I have tried to make electronic listening and analyzing appratus, which were used for temporomandibular disorder patient’s. It can be heard T.M.J.D’s sounds. Normal person heard 20~20,000 Hz sound. Electronic appratus can capture furthermore. Electronic appratus composed of stethoscope rubber tube,small microphone, amplifier, telemetry, oscilloscope and speaker. The aim of oscilloscope and speaker are seen and heard T.M.J. sounds both dentists and patients.In developing countries, they use electronic stethoscope for diagnosis of heart sound and use for tele diagnosis. In my nation, laws of food and drugs were very rigid, so many researcher’s developed electronic stethoscope, but they could not produce it because of law. I suggest that soften the rigid law, and many new product will be produced. The apparatus that I developed was operated quite well both wired and wireless. It is suggested that we must develop new apparatus for T.M.D. patients and Telemedicine.

This study was performed to analyze the psychologic change of Tae-kwon-do Athletes who were wearing the mouth guard and one of contact sports during their matches of Tae-kwon-do 10 selected Tae-kwon-do athletes who had no injuries which they had college Tae-kwon-do sparring matches in the Cheon-an area have participated in the study. The oral impressions if the selected athletes were taken to produce for individual custom mouth guards. After the mouth guards were produced, each of them sat in a chair and attached G.S.R. surface electrodes in the palms of the ends of the second and third fingers of their left hands without moving their left hands, And then they were asked to watch footages of Tae-kwon-do games to stimulate them as if the had have a mock match, and Labscribe2 which are one of polygraphy was used to record their G.S.R. values. To determine whether the mouth guards affected the changes of their psychological status during the sparring matches of not, the experimental group wore the mouth guards while they watched the footages, and the control group didn’t wear any mouth guards. The G.S.R. values of the two groups were measured while the watched the footages. To see if there were and significant polygraphy differences between the experimental group and the control group in G.S.R. values, a statistical package SPSS was used to make a comparative analysis. And there were significant change in between the experimental and control group that wore the mouth guards, and it was concluded the wearing mouth guards exerts an influence on change in the psychological state of Tae-kwon-do athletes while they watch a footage of mock match.

It is necessary to make preventive method for the trauma and disturbance complications of orofacial area because athletic trauma are physical and mental defects. Since 1913, an italian boxer discussed mouth guard with dentist and used it. It was reported that mouth guard from field prevented trauma, increased the muscle force and activated electromyogram although the history of mouth guard wearing was short. The mouth guard has prevented the trauma and also increased the muscle force. The purpose was to study muscle force and activity of EMG with mouth guard wearing. It concluded that mouth could prevent trauma and increase the muscle force

Dental implants were used for reconstruction of oromaxillofacial defects and they were widely used in dental and medical fields. The implant materials are various , including titanium and ceramics such as zirconium. The property of implant materials have biocompatibility and mechanical strength. Titanium has direct bone anchorage without any other tissues between implant's interface. many researcher's had studied for raising the osseointegration success rate through various method. It was reported over 95% success ratio. many researcher's study the enhancing the speed of bone remodelling and osseointegration. Low Level Laser Therapy is one of the method to accelerlate the speed of bone remodelling and osseointegration. Thus it raise initial stability. The purpose of this study was to evaluate the effect of diode laser irradiation for ossoeintegration in implant interface and between the implants threads. 24 New Zealand white rabbits which were about 3Kg, used for experiment. 2 implant's were implanted every rabbit's tibia. 2 weeks, 4 weeks, 8 weeks after implantation, tissue sample were removed from sacrificed rabbit's tibia. 8 rabbit's were sacrificed every 2, 4, 8 weeks and undecalcified sample were got from tissue sample. The undecalcified samples were investigated by optical microscope. 2 weeks, 4 weeks, 8 weeks experimental groups which were irradiated low level laser therapy showed rapid bone remodelling than control groups. it showed many difference especially in initial stage. Low level laser irradiation increase the volume of new bone formation in implant interface . It was suggested that there were many influence in bone remodelling in early stage, because these were many differences between experimental and control groups. Low level laser irradiation were helpful for immediate loading implant

