• Restorative Dentistry and Endodontics
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• v.30 no.3
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• pp.170-177
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• 2005

This study was conducted in order to assess whether the form of the shade guide affects in deciding the color of the teeth using the shade guide Eight shade light cured composite resins (Esthet-X, Dentsply, Milford, USA) were used in this study. Shade guides including the model of maxillary central incisors, teeth-form shade guide, doughnut form shade guide, and shade guide with perforated gray shield were prepared with eight shade composite resins and provided the codes randomly After arranging the models of teeth, 19 dentists working at the clinic of the Dentistry of Chonnam University Hospital and 65 students of college of dentistry, Chonnnam University selected the shade guides corresponding to the color of each tooth on the gray board under the D$_{65}$ standard illuminant. Bl shade showed highest accuracy of about 95% among all shade guides of 3 forms applied to the test and regardless of observer, tooth form shade guide showed the highest accuracy (p < 0.05) , and the doughnut form showed the lowest accuracy (p < 0.05). At the time of deciding on the color of the teeth using the shade guides as a result of above, the forms of the shade guides can affect the accuracy, and it suggests that the development of the diversified forms of shade guides, which may obtain more accurate results, is required.

• Imaging Science in Dentistry
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• v.48 no.2
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• pp.97-101
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• 2018

Purpose: This study evaluated the radiopacity of contemporary luting cements using conventional and digital radiography. Materials and Methods: Disc specimens (N=24, n=6 per group, ø$7mm{\times}1mm$) were prepared using 4 resin-based luting cements (Duolink, Multilink N, Panavia F 2.0, and U-cem). The specimens were radiographed using films, a complementary metal oxide semiconductor (CMOS) sensor, and a photostimulable phosphor plate (PSP) with a 10-step aluminum step wedge (1 mm incremental steps) and a 1-mm-thick tooth cut. The settings were 70 kVp, 4 mA, and 30 cm, with an exposure time of 0.2 s for the films and 0.1 s for the CMOS sensor and PSP. The films were scanned using a scanner. The radiopacity of the luting cements and tooth was measured using a densitometer for the film and NIH ImageJ software for the images obtained from the CMOS sensor, PSP, and scanned films. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: Multilink (3.44-4.33) showed the highest radiopacity, followed by U-cem (1.81-2.88), Panavia F 2.0 (1.51-2.69), and Duolink (1.48-2.59). The $R^2$ values of the optical density of the aluminum step wedge were 0.9923 for the films, 0.9989 for the PSP, 0.9986 for the scanned films, and 0.9266 for the CMOS sensor in the linear regression models. Conclusion: The radiopacities of the luting materials were greater than those of aluminum or dentin at the same thickness. PSP is recommended as a detector for radiopacity measurements because of its accuracy and convenience.

• Journal of Periodontal and Implant Science
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• v.31 no.2
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• pp.277-285
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• 2001

Periodontal disease is characterized by inflammation and subsequent loss and/or damage to tooth-supporting tissues such as bone, cementum,and periodontal ligament. Periodontal ligament and cementum are the key tissues in the initial process of regeneration following periodontal disease. Therefore, studies on cementoblasts, which form cementum are emphasized. It is still unclear which cells cementoblast differentiate from. This study was conducted under the hypothesis that PDL fibroblast can differentiate into either cementoblast or osteoblast depending on the conditions of surrounding tissue. Clinically, with excessive traction force of orthodontic appliances or excessive occlusion hypercementosis is observed, and this has been confirmed histologically. Consequently, activation of cementoblast can be expected in rats when mechanical stimuli are given to PDL fibroblast. Therefore, the purpose of this article is to prove that PDL fibroblast differentiates into cementoblast in rats under mechanical stimuli using histologic and molecular methods. In this study, twenty rats were given hard diet. Ten of them were sacrificed after 1 week, and the others were sacrificed after two weeks. Slides were made from tooth specimen, and they were studied under the microscope. In addition, PDL fibroblast and cementum from the extracted teeth were analyzed with Northern blotting. In histologic examination, as time passed, PDL fibroblast migrated to the dentin side, differentiated into cementoblast, and formed new cementum. In Northern blotting, it was found that mRNA expression of cementoblast-specific proteins such as BSP, OC, OPN, and type I collagen were more prominent in rats sacrificed after 2 weeks of hard-diet than rats sacrificed after 1 week. From these findings we can conclude that PDL fibroblast can differentiate into cementoblast under mechanical stimuli. We think that 'Rat Models' used in this study will be beneficial to future studies regarding cementoblast.

