• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.249-257
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• 2012

Purpose: This study was designed to help to provide the criteria of the esthetic smile in oromaxillary region on twenties, fifties and sixties. Materials and methods: The facial straight photographs of 33 adults (male 15, female 18, mean age 27.2 years old) and 20 seniors (male 7, female 13, mean age 55.6 years old) in resting and smile position were taken. The measurements and proportion of lip-teeth relation during smile were statistically analyzed, and survey of freshmen and seniors who belong to School of Dentistry, Chonnam National University were taken to select the best esthetic smile among the photographs. Results: In the relationship between the upper lip and the teeth, average smile was the most frequent, and mean of smile line ratio was 1.090 in young group and 0.90 in old group. The correlation between the buccal corridor ratio and exposed teeth count was inversed. At smile, most frequently exposed tooth was the second premolar (63.64%) in young gourp and the first premolar (35.00%) in old group. The correlation between the upper lip change ratio and exposed clinical crown length of maxillary central incisor was inverse, but there was no correlation between the lower lip change ratio and exposed clinical crown length of maxillarycentral incisor. Conclusion: In the result of survey, the students selected the case exposed to the first premolar as the most esthetic smile. The most esthetic smile between full facial photograph and the lip only photograph by the freshmen was different, but that by seniors was identical.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.3
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• pp.207-217
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• 2014

The purpose of the present study was to evaluate the relationship between the malocclusion and dental caries in adolescents with permanent dentition. The subjects of the study were 385 adolescents aged 12 to 15 years. Dental Aesthetic Index (DAI) and DMFT index were recorded as clinical indicators of malocclusion and dental caries. The mean Dental Aesthetic Index (DAI) score of the subjects was 12.42 and the mean DMFT index of the subjects was 2.89. Four students (1.04%) were included in the group of orthodontic treatment mandatory, which signifies the handicapping malocclusion. Moreover, the result of gender-specific analysis of the DAI components observed that the prevalence of midline diastema and mandibular overjet were significantly higher among boys (p < 0.05). In 7 components (missing teeth, incisal segment crowding, maxillary anterior irregularity, mandibular anterior irregularity, mandibular overjet, anterior openbite, antero-posterior molar relationship) among the 10 DAI components, abnormal groups showed significantly higher DMFT index than normal groups (p < 0.05). The subjects in the group of definite to handicapping malocclusion (DAI ${\geq}$ 26) showed significantly higher DMFT index than the subjects in the group of minor or no malocclusion (p < 0.01). In addition, the DAI score had significant positive linear correlation with the DMFT index (r = 0.584, p < 0.01). Consequently, the current findings suggested a positive relationship between the malocclusion and caries prevalence. And several specific types of malocclusion were supposed to be significantly correlated with dental caries.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.3
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• pp.257-265
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• 2014

The aim of this study was to establish the appropriate guidelines in the sedation techniques and to organize the continuing education programs for the sedation in future under the direction of Committee on Sedation, Education and Research under the Korean Academy of Pediatric Dentistry(KAPD). The surveys on the sedation technique were performed on 111 organizations which practices the sedation and responded to the survey via online and e-mail by February 2014. The collected survey were analyzed. The purpose of sedation was mainly to manage the children's behavior and its uses were primarily on 3~4 years old children. The most frequent duration of treatment was 1~2 hours to treat both maxillary and mandible. The preferred dosages of sedative drugs were chloral hydrate(CH) 50~70 mg/kg, hydorxyzine(Hx) 1~2 mg/kg, and intramuscular midazolam(Mida IM) 0.1~0.2 mg/kg. The preferred combination of the sedative drugs were CH + Hx + $N_2O/O_2$(67.6%), CH + Hx + Mida submucosal administration (SM) + $N_2O/O_2$(29.7%), and Mida IM + $N_2O/O_2$(23.4%). The administration of additional sedatives was carried out at 48%, mainly using Midazolam. 87.5% of the respondents experienced the adverse effects of the sedation such as vomiting/retching, agitation during recovery, subclinical respiratory depression, staggering, and etc. Among them, only 20% periodically retrain the emergency management protocol. About the discharge criteria for patients after the sedation, the respondents either showed a lack of clear criteria or did not follow the recommended discharge criteria. 86% of the respondents expressed the interests in taking a course on the sedation and they wanted to learn mostly about the sedation-related emergency management, the safe dosage of the sedative drugs, and etc. The use of sedation in pediatric dentistry must be consider a patient's safety as top priority and each dentist must show the evidence of sound practices for the prevention of any possible medical errors. Therefore, KAPD must establish the proper sedation guidelines and it needs to provide the systematic technical training program of sedation-related emergency management for pediatric dentists.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.3
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• pp.376-381
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• 2002

