ}{\ae}$0.50 on the basis of 5 point, which showed that they were exposed to a fairly severe job stress. (2) By area, they were most stressed out from heavy workload (4.12), and they also were severely stressed from role and job knowledge(4.02) and personal matters(4.00). (3) By situation, they were most stressed when the disagreement of prosthesis that results from a specific error is unconditionally attributed to them(4.43). And they were also stressed a lot when their workload increases due to the rework(4.38), when a dentist asks something difficult for them to resolve(4.20), when heavy workload makes their working hours irregular and it's impossible to lead a personal life or have leisure time(4.16), and when they are o work for an excessively short time(4.16). This fact indicated that most of the dental technicians were exposed to a lot of stress in conjunction with job performance. 4. The main duties they took charge of didn't make any significant difference to their job stress, but yielded a significant difference to the extent of job stress in individual areas and the order of the most stressful one. Those who were engaged in grinding were most stressed from their own matters, whereas heavy workload was most stressful for those who were engaged in the other types of works. 5. As a result of seeing if their personal characteristics yielded any differences to job stress, the personal characteristics that made their job stress vary significantly were working hours, motivation of being a dental technician, job satisfaction and willingness to continue doing dental technology works. There was a tendency that longer working hours led to severer job stress, and those who chose to be a dental technician according to their own aptitude were less stressed than the others who became a dental technician because of economic reason or advices from others. And the people who were satisfied with their job were exposed to less job stress than the others who weren't, and those who had an intention to keep that job as much as possible were less stressed, compared to the others who hadn't.

• 대한치과기공학회지
• /
• 제23권2호
• /
• pp.121-149
• /
• 2002

This Study aims at investigating the tendency of individual problems that the students at the departments of dental technology are faced with, their efforts and types of activities to solve the problems. Surveyed for this purpose were 700 freshmen to juniors enrolled in the departments of dental technology at the universities across the country and they were analyzed by area, grade and sex. 1. Tendency of Problems The areas of problems the students at the departments of dental technology considered as most serious were health, human relation, view of value and economy in sequence, while the areas they considered as least serious were future course and employment. In general, there were tendencies as follows: divided by grade, the higher the grades of the students are, the higher scores of problems they get(F=12.14, P=.000) : in the areas of health and human relation, as the grade gets higher, the scores of their problems also increase, accordingly(F= 17.58, P=.000)(F=8.39, P=.000) : in the areas of economy, parents and home, freshmen and juniors are found to have higher scores of problems compared to sophomores,:F=7.89, P=.000)(F=11.63, P=.000) : divided by sex, female students recorded higher scores of problems than their counterparts(F=31.85, P=.000) 2. Efforts for Problems View of value, human relation, parents and home appeared to be the areas for which the students made the highest rate of efforts in sequence while the areas for which they paid lowest grade of efforts were health and economy. In other words, the students gave higher scores for human relation and view of value in terms of tendency as well as efforts of problems, while they rated high for health and economy in the tendency but low in the efforts of problems. Divided by grade, freshmen and juniors appeared to score higher points than sophomores in their efforts to solve problems, even though juniors made relatively higher efforts than freshmen(F=6.53, P=.002). Divided by sex, female students scored higher points in their efforts than males(F=15.98, P=.000) 3. Difference of Efforts to Solve Problems. In the analysis into the scores of difference showing the disagreement between the tendency of problems and the efforts to solve problems, the area of health was rated as highest, followed by economy. There was little difference of scores between human relation and view of value, an indicator of agreement between the scores of problems and efforts. The difference of scores between future course and employment, between liberal arts and recreation, between characters/parents and home/school work turned out to be negative in the listed sequence, leading to a conclusion that the students enrolled in the departments of dental technology are making more efforts to solve problems than actually needed in most areas. By grade, there was a significant difference only in the area of health(F=3.00, P=.050). This difference itself was widening as the students come to higher grades. By sex, females showed bigger difference than males. 4. Types of Activities to Solve Problems. The analysis into types of activities to solve problems revealed that the surveyed students seemed to actively cope with the problems in all areas, relying at the same time on personal relationship. Especially in the areas of health, economy, parents, home, human relation, future course and employment, the students appeared to deal with the problems actively as well as emotionally.

