• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.185-191
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• 2000

The water-soluble glucan produced by Lactococcus lactis 1370 affects the formation of dental plaque by Streptococcus mutans. In this study the factors affecting the formation of water-soluble glucan were assessed as the optical density of culture supernatant of Lactococcus lactis 1370 in the spectrophotometer. 1. The optical density of culture supernatant was high when Lactococcus lactis 1370 was cultured in M17 broth with 5% sucrose, while being low in culture supernatant of Streptococcus mutans. 2. The optical density of culture supernatant was higher when Lactococcus lactis 1370 was cultured in M17 broth with 10% sucrose than when being cultured without sucrose (p<0.05), and was higher at pH 7 than pH 5 (p<0.05). 3. The optical density of culture supernatant was the highest at $37^{\circ}C$ among $32^{\circ}C,\;37^{\circ}C\;and\;42^{\circ}C$, and was higher in the anaerobic incubator than in the aerobic incubator (p<0.05). 4. The optical density of culture supernatant was the highest in the media containing 1.0mM $CaCl_2$ (p<0.05), 2.5mM KCl (p<0.05), and 1.6mM $MgCl_2$. 5. When Streptococcus mutans was cultured in the media containing a quarter culture supernatant of Lactococcus lactis 1370 grown in M17 broth, the mean weight of produced artificial plaque was 103.0mg on the wire, whereas being significantly reduced to 5.6mg in the media containing a quarter culture supernatant of Lactococcus lactis 1370 grown in M17 broth containing 5% sucrose (p<0.05). These results indicate that the water-soluble glucan is more formed by Lactococcus lactis 1370 in the media containing sucrose or under the adequate conditions for the growth of bacteria, and inhibits the formation of artificial plaque by Streptococcus mutans.

• Journal of Periodontal and Implant Science
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• v.30 no.2
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• pp.403-420
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• 2000

The treatment and prevention of periodontitis is focused on the reduction and the elimination of pathogenic bacteria, especially A. actinomycetemcomitans and black pigmented bacteria such as P. gingivalis. To prevent recurrent disease, the recolonization of these bacteria should be inhibited in the periodontal pocket. Since the replacement therapy was introduced in periodontics by Hillman et al, Jeong et al reported that hydrogen peroxide-producing Lactobacillus acidophilus V-20 completely inhibited P. gingivalis and A. actino - mycetemcomitans in vitro and mouth gargling with Lactobacillus acidophilus V-20 in periodontitis patients during the maintenance phase improved clinical condition and reduced the No. of P. gingivalis and A. actinomycetemcomitans at 4 weeks of treatment. Prior to replacement therapy with bacteria, dynamics of microbial colonization should be considered. This study was performed to evaluate the change in the viable cell number of Lactobacilli and P. gingivalis after oral administration of L. acidophilus V-20. In periodontal health, gargling increased the No. of Lactobacilli in saliva, buccal mucosa, supragingival plaque from the first week, which maintained for 2-3 weeks after gargling stop, and then returned to the undetectable baseline level at the ninth week. In the periodontal pocket of moderate periodontitis patients, daily irrigation for 1 week and weekly irrigation for subsequent 3 weeks decreased the viable cell number of P. gingivalis during the period of irrigation and increased the number of Lactobacilli, which was maintained from the second to the seventh week. L. acidophilus V-20 was isolated for the first 2 weeks of oral administration, and the 3 different strains of Lactobacilli were isolated continuously for remaining period and identified as L. ali - mentarius, L. casei subspecies casei and L. fructosus. The first two Lactobacilli strains completely inhibited P. gingivalis in vitro and all the isolated Lactobacilli strains reduced the artificial plaque formation by 55-63%. These results showed that mouth gargling or pocket irrigation with L. acidophilus V-20 increased the No. of intraoral Lactobacilli and caused to decrease in the No. of P. gingivalis. This suggests that the replacement therapy by these Lactobacilli might be useful in the maintenance care of periodontal patients.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.1
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• pp.88-95
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• 1999