• Journal of Korean society of Dental Hygiene
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• v.16 no.6
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• pp.931-941
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• 2016

Objectives: The purpose of this study was to examine the association between depression and poor oral health in Korean elderly using Korean version of the Patient Health Questionnaire-9 (PHQ-9) for assessment of depressive symptoms. Methods: This study used the data from Korean National Health and Nutrition Examination Survey (KNHANES VI-2). The study included 1,454 elderly Korean aged over 65. Variables included demographic characteristics (gender, age), socioeconomic factor (income, education), systemic diseases, oral health related factor (tooth brush, dental products), health related factor (alcohol drinking, smoking), and depression. Logistic regression analysis was used as sequential models. Effects were quantified as odds ratios (OR) and 95% confidence intervals (CI). Results: From frequency analysis, being female, primary school or less, non-alcohol drinking, poor oral health were significantly related to depression. In the multiple logistic regression model, depression was significantly associated with poor oral health (OR=1.96, CI=1.15-3.53) after adjustment for other covariates including demographic characteristics, socioeconomic factor, systemic diseases, oral health related factor, and health related factor (OR=1.91, CI=1.13-3.27). Conclusions: Depression had an influence on the poor oral health after adjustment as confounding variable in the elderly. It should be focused on the health promotion for the elderly vulnerable to depression and poor oral health. The development of the mental health and oral health should be established.

• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.93-98
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• 2017

PURPOSE. The purpose of this study was to compare the width ratio of maxillary anterior teeth according to age in the Korean population and to evaluate the maxillary central incisor width-to-length (W/L) ratio, given differences in age and gender. MATERIALS AND METHODS. Ninety-three Korean adults were divided into 3 groups (n = 31) by age. Group I was 20 - 39 years old, Group II was 40 - 59 years old, and Group III was over 60 years of age. After taking an impression and a cast model of the maxillary arch, the anterior teeth width ratio and central incisor W/L ratio were calculated from standard digital images of the cast models using a graph paper with a digital single lens reflex (DSLR) camera. The calculated ratios were compared among all groups and central incisor W/L ratio were analyzed according to age and gender. All comparative data were statistically analyzed with one-sample t-tests, one-way ANOVAs with Tukey tests, and independent t-tests. RESULTS. No significant differences in maxillary anterior teeth ratios were found among the age groups. The maxillary central incisor W/L ratios in Group III were the greatest and were significantly higher than those in the other groups. The central incisor W/L ratio of men was higher than that of women in Group II. CONCLUSION. Maxillary anterior teeth width ratios were similar in all age groups in the Korean population. The maxillary central incisor was observed as worn teeth in the group over 60 years of age, and a significant difference between genders was found in 40 to 50 year olds.

• The Journal of the Korean dental association
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• v.54 no.11
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• pp.865-873
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• 2016

Background/Purpose: The purpose of this study was to evaluate the effect of Nd:YAG irradiation on adherence of retrograde filling materials (mineral trioxide aggregate [MTA] and Super-EBA) by micro-computed tomography (CT) measurement and to observe the dentinal surface after irradiation by scanning electron microscopy (SEM). Materials and methods: Forty retrofilling models using extracted human teeth were divided into four groups according to the material and method used: ProRoot MTA (MTA group), Super-EBA (EBA group), MTA with Nd:YAG laser irradiation (LMTA group), and Super-EBA with Nd:YAG laser irradiation (LEBA group). All specimens were stored in 100% humidity for 24 hours until micro-CT was performed. The gap volume of the tooth/material interface was measured using the CTAn program. In six samples, the laser-irradiated dentin surface was observed using SEM. Results: The mean percent difference in gap volume was not statistically significant between the Nd:YAG laser-irradiated groups and non-irradiated in both materials(P > 0.05). The gap volume in the MTA group was significantly lower than that in the EBA group (P < 0.05). Examination of the non-irradiated specimens by SEM showed patent dentinal tubules. In contrast, alterations in the texture of the dentin surface and obliteration of the dentinal tubules were evident in the Nd:YAG laser-irradiated specimens. Conclusion: In this study, changes in the dentinal surface after Nd:YAG irradiation did not affect adherence between the apical filling material and the dentin wall.

• The korean journal of orthodontics
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• v.46 no.2
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• pp.96-103
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• 2016

Objective: To compare the transverse dental changes induced by the palatally applied Frog appliance and buccally applied Karad's integrated distalizing system (KIDS). Methods: We evaluated the pre- and post distalization orthodontic models of 39 patients, including 19 treated using the Frog appliance, which is palatally positioned (Frog group), and 20 treated using KIDS, which is buccally positioned (KIDS group). Changes in intermolar and interpremolar distances and the amount of maxillary premolar and molar rotation were evaluated on model photocopies. Wilcoxon and Mann-Whitney U tests were used for statistical evaluations. A p-value of < 0.05 was considered statistically significant. Results: Significant distopalatal rotation of premolars and distobuccal rotation of molars were observed in Frog group (p < 0.05), while significant distopalatal rotation of molars (p < 0.05), with no significant changes in premolars, was observed in KIDS group. The amount of second premolar and first molar rotation was significantly different between the two groups (p < 0.05 and p < 0.001, respectively). Furthermore, expansion in the region of the first molars and second premolars was significantly greater in KIDS group than in Frog group (p < 0.001 for both). Conclusions: Our results suggest that the type and amount of first molar rotation and expansion vary with the design of the distalization appliance used.

