• Restorative Dentistry and Endodontics
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• 제38권2호
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• pp.73-78
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• 2013

Objectives: This study evaluated the effect of three different air-drying times on microleakage of three self-etch adhesive systems. Materials and Methods: Class I cavities were prepared for 108 extracted sound human premolars. The teeth were divided into three main groups based on three different adhesives: Opti Bond All in One (OBAO), Clearfil $S^3$ Bond (CSB), Bond Force (BF). Each main group divided into three subgroups regarding the air-drying time: without application of air stream, following the manufacturer's instruction, for 10 sec more than manufacturer's instruction. After completion of restorations, specimens were thermocycled and then connected to a fluid filtration system to evaluate microleakage. The data were statistically analyzed using two-way ANOVA and Tukey-test (${\alpha}$ = 0.05). Results: The microleakage of all adhesives decreased when the air-drying time increased from 0 sec to manufacturer's instruction (p < 0.001). The microleakage of BF reached its lowest values after increasing the drying time to 10 sec more than the manufacturer's instruction (p < 0.001). Microleakage of OBAO and CSB was significantly lower compared to BF in all three drying time (p < 0.001). Conclusions: Increasing in air-drying time of adhesive layer in one-step selfetch adhesives caused reduction of microleakage, but the amount of this reduction may be dependent on the adhesive components of self-etch adhesives.

• 대한치과보철학회지
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• 제39권2호
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• pp.220-229
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• 2001

This study was performed to evaluate the fracture resistance of three improved die stone materials according to water/powder ratio. There are lots of handling conditions which affect the physical properties of improved dental stone, and it's well known that the water/powder ratio significantly affect the strength of die stone. If water/power ratio was incorrect, following disadvantages were showed : (1) susceptibility to dimensional change due to abrasion, (2) limited reproduction of fine detail, (3) lack of strength. The maxillary master casts were made of additional silicone impressions(Exaflex, GC America. Inc. USA). Three type IV die stones such as Fuji Rock (GC Europe Intreleuvenlaan, Leuven, Belgium), Velmix(Kerr, Manufacturing company, USA), and Crytal Rock( Maruishi Gypsum Co. Ltd, Japan) were tested. A total of 160 casts were prepared, separated, and tested on the Instron Testing Machine(Model 4201, Co. USA). The obtained results of this study were as follows : 1. Fuji Reck and Velmix less 3ml than the water/power ratio of manufacturer's instruction showed the highest resistance to fracture. According to increasing water/powder ratio, fracture resistance was significantly increased(P<0.05). Crystal Rock showed the highest fracture value when it was mixed with the water/power ratio of manufacturer's instruction. 2. Water/powder ratio of the manufacturer's instructions and less 3ml than that showed lower fracture value of hand mix than that of vacuum mix. Water/powder ratio of more 3ml, 6ml than manufacturer's instructions was not significantly different between hand mix and vacuum mix(p>0.05). 3. Velmix had the highest viscoelastic value among three die materials when it was mixed with the manufacturer's instruction. Viscoelasticity was decreased according to increasing water/powder ratio.

• 대한치과보철학회지
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• 제39권5호
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• pp.492-501
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• 2001

The use of alginate impression materials today is prevalent because of its efficiency and simplicity in clinical settings. Unfortunately, the simplicity of the procedure tends to lull the dentist into a sense of well-being, and lead him into using careless or sloppy technique. Alginate impression materials are used to fabricate diagnostic and preliminary casts, and the final cast. Incorrect use of this material is known to affect the accuracy of the final prosthesis. The purpose of this study was to compare the effect of different mixing methods of alginate impression material and tray adhesive on the accuracy of the stone cast produced by each method. A total of 30 stone casts were produced by using 3 different types of mixing methods (10 stone cast for each mixing method, respectively). The first method utilized an automatic-mixing machine to mix alginate while the second method was carried out manually, strictly following manufacturer's instructions. The third method also involved manual mixing, but did not follow the manufacturer's instructions and was done in a random fashion. Also, 20 additional stone casts were produced by using alginate with or without tray adhesives were included in the study to evaluate effects of tray adhesives on the accuracy of alginate impression. 10 stone casts were produced by adding tray adhesives to the interior surface of the impression tray prior to taking the impression. The other 10 excluded this step. A total of 50 stone casts were analyzed by the three-dimensional measuring machine to measure and compare the dimensional changes of the impression material of each group. The results are as follows. 1. No significant difference was found between the automatic mixing group and the manually-mixing group(p>0.05). 2. For the group that followed manufacturer's instructions, less dimensional changes were record ed than the group that didn't in measuring distanced 4(p<0.05). 3. The group that used tray adhesives showed less dimensional changes(p<0.05). The findings revealed that mechanical methods of mixing alginate impression materials had little influence on dimensional changes. However, it is proven that following manufacturers instructions in alginate impression taking is an important step in acquiring accurate impressions and tray adhesives may play an important role in enhancing the results.