구강내의 교정 장치는 미생물 전파에 있어서 다양한 장소를 제공한다. 치태는 치아 우식증 발생에 있어 매우 큰 역할을 하며 미생물, 비세포성 물질로 구성되어 있다. 본 연구의 목적은 생체외에서 교정용에서의 인공 치태 생성에 영향을 주는 요인을 평가하는 것이다. Streptococcus mutans type c는 $CO_2$ incubator내의 $37^{\circ}C$에서 brain heart infusion broth에서 배양 되었다. 중절치에 사용하는 9개의 $.018"{\times}.025"$ standard edgewise brackets을 3개씩 비이커의 배양액에 매달았다. 3개 비이커의 배양액 pH는 각 각 pH 5.5, 7.0 그리고 8.5로 조절되었다. 5시간 후에 비이커에서 각각의 bracket을 꺼내서, bracket의 평균 무게를 측정하였다. 배지의 stirring effect를 측정하기 위하여 3개씩 $.018"{\times}.025"$ standard edgewise brackets을 2개의 비이커에 위치시켰다. 12개의 brackets을 $CaCl_2$(0.25, 1.0, 4.0 그리고 16.0mM). KCl(2.5, 10, 40 그리고 160mM) 그리고 $MgCl_2$(0.1, 0.4, 1.6, 그리고 6.4mM) 용액에 각각 매달았다. 6개의 $.018"{\times}.025"$ standard edgewise brackets, 6개의 $.022"{\times}.028"$ Roth brackets과 6개의 $.022"{\times}.028"$ Broussard brackets을 각각의 비이커 내에 매달았다. 배양액 내에서 5시간 동안 배양한 후 각각의 brackets을 근사값의 milligram 단위로 측정하였다. 그룹 사이의 차이는 Mann-Whitney와 Kruskal-Wallis tests를 이용하여 비교하였다. p value<0.05의 조건에서 이들의 차이는 통계학적 유의성을 갖는다. 5시간 동안 pH 5.5에서 배양된 Streptococcus mutans에 의해 형성된 인공 치태는 pH 7.0 이나 pH 8.5에서 배양된 것보다 작았다(p<0.05). 인공 치태는 배양하는 동안 저어졌을 때 더 많이 형성되었다(p<0.05). 결론적으로 bracket에 형성된 인공 치태는 좀 더 높은 알칼리성 배지에서 배양됨으로써, 그리고 배양 동안 배지를 저어줌으로써 유의성있게 증가하였다. 그러나 배지의 $CaCl_2,\;KCl,\;MgCl_2$의 농도와 상업적으로 다른 종류의 이용 가능한 교정용 bracket에 대해서는 유의한 차이가 없었다.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.361-369
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• 2000

Enterococcus is a normal inhabitant of the human oral cavity, the vagina, and the gastrointestinal tract. Four isolates of Enterococcus in this study were identified as E. durans. These bacteria were characterized and the interaction of these bacteria with the important oral bacteria as like S. mutans and S. oralis was studied as follows. 1. The carbohydrate fermentation test and biochemical test showed similar results in 4 isolates. 2. The susceptibility test against erythromycin, penicillin, tobramycin, ampicillin, teicoplanin, ciprofloxacin, vancomycin, gentamicin, kanamycin, and streptomycin showed to be susceptible in all four isolates. 3. The optical density of absorbance at 550 nm was 1.405 in the culture of S. mutans in disposable cuvette, whereas being 0.855, 0.867, 0.797, and 1.083 in the combined culture of S. mutans and each E. durans. 4. The mean weight of produced artificial plaque on the wires in the beaker was $1566{\pm}103mg$ in culture of S. mutans only, whereas being reduced to $44{\pm}5mg,\;41{\pm}12mg,\;34{\pm}7mg,\;and\;38{\pm}12mg$ in the combined culture of S. mutans and each E. durans. The viable cells were $2.0\times10^9$ per ml in the culture of S. mutans wheras being $2.0\times10^7\;to\;6.0\times10^7$ per ml in the combined culture S. mutans and E. durans. 5. The viable cells were $2.1\times10^8$ per ml in the culture of S. oralis, wheras being $1.4\times10^7\;to\;7.0\times10^7$ per ml in the combined culture of S. oralis and E. durans. 6. Plasmid of about 60 kb was isolated in three isolates of E. durans. These results suggested that E. durans isolated from the oral cavity inhibited the replication of S. mutans and formation of artificial plaque, while inhibiting the replication of S. oralis a little.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.2
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• pp.205-216
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• 2023