The purpose of this study was to investigate the effect of cytokine-induced osteoclastogenesis on tooth movement related to orthodontic force. We evaluated the cytotoxicity as well as the expression of OPG and RANKL, which influence the homeostasis of bone metabolism. Titanium particles were applied to human periodontal ligament cells and subcultured fourth generation cells. The ALP assay and the MTT assay were used to assess changes in cytotoxicity. After 48 hours, cytotoxicity increased proportionally with the concentration of titanium. With 20 mg, the cytotoxicity was the lowest. R T-PCR was u sed for assessing m R NA l evels of O PG a nd R ANKL; after 96 hours, t he m R NAs of O PG a nd R ANKL increased steeply. A western blot analysis showed that with 20 mg of titanium, the protein expression of OPG increased linearly with time, especially a fter 96 hours, while t he p rotein e xpression o f RANKL d id n ot s how significant changes with titanium processing. Given the increase in OPG expression after the initial cytotoxicity, changes in cytotoxicity with titanium may be attributable to the antagonistic effect of OPG on cytotoxicity

Currently, dental implants are generally used for reconstruction of oromaxillofacial defects. Implants are widely used in dental and medical fields. The materials of implants are variable such as metals and ceramics. The materials of implants must be have not toxicity and biocompatibility to host and mechanical(physical) strength. Bones must be attached to titanium surface without any other tissues. many researcher's had studied for raising the osseointegration through various method which are including implants designs and materials. It was reported over 95% success ratio. many researcher's study the methods which are enhancing the speed of bone remodelling and osseointegration. Thermo dynamic therapy is one of the method to accelerlate the speed of bone remodelling and osseointegration. Thus it raise stability of implants. The purpose of this study was to evaluate the effect of diode laser irradiation for ossoeintegration in implant interface and between the implants threads. 24 New Zealand white rabbits which were about 3kg weight, used for experiment. 2 implant's were implanted every rabbit's tibia. 2 weeks, 4 weeks, 8 weeks after implantation, tissue sample were removed from sacrificed rabbit's tibia. 8 rabbit's were sacrificed every 2, 4, 8 weeks and undecalcified sample were made from tissue sample. We have investigated the undecalcified samples by back scattered electron microscope. We have analysied the length rate and area rate in implant interface and inside the threads. The results were as follows. 2 weeks, 4 weeks, 8 weeks experimental groups which were irradiated low level laser therapy showed rapid bone remodelling than control groups. It was suggested that Initial bone remodelling may be effected by LLLT because of implant bone contact ratio between 4th weeks and 8th weeks had no siginifant difference. Initial bone remodelling may be more influenced than later bone remodelling by LLLT because of new bone formation area ratio between implant threads had no significant differences during 4th to 8th weeks. According to above results, low level laser irradiation accerlate the new bone formation in implant interface and inside the implants threads at initial stage. there were many factors which are increasing the bone remodelling, because there were many differences between experimental and control groups. Low level laser irradiation were helpful for increasing the initial stage of bone remodelling because of above results.

Currently, Low-level laser therapy (LLLT) is widely used in medicine and dentistry. It has been suggested that LLLT may be beneficial in management of many different medical conditions, including pain, wound healing and nerve injury. Stimulation with LLLT can enhance bone repair as reported in experimental studies on bone defects and fracture healing also. As far as hard tissue is concerned, the biostimulating effect of laser has been demonstrated more rapid healing of tibial bone fracture in mice. This study was performed to compare new bone formation between with LLLT and without LLLT. Two cylinder implants(5mm diameter, 5mm length) were implanted on rabbit's tibia. LLLT was done to one implant with 632mm diode laser. And than Rabbit's were sacrificed after 2nd, 4th, 6th, 8th weeks after implantation. Bone with implant were removed and fixed with 10% formaline. Undecalfied sample were prepared after spurr low resin embedding. Sample were grind and polished to 100㎛. The results were as follows. The amount of trabeclue of experimental group were superior to that of control group from 2 weeks to 8 weeks. There were no difference in arrangement of trabecule between two groups. Bone implant contact were significantly increased at 4th weeks in experimental group. The number of ostecytes in trabecule were different at 4th weeks experimental group. Osteone were appeared dominantly at 6th weeks experimental group, while at 8th weeks experimental group were superior than control group. LLLT group showed increased amount of trabecule, bone implant contact, number of osteocytes & osteone. It suggested that LLLT might be increase the bone formation rate and accelerate the bone formation time.