• 대한의생명과학회지
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• 제22권4호
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• pp.115-126
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• 2016

Audiometric calibration is a prerequisite for securing the reliability of audiometric test results by checking the internal consistency of the relevant instrument. The purpose of this review is to help instrument operators understand the calibration procedure of aural acoustic immittance instrument which is frequently used for objective assessment. By referring to the latest international standards and the national standards relevant to the aural acoustic immittance instrument, the following parameters will be reviewed: 1) introduction of performance characteristics, 2) detailed procedure of the calibration method. According to the newest international and national standards [IEC 60645-5 (2004), ANSI S3.39-1987 (R2012)], the aural acoustic immittance instrument basically includes six components: 1) calibration cavity, 2) acoustic immittance analysis system, 3) probe assembly/unit and signal, 4) pneumatic air-pressure pump system, 5) acoustic reflex activator system and 6) tympanogram and acoustic reflex plotting system, each of these components should meet set standards. The result of behavioral hearing tests is influenced by various complex factors including the examinee's cooperation, background noise of the examination room, measurement method, skill level of the audiologist and calibration status, but the objective hearing tests is more influenced by the calibration status of the instrument than any other factors. The audiologist should take full responsibility for the reliability of the hearing test result, so he/she should carry out the calibration check and adjustments of aural acoustic immittance instrument periodically and maintain the instrument continuously by referring to the newest standards and the manufacturer's instruction manual.

• 한국동물위생학회지
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• 제40권2호
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• pp.133-137
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• 2017

Three swine farms which were suffering from slight economic loss due to suckling piglets' diarrhea, were selected to apply commercialized multivalent vaccine for sow use; $SUISENG^{(R)}$ (Hipra, Spain). Farms were pre-diagnosed with clinical symptoms and molecular detection of C. perfringens Type A and C and E. coli pili by PCR. Sows were vaccinated twice 2 ml of the vaccine at 6 and 3 weeks ante partum intramuscularly according to the manufacturer's instruction. All vaccinated sows did not show any adverse reaction or clinical signs; hypersensitivity, fever, granuloma or abscess on the injection site, appetite loss, and so on. Also, no reproductive disorder was appeared in vaccinated sows compared with non-vaccinated control sows. The results suggested that piglets born from vaccinated sows show significantly better performance in regard of the diarrhea index and mean daily weight gain compared with piglets from non-vaccinated sows. Therefore, the commercial vaccine for the prevention of neonatal diarrhea is found to be effective in reducing diarrhea in the first suckling period of piglets after birth.

• 대한치과보철학회지
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• 제44권2호
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• pp.157-164
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• 2006

Purpose: The purpose of this study was to compare the fracture strength of the zirconia monolithic all-ceramic crowns according to the thickness(0.5 mm, 0.8 mm, 1.1 mm) and IPS Empress II ceramic crown of 1.5 mm thickness. Material and method: Eight crowns for each of 3 zirconia crown groups were fabricated using CAD/CAM system(Kavo, Germany) and eight Empress II crowns were made from silicone mold and wax pattern. Each crown group was finished in accordance with the specific manufacturer s instruction. All crowns were luted to the metal dies using resin cement and mounted on the testing jig in a universal testing machine. The load was directed at the center of crown with perpendicular to the long axis of each specimen until catastrophic failure occurred. Analysis of variance and Tukey multiple comparison test(p<.05) were applied to the data. Results and Conclusion: 1. The fracture strength of the zirconia monolithic all-ceramic crown was higher thickness increased(p<.05). 2 The fracture strength of 1.1 mm thickness zirconia monolithic all-ceramic crown was higher than the fracture strength of 1.5 mm thickness IPS Empress II crown(p<.05). 3. The fracture strength of 0.5 mm thickness zirconia monolithic all-ceramic crown exceeded maximum occlusal forces.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.403-424
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• 1996

Cell culture methods have been used to assess the cytotoxicity of dental materials. Different paramaters are used to monitor cytotoxic effects. But it is difficult to compare each investigator's results with different methods. The objective of this study was to investigate cytotoxic effect of several retrograde filling materials according to cell lines and assay methods. Cytotoxicity of Bestalloy (Dogmyung, Korea), Prisma APH(Densply International Inc., U.S.A.), Clearfil FII (Kuraray Co., Japan), Fuji II (GC Co., Japan), Fuji II LC (GC Co., Japan) and IRM (Densply Co., U.S.A.) on L929, 3T3 and KB permanent cell lines was measured. Radiochromium, Lactate dehydrogenase (LDH) release method and colorimetric assays, namely neutral red (NR) and MTT were used. Each material was mixed according to the manufacturer's instruction. They were tested as solid and extracted state. Cell culture media were added to each mixed or solid materials then the solution was collected and used as extract solutions. Solid Fuji II showed mild cytotoxicity on three cell lines using radiochromium release method. There was no difference in cytotoxicity of extract solution group using radiochromium release method. In colorimetric assay immediate Fuji II group and all the IRM groups showed severe cytotoxic effect. Difference in cyctotoxicity was due to rather kinds of cell lines than assay methods. Solid Fuji II and IRM showed mild cytotoxicity on three cell lines. But extract solutions had different cytotoxic effect according to cell lines using LDH release assay. Light-cured glass ionomer had mild to moderate degree of cytotoxicity on three cell lines. Cytotoxicity was affected by specimen prepaton. Susceptibility of each cell ines were also affected by assay emthods. It was suggested that cytotoxicity study using only one cell line and/or assay method might not accurately reflect the real toxic nature of dental biomaterials.

