• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.1-2
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• 2003

While aromatic polyimides and polyamides have found widespread use as high performance polymers, the present work addressed the need for organosoluble materials through the use of a hyperbranching scheme. The $AB_2$ monomers were prepared. The $AB_2$ monomers were then polymerized via aromatic fluoride-displacement and Yamazaki reactions to afford the corresponding hydroxyl-terminated hyperbranched polyimides (HT-PAEKI) and amine-terminated hyperbranched polyamides, respectively. HT-FAEKI was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketone-imide)s were soluble in common organic solvents. AT-PAEKI was blended with a bisphenol-A-based bismaleimide (BFA-BMI) in various weight ratios. Thermal, rheological, and mechanical properties of these blend systems were evaluated. Two characteristic hyperbranched polyamides, which the one has para-electron donating groups to the surface amine groups and the other has para-electron withdrawing groups to the surface amine groups, were selected to compare BMI curing behaviors. The electron rich polymer displayed ordinary Michael addition type exothermic reaction, while electron deficient polymer did display unusual curing behaviors. Based on analytical data, the later system provided the strong evidences to support room temperature curing of BMI by reactive intermediates instead of reactive primary amine groups on the macromolecule surface.

• International Journal of Oral Biology
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• 제40권3호
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• pp.143-146
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• 2015

The purpose of this study was to compare the effect of different methods of hand washing by counting the number of bacteria on the hand surface. Eighteen clinicians were chosen and divided into three groups, consisting of six clinicians each. Culturing of the right raw palms of all individuals was performed. Individuals in the control group washed hands for 5 seconds with antimicrobial soap. Group 1 washed their hands for 10 seconds with antimicrobial soap. Group 2 washed with an instant alcohol-based hand sanitizer. After the respective washes, re-culturing of the right raw palm was done for each member of all groups. The colony-forming units (CFU) were calculated at each time point, and the reduction rate of CFU among the three groups were statistically evaluated using student t-test. All groups showed a significant decrease in CFU, according to the time applied (P<0.01). In addition, the reduction rate of CFU between the groups were statistically evaluated with ANOVA (P<0.01). It showed statistically difference between the control group and group 1, control group and group 2. The present study confirmed that the hand washing method with antimicrobial soap for 10 seconds and hand sanitizer, including alcohol, were excellent for decreasing the number of bacteria on the hand surface.

• 대한치과기공학회지
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• 제43권2호
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• pp.35-41
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• 2021

Purpose: This study aimed to investigate the flexural strength and surface microstructure of the zirconia crown according to the number of glazing zirconia prostheses. Methods: The specimens were made as follows. A specimen without glazing: 1ea, first glazed specimens (group B): 10ea, second glazed specimens (group C): 10ea, third glazed specimens (group D): 10ea. Three-point measuring strength equipment and electron microscopes were used for strength measurement and microstructure observation. As for statistical analysis, one-way ANOVA and t-test (level of significance level=5%) were used to determine the difference in the change in flexural strength according to the number of glazing zirconia prostheses. Results: ANOVA analysis of groups B (1st glazing), C (2nd glazing), and D (3rd glazing) revealed that the change in strength between the groups is statistically significant (p=0.023). The Mann-Whitney test for each group revealed that the difference in flexural strength between groups B and C was not statistically significant (z=-0.302, p=0.762) while that between groups C and D was statistically significant (z=-0.257, p=0.01). Microstructure observation revealed 3 changes in the microstructure of the surface of the glaze powder were observed. Conclusion: According to the number of glazing zirconia prostheses, it was found that the difference in strength between groups was statistically significant, and changes in the microstructure were observed.

• 대한치과보철학회지
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• 제44권5호
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• pp.549-560
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• 2006

Purpose : This experiment examined the effects of anodization on commercially pure titanium implant fixtures. Material & methods : The implant fixtures were anodized at three different voltage levels, producing three different levels of oxidation on the surface of the fixure. Implant were divided into four groups according to the level of oxidation. Group 1 consist of the control group of machined surface implants, Group 2 implants were treated by anodizing to 100 voltage, Group 3 implants were treated by anodizing oxidation to 200 voltage Group 4 implants were treated by anodizing oxidation to 350 voltage. Surface morphology was observed by Scanning Electron Microscope(SEM) and the surface roughness was measured using NanoScan $E-1000^{\circledR}$. Implantation of the fixtures were performed using New Zealand white rabbits. $Periotest^{\circledR}$ value(PTV) resonance frequency analysis(RFA), and removal torque were measured in 0, 2, 4, 8, 12 weeks after implantation. Results : The results of the study were as follows: 1. Values for the measured surface roughness indicate statistically significant differences in Ra, Rq, and Rt values among group 1, 2, 3, and 4 at the top portion of the thread,(p<0.05) while values at the base of the threads indicated no significant difference in these values. 2. A direct correlation between the firming voltage, and surface roughness and irregularities were observed using scanning electron microscope. 3. No statistically significant differences were found between test groups regarding $Periotest^{\circledR}$ values. 4. Analysis of the data produced by RFA, significant differences were found between group 1 and group 4 at 12 weeks after implantation.(p<0.05) Conclusions : In conclusion, no significant differences could be found among test groups up to a certain level of forming voltage threshold, beyond this firming voltage threshold, statistically significant differences occurred as the surface area of the oxide layer increased with the increase in surface porosity, resulting in enhanced bone response and osseointegration.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.65-80
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• 1999

