• Journal of Technologic Dentistry
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• v.6 no.1
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• pp.11-14
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• 1984

The auther performed this experimental study on cervical margin distortion in preheating method during soldering. 1. In soldering methods, the method using the furnace has less distortion than the method using open-flame and longer the bridge spon, the larger the distortions. 2. Table Ⅰ Showed that buccal margin, lingual margin, mesial margin and distal margin had respectively 0.01mm, 0.02mm, 0.03mm, 0.03mm closer adaptation in 3 unit bridge than in 5 unit bridges. 3. Table II showed that buccal margin, lingual margin, mesial margin and distal margin had respectively 0.06mm, 0.07mm, 0.11mm, 0.05mm closer adaptation in 3 unit bridge than in 5 unit bridges.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.17-21
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• 2009

This experimental study was to determine the fitness on each cervical margin of recast using crown base metal alloy. The alloy used in this experimental study was a Ni-Cr alloy(Wirolloy, Bego, Germany) for the fabrication of full cast crown prosthesis. Twenty-five copings were divided into the five groups. And the group A, B, C, D and E were cording successively according to the frequency of recast to five times. Each specimen was recasted without adding new metal. The experimental results were as follows: 1. The group A and B showed good fitness had subtle differences in each cervical margin adaptation, in other words, the mesio and disto cervical margin showed worse adaptation than the bucco and linguo cervical margin. 2. The group C got good fitness in bucco and linguo cervical margins, but the mesio and disto cervical margin showed inaccurate fitness. And I could not get good casting bodies without adding new metal. 3. The group D and E showed bad fitness for each cervical margin. Therefore the group D and E lost its function as a dental restoration.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.95-103
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• 2002

For this study, self curing resin and heat curing resin used for existing usual resin denture base in the denture industry were chosen by manufacturer. Curing tests for 30-minute, I-hour, 2-hour and 3-hour were conducted to know the strength of the resins and conduct analysis to get other necessary information. The results obtained are as follows: 1. Heat curing resins show a little differences among the manufacturers. However 30-minute curing resin shows great difference as shown in the fracture strength test. 2. The effect from the granularity of the resins on the fracture strength was found insignificant which means there is no difference between coherence and strength. 3. To summarize the results from each time level, the longer the time is, the more the minute cracks on the surface, which is the cause of reduced strength. From this test, it was identified that in making the denture base for patients in dental clinics, 30-minute curing is most efficient and effective in reducing discoloration and monomers, although long-time curing has been considered to be the principal.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.121-130
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• 1997

This study was aimed to help the construction of naturally dental prosthesis by investigation of the factors affecting on the attrition position and attrition angle of maxillary canines. Therefore 163 complete cast of maxillary and mandibular extracted from the student of K. college were subjected for this study, and result through the study are as follows. 1. None attrite rate of the maxillary canine was 7%, of examined teeth. 2. Throughout mesiodistal attrition of 1) Throughout mesiodistal attrition area of the maxillary canines showed that mesial area and mid area of cusp was more frequence in attrition than distal area of it. 2) Sex, dental arch type, vertical overlap, horizontal overlap, did not affect significantly to throughtout mesiodistal attrition statistically 3. Througout labiolingual attrition area 1) Throughout labiolingual attrition area of the maxillary canines showed that attrition of the from lingual to labioncisal edge was more frequence than it of linguoincisal edge 2) It showed that attrition of the from lingual to labioincisal edge was more frequence when the length of horizontal overlap is shorter, by horizontal overlap 3) The attrition of the from lingual to labioincisal edge in maxillary left canines showed that male was more frequence in attrition than female. 4) Dental arch type, vertical overlap, did not affect signioficantly to labiolingual attrition, statistically. 4. Attrition angle 1) It showed that average attrition angle of the maxillary right canines were $19{\pm}11.02$ dagree, and it of left canines were $18{\pm}11.83$ degree. 2) It showed that famale have a bigger attrition angle than male, by sex. 3) It showed that attrition angle was bigger when the length of horizontal ovelap is bigger, by horizontal overlap.

• Journal of Technologic Dentistry
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• v.14 no.1
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• pp.55-65
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• 1992

The purpose of this study was to investigate the comparison of physical properties of nonprecious metal alloys colored goldish yellow. The experimental groups were copper based dental alloy and control group was Ni-Cr based dental alloy used crown and bridges frameworks. Hardness was tested by vickers hardness tester, tensile strength was tested by universal tension tester. After testing the tensile strength of castings, the microstrucure and the pattern of fracture were investigated by scanning electron microscope and metallurgical microscope. The results were as follows : Hardness of Ni based alloy was higher than Cu based alloys. Hardness number of A group was 200.41$\pm$16.10 Hv, B group was 194.33$\pm$1.69 Hv, C group was 139.29$\pm$2.19 Hv and D group was 293.81$\pm$27.17 Hv, respectively. Tensile strength of D group was 56.42$\pm$6.17 $kg/m^2$, A group was 50.39$\pm$5.68 $kg/m^2$, C group was 45.13$\pm$4.53 $kg/m^2$, B group was 45.25$\pm$9.25 $kg/m^2$, in order, and D group was maximum tensile strength. The fractured surfaces of tensile specimens in the all groups showed the tendency to form large voids in the center of specimens. Thus the ductile fracture was changed into the brittle fracture with the fine grain size.