We conducted a series of in vitro experiments to evaluate the anticancer effect of photodynamic therapy using hypericin and 532㎚ DPSS (diode pumped solid state laser). The cultured KB cells were treated with serial concentrations of hypericin ranging from 0.01㎍/㎖ to 5㎍/㎖ (two-fold dilution) with variable laser dosage (10J, 20J, 30J). The cell viability was evaluated by MTT assay. The type of cell death was detected by fluorescent microscope using Hoechst 33342 / PI (propidium iodide) stain methods. In this study, IC50 value with hypericin-mediated PDT with 10J DPSS laser was 35 ng/ml. The maximum cytotoxicity with Photofrin II-based PDT was observed at high drug concentrations(> 90 ng/ml) independent with laser dose. And the in vitro PDT effects depended on the laser dose and drug concentrations were displayed by the difference in the type of cell death, namely apoptosis or necrosis. According to this result, the hypericin based photodynamic therapy with DPSS laser was effective photodynamic therapy.

Currently, implants are widely used in dental and medical fields. Especially dental implants are widely used for reconstruction of oral and maxillofacial defects. Many researcher's had studied for raising the osseointegration through various method. It was reported high success rate. Also they study the enhancing the speed of bone remodelling and osseointegration. Low level laser therapy is introduced one of the methods to accelerate the speed of bone remodelling and osseointegration. The purpose of this study was to evaluate the effect of diode laser irradiation about to raise ossoeintegration. Twenty four New Zealand white rabbits which were about 3Kg were used for experiment. Two implants were implanted same side of rabbits tibia. Diode laser was irradiated 1cm diameter, 0.5 watt power, 1 minute duration at periphery of one of implants. Eight rab b its were sacrificed every 2, 4, 8 weeks, made undecalcified sample. We investigated in the undecalcified samples histological and histomorphometrc analysis by light microscope. The results were as follows. 2 weeks, 4 weeks, 8 weeks experimental groups which were showed rapid bone remodelling than control groups. They showed many difference especially in early healing time. Bone Implant contact rate were 47% in 2 weeks experimental group. 28% in 2 weeks control groups, 82% in 4 weeks experimental groups, 62% in 4 weeks control groups, 98% in 8 weeks experimental groups and 84% in 8 weeks control groups then experimental groups show statistically significant difference(p＜0.05). Bone remodelling area rate inside the implant threads were 49% in 2 weeks experimental groups. 31% in 2 weeks control groups, 90% in 4 weeks experimental groups, 82% in 4 weeks control groups, 99% in 8 weeks experimental groups and 97% in 8 weeks control groups then 2,4 weeks experimental groups show statistically significant difference(p＜0.05). Implant-bone contact length rate and bone remodelling area rate were no significant difference of linear regression equation of control and experimental groups then bone remodelling were different at early healing time but there were no differences of time changes. According to above results, one of the low level lasers diode laser irradiation was effected on the volume of new bone formation in implant interface and between the implants threads. Low level laser irradiation were helpful for initial stage of bone remodelling.

Low energy photon irradiation by light in the far red to near infrared spectral range(630~1000nm) using low energy lasers or light emitting diode arrays has been found to modulate various biological processes in cell culture and animal models. The purpose of this study was to examine the light emitting diode irradiation effect on activity of normal human osteoblast on titanium plate in vitro by various energy density, and to observe morphologic change of NHost on titanium plate and to analysis concentration of Ca++, IP and ALP. NHost were cultured in DMEM containing 10% FBS, and observed by inverted microscope for attatchment to the surface of titanium plate. Ca++, I.P., and alkaline phosphatase( ALP) concentration in medium was calculated during 4 weeks, which was treated with Wilcoxon rank, Anova test and linear regression. Morphologic changes showed LED produced in vitro increases of cell growth of 144~256% in NHost. During a culture period, Ca++ concentration was decreased. LED treatment(>3J/cm2) stimulate calcium consumption in NHost. Statistically, a significant difference was not found between LED power density. LED treated group(>3J/cm2) had higher total inorganic phosphate concentrations than control group in NHost. Statistically, a significant difference was not found between LED power density. No significant changes were observed between ALP acitivity and LED treatment. In spite of LED power density, there were rapid growth rate of NHost and no significant of Ca++, IP and P concentration but these concentration showed predominant change than that of control.