The purpose of this study was to evaluate the effects of periodontal curet and various rotating instruments on the root surfaces. Thirty-five extracted teeth with advanced periodontal disease were used. They was root planed with periodontal curet, periodontal Perio-Clean bur, periodontal Roto-Perio bur, resin polishing ET bur, and resin polishing diamond fissure bur. To find dentinal tubule orifices on the root surface, tetracycline HCI solution was applied to the one tooth of treated each group. Then, root surfaces were investigated using scanning electron microscope. Amount of loss of cementum was evaluated by loss of tooth substance index. The results were as follows. 1. Groups treated with periodontal curet and Perio-Clean bur showed irregular surface and concavities. Concavities seemed to be lacunae of cementocyte. Other groups treated with Roto-Perio bur, resin polishing ET bur, and resin polishing diamond fissure bur showed partially opened dentinal tubule orifice. 2. Groups treated with periodontal curet and Perio-Clean bur and tetracycline HCl showed irregular surface. No dentinal tubule orifice was seen. Other groups treated with Roto-Perio bur, resin polishing ET bur, and resin polishing diamond fissure bur and tetracycline HCl showed dentinal tubule orifice with various shape and size. 3. Loss of tooth substance indices were compared between groups. There was no statistically difference between periodontal curet and Perio-Clean bur groups. There were statistically differences between periodontal curet and Roto-Perio bur, ET bur, and diamond fissure bur groups. As a result of this study, groups treated with Roto-Perio bur, resin polishing ET bur, and resin polishing diamond fissure bur showed more cementum removed than groups treated with periodontal curet and Perio-Clean bur. Therefore, in a conventional treatment for periodontal disease, it was recommended that periodontal curet or Perio-Clean bur should be used. In a treatment for regeneration of periodontal tissue, it was recommended that Roto-Perio bur, resin polishing ET bur, or resin polishing diamond fissure bur should be used

• 구강회복응용과학지
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• 제25권2호
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• pp.83-94
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• 2009

본 연구는 지르코니아의 연마 정도와 tribochemical coating 등 두 가지 표면처리가 두 가지 레진 시멘트, 즉 Bis-GMA 계 레진 시멘트와 자가접착형 레진 시멘트와의 결합력에 어떠한 영향을 미치는가를 연구 비교하였다. $1{\mu}m$과 $50{\mu}m$ 의 다이아몬드 디스크로 연마한 지르코니아 시편을 만들어 접착기전이 다른 두 가지 레진 시멘트 RelyX ARC(3M Espe, USA)와 RelyX Unicem(3M Espe, USA)으로 결합시켰다. 지르코니아 표면에 로카텍 시스템 처리를 한 군과 하지 않은 군을 비교해 지르코니아와 레진 시멘트 사이의 전단결합강도를 측정하여 다음과 같은 결론을 얻었다. 1. 로카텍 시스템으로 표면처리를 한 군이 하지 않은 군에 비해 높은 전단결합강도를 보였다(P < 0.001). 2. 로카텍 시스템으로 표면처리를 한 군에서는 $50{\mu}m$ 연마 군이 $1{\mu}m$ 연마 군에 비해 높은 전단결합강도를 보였으며 통계학적 유의성을 보였다(P <0.001). 그러나 로카텍 처리를 하지 않은 군에서는 $50{\mu}m$ 연마 군과 $1{\mu}m$ 연마 군 간의 차이는 없었다(P >0.01). 3. RelyX Unicem을 이용하여 접착한 군이 RelyX ARC를 이용하여 접착한 군에 비해 높은 전단결합강도를 보였다(P < 0.01). 본연구의 결과에 따르면, 새로운 형태의 자가접착형 레진 시멘트의 지르코니아와의 전단결합강도는 기존의 Bis-GMA 계 레진 시멘트보다 우수하였으나, 제조자의 지시와 달리 지르코니아 표면에 로카텍 처리를 하는 것이 전단결합강도의 증진에 매우 효과적이었다.