• The korean journal of orthodontics
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• v.43 no.4
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• pp.193-200
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• 2013

Objective: To evaluate the psychosocial impact of malocclusion, determine its relationship with the severity of malocclusion, and assess the influence of gender and social class on this relationship in adolescents. Methods: A random sample of 627 Spanish adolescents aged 12 - 15 years underwent intraoral examinations by 3 calibrated examiners (intraexaminer and interexaminer kappa > 0.85) at their schools. Psychosocial impact was measured through a self-rated Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ). The severity of malocclusion was measured by the Index of Orthodontic Treatment Need (IOTN). Gender and social class were also recorded. Results: The total PIDAQ score and those of its 4 subscales, social impact, psychological impact, aesthetic concern, and dental self-confidence, presented significant differences ($p{\leq}0.05$ by analysis of variance) and linear relationships with the IOTN grades ($p{\leq}0.05$ by linear regression). Stepwise linear regression models showed that the IOTN dental health component was a predictive variable of the total and subscale PIDAQ scores. Neither gender nor social class was an independent predictive variable of this relationship, except the linear model for psychological impact, where gender was a predictive variable. The occlusal conditions responsible for higher PIDAQ scores were increased overjet, impeded eruption, tooth displacement, and increased overbite. Conclusions: Malocclusion has a psychological impact in adolescents and this impact increases with the severity of malocclusion. Social class may not influence this association, but the psychological impact seems to be greater among girls.

• The korean journal of orthodontics
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• v.47 no.1
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• pp.21-30
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• 2017

Objective: The aim of this study was to investigate the three-dimensional (3D) position of the center of resistance of 4 mandibular anterior teeth, 6 mandibular anterior teeth, and the complete mandibular dentition by using 3D finite-element analysis. Methods: Finite-element models included the complete mandibular dentition, periodontal ligament, and alveolar bone. The crowns of teeth in each group were fixed with buccal and lingual arch wires and lingual splint wires to minimize individual tooth movement and to evenly disperse the forces onto the teeth. Each group of teeth was subdivided into 0.5-mm intervals horizontally and vertically, and a force of 200 g was applied on each group. The center of resistance was defined as the point where the applied force induced parallel movement. Results: The center of resistance of the 4 mandibular anterior teeth group was 13.0 mm apical and 6.0 mm posterior, that of the 6 mandibular anterior teeth group was 13.5 mm apical and 8.5 mm posterior, and that of the complete mandibular dentition group was 13.5 mm apical and 25.0 mm posterior to the incisal edge of the mandibular central incisors. Conclusions: Finite-element analysis was useful in determining the 3D position of the center of resistance of the 4 mandibular anterior teeth group, 6 mandibular anterior teeth group, and complete mandibular dentition group.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.675-694
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• 2000

The purpose of this study was to investigate the displacement of and the stress distribution on the prosthesis, abutment, and its supporting tissues under functional load, and the effect of alteration in root length of 2nd abutment. The 3-dimensional finite element method was used and the finite element models were prepared in which the abutments of left mandibular 5 unit axed partial denture were canine, the 1st pre-molar and the 2nd molar, and the root lengths of canines were as follows. Model I : Root length of canine was 2mm longer than the 1st premolar Model II : Root length of canine was 2mm shorter than the 1st premolar Static compressive force of 300N was applied to connector between 2nd premolar & 1st molar, and then von Mises stress, displacement and reaction force were obtained. The results were as follows : 1. In fixed partial denture, prosthesis under load on pontic was rotated around mesio-distal long axis of it from longual side to buccal, and simultaneously bended in buccal and gingival direction with mesial end deformed in gingival direction and distolingual end in occlusal. 2. Clinical crowns of abutments were bended in the same directions with those in which prosthesis deforms. Due to that, roots of anterior abutments were twisted in counterclockwise with concentration of shear stress on distal or distobuccal sides of their cervices, and that of posterior was in clockwise with concentration of shear stress on mesiobuccal side of it in the same level with anterior abutments. 3. In case that root length of the 2nd abutment was longer than that of the 1st abutment, its displacement and reaction force which means the force tooth exerts on the surrounding periodontal tissues were smaller but shear stress on itself was larger than in the case root length of 2nd abutment was shorter.