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The present study reviews the license registration status of dental technicians and dentists from1970 to 2002, the number of technician members of The Korea Dental Technician Association from1990 to 2003, and the number of dentist members in 2003. It also considers the yearly membershipfluctuations, 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 andpredict the problems in the demand/supply of dental technicians and the regional imbalance ofmanpower distribution. By doing so, this study attempts to propose the appropriate standard for thesupply of dental technicians and point out the necessity of making mid- or long-term plans forensuring the efficiency of manpower supply and balanced regional distribution. The result is asfollows:1. The number of dental technicians and dentists in 2002 has grown 36.79 and 9.27 times from1970, and 2.20 and 2.05 times from 1990, respectively. It tool 11 years for the twofold increase ofdental 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 certificationexamination, 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 themetropolitan 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 dentaltechnicians who practiced in the metropolitan areas (about 70% of the entire population) were inservice in the three major cities. 3. Compared with 1990, the number of dental technicians in 2003 grew 2.28 times in the largecities, and 2.05 times in other smaller regions. The yearly growth rate was the highest in 1994 overthe 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 yearsfrom 1998 to 2003), In the rest of the regions, the increase of dental technicians was the highest inGyeonggi (6.5 times from 1990 to 2003).4. In 2003, as much as 73.40% of all the members of the Korea Dental Technician Associationwere 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 inservice at other regions. This result indicates that more dental technicians than dentists areconcentrated in large cities.More than half of all the technician members of the Association are distributed in the three majorcities (i.e. Seoul, Busan, Daegu). On the other hand, 42.03% of dentist members are in these threecities 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 inthe 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 DentalTechnician Association, while 66.82% of all the licensed dentists are its members.

Two diketones, 1-phenyl-1,2-propanedione(PD) and 2,3-butanedione (BD) were investigated asnew visible light photosensitizers for a dental resin composite of bis-GMA in order to improvephotopolymerization effect. And the photopolymerization efficiency of mixed photosensitizers,PD-CQ and DA-CQ, was studied. Photopolymerization effect of photosensitizers were comparedwith that of camphorquinone(CQ), the most widely used photosensitizer. The photopolymerizationefficiency of bis-GMA containing the photosensitizer increased with irradiation time. The increasewas in the order: BD < CQ < PD. The photopolymerization efficiency of this mixture was not soefficient as CQ or PD.

The purpose of this study was to research the recognition of Korean Dental Technicians in Busanregion about retitle of the name of 'Dental Technician'(DT), then to figure out the reality of retitleof the name(DT), so to provide data for whole country survey and to drive of the retitle of DT byKorea Dental Technicians Association.For these purpose, 250 subjects were sampled out of dental technicians in Busan, and the surveywas performed with self-administered questionnaire. Out of all collected questionnaires, 192pieces(76.8%) were addressed for this study.1) Their desires on changing of the name(DT), 57.4%(74/129) was agreed.2) If they could change the name(DT), they hope 3 main new names and the others, Dental LabArt Technician(39.2%), Certified Dental Technician(23.0%), Dental Prosthetic Technician(23.0%),the others(14.8%).

The objective of this finite element method study was to analyze the stress distribution inducedon a supporting bone by 3.75, 4.0, 5.0diameter of dental implant fixture(13length). 3-dimensional finite element models of simplified gold alloy crown(7height) and dental implantstructures(gold cylinder screw, gold cylinder, abutment screw, abutment, fixture and supportingbone(cortical bone, cancellous bone) designs were subjected to a simulated biting force of 100 Nwhich was forced over occlusal plane of gold alloy crown vertically.Maximum von Mises stresses(MPa) under vertical loading were 9.693(3.75diameter offixture), 8.885(4.0diameter of fixture), 6.301(5.0diameter of fixture) and the highest vonMises stresses of all models were concentrated in the surrounding crestal cortical bone. The wide diameter implant was the good choice for minimizing cortical bone-fixture interface stress.

Glass ceramics for dental crown prosthesis were prepared by crystallization of CaO-MgO-SiO2-P2O5-TiO2 glasses. Their crystallization behaviors have been investigated as a function of heat-treatment temperature and holding time in relation to mechanical properties.The results are as follows:Vickers hardness and bending strength of glass ceramics increased due to the precipitation ofapatite, whitlockite, -wollastonite, magnesium titanate, and diopside crystal phases within glassmatrix. The final crystalline phase assemblages and the microstructures of the glass ceramics were foundto be dependent on heat-treatment temperature and holding time.Vickers hardnes and bending strength of glass ceramics increased with increasing heat-treatmenttemperature and holding time.

Hydroxyapatite powder were synthesized by precipitation method, varying pH, and reactiontemperature. The powders were heated at 1,200°… and 1,300°… for fabrication of dentalprosthesis.The results are as follows:Synthesized powder showed the smallest particle in size, under the conditions of pH 11 andreaction temperature 37°…. The hydroxyapatite was partially converted to , ‚-TCP at 1,200°…and 1,300°….Mechanical strength of sample was affected by such powder preparation conditions as pH andreaction temperature and sintering temperature. The mechanical strength of sample prepared under the same conditions was increased withincreasing pH, reaction temperature and sintering temperature

A new Ti-10Ta-10Nb alloy has designed and examined some possibility of forming more passiveoxide film by oxidation treatment which is closely related to corrosion resistance andbiocompatibility. Ti-6Al-4V and Ti-10Ta-10Nb alloys were prepared by consumable vacuum arcmelting and homogenized at 1050for 24hours. Alloy specimens were oxidized at thetemperature range of 400 to 750for 30minutes, and the oxide films on Ti alloys were analysedby optical microscope, SEM, XPS and TGA. Cytotoxicity test was performed in MTT assay treatedL929 fibroblast cell culture by indirect method.It is found out that the oxide film on Ti-10Ta-10Nb alloy is denser and thinner compared to Ti-6Al-4V alloy. The weight gain during the oxidation was increased rapidly at the temperature above650for Ti-6Al-4V alloy and above 700for Ti-10Ta-10Nb alloy respectively. It was analysedthat the passive film of the Ti alloys consisted of TiO2 through X-ray photoelectron spectroscopy(XPS) analysis. It is found out by cytotoxicity test that moderate oxidation treatment lowers celltoxicity, and Ti-10Ta-10Nb alloy showed better result compared to Ti-6Al-4V alloy.