The purpose of this study was to analyse the color of natural deciduous teeth in Korean children and to compare with that of composite resin specimens. The subjects were 148 children (80 boys and 68 girls) with good general condition and normal teeth color, aged between 3 and 6 years. The color of middle third of maxillary central incisor in deciduous teeth was examined with shade guide and then measured by means of the colorimeter CV300 which can be measured by CIELAB system. The data were analyzed statistically by SPSS program. The results were summerized as follows; 1. Over 90% of the color for the deciduous anterior teeth was in A1, A2, B1, B2 and P shade. 2. The means of deciduous teeth color were $L^*=58.72,\;a^*=-1.18,\;b^*=-0.63$ by colorimeter CV300. 3. $L^*,\;a^*\;and\;b^*$ prices for A1, A2, B1, B2, P were $L^*=52.52,\;a^*=-1.90,\;b^*=1.18$ in A1 specimen, $L^*=54.90,\;a^*=-1.87,\;b^*=1.60$ in A2 specimen, $L^*=59.80,\;a^*=-2.70,\;b^*=-0.63$ in B1 specimen, $L^*=56.90,\;a^*=-1.70,\;b^*=1.63$ in B2 specimen, $L^*=52.93,\;a^*=-2.33,\;b^*=1.10$ in P specimen. The means of B1 color specimen were most similar to those of deciduous teeth color. The A1 color values were similar to the P color values. 4. The standard deviation of $L^*,\;a^*$ was small among colors, but that of $b^*$, in the yellowish color, was large.

• Journal of dental hygiene science
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• v.10 no.6
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• pp.451-457
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• 2010

It is well known that most of the beverages on sale contain acid. Among these beverages, one of the most typically purchased products is Coca-Cola ($Coke^{(R)}$), which affects the demineralization of the tooth enamel surface. However other beverages also affect the erosion of the tooth enamel surface. Therefore, the aim of this study was to observe the influence that acid containing beverages have upon the tooth enamel surface. In this study, 30 enamel specimens were obtained from extracted maxillary third molars without cracks. The study measured the pH concentrations and the Ca and P concentration levels of the acidic beverages. The control without exposure was kept in distilled water, and each enamel specimen was stored for 30-min, 60-min, and 120-min. The erosion effect of the enamel surface was observed by SEM. The results obtained from this study can be summarized as follows: 1. The pH concentration of acidic beverages, without milk, was 3.105 on average. The beverages eroded the enamel surface and the erosion degree was determined by the pH concentration of beverages. 2. The erosion degree significantly increased by as the exposure time increased. The difference in the erosion degree between the 30-min group and the 60-min and the 120-min group was significant, but the erosion degree of the 120-min group was significantly less than that of the initial group. 3. When compared with the beverages containing similar pH concentrations, the demineralization degree of the beverages containing higher concentrations of Ca and P was lower.

• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.413-421
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• 2000

The purpose of this study was to observe the effects of pregnancy on the experimental tooth movement and alveolar bone turnover process of Sprague-Dawley female rat. Sixty rats were divided into pregnant-tooth movement group(P-Tm), normal-tooth movement group(N-Tm) and normal group(N). Maxillary first molar appliances were inserted bilaterally and activated to 40grams. To measure the amount of tooth movement, x-ray was taken 2 times after appliance insertion and before sacrifice. Animals were sacrificed at 1,3,7,14 days(N=5). Just after sacrifice, alveolar bones were collected and frozen immediately for biochemical analysis. Tooth movement was assessed cephalometrically and tartrate-resistant acid(TRAP) and alkaline phosphatase (ALP) activities were measured in extracts of paradental alveolar bone. The results were as follows: 1. The amount of tooth movement in P-Tm group was greater than that of N-Tm group(p<0.01). 2. Alveolar bone ALP of normal tooth movement group was not significantly different from the control, TRAP was significantly different from the control(p<0.01). In normal tooth movement group, alveolar bone ALP was increased gradually and peak(day 7) fell off significantly at day 14(p<0.05). The Peak of alveolar bone TRAP(day 7) fell off slightly, sustained day 14(p<0.01). 3. Alveolar bone ALP and TRAP of pregnant tooth movement group were not significantly different from that of normal tooth movement group. In pregnant tooth movement group, alveolar bone ALP was increased at day 3(p<0.01) and fell off significantly at day 7-14, alveolar bone TRAP were increased at day 3 and sustained day 14. 4. The peak of alveolar bone phosphatases in pregnant tooth movement group(day3) preceded the peak in normal tooth movement group(day7) (p<0.01). According to the above results, we suggested that bone resorption activity was increased in alveolar bone of pregnant rat, and the degree of tooth movement in pregnancy may be greater than that of normal group because of high bone turnover of alveolar bone in pregnant rat.

• The korean journal of orthodontics
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• v.41 no.5
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• pp.324-336
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• 2011

Objective: The aim of this study was to conduct three-dimensional finite element analysis of individual tooth displacement and stress distribution when a posterior retraction force of 200 g was applied at different positions of the retraction hook on the transpalatal arch (TPA) of a molar, and over different lengths of the lever arm on the maxillary anterior teeth in lingual orthodontics. Methods: A three-dimensional finite element model, including the entire upper dentition, periodontal ligaments, and alveolar bones, was constructed on the basis of a sample (Nissan Dental Product, Kyoto, Japan) survey of Asian adults. Individual movement of the incisal edge and root apex was estimated along the x-, y-, and z-coordinates to analyze tooth displacement and von Mises stress distribution. Results: When the length of the lever arm was 15 mm and 20 mm, the incisal edge and root apex of the anterior teeth was displaced lingually, with a maximum lingual displacement at the lever arm length of 20 mm. When the posterior retraction hook was on the root apex, the molars showed distal displacement. When the length of the lever arm was 20 mm, anterior extrusion was reduced and the crown of the canine displaced toward the buccal side, in which case, the retraction hook was on the edge, rather than at the center, of the TPA. Conclusions: The results of the analysis showed that when 6 anterior teeth were retracted posteriorly, lateral displacement of the canine and lingual displacement of the incisal edge and root apex of the anterior teeth occur without the extrusion of the anterior segment when the length of the lever arm is longer, and the posterior retraction hook is in the midpalatal area.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.4
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• pp.324-332
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• 2011

Purpose: The purpose of this study was to compare the stress distribution of teeth and jaw on load by differentiating property of materials according to each layer of widely used mouthguard. Materials and methods: A Korean adult having normal cranium and mandible was selected to examine. A customized mouthguard was constructed by use of DRUFOMAT plate and DRUFOMAT-TE/-SQ of Dreve Co. according to Signature Mouthguard system. The cranium was scanned by means of computed tomography with 1mm interval. It was modeled with CANTIBio BIONIX/Body Builder program and simulated and interpreted using Alter HyperMesh program. The mouthguard was classified as follows according to the layers. (1) soft guard (Bioplast)(SG) (2) hard guard (Duran)(HG) (3) medium guard (Drufomat)(MG) (4) soft layer + hard layer (SG + HG) (5) hard layer + soft layer (HG + SG) (6) soft layer + hard layer + soft layer (SG + HG + SG) (7) hard layer + soft layer + hard layer (HG + SG + HG) The impact locations on mandible were gnathion, the center of inferior border, and the anterior edge of gonial angle. And the impact directions were oblique ($45^{\circ}$). The impact load was 800 N for 0.1 sec. The stress distribution was measured at maxillary teeth, TMJ and maxilla. The statistics were conducted using Repeated ANOVA and in case of difference, Duncan test was used as post analysis. Results: In teeth and maxilla, the mouthguard contacting soft layer of mandibular teeth presented lowest stress measure and, in contrast, in condyle, the mouthguard contacting hard layer of mandibular teeth presented lowest stress measure. Conclusion: For all impact directions, soft layer + hard layer + soft layer, the mouthguard with three layers which the hard layer is sandwiched between two soft layers, showed relatively even distribution of stress in impact.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.2
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• pp.145-151
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• 2011