• Journal of Periodontal and Implant Science
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• 제26권4호
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• pp.889-905
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• 1996

It is known that growth factors function as potent biologic mediators regulating numerous activities of wound healing via cell proliferation, migration and extracellular matrix formation and they also promote periodontal regeneration. But, method of growth factor application is controversial yet. So purpose of this study is to evaluate the effect of demineralized root surface as one of method of growth factor application. The ginigival fibroblasts were primary cultured and fifth or sixth subpassages were used in these experiments. In first experiment, root surface blocks demineralized with 100mg/ml tetracycline for 5 minutes and pH 1 citric acid for 3 minutes(experimental groups) and nonteminerilized root surface blocks (control groups) were placed in 100ng/ml PDGF-BB for 5 minutes. Then the cells were seeded on each root surface blocks and cultured for 6, 24, 48, 72 hours. In second experiment, root surface blocks deminerilized with tetracycline and citric acid and nondemineralized root surface blocks were placed in 200ng/ml PDGF-BB for 5 minutes and another non-demineralized root surfcae blocks were placed in DMEM without PDGF-BB. At 1, 2, 4, 6, 8 days, the cells were seeded in 24-well plate and using of each eluent, cultured for 72 hours. The results of the four determinants were presented as mean and S.D.. The results were as follows : The attachment and proliferation of human gingival fibroblast on root surface were more increased when PDGF-BB was applicated on root surfrace demineralized with tetracycline or citric acid than non-demineralized root surface. And, in comparision tetracycline with citric acid, there were more attachment and proliferation of human gingival fibroblast on root surface demineralized with tetracycline than citric acid, and proliferation of human gingival fibroblast on demineralized root surface was increased time dependently 1 day to 3 days. In second experiment using eluent, proliferation of human gingival fibroblast was more increased to 6 days when human gingival fibroblast was cultured in eluent that PDGF-BB was applicated on demineralized root surface than two control groups, and degree of proliferation was decreased time dependently 1 day to 6 days. Proliferation of human gingival fibroblast cultured in eluent without PDGF-BB was constant 1 day to 6 days. After 6 days, degree of proliferation of human gingival fibroblast was similar in four groups. This means that release duration of PDGF-BB from demineralized root surface is 6 days. And in comparision tetracycline with citric acid, there was more proliferation of human gingival fibroblast in tetracycline-treated group than citric acid. In conclusion, demineralized root surface as primary site for PDGF-BB application, especially demineralized with tetracycline has important roles in attachment and proliferation of human gingival fibroblast, and may be useful clinical applications in periodontal regenerative procedures.

• Restorative Dentistry and Endodontics
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• 제25권4호
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• pp.550-560
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• 2000

In this study, shear bond strength of two bonding systems were measured and appearance of dentin surfaces were observed with SEM according to the storage time of eugenol on dentin surface, thus evaluated the effect of eugenol on bond strength of two dentin bonding systems. Control groups were directly bonded to dentin surface with One Step, Prime & Bond 2.1. Experimental groups were divided into experimental I and II according to dentin bonding agents. After eugenol application, dentin surfaces were bonded with One Step and Prime & Bond 2.1 according to the each storage time of immediately, 3min, 24hour, 48hour and 1week, and then control and experimental groups were filled with light cured composite resin(Z-100). After 24 hours water storage at $37^{\circ}C$, all samples were subjected to a shear load to fracture at a cross head 1.0mm/min with Instron universal testing machine(No. 4467). Etched dentin surface storaged for each time of immediately, 3min, 24hour, 48hour and 1 week after eugenol application were observed under Scanning Electron Microscope(Hitachi S-2300) at 20kvp. The data were evaluated statistically with two-way ANOVA and Tukey's HSD. The results were as follows; 1. Shear bond strengths were higher in control groups than in the experimental groups. 2. As storage time was increased after eugenol application, the shear bond strengths were decreased in experimental groups. 3. In experimental I, II the shear bond strengths were the lowest in which storage time was 1 week after eugenol application. 4. As storage time was increased after eugenol application, etched dentin surfaces showed obstructed dentinal tubule.

• The Journal of Korean Physical Therapy
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• 제33권6호
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• pp.265-271
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• 2021

Purpose: We aimed to analyze the reliability of the test for choice stepping reaction time (CSRT) under an unstable surface and determine whether there were differences in CSRT between support surface conditions (stable vs. unstable conditions) and between age groups (young adults vs. community-dwelling older adults). Methods: Twenty healthy community-dwelling older adults and twenty young adults performed the stepping task under an unstable condition over two visits. The mean of the two trials measured for each visit was used for the analysis. The test-retest reliability was analyzed using intra-class correlation coefficient (ICC) with a 95% confidence interval, standard error of measurement (SEM), and minimal detectable change (MDC). Differences in CSRT between support surface conditions and age groups were analyzed using the independent t-test with Bonferroni correction. Results: Excellent consistency was observed for ICC >0.90 in both groups. Moreover, the SEM and MDC values of the CSRT in older and young adults were 0.03 and 0.09 and 0.01 and 0.04, respectively. There was a significant difference in the CSRT between the age groups under stable (p<0.001) and unstable conditions (p<0.001). Conclusion: The findings demonstrated that the test for CSRT under an unstable condition had reliable results in both groups. Although older adults demonstrated longer reaction times than younger adults in all surface conditions, increasing the balance control demand by implementing a choice stepping task concomitant with a balance task had no influence on the reaction time in both age groups.

• The Journal of Advanced Prosthodontics
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• 제14권5호
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• pp.305-314
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• 2022

PURPOSE. The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling. MATERIALS AND METHODS. Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM). RESULTS. Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone. CONCLUSION. Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.