• 대한치과기공학회지
• /
• 제24권1호
• /
• pp.83-93
• /
• 2002

This study was performed to evaluate the importance of parents, knowledge, cognition and behaviour about dental health care on the development of dental caries in preschoolers. Subjects were comprised of 170 preschoolers collected from three preschoolers placed in Pusan and Kimhae area and study period were 6 months from January, 2000. Examination on the preschoolers' dental health and questionnarie survey on parents' knowledge, cognition and behaviour about dental health care were conducted. Collected data were analyzed by chi-square test and t-test using SAS program. Dental caries was so prevalent as the rate of 73.5%. And, the rate was different by the area(p=0.001), and increased with preschooler's age(P=0.004). The parents gain the knowledge about dental health care mainly from dentist or dental hygienist(32.9%), newspaper, magazine booklets(26.5%), TV and VTR tape(20.0%), etc, but rarely from school health education(4.7%). Caries prevalence was significantly lower in case of regular brushing than that of insufficient brushing(p=0.002) and in case of consistently informing brushing time to their children(p=0.014). This results showed that the dental health care for preschoolers is insufficient and the most important factor for caries prevention is regular brushing. And it seemed that the parent's concern and knowledge play an important role for the prevention of preschooler's dental caries. Dental health education would be focused on the parents, especially for the practice of preventive behavior by preschoolers themselves.

• 치위생과학회지
• /
• 제2권2호
• /
• pp.85-88
• /
• 2002

구강에서 분리한 세균에 대한 오미자 추출물의 증식저해를 조사하였다. 물을 추출용매로 사용할 때의 추출수율은 53.8%로 메탄올보다 높았고, 추출온도가 높은 것이 보다 유리하였다. 구강에서 분리된 세균의 생육에 대한 오미자 물추출물의 영향을 조사한 결과, 오미자 물추출물은 강한 항균력을 보였다. 구강에서 분리된 세균에 대한 오미자 물추출물의 최소저해 농도는 ${125{\sim}1000{\mu}g/ml}$의 범위인 것으로 나타났다.

• 대한치과기공학회지
• /
• 제23권1호
• /
• pp.31-43
• /
• 2001

This study was performed to observe the micro-structure change of surface, behavior of oxide change of element, the component transformation of the alloy and the bonding strength between the porcelain interface in order to investigate effects of indium, tin on interfacial properties of porcelain fused to low gold alloy. Hardness of castings was measured with a micro-Vicker's hardness tester. The compositional change of the surface of heat-treated specimen was analyzed with an EDS and an EPMA. The interfacial shear bonding strength between alloy specimen and fused porcelain was measured with a mechanical testing system(MTS 858.20). The results were as follows: 1) The hardness value of alloy increased as increasing amount of indium addition. 2) The formation of oxidation increased as increasing indium and tin contents after heat treatment. 3) Diffusion of indium and tin elements increased as increasing indium and tin contents in metal-porcelain surface after porcelain fused to metal firing. 4) The most interfacial shear bonding strength was increased as increasing a composition of adding elements, and a heat-treatment time, and an oxygen partial pressure. From the results of this study it was found that the addition of alloying elements such as indium and tin increase hardness of as-cast alloy, produce surface oxide layer of adding elements by heat-treatment which may improve interfacial bonding strength between alloy and porcelain.