• 대한치과기공학회지
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• 제30권1호
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• pp.57-63
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• 2008

The purpose of this study was to ascertain the effect of different abutment height and different taper of abutment on retention force of cemented implant-supported prostheses. Test specimens consisted of different abutment height group(3mm, 4mm, 5mm, 6mm, 7mm) and different taper(degrees) abutment group($4^{\circ},\;5^{\circ},\;6^{\circ},\;7^{\circ},\;8^{\circ}$). The surfaces of abutments and crowns were manufactured and finished by automatic lathe(CNC). Luting cement(Tokuso Ionomer) was prepared according to the manufacturer's instruction. And the cylinders were sealed onto the abutments and loaded in compression at 5kg for 10minutes. Excess cement was removed from the abutment-cylinder junction and the specimens were stored at room temparature for 24 hours. Specimens were tested in tension using a universal testing machine. Within the limits of this study, the following conclusions were drawn: 1. The increase in abutment height result in improvement in retention strength(P<0.05). 2. The increase in taper of abutment result in decrease in retention strength(P<0.05). 3. The decrease in abutment height result in decrease in retention strength, besides has a significantly lower retention strength at 3mm abutment height. 4. The increase in taper of abutment result in decrease in retention strength, besides has a significantly lower retention strength at $7^{\circ}$ abutment.

• 한국동물위생학회지
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• 제33권1호
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• pp.59-66
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• 2010

This study was carried out to investigate the characters of Listeria monocytogenes isolated from food, animal feces, dry cattle food, and the environment in Seoul and Kyonggi province during the period from 1998 to 2003. Serotyping of 70 L. monocytogenes isolates was performed according to the manufacturer's instruction. Minimum inhibitory concentrations (MICs) were determined by the microdilution method according to the guidelines of the Clinical and Laboratory Standards Institute. All the isolates were tested against 20 antimicrobial agents. The serotypes of the 70 L. monocytogenes isolates were 1/2c (62.8%), 1/2a (20%) and 1/2b (17.2%). Of the 70 L. monocytogenes isolates, 67.1%, 57.1%, 11.4%, 5.7%, 2.8%, 1.4% and 1.4% were resistant to tetracycline (Te), minocycline (Mi), norfloxacin (Nor), ciprofloxacin (Cip), neomycin (N), chloramphenicol (C) and cephalothin (Cf), respectively. However, all isolates were 100% sensitive to antibiotics such as amikacin, ampicillin, erythromycin, gentamycin, imipenem, kanamycin, ofloxcin, streptomycin, penicillin, trimethoprim, trimethoprim/sulfamethoxazole, tobramycin, and vancomycin. Multiple resistance patterns of the isolates were observed in TeMiNor Cip (1.4%), TeMiNor (7.1%), TeMiCip (2.9%), TeMiN (1.4%) and TeMi (44.3%). The results of this study indicate that many L. monocytogenes isolates are resistant to antimicrobial agents including Te and Mi. The possibility that the isolates could increasingly acquire multiple antimicrobial resistant properties cannot be precluded.

• 대한치과기공학회지
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• 제12권1호
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• pp.113-119
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• 1990

The purpose of this study was to investigate the effect of surface tretment on strength of denture repair as influenced by repair resin. Specimens were fabricated from VERTEX heat cured resin. Rectangular specimens($60\times10\times3mm$) were prepared according to the manufacturer's instruction for mixing and packing the resin into molds. Two methods of surface treatment were used and two methods of repair were also tested. The transverse strength of the resin was measured before repair and after repair by AUTOGRAPH testing machine. Six specimens of each category were prepared for testing for a total of 24 specimens. The mean value of the percent of recovery was calculated from the percent of recovery for six specimens. The results were as follows : 1. The mean value of the percent of recovery of each category makes a significant difference statistically one another(p<0.01), and "C" category, chloroform solvent-heat cured resin, has a better effect on repair srength than any other. 2. When no chloroform is used to treat the fractured surface there is no significant difference between the mean values of the percent of recovery influenced by the self curing resin and heat cured resin. But, when chloroform is used there is a significant difference between the two repair resins(p<0.01). 3. When self curing resin repair is used there is no significant difference between repair with and without the surface treatment of chloroform. But, when heat cured resin repair is used the use of chloroform treatment become significant statistically (p<0.01).