This study aimed to compare the color stability and surface roughness of three-dimensional (3D) printing resin according to polishing methods. 3D-printed resin specimens were fabricated at TC-80DP (Graphy, Seoul, Korea) with a stereolithography 3D printer, and the specimens were divided into three groups, each of which was not polished, was polished using Enhance^®, and was polished using a Sof-Lex^TM disc. The CIE L^*a^*b^* value and the surface roughness of each group were measured and immersed in artificial saliva and orange juice after 0, 1, 7, 30, and 60 days, and the color difference (ΔE^*) was calculated. As a result of the study, no noticeable color change was observed in artificial saliva, but a noticeable color change was demonstrated in orange juice after 60 days of immersion, and the difference was significant. In the Sof-Lex^TM group, surface roughness according to the solution was found to be significantly higher in the orange juice than that in artificial saliva. No significant difference in color change was found according to the polishing method, but surface roughness was significantly lower in the Sof-Lex^TM group than both that of the unpolished group and that of the Enhance^® group. Nevertheless, all groups exhibited clinically acceptable properties regardless of their higher surface roughness than the threshold for plaque accumulation. Overall, this study recommends utilizing Sof-Lex^TM for polishing 3D printing resin when used in primary anterior tooth coverage.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.83-91
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• 2008

Dental caries which is one of the most common chronic disease complexly developed by the action of oral bacteria, diet, and host factor. Various prevention program enhance resistance of demineralization and reduce the acidogenecity of oral bacteria have been introduced, representative material is fluoride and chlorhexidine. The purpose of the study was to evaluate and compare effectiveness of fluoride varnish and chlorhexidine varnish in vivo. Bovine tooth specimens were implanted in the lower space maintainers and applied with fluoride varnish and chlorhexidine varnish. After seven days in oral environment, metal mesh was covered to make similar condition of plaque accumulation and induce caries. All specimens were analysed by EPMA to evaluate quantitative change of Ca, P and by polarized microscope to identify histological changes. The results were as follows : After initial artificial caries induction in the mouth, there were remarkable enamel caries lesion in the control group under polarized light microscopy. The highest amount of mineral decrease were showed in control group. No statistically significant mineral decrease were showed in fluoride varnish group, while chlorhexidine varnish group showed only significant decrease of P(P<0.05). In conclusion both fluoride varnish and chlorhexidine varnish seemed to be effective for protecting enamel surface from caries activity, although fluoride varnish has more anticariogenic effect than chlorhexidine varnish.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.9-18
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• 1996

Streptococcus mutans has been implicated as primary causative agents of dental caries by insoluble glucan (IG) in human and experimental animals. An attempt was made to search for the ${\alpha}$-1,3 glucanase that degrades IG produced by S. mutans. ${\alpha}$-1,3 glucanase was detected in the culture supernatant of microorganisms, which are isolated from soils on agar medium containing IG as a sole carbon source. This Streptomyces sp. hydrolysed IG produced by immobilized S. mutans and was named as Y9373. This enzyme required ${\alpha}$-1,3 glucan (IG) as an inducer. The optimum conditions for enzyme production were studied. The enzyme was purified by 30~70% $(NH_4)_2SO_4$ precipitation, anion exchange chroma tography on DEAE-cellulose and gel filtration on Sepadex G-75. The purified enzyme has a specific activity of 7840.0 U/mg protein giving 32.1-fold purification and final yield of 0.53%. The molecular weight was estimated to be about 22.5 kDa by SDS-PAGE. The optimum pH and temperature for enzyme reaction were 6.5 and 37$^{\circ}C$, respectively and the enzyme was relatively stable at the temperature below 60$^{\circ}C$. The activity of purified enzyme was enhanced by adding $Co^{2+},\;Mn^{2+}\;and\;Mg^{2+}$ into the medium, whereas inhibited by adding $Hg^{2+},\;Zn^{2+}$ and SDS. The $K_m\;and\;V_{max}$ value of ${\alpha}$-1,3 glucanase for IG were estimated to be 2.50 mM and 0.0431 mM/min, respectively. The thin layer chromatographic analysis of hydrolysates from IG with ${\alpha}$-1,3 glucanase showed that glucose was the main product of reaction. This enzyme activity was about 14 times higher than marketing dextranase as preventive agent against artificial dental caries by S. mutans in TH medium including 5% sucrose after 30 minutes.