• Journal of Technologic Dentistry
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• v.25 no.1
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• pp.111-118
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• 2003

I measured the movement range on the hinge articulator and the movement range in an oral. And then I studied to analyze the gap. I got wax records by the movement on the hinge articulator, the movement in an oral and the movement on the hand articulating. I measured the distance of the cusp tips that are close to the mesial direction and the distal direction, the buccal direction and the lingual direction then I compared gaps. As I saw results on data, I knew that the hinge articulator represented the range of mandibular movement restrictively. I could find the decisive contradiction that the sliding movement finished on the hinge articulator although it did not finish in an oral. If the sliding movement does not reappear exactly, it brings a fatal failure to the dental prosthesis. In addition it is impossible that the hinge articulator restores the movement in an oral because the lateral condyle inclination and the horizontal condyle inclination are fixed previously. Therefore dental prosthesisses were made by the hinge articulator, they will interfere with a mastication. I have obtained the following results; 1. The distance of sliding movement on the hinge articulator showed shorter than the distance of sliding movement in oral. This means the increase of cusp inclination of the dental prosthesis that was made on the hinge articulator. Therefore, when the lateral movement occurs in oral, there is a possibility to become the premature as the increase of cusp inclination. 2. The results that were impressed records in oral and impressed records on the hand articulating have many congruities. I think that the simple crown etc. that were made by the hand articulating method except the long span bridge and the free end case that can not measure the vertical dimension exactly can represent similarly the mandibular movement. 3. If we want to represent the mandibular movement similarly, we have to use the articulator that can adjust the horizontal condyle inclination and the lateral condyle inclination at least.

• Imaging Science in Dentistry
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• v.30 no.1
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• pp.55-62
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• 2000

Purpose: This study was performed to develop the electronic textbook (CD-rom title) about preclinical practice of oral and maxillofacial radiology, using multimedia technology with interactive environment. Materials and Methods: After comparing the three authoring methods of multimedia, i.e. programming language, multimedia authoring tool and web authoring tool, we determined the web authoring tool as an authoring method of our electronic textbook. Intel Pentium II 350 MHz IBM-compatible personal computer with 128 Megabyte RAM, Umax Powerlook flatbed scanner with transparency unit, Olympus Camedia l400L digital camera, ESS 1686 sound card, Sony 8 mm Handycam, PC Vision 97 pro capture board, Namo web editor 3.0, Photoshop 3.0, ThumbNailer, RealPlayer 7 basic and RealProducer G2 were used for creating the text document, diagram, figure, X-ray image, video and sound files. We made use of javascripts for tree menu structure, moving text bar, link button and spread list menu and image map etc. After creating all files and hyperlinking them, we burned out the CD-rom title with all of the above multimedia data, Netscape communicator and plug in program as a prototype. Results and Conclusions : We developed the dental radiology electronic textbook which has 9 chapters and consists of 155 text documents, 26 figures, 150 X-ray image files, 20 video files, 20 sound files and 50 questions with answers. We expect that this CD-rom title can be used at the intranet and internet environments and continuous updates will be performed easily.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.83-96
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• 2008

This study aims to analyze the major factors in their working conditions affecting the enlargement of leisure activities of dental technicians. We also present a need for dental technicians to assign more time many different kinds of leisure activities for their quality life. To this end, we examined the status and the characteristics of dental technicians' leisure activities among the randomly selected subjects who are working in the area of Seoul, Gyonggido, and Gangwon-do through the analysis of the 311 sheets of self-administered questionnaires. The conclusions from this analysis are as follows; 1. On weekdays, non participants in leisure activities were found to be 64.0%, and in the case of weekends, the participants were reached to 70.7%. Those who enjoy any leisure activities in either of weekdays and weekends were 34.1%, 27.3% of the dental technicians did not have any leisure activities. Therefore, statistical significance was shown in the participations of leisure activities between weekdays and weekends. 2. Of the types of leisure activities in both weekdays and weekends, sports activities were ranked at the top 33.4%, 29.6% respectively, which is followed by going to the cinema/theatre/exhibitions, etc 21.9%, 26.0%, games/entertainment 14.5%, 14.8%, hobbies/cultural activities 14.1%, 12.5%, sightseeing/picnic 6.4%, 7.4%. 3. Of the differences in the characteristics of leisure activities, the types of leisure activities between weekdays and weekends showed difference in gender, company and information regarding leisure activities in age, company and the place of leisure activities, and leisure information in the marital status, career and monthly income in company, company and leisure information in the job position, which is statistically significant (p<.001). However, no statistical significance was found among the other general items of the characteristics of leisure activities. Considering only works on weekdays policy is currently permeating into almost every business sector, dental business owners or managers are advised to consider more effective time management or human resources management, such as keeping reasonable manufacturing time through cooperations with the dentists, regularity of working hours, incentive system, introduction of credible over time payment. Which will provide their staff with more times and opportunities to enjoy their leisure activities. Additionally, the concrete and feasible ways of motivating and activating the leisure activities of dental technicians are in need of further researches and studies.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.9-34
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• 2004