• 대한치과기공학회지
• /
• 제11권1호
• /
• pp.115-120
• /
• 1989

Many attempts for the compfrt, esthetics and improvement of Masticatory function of the patients with removable prosthesis have been made for several decades. The search for the ideal denture occlusion has been going on in an effort to find the tooth form which provides maximum denture stability and masticatory efficiency without damaging the health of the underlying bone. For the purpose, the basic concept of lingualized occlusion were suggested by payne(1941) and pound(1973) discussed a similar occlusal concept and used term " lingualized occlusion." The purpose of this literature study is to clarify and amplify a method to achieve bilateral balanced occlusion with the occlusal arrangement termed " lingualized occlusion." Lingualized occlusion can be achieved by use of anatomic teeth for the mandibular denture. Lingualized occlusion can be used in most denture combination. It is particulary helpful when the patient places high priority on esthetics but a nonanatomic occlusal scheme is indicated by oral conditions such a severe alveolar resorption, a class II jaw relationship or displaceable supporting tissue. Advantages of lingualized occlusion are summarized as follows : 1) Most of the advantages attributed to both the anatomic and nonanatomic forms are retained. 2) Cusp form is more natural in appearance compare to nonanatomic tooth form. 3) Good pnetration of the food bolus is possible. 4) Bilateral mechanical balanced occlusion is readily obtained for a region around arotric relation. 5) Bertical forces are centralized on the mandibular teeth. Lingualized occlusion provides a useful combination of several occlusal concept. Many. advantages of anatomic and nonanatomic occlusions are accomplished but the lingualized occlusal concept is not is not a panacea, and all other procedures still must be carefully excuted.

• 대한치과기공학회지
• /
• 제37권4호
• /
• pp.219-227
• /
• 2015

Purpose: The purpose of this study was to evaluate the effect of the chemical surface treatment on the flexural bond strength of heat curing denture base resin and reliners. Methods: Denture base resin surface was treated with MMA 95% and TEGDMA 5%, MMA 95% and silane coupling agent 5%, heat curing resin monomer. After denture reliners were injected, flexural bond strength was measured. Results: The repair resin of Vertex SC was higher than Lang, hard reliner of Kooliner was higher than Rebase. Soft reliner of Dura base and Coe-soft showed differently according to the surface treatment. The all chemical treatment groups on Vertex SC were significantly higher than control(p<0.05). In Lang group, 5% MPS treated group showed significantly higher flexural bond strength than others(p<0.05). In Kooliner group, all chemical treatment groups showed significantly higher than control(p<0.05). In Rebase group, the 5% MPS and the monomer denture base resin treated groups showed significantly higher than others(p<0.05). In Dura base group, 5% MPS treated group showed significantly higher flexural bond strength than others(p<0.05). In Coe-soft group, all treated groups were significantly higher than control group(p<0.05). Conclusion: TEGDMA, MPS, and the monomer of heat-cured denture base resin were effective to improve the bond strengths between denture base and denture relining materials. Especially, 5% MPS expected to strengthen effectively the bonding property of denture base and denture reliners within the results of this study.

• 대한치과기공학회지
• /
• 제35권4호
• /
• pp.295-302
• /
• 2013

Purpose: The grindability of Ti-10%Zr-X%Cr(X=0,1,3) alloys in order to develop Ti alloys for dental applications with better machinability than unalloyed titanium has been evaluated. Methods: Experimental Ti-10%Zr-X%Cr(X=0,1,3) alloys were made in an argon-arc melting furnace. Slabs of experimental alloys were ground using a SiC abrasive wheel on an electric handpiece at one of the four rotational speeds of the wheel (12000, 18000, 25000 or 30000rpm) by applying a force(100gf). Grindability was evaluated by measuring the amount of metal volume removed per minute(grinding rate) and the volume ratio of metal removed compared to the wheel material lost, which was calculated from the diameter loss (grinding ratio). Experimental datas were compared the results with those of cp-Ti(commercially pure titanium) Results: It was observed that the grindability of Ti-10%Zr-X%Cr(X=0,1,3) alloys increased with an increase in the Cr concentration. More, they are higher than cp-Ti, particularly the Ti-10%Zr-3%Cr alloy exhibited the highest grindability at all rotational speeds except 12000rpm. There was significant difference in the grinding rate and grinding ratio between Ti-10%Zr-3%Cr alloy and cp-Ti at all rotational speeds(p<0.05). Conclusion: The Ti-10%Zr-3%Cr alloy exhibited better grindability at high rotational speeds, great potential for use as a dental machining alloy.