Laser is used to prevent the early dental caries in dental f ield and to apply for treatment of stomatitis and hyper sens it ivity , and laser mass Recently it is reported that laser i1'r adiation affect on soft tissue treatment and bone 1'emodelling after dental implantation. The purpose of this study was to examine laser irradia ti on effect on activity of normal human osteoblast on titanium plate in vitro by various laser wave length, and to observe morphologic change of NHost on LiLa nium plate and to a nalysis concentration of Ca"++ , IP and ALP NHost were cultured in DMEM containing 10% FBS, and observed by in verted microscope 1"or attatchment to the surface of titanium plate. Ca ++, I.P. , and a lkaline phosphat ase(ALP) concent ration in medium was calculated during 4 weeks, which was treated with Wilcoxon rank, Anova test and linear regression. The obtained results were as follows Morphologic changes showed rapid growth rate of NHost ++ at 3 days of laser lrradiatlOn ln spite of laser wave type, Ca" and P concentration was decreased at 2 weeks and was the hig hest at 3 weeks, but decreased at 4 weeks In spite of laser wave type, ALP concentration was decreased at 2 weeks but was increased at 3-4 weeks, From the aboving results, in spite of laser wave type, there were rapid growth rat e of NHost a nd no significant of Ca"++ , IP and P concen tr ation but these concentration showed predominant change than that of control

Most Authors reported that mouth guard is a part of equipment for body-contact sports players. Mouth guards protect orofacial injuries but have some problems in breathing and speaking. Some authors reported that mouth guards have also improve the muscle strength and sport ability. This experiment was performed to study the change of masseter muscle EMG after wearing of mouth guard. 10 D university male base ball players were participated in this study. After impression taking, mouth guards were constructed and weared. Masseter muscle EMG and nasal ventilation after ten day's adaptation were checked. They were requested clenching with or without mouth guard. EMG and nasal ventilation were checked by iworx 104 instrument simultaneousley. The result showed that masseteric EMG were improved and nasal ventilation were stable after wearing mouth guard. It concluded that mouth guard had improved muscle activity and stabilized the nasal ventilation depend on experimental method.

This experiment was performed to study the biocompatibility of xenograft materials (ABBM. coralline HA). Both autogenous bone grafts and allogenic banked bone were frequently and successfully used to promote regeneration of parts of skeleton. The use of these types of grafts were limited by the cost of donor site operation for autogenous boneor by fear of the risk of infection of allogenic materials. Another type of graft is xenograft which include ABBM and coralline HA. For investigating the biocompatibility, generally many investigators used cancer cell lines or animal cell lines. But cancer cell lines and animal cell lines had functioned different metabolism from normal human cell. So the experiment used normal human osteoblast for compare the biocompatibility of ABBM with coralline HA which were fixed in 24 well base contained culture medium. After 1st, 3rd, 7th, 14th, 28th days, the culture medium were taken out and checked the concentrations ofcalcium( Ca), inorganic phosphate(IP) and alkaline phosphatase(ALP). In another method, histologic samples were investigated after 8weeks of xenograft materials implantated on rabbit's tibia, the bone was cut and made undecalcified ground samples and checked with fluorecent microscope, polarizing microscope, reflection electron microscope and electron probe microanalysis. The statistical results of concentrations (Ca, IP, ALP) of materials in the culture medium have decreasedby day's, which meant that xenograft materials were effective for bone remodelling. The concentrations in the culture medium of ABBM were lower than that of coralline HA, that meant that biocompatibility of ABBM were superior than that of coralline HA. Histologic samples showed that ABBM had better bone remodelling effect than coralline HA. ABBM showed good alizarin red marking lines, more deposition of Ca, IP, and dense color of bone around newly formed osteon and bone trabeculae. it was concluded that ABBM was more biocompatible than corallineHA in vivo and in vitro test

Since ancient Eygypt, various dental materials were used for lost teeth including gold. The key point of this materials were nontoxic to human body. Since early of 1990's, dental implant was done for recovery of maxillofacial defects. From middle of 1970's, osseointergation concept of implant was introduced and performed in dental field. Biocompatibility of titanium showed good effect for osseointergration but had some problems (Galvance current and toxic corrosion) with suprastructures such as gold crowns. This study was performed to make safe dental implants which have reduced Galvanic currents and corrosion. 3 kind of dental casting gold alloys (different Gold contents, 1㎝×1㎝×0.1㎝ plates.) were used as experimental group, while Titanium were used as control group. Normal human osteoblasts(NHOsts)were cultured during 1-4weeks for histologic study. For analysing the calcium(Ca), Phosphorus(P) and alkaline phosphatase(ALP), NHosts were cultred during 2-23days. After experiments, histologic finding were observed by LSM and SEM. Ca, P, ALP concentration by automatic biochemical analyzer were analyzed by ANOVA test and linear regression method. The results were as follows. Biocompatibility of dental casting gold alloys were similar to titianium alloys histolgically. Biochemical analysis of dental casting gold alloys had no significant difference to titianium alloy except AIGIS-Fine. We could conclude that biocompatibility of dental casting gold alloys with high contents of gold were superior to that of low contents and alloys with high contents of gold had no significant difference from titanium on NHost culture. Gold dental implant might be better than titanium implant due to similar biocompatibility and no galvanic currency.