• Journal of Periodontal and Implant Science
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• v.27 no.1
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• pp.61-78
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• 1997

PDGF-BB has been recognized as a highly potential growth factor for guided tissue regeneration in periodontal defect. This study carried out histologic and histometric evaluation of $200ng/cm^2$ PDGF-BB loaded bioresorbable membrane made from polyglycolic and polylactic acid. It was tested for its biocompatibility, ability to prevent epithelial downgrowth and amount of periodontal regeneration. Without membrane and PDGF-BB unloaded bioresorbable membrane were used as control. Healthy six beagle dogs were used. Each dog was anesthetized and buccal flaps were reflected in the mandibular and maxillary premolar areas. Buccal alveolar bone between the mesiobuccal and distobuccal line angles was surgically removed on the lower 2nd and 4th premolar in mandible, 2nd premolar in maxilla, to a level 4mm apical to the cementoenamel junction with creating a Class II buccal furcation defect for available space. Care was taken not to remove the root cementum layer and rubber impression materials were placed over each surgically created defect. Flaps were repositioned and sutured. Reconstructive surgery was performed 1 month after defect preparation. PDGF-BB loaded membranes and controls were randomly placed on maxillary 2nd premolars and mandibular 2nd and 4th premolars. Plaque control regimen was instituted with daily brushing with a 0.1% chlorhexidine digluconate during experimental periods. The animals were sacrificed 2 and 5 weeks after surgery and undecalcified specimens were prepared for histologic evaluation. The degree of coronal regrowth of new bone, new cementum and the amonut of new bone areas formed on the defected area of the PDGF-BB loaded membrnae turned superior to without membrane and drug unloaded membrane. Experimental membrane could prevent the epithelial downgrowth irrespective of drug loaded or not and showed good biocompatiblity, These results implicated that PDGF-BB loaded bioresorbable membrane could be highly useful tool for guided tissue regeneration of periodontal defects.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.1-16
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• 2000

It is difficult to treat the endodontic apical perforation successfully. In this study, we hypothesized that the application of PDGF-BB and IGF-I into periapical perforation site may accelerate periapical healing and lead to bone deposition. And the specificity of osteonectin in periapical healing was investigated. The experiments were performed on the upper and lower 51 premolar teeth of 4 beagle dogs. The pulp chamber of each tooth was opened and the dental plaque was inserted into the canal for developing the periapical lesion for 5 weeks. Then, the roots were artificially perforated at the apex with the number 4 profile of .06 taper. In each step, standard periapical radiographs were taken to compare the size of lesion each other. The radiographs were scanned and analyzed by image analysis system. The mean and standard deviation of periradicular radiolucency ratios were calculated in each group. ANOVA was used for comparison. 51 premolars were grouped into 3 groups; control group, calcium hydroxide-treated group and calcium hydroxide plus growth factors-treated group. In the control group, the apical perforations were not sealed and obturated with gutta-percha and ZOE sealer by lateral condensation technique. In the experimental groups, the apical perforation were sealed with calcium hydroxide and with/without $4{\mu}g$ of PDGF-BB & IGF-I in cellulose gel and obturated by lateral condensation technique. Fluorescent bone markers were used to measure new bone formation. Following 2, 4, 12 weeks after experiment the dogs were sacrificed and histologic sections were prepared. Each tooth block including periapical lesion was sectioned mesiodistally. One half of the sections were decalcified with 6% nitric acid and processed by standard paraffin embedding technique. The sections were stained by hematoxylin and eosin, and immunostained for osteonectin. Histomorphometrical measurement of neoformed bone was performed using a light microscope. And the other half of the sections were prepared by undecalcified preparation, and confocal laser scanning microscopic investigations were done.

• The korean journal of orthodontics
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• v.26 no.1 s.54
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• pp.17-32
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• 1996

It is important to understand the operating mechanism and force system of fixed appliance that most effective for individual tooth movement in various orthodontic appliances. The archwire system of fixed appliance is devided into 3 types, which is continuous arch, segmented arch and sectional arch. The last two types have longer interbracket distance and simple force operating points, so it is easy to control force system by operator. But the continuous arch has shorter interbracket distance and various bracket geometry, so it is hard to control and anaylze the force system. The purpose of this study was three dimentional force and moment analysis of continuous arch system by finite element method, which is similar situation to three dimentional elastic beam in structural engineering. Several sample form of various bracket geometry and artificial lower crowding typodont made by author were constructed, analyzed and compared each other. The results were as follows : 1. The force magnitude is linear proportional to the degree of displacement or tilting of the bracket. 2. The force magnitude is inversely non-linear proportional to the interbracket distance. 3. In three dimensional typodont model, while the force can be compared with that of the sample form in the area where adjacent bracket geometry is simple, the force is much more than the expected value in the area where adjacent bracket geometry is complex.