This study obtained the following consequences, as a result of the comparative analysis for thecastability depending on an angle of the sprue and wax pattern in case of manufacturing dentalprostheses, for the castability depending on direction, and for the castablility of sprue, whichattached the reserve to each different 3.5mm roll wax(sprue wax) and to 2.5mm sprue wax. 1. As a result of the comparative analysis for the castability depending on an angle of the sprueand wax pattern, the best castability was shown when the angle of the sprue and wax pattern is180°∆(straight line), and the lowest castability was shown in 45°∆, which was curved most, andthere was no statistical significance. 2. As a result of the comparative analysis for the castability of an angle depending on direction,the best castability was shown in the farthest side from the direction of centrifugal casting, and thelowest castability was shown in the same side as the direction of centrifugal casting, and therewas no statistical significance. 3. Given comparing the castability depending on the pattern of sprue, the better castability wasshown in 135°∆and 180°∆when using 3.5mm roll wax(sprue wax), compared to attaching thereserve to 2.5mm sprue wax.

In this study, optical and mechanical properties were investigated with 4 kinds of commercialdental enamels. As a result of EDS analysis SiO2, Na2O, Al2O3and K2O were the main components of commercialdental enamels. In case of H specimen, content of SiO2and K2O were more than that of anotherspecimens. Starting powder and fired specimens were glass ceramics which were consist ofamorphous phase and leucite (crystalline) phase. Crystallization did not occurred during firingprocess, since the XRD peak intensity was similar between starting powder and fired specimens.As a result of differential thermal analysis, Tgand crystalline temperature was varied withcomposition in the range of 548~576and 735~780respectively. 0.5thickness dental enamelspecimens showed sufficient translucent properties. However, transmittance and reflectance werelower than 5% result from scattering due to the refractive index difference between glass andcrystalline phase. 3 point bending strength was in the range of 73.9~101.8MPa which was similaror slightly higher than enamel of natural teeth and Vickers hardness was higher than enamel ofnatural teeth more than 100.

The organization to which we belong is the place where we make social relationships, satisfy ourdesires of self-realization, and accomplish our common object. The emotional and psychologicalstate of individual as well as the whole organization is able to be explained in the concept ofmorale. The researcher selected a total 238 dental technicians living in seoul, and conducted a research ina period ranging from April 1, 2004, to April1 10, 2004. The researcher analyzed the findings with the aid of SPSS (Statistical package for socialsciences). The researcher came to reach the following conclusions on the basis of frequency,percentage, T-test, F-test, and multiple regression. The results of this study were as follows: First, there is a significant difference in recognizing morale due to their age, academicbackground, their work places, position, part of objective, and working hours(p<.05). Secondly, The researcher there is a significant difference in recognizing due to their socialwelfare, payment, fair and objective personnel management, enough opportunities of selfdevelopment, and autonomy(p<.05). Lastly, this study is very limited in generalization because it deals with a small part of moralemanagement plans and objectifies very limited organization. But, it is very meaningful in trying to approach morale management plans with an object ofdental technicians. It is necessary that dental technicians should make efforts to control themselves.

In the present study, a simple method was successfully used for hydroxyapatite coatings on Ti-6Al-4V substrates deposited by using a sol-gel derived precursor. Prior to hydroxyapatite coatingthe samples were micropolished (0.1 micron) and divided into three sets. The first set,were themicropolished samples kept as such. The second set were coated with titania sol and the third setwas treated with 5M NaOH. After three repetitions of hydroxyapatite coating procedures on eachset and heat treatment at 600 °∆C, the formation of hydroxyapatite has been confirmed by XRDanalyses and the substrate material was found to be oxidized with negligible amount of CaO in thecoating. The SEM studies revealed surface morphology. Hydroxyapatite, calcined at 600°∆C,displaying a porous structure arisen from heating of the bulk But, it is very meaningful in trying to approach morale management plans with an object ofdental technicians. It is necessary that dental technicians should make efforts to control themselves.

The purpose of this study is to introduce how to make implant supported over denture with O-ring.Many kinds of attachments have used to dental restorations. The application of attachment haswidely increased implant fixed prosthesis and implant supported over denture.In order that implant supported over denture have properly retention, generally used O-ring,magnetic, bar attachment. O-ring give us an advantage that is required more minimum verticaldimension than bar-type and easily replace with new part.When we make these prosthesis using O-ring, Bar, Ball attachment, we should followingprocedures. Strong occlusion force leads to fracture of over denture because part of functionalmechanism as implant abutment or attachment is spaced.Clips are regularly activated. O-ring and springs are changed every year. The pattern ofresorption should be carefully monitored and compensated for by relining procedures.If the over denture appears to rest on the bar or the ball attachments, relining should beperformed and clips/caps should be changed.