In order to investigate stresses of dental patients in dental clinic by dental-analogous stimulations, we selected 23 women and 36 men who are students of dental college in D university. This experiment was performed to compare and analyze the changes of Galvanic skin resistance and heart rate by dental-analogous stimulations. In paired t-test of male group's GSR average, there were significant differences between sound and touch, and among pain and other stimulations. And in paired t-test of female group's GSR average, there were significant differences among pain and other stimulations. In paired t-test of male group's heart rate average, there were significant differences between vision and pain, and between touch and pain. And in paired t-test of female group's heart rate average, there were significant differences between smell and pain. In unpaired t-test of male and female group's GSR average, there were no significant differences in smell, sound, vision, touch, and pain. In unpaired t-test of male and female group's heart rate average, there were no significant differences in smell, sound, vision, touch, and pain. It seemed that stresses during dental treatment could be changed by surrounding circumstances and sex distinction.

1'hi s s t u dy was pe rformed to investigate the osseointegration on the interface between bone and dental casting gold alloy's impla nts . Some inves tigators prese nted that only fi brous integratioJ1 in implant interface of precious met al im plants was occu red. 1'he mate ri a ls of dental implant must have biocompatibility and have no phY5ical 01' chemical s ide effect lmpla nts whi ch we re made of pure t itanium or titanium alloys had 50me chemical problem such as Galvanic current wi th s uprastru ctu re cur re ntly. So. we t hought that there was no problem if dental casting gold al1 0y’s impla nts had 5ucceed osseoin tegration. Thi s s tudy used 99%. 86%. 70% gold composition ìmplant as experimental group and tita niuITI implant as cont ral g rOllp. After 4th a nd 8th weeks of implant impLantation. experimental animals were saC l 나 i ce d and hi stologic sections we re made. All sections were examined by 8EM. PM. L8M. and EPMA. lmplants made of dental casting gold a ll oys occllrred good osseointegration as titanium implants. Osseointegr ation were not depend on the gold composit ion in implant groups ’ denta l casting gold al1oys. Both groll ps‘ osseointegration were 1TI0re completed in 8th weeks than 4th weeks . From t he a boving results. dental casting gold alloy's implants had induced similar osseointegrat ion to t h at 01" titan iu rn irnplants . So if we make implant and suprastructllre of dental casting gold alloys. Galvanic current and chemical co rrosio ns wOllld be sllppressed

The aim of this study was to investigate the cytotoxicity of dental casting gold alloys. Recently, "biocompatability" is considered the most important requirement of dental materials. Dental metals and alloys were estimated by quantity of released ions, which had influenced to living tissues. The requirement of using normal human cells for cytoxicity strudy were abruptly increased. We used the cultured normal human gingival fibroblasts to estimate the cytotoxicity of dental casting gold alloys. The product of S company(Korea, AIGIS-SOFT, AIGIS-PLUS, AIGIS-A, AIGIS-PT, experimental group) and D company's (German, Biocclus inlay, Biolor SG, Stabilor NF Ⅳ, Degulor B, control group) dental casting gold alloys were used. The morphological investigation, hemolysis test, MTT assay and SRB assay were done in vitro. In vivo, inflammatory reaction in rat was examined for 2 weeks. 1. In the result of cytotoxicity assay, there were some differences but was no significancy among the results between two group's hemolysis, MTT and SRB assay. 2. The gingival fibroblasts attached to the surface of dental casting gold alloy showed various features and increased in number as the time had passed. 3. In vivo, chronic inflammatory cell infiltration was prominent from 3 days to 1 week and inflammation was reduced as time had gone. From the aboving results, there were no significant differences in cytoxicity depending on the ratio of gold content, but showed differences depending on the ratio of total precious and non-precious metal content between two groups. In vitro study showed few differences in inflamation reaction.

