• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.64-80
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• 1998

The risk of cross-contamination in dental clinic is very high. Those who are engaged in dental clinic are exposed to various microorganisms in saliva and blood of patient. Potential possibility of cross-contamination of patient to patient, patient to dentist, dentist to laboratory technician always exist, which is important in the view of public health. It is well known that microorganisms may cause cross-contamination by suck-back of microorganisms into the water supply line or air supply line of dental unit and sprayed back into the next patient's oral cavity. The majority of microorganisms coming from dental unit are water microorganisms from the main water supply which have colonized the tube within the units and multiplied in the relatively warm and stagnant conditions. The purpose of this study is to measure the extent of microbial contamination of dental unit and ultrasonic scaler, to evaluate that dental unit water supply is suitable for drinking water, and to assess the effect of flushing on reduction of microbial contamination of dental unit and ultrasonic scaler. In the first experiment, water samples(50ml) from 20 dental units and 10 ultrasonic scalers in Seoul National Univ. Hosp. were tested for the presence of coliform. The samples were filtered by membrane filtration technique.(Microfil system, Millipore Co. U. S. A.) The filter was then placed onto MacConkey agar plate and the plates with filter on it were incubated aerobically at $37^{\circ}C$ for 5 days. The colors and shapes of colonies were examined if those were coliform. To verify the presence of coliform, the colonies were inoculated into phenol red lactose broth and incubated aerobically at $37^{\circ}C$ for 2 days. The fomation of gas was observed. In the second experiment, water samples from 20 handpieces, 10 ultrasonic scalers and 30 A/W syringes after 0, 2, 4, 6 min. flushing respectively were taken. $200{\mu}l$ water samples were spreaded on Brain Heart Infusion agar plate and the plates were incubated aerobically at $37^{\circ}C$ for 5 days. The number of colony was counted. The results obtained were summarized as follows 1. The water from dental unit and ultrasonic scaler was not suitable for drinking water. 2. No coliform was founded in dental unit and ultrasonic scaler water supply. 3. The number of colony of dental unit and ultrasonic scaler was highest in the group of o min. flushing(p<0.05). 4. There was no statistically significant difference in the extent of microbial contamination among handpiece, ultrasonic scaler and A/W syringe (p>0.05). 5. The number of colony was lowest in the group of 4 min. flushing, but there was no statistically significant difference among 2, 4, 6 min. flushing groups.(p>0.05) 6. It is recommended to flush dental unit water line for 4 min. after use on each patient.

• Journal of Korean society of Dental Hygiene
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• v.18 no.4
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• pp.433-440
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• 2018

Objectives: The purpose of this study was to investigate the pathogenicity of microorganisms by quantitative and qualitative analysis of microorganisms before and after flushing of dental unit water. Methods: This study was conducted on the supply of high-speed handpieces, ultrasonic scalers, and air-water syringes, which sterilized from 10 dental unit chairs at a dental clinic in South Gyeongsang Province. The number of bacterial communities was calculated by collection before and after flushing (2, 4, and 6 minutes). Results: The mean number of bacteria in the handpiece water before flushing was $27,208CFU/m{\ell}$; 2 minutes after flushing, $2,180CFU/m{\ell}$; 4 minutes after flushing, $900CFU/m{\ell}$; and 6 minutes after flushing, $412CFU/m{\ell}$. Conclusions: To minimize the risk of cross-infection and intra-clinic infection in dental clinics, education and water quality monitoring may be needed.

• Journal of Microbiology
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• v.45 no.1
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• pp.1-5
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• 2007

The bacterial compositions between the dental unit water system and human saliva were characterized and compared by direct sequence analysis of 16S rDNA clone libraries. Based on the species richness estimation, bacterial diversity in the dental unit water system (DUW) was more diverse than that of the human saliva (HS). The Chaol estimates of species richness in HS and DUW samples were 12.0 and 72.4, respectively. The total numbers of OTUs observed in the combined libraries accounted for 83% (HS) and 59% (DUW) of the Chaol diversity estimate as defined at the 80% similarity threshold. Based on the sequence analysis, the phylum Proteobacteria was the major group in both clone libraries at phylum level. DUW clone library contained 80.0% Proteobacteria, 8.0% Bacteroides, 4.0% Nitrospira, 4.0% Firmicutes, 2.0% Planctomycetes and 2.0% Acidobacteria. On the other hand, human saliva (HS) clone library contained 55.5% Proteobacteria, 36.1% Firmicutes and 8.4% Bacteroides. The majority of bacteria identified belonged to phylum Proteobacteria in both samples. In dental unit water system (DUW), Alphaproteobacteria was detected as the major group. There was no evidence of the bacterial contamination due to a dental treatment. Most sequences were related to microorganisms derived from biofilm in oligotrophic environments.

• Journal of Korean society of Dental Hygiene
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• v.16 no.4
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• pp.507-516
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• 2016

Objectives: The purpose of the study is to investigate the awareness and practice of dental unit waterline management in dental hygienist. Methods: A self-reported questionnaire was completed by 377 dental hygienists in Seoul and Gyeonggido from March 2 to April 30, 2015. The data were collected by direct visit and informed consent was received after explanation of the study. The questionnaire consisted of general characteristics of the subjects, awareness of dental waterline, practice of dental waterline, and implementation of dental waterline disinfection. Data were analyzed using SPSS 12.0 program. Results: There was a significant correlation between the dental unit waterline disinfection and the appropriateness of the water used for dental treatment(p<0.01, p<0.001). The handpiece was the most commonly used device before treatment and the majority of the subjects answered that they didn't take water out of ultrasonic scaler and air-water syringe on a daily basis. Conclusions: The majority of the dental hygienists did not know the right understanding and proper practice of dental unit waterline management. To reduce the dental device contamination, the continuing education of waterline management should be done for the dental hygienists.