Purpose: The purpose of this study was to compare the marginal fit of three-unit zirconia fixed dental prostheses (FDPs) fabricated using CAD/CAM and MAD/MAM system. Materials and methods: Dentiform maxillary central and lateral incisor were prepared for 3-unit FDP and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, fifteen 3-unit FDPs were fabricated. Metal-ceramic group was three-unit metal-ceramic FDPs, $Everest^{(R)}$ group was zirconia three-unit FDPs fabricated using the $Everest^{(R)}$ system (Kavo Dental GmbH, Biberach, Germany) and $Rainbow^{TM}$ group was zirconia three-unit FDPs fabricated using the $Rainbow^{TM}$ system (Dentium Co. Inc., Seoul, South Korea). They were cemented to resin dies with adhesive resin cement. After removing pontics, each retainers were separated and observed under measuring machine (Presize 440C) and analyzed through one-way ANOVA and Duncan test (${\alpha}$ = .05). Results: Mean values and standard deviations of marginal gap dimensions in each group for three-unit FDPs were $78.5{\pm}11.05\;{\mu}m$ for the metal-ceramic group, $59.30{\pm}11.63\;{\mu}m$ for the $Everest^{(R)}$ group and $70.34{\pm}13.98\;{\mu}m$ for the $Rainbow^{TM}$ group. Conclusion: 1. The $Everest^{(R)}$ group in comparison with metal-ceramic group showed better marginal fit, which had significant differences P<.05. 2. The mean marginal gap values between $Everest^{(R)}$ and $Rainbow^{TM}$ group did not showed significant differences (P>.05). 3. The mean marginal gap values between $Rainbow^{TM}$ group and metal-ceramic group did not showed significant differences (P>.05). 4. The mean marginal gaps of each group were within clinically acceptable range ($120\;{\mu}m$).

• Restorative Dentistry and Endodontics
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• v.33 no.4
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• pp.332-340
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• 2008

The purpose of this study was to evaluate the viability of periodontal ligament cell in rat teeth using slow cryopreservation method with magnetic field through MTT assay and TUNEL test. For each group, 12 teeth of 4 weeks old white female Sprague-Dawley rat were used for MTT assay, and 6 teeth in TUNEL test. The Maxillary left and right, first and second molars were extracted as atraumatically as possible under tiletamine anesthesia. The experimental groups were group1 (immediately extraction), group 2 (cold preservation at 4$^{\circ}C$ for 1 week), group 3 (rapid cryopreservation in liquid nitrogen), group 4 (slow cryopreservation with magnetic field of 1 G), and group 5 (slow cryopreservation). F medium was used as preservation medium and 10% DMSO as cryoprotectant. After preservation and thawing, the MTT assay and TUNEL test were processed. One way ANOVA and Scheffe method were performed at the 95% level of confidence. The value of optical density obtained after MTT analysis was divided by the value of eosin staining for tissue volume standardization. In both MTT assay and TUNEL test, it had showed no significant difference among group 3, 4, and 5. And group 3 had showed higher viability of periodontal ligament cell than group 2. From this study, slow cryopreservation method with magnetic field can be used as one of cryopreservation methods.