• The korean journal of orthodontics
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• v.48 no.1
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• pp.57-62
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• 2018

Piezoelectric surgery is a novel surgical approach used in orthodontic treatment for rapid tooth movement. This paper presents a case series wherein osseous outgrowths were observed in response to piezosurgery-assisted en-masse retraction. Sixteen patients requiring upper premolar extractions were treated with miniscrew-supported en-masse retraction and received minimally invasive decortication via piezosurgery. Computed tomography (CT) of the maxillary anterior region was performed to investigate the nature of the outgrowths. In 8 of the 16 patients, hemispheric or disc-shaped osseous outgrowths were observed on the sites where piezosurgery was performed during retraction. CT images revealed that these outgrowths were alveolar bone. This case series presents a previously unreported osseous response to piezosurgery-assisted tooth movement during orthodontic treatment. The response is mostly transient and is observed in 50% of the treated patients, suggesting a bone turnover that can be assessed clinically and radiographically.

• Journal of Korean Dental Science
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• v.9 no.1
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• pp.28-34
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• 2016

Purpose: The purpose of the present retrospective cohort study was to investigate the incidence of sinus perforation during endodontic microsurgery and to assess healing of cases with sinus perforation. Materials and Methods: Clinical and radiographic records were collected from patients who were treated with endodontic microsurgery in the Microscope Center of the Department of Conservative Dentistry at Yonsei University College of Dentistry, Seoul, Korea, between March 2001 and January 2016. To determine the incidence of sinus perforation, all cases involving maxillary premolar and molar teeth were assessed, and cases with perforation of maxillary sinus during the procedure were counted. To assess the outcome of the endodontic microsurgery, cases with sinus perforation were recalled at least 1 year after surgery. Result: Two hundred and forty-nine maxillary premolars and molars were treated with endodontic microsurgery. Among these cases, 16 cases had sinus perforations. Overall incidence of sinus perforation was 6.4%. Thirteen cases with sinus perforation were followed up for 1 year after endodontic microsurgery. Outcome assessment revealed that 2 of 13 cases with sinus perforation had failed. The success rate of endodontic microsurgery with sinus perforation was 84.6%. Conclusion: Endodontic surgery performed using microsurgical techniques decreases the risk of sinus perforation. Predictable outcomes of endodontic microsurgeries and healing of sinus membrane can be expected with adequate treatment steps and careful periodic follow-ups in cases with maxillary sinus perforations.

• The Journal of the Korean dental association
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• v.22 no.11 s.186
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• pp.961-971
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• 1984

The purpose of this study was designed to evaluate the existence of the junctional epithelia on the tooth surface in periodontal pocket, and what were the morphologic differences between the junctional epithelia on the healthy and advanced periodontitis tooth. Fifteen premolar teeth from patients of Yon Sei University, Dental Infirmary were selected for this study. After extration, the teeth were prepared and examined in Scanning electro microscope. The results were as follows. 1. The junctional epithelia from healthy tooth surface were irreguraly round, oval, polygonal and slightly elongated while those from periodontal pocket were so elongated that difficult to distinguished the individual cell boundary. 2. There were a lot of round space so called 'HOLE or WHORL' which seemed tunnel in periodontal pocket with advanced periodontitis. 3. Microvilli were going to destructed and disappeared on surfaces of junctional epithelia in periodontal pocket with advanced periodontitis. 4. There were a lot of Filopodia on Junctional epithelia from healthy surfaces. %. Junctional epithelia from periodontal pocket with advanced periodontitis contained more inflammatory cells than healthy junctional epithelia did.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.83-93
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• 2005

This study was designed to investigate the fitness of adjustable dental impression trays. The size and shape of these trays were designed from the results of the dental arch size of Korean adults. Tray samples were made by CAD-CAM working. A hundred dental students(male:50, female:50) were selected for taking irreversible hydrocolloid impression using these trays. The author measured the width and length of impression material on the several measuring points. The results obtained were as follows : 1. Uniform impression material thickness was achieved by controlling the width of the tray using stops and beveled guides. 2. In the upper tray, the impression material thickness was measured to be rather great showing thickness of the labial vestibule 8.3 mm and the midpalatal part 8.6 mm. 3. In the lower tray, length of the impression material of the labial vestibule of first, second premolar contact point was 7.8 mm, and thickness of the lingual part of premolars(1.8 mm) and molars(1.9 mm) showed small values. 4. In the lower tray, the impression material thickness of the buccal shelf area(0.2 mm) and the retromolar pad area(0.6 mm) was measured to be too small.

• Imaging Science in Dentistry
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• v.30 no.3
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• pp.223-227
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• 2000

A 35-year-old man was referred to the department of Oral and maxillofacial surgery of Chonnam university hospital for the chief complaint of asymptomatic swelling on the buccal vestibule of upper right canine area. Radiographs revealed that the upper right canine was impacted and there was a well-circumscribed pericoronal radiolucency related with the canine. Multiple radiopaque foci were scattered in the radiolucent lesion, and the roots of the lateral incisor and the first premolar related to the lesion showed external resorption. The radiographic features of this lesion were typical of adenomatoid odontogenic tumor, but considering the gender and age of the patient, the tentative diagnosis was made as calcifying odontogenic cyst. Microscopically this lesion was diagnosed as calcifying odontogenic cyst. Because calcifying odontogenic cyst has no pathognomonic feature of radiographs, to consider radiographic features with clinical findings is necessary in order to establish more correct diagnosis.

• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.135-143
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• 2012

Purpose: The purpose of this in vitro study was to compare the marginal fit of POM restorations with 3 different thickness of metal coping. Methods: 2.0mm Occlusal reduction, 1.0mm preparation of axial wall with 6degree taper, and chamfer margin was prepared a maxillary first premolar on dentiform. Duplicate prepared die and, make 30 individual dies with Ni-Cr metal. Make 3 groups of 30 press ceramic on Metal crown with different thickness of metal coping; 10 of 0.1mm, 10 of 0.3mm, 10 of 0.5mm thickness metal coping. The marginal fit of the crowns was evaluated 50 points per 1 crown, around the crown margin circumference under a optical microscope at original magnification ${\times}100$. A 1-way analysis of variance (ANOVA) was used to compare data. Results: The mean marginal discrepancy for POM with 0.1mm metal copings was $72.56{\mu}m$, $67.83{\mu}m$ for 0.3mm metal coping POMs, and $72.56{\mu}m$ for 0.5mm metal coping POM. The 1-way ANOVA showed significant difference among 3 groups. Conclusion: The marginal fit of pressed-on-metal (POMs) was best with 0.3mm thickness of metal coping, fallowing by 0.1mm, and 0.5mm in the order.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.13 no.1
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• pp.6-13
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• 2017

Premolars show the greatest variation in development and eruption. The present case report identified characteristics of eruption of maxillary premolars with delayed development. Multiple maxillary premolars with delayed development were found to have a palatal ectopic eruption pattern, which was self-corrected through eruption guidance by extraction of preceding primary teeth at the stage of root development when eruption force was maximal. In addition, delayed eruption due to delayed development was substantially improved by eruption guidance. Early erupted premolars with less than 1/3 of root development were induced to have normal root development using stabilizing appliance. The maxillary premolars with delayed development reported in the present study showed no complications such as impaction, space loss by delayed eruption, or insufficient root development.

• Journal of Periodontal and Implant Science
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• v.27 no.2
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• pp.291-303
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• 1997

Periodontal ligament cells may have a role in the regulation of hard and soft periodontal tissues, but their specific function has not yet to be determined. To evaluate further their role in periodontal regeneration, they were examined for osteoblast-like behavior. Periodontal ligament cells and gingival fibroblasts were primarily cultured from extracted premolar with non-periodontal diseases. Cells were cultured with DMEM at $37^{\circ}C$, 5% $CO_2$, 100% humidity incubator, and as a measure of cell characterization, it was examined that the morphology, alkaline phosphatase activity, collagen synthesis, and immunocytochemistry for osteonectin, osteocalcin, and collagen type I. Healthy periodontal ligament cells has more osteoblastic-like cell property in alkaline phosphatase activity. and collagen synthesis than gingival fibroblast. Immunocytochemistry localization explained that calcitonin were expressed in periodontal ligament cells only, and osteonectin and type I collagen were produced in both cells simultaneously. This results indicate that the growth characteristics of periodontal ligament cells and gingival fibroblasts exhibit some differences in proliferative rates and biochemical synthesis. The differences may help to calrify the role such cells play in the regenearation of periodontal tissues.

• The korean journal of orthodontics
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• v.20 no.2
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• pp.283-291
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• 1990

The purpose of this study was to measure and compare tensile and shear strength for 4 types of new direct-bonding brackets and same brackets after recycling and to evaluate the change of bracket slot width after recycling. Four types of new direct-bond brackets were bonded to recently extracted human premolar teeth and the tensile and shear strength was measured by Universal Testing Machine. The brackets were recycled by chemical process and the tensile and shear test was repeated. To evaluate the change of the bracket slot width, slot width was measured by the Topcon Universal Measuring Microscope before and after recycling. Following results were obtained: 1. There was no satistically significant difference between the tensile and shear strength of recycled brackets and those of new brackets. 2. In both new and recycled brackets, the tensile and shear strength of perforated base bracket was lower than those of photoetched, foilmesh and contou-lok mesh base brackets. (P<0.01) 3. There was no statistically significant difference in bonding strengths of control group bonded only once and two times. 4. There was no statistically significant difference in the change of the bracket slow width after recycling process. 5. Of the failure, the combination type (58%) in the tensile strength and the tooth adhesive interface (65%) in the shear strength was the most common type.

• The korean journal of orthodontics
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• v.45 no.2
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• pp.95-101
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• 2015

The aim of this case report is to describe the treatment of a patient with skeletal Class III malocclusion with maxillary retrognathia using skeletal anchorage devices and intermaxillary elastics. Miniplates were inserted between the mandibular lateral incisor and canine teeth on both sides in a male patient aged 14 years 5 months. Self-drilling mini-implants (1.6 mm diameter, 10 mm length) were installed between the maxillary second premolar and molar teeth, and Class III elastics were used between the miniplates and miniscrews. On treatment completion, an increase in the projection of the maxilla relative to the cranial base (2.7 mm) and significant improvement of the facial profile were observed. Slight maxillary counterclockwise ($1^{\circ}$) and mandibular clockwise ($3.3^{\circ}$) rotations were also observed. Maxillary protraction with skeletal anchorage and intermaxillary elastics was effective in correcting a case of Skeletal Class III malocclusion without dentoalveolar side effects.