• Journal of dental hygiene science
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• v.15 no.4
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• pp.383-392
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• 2015

Dental chair unit (DCU) is the most essential equipment for the dental treatment in dentistry. DCU output water is used for various applications during dental treatment. DCU output water must be clean at the same level as drinking water since patients and dental staff are regularly exposed to water and aerosols generated from the DCU. Many studies demonstrated that DCU output water is frequently contaminated with microorganisms including opportunistic pathogen such as Legionella and Pseudomonas species. Thus, DCU output water may be a potential source of infection. In order to reduce microbial contamination levels in DCU output water, periodic management and continuous disinfection are necessary. Currently, there are a variety of disinfection methods for managing DCU output water and its efficacy is also diverse. We reviewed the level of microbial contamination, clinical implications of contaminated DCU output water and the various DCU disinfection methods.

• Journal of Technologic Dentistry
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• v.12 no.1
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• pp.103-106
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• 1990

The purpose of this study was to determine if homogeneity of the resin associated with benchcuring could be obtained in the curing unit as the water increased from room temperature to curing temperature. The results of the experiment were as follows : 1. Long periods of bench-curing are not necessary. 2. Bench-curing can take place in the water bath of the curing unit. When this procedure is used, the water should be far enough below the temerature at which active polymerization of the resin proceeds to allow the bench-curing to occur.

• Journal of dental hygiene science
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• v.15 no.2
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• pp.232-237
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• 2015

The water supplied from dental unit water systems (DUWS) in dentistry may be heavily contaminated with bacteria and thus may be a potential source of infection for both practice staff and patients. The aim of this study was to evaluate the level of heterotrophic bacteria and to confirm the presence of opportunistic pathogens from DUWS in student clinical simulation laboratory of college of dentistry. Water samples were collected from 36 ultrasonic scalers in student clinical simulation laboratory. The levels of heterotrophic bacteria in water samples were quantified by counting colony forming units (CFUs) on R2A agar media. In addition, opportunistic pathogens were detected by using the polymerase chain reaction (PCR) method. The mean CFUs were 16,095 CFU/ml for water samples and all of water samples exceeded current American Dental Association recommendations of 200 CFU/ml. Pseudomonas species and non-tuberculous Mycobacterium species were detected in the one sample and two samples, respectively, among the 36 water samples by the PCR with specific primers for these bacteria. Our study indicated that DUWS in student clinical simulation laboratory can cause potential infection in students and participants. This study suggested the dental unit water line management and wearing personal protective equipment in student clinical simulation laboratory will be needed to reduce bacterial contamination.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.4
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• pp.391-396
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• 2006

The CT number is called Hounsfield unit(HU). Generally HU has a score between +1000 from -1000, and it is standardized usingthe air(-1000), water(0), and compact bone(+1000). Hounsfield Unit to standardize the density in computed tomography using the air and water has been used to analysis of lesion in other medical field. Computed tomography is popular method to analysis of lesion in oral & maxillofacial field but the analysis about density of lesion by Hounsfield unit is still obscure. For this study, computed tomography taken in Dankook University Dental Hospital and Hounsfield unit was measured to compare the difference of jaw bone lesion as cystic lesion, benign tumor, malignant tumor.

• Journal of Korean society of Dental Hygiene
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• v.13 no.1
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• pp.166-173
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• 2013

Objectives : The purpose of this study was to survey some soldiers oral care products along recognition, and thereby to identify possible correlations among those factors. Methods : Questionnaire survey was carried out targeting 272 soldiers. The collected data was performed frequency & percentage, fisher's exact test, chi-square test and multiple regression analysis. Results : Respondents approving the implementation of water fluoridation were 50.5%. The general factors of approval were age, education, Monthly household income. The knowledge factors of approval were experience of hearing of this program, the knowledge of the purpose of this program, the knowledge of the some regions in South Korea had been implement water fluoridation. The results of multiple logistic regression analysis were the awareness of oral health and the knowledge level of water fluoridation were related with this program approval. Conclusions : The study suggest that oral care products should be include in military dental health care program. In addition to development dental health programs each military unit is dental health care between Korean soldiers.

• Journal of Korean Academy of Dental Administration
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• v.11 no.1
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• pp.38-46
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• 2023

Composite resins, commonly used in clinical practice, have been developed to improve aesthetics to obtain smooth surfaces. Although the restored composite resin has a smooth surface, it gradually becomes rough over time. Therefore, this study measured glossiness to evaluate the surface of various composite resins and attempted to evaluate the maintenance of glossiness of composite resins by observing surfaces that change to roughness. Specimens were produced using resin used in clinical practice: Gradia direct anterior (GA), Tetric N-Ceram (TN), Ceram.X Sphere TEC one (CX), Filtek Z350XT (FT), Estelite sigma quick (ES). After creating a smooth surface with slide glass, five locations were randomly selected to measure surface gloss, and the average was the representative value of the specimen. Roughness was applied to the specimen under water pouring at the same speed and pressure using SiC paper #2400, 1200, and 400. The gloss unit of different SiC papers was measured. To evaluate the gloss unit and gloss retention between composite resins, one-way analysis of variance and Tukey multiple comparisons test were used. As a result of the study, there was a difference in gloss unit of specimens produced under the same conditions. Although the degree differed depending on the composite resin, there was also a difference in gloss retention. Based on the findings, composite resins show differences in gloss due to their different characteristics. Ceram.X Sphere TEC one (CX) showing the lowest gloss retention and Estelite sigma quick (ES) showing the highest.