This study was conducted to test the anticancer effect of photodynamic therapy using chlorophyll derivative (9-HpbD-a) and 632nm diode laser. Human SNU 1041 cells were seeded into 96 well plate of 104cells/well and cultured for 24 hours. Cells were washed with media containing various concentration of 9-HpbD-a ranging from Oug/ml to 3.75ug/ml. Then 932 nm diode laser was given at various lasering time setting, and at various starting time after ini tial 24 hours of culture. The treated cells were incubated 48 hours and tetrazolium-based colorimetric(M'IT) assay was done to measure the viability of cells For in vivo study, SNU- 1041 cells were xenografted into the back of nude mouse. When the xenografted tumors grew up to 400-600 mm3, the animals were randomly placed into 4 groups: Group 1 (n=20) , PDT group, interstitial injection of 9-HpbD- a (47 ug/kg) followed by irradiation with 3.2 J/c야 of light 6 hours after then i띠 ection; Group II (n=lO) , irradiation with 3.2 J/crrf of light using diode laser; Group III (n=lO), in terstitial injection of 9-HpbD- a only(47 ug/kg); Group IV (n=lO), normal control group. The viability of cells was de creased with increasing lasering time No significant difference of cell viability was noted by variously delayed starting time of lasering. PDT effects were observed in the xenografted nude mouse model Group IV (no 9-HpbD-a, no laser irradiation) was a control group which showed a continuous tumor growth. Group III (9-HpbD-a i띠 ection only) showed no response, Group II (laser irradiation only) sho￦ed 1 complete remission out of 10 (10%) , Group 1 (9-HpbD-a and laser irradiation) showed 13 cpmplete remission out of 20 (65%) , Group 1 showed significant remission rate, comparing to other groups (p<0.05). This study demonstrated anticancer effect of photodynamic therapy using 9-HpbD-a and 632nm diode laser on human squamous cell carcinoma cell line.

We conducted a series of in vitro experiments to evaluate the efficiency of photodynamic therapy on head and neck cancer cell using hydroxybacteriochlorine from photosynthetic bacteria. We tested the cytotoxicity of the hydroxybacteriochlorine by MTI assay and observed the cell death pattern(apoptosis or necrosis) after PDT by hoechst 33342 and propidium iodide staining methods IC50 value of the hydroxybacteriochlorine was 0.22μg/rrúi. At higher doses of hydroxybacteriochlorine () 0.6μg/rrúi) , cancer cells died exclusively by necrosis after PDT. By contrast, at IC50 value, hydroxybacteriochlorine induced cancer cell to undergo apoptotic cell death. The induction begins approximately 6 hours after PDT. We investigates intracellular localization of hydroxybacteriochlorine by head & neck cancer cell via confocal laser scanning microscopy. Head & neck cancer cells dual-stained with hydroxybacteriochlorine and a panel of organelle- specific fluorescence probes (Mitotracker, Lysotracker, ER-Tracker) revealed an intracellular fluorescence distribution restricted to cytoplasmic compartments with no detectable fluorescence in the nucleus Confocal images of cells containing hydroxybacteriochlorine were never overlap in subcellular organelle fluorescence when digitally over layed with the organelle-specific fluorescence probe images of the same cells. These results demonstrated that the hydroxybacteriochlorine may have a function as a photosensitizer.

This expe띠nent was performed to evaluate the contamination of private dental clinics and the effect of antiseptics. 까lere are high risks of cross infection in dental clinic during the dental treatffient both in dental clinic workers and dental pa디ents. We took the samples in 30 dental clinics. 4 sites(hand piece, head rest, room air, and cuspidor) were sampled in each clinic. Each samples were studied with molecular biologically using DNA sequencing. After DNA sequencing, all microorganisms were tested with 4 commercial antiseptics. The results were as followings. 1. 30 species and 54 strains of pathogenic microorga띠sms were found in 30 dental cωúcs. 2. 깨ere were no signifìcant difference in regions for fmding the micr，∞rganisms(p(O. 06). 3. 8 species and 13 sσains of micr∞rganisms were found in room air of Seoul area, and 6 species and 10 strains were in head rest of An-yang area were the most frequent sites. 4. Staphylococcus epidermidis was found the most frequently. 5. Calymatobacterium granulomatis and Enterococcus faecalis were found, which were not concemed with oral disease 6. Sterilization effect showed difference by antiseptics and also showed difference by sterilization method and sites. From the aboving resutls, there were no significant difference in regions for finding microorganisms, but little differences in sampling site. There were quite differences depend on the sterilization method and antiseptic drugs. It may be exist that there are high risks of cross contamination between dental c뼈c workers and patient.