The present study reviews the license registration status of dental technicians and dentists from 1970 to 2002, the number of technician members of The Korea Dental Technician Association from 1990 to 2003, and the number of dentist members in 2003. It also considers the yearly membership fluctuations, its growth rates, yearly increase/decrease, the rate of dentist to dental technician, regional distribution of association members, regional yearly increase/decrease of the members, and the regional distribution of dentists and dental technicians. The purpose is to identify and predict the problems in the demand/supply of dental technicians and the regional imbalance of manpower distribution. By doing so, this study attempts to propose the appropriate standard for the supply of dental technicians and point out the necessity of making mid- or long-term plans for ensuring the efficiency of manpower supply and balanced regional distribution. The result is as follows: 1. The number of dental technicians and dentists in 2002 has grown 36.79 and 9.27 times from 1970, and 2.20 and 2.05 times from 1990, respectively. It tool 11 years for the twofold increase of dental technicians from 1990, one year faster than the same increase of dentists. The number of dental technicians per a dentist was the lowest in 1972 (0.21 person), and the highest in 2002 (0.86 person). Specifically, the fastest growth was observed for a year from 1983 (0.47 technician per a dentist) to 1984 (0.6). From 1984 to 1986, the ratio grew by 0.1 every year. Summing up the numbers of dentists and dental technicians who passed the national certification examination, this study predicted the number of dental technicians per a dentist to be 0.88 in 2003, and 0.90 in 2004. 2. From 1990 to 2003, the average distribution of dental technician was 71.76% in the metropolitan areas and 28.24% in other smaller regions. The proportion of dental technicians working in the three major cities (Seoul, Busan, and Daegu) was the lowest in 2001 (52.39%) and the highest in 1996 (62.66%). The majority number of dental technicians who practiced in the metropolitan areas (about 70% of the entire population) were in service in the three major cities. 3. Compared with 1990, the number of dental technicians in 2003 grew 2.28 times in the large cities, and 2.05 times in other smaller regions. The yearly growth rate was the highest in 1994 over the previous year: 26.06% in large cities and 17.86% in the other regions. In the large metropolitan cities, the growth rate was the highest in Incheon (5.8 times for 5 years from 1998 to 2003), In the rest of the regions, the increase of dental technicians was the highest in Gyeonggi (6.5 times from 1990 to 2003). 4. In 2003, as much as 73.40% of all the members of the Korea Dental Technician Association were distributed in the large metropolitan cities, and the rest 26.60% were in other smaller regions. Meanwhile, 54.35% of the dentists practiced in the metropolitan cities, and the rest 45.65% were in service at other regions. This result indicates that more dental technicians than dentists are concentrated in large cities. More than half of all the technician members of the Association are distributed in the three major cities (i.e. Seoul, Busan, Daegu). On the other hand, 42.03% of dentist members are in these three cities and 53.97% of them practice in Seoul, Gyeonggi, and Busan. In 2003, the ratio of dentist to dental technician is 1:0.43 in general, while the ratio is 1:0.58 in the metropolitan cities, and 1:0.43 in other regions. In 2003, 33.30% of all the certified dental technicians are the member of the Korea Dental Technician Association, while 66.82% of all the licensed dentists are its members.

• Journal of Technologic Dentistry
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• v.31 no.1
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• pp.7-15
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• 2009

Purpose: This study was to propose the clear understanding for stress distribution of supporting bone by use of staggered buccal offset tripodal placement of fixtures of posterior 3 crown implant partial dentures. We realized posterior 3 crown implant fixed partial dentures through finite element modeling and analysed stress effect of implant arrangement location to supporting bone under external load using finite element method. Method: To understand stress distribution of 3 crown implant fixed partial dentures which have 2 different arrangement by finite element analysis. In each model, for loading condition, we applied $45^{\circ}$ oblique load to occlusal surface of crown and applied 100 N for 3 crown individually(total 300 N) for imitating possible oral loading condition. at this time, we calculated Von Mises stress distribution in supporting bone through finite element method. Result: When apply $45^{\circ}$ oblique load to in-line arrangement model, maximum stress result for 100 N for each 3 crown 47.566MPa. In tripodal placement, result for 1mm buccal offset tripodal placement implant model was maximum distributed load 51.418MPa, so result was higher than in-line arrangement model. Conclusion: In stress distribution result by placement of implant fixture, the most effective structure was in-line arrangement. The tripodal placement does not effective for stress distribution, gap cause more damage to supporting bone.