• The Journal of Advanced Prosthodontics
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• 제8권3호
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• pp.214-218
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• 2016

PURPOSE. We assessed the repeatability and reproducibility of abutment teeth dental impressions, digitized with a blue light scanner, by comparing the discrepancies in repeatability and reproducibility values for different types of abutment teeth. MATERIALS AND METHODS. To evaluate repeatability, impressions of the canine, first premolar, and first molar, prepared for ceramic crowns, were repeatedly scanned to acquire 5 sets of 3-dimensional data via stereolithography (STL) files. Point clouds were compared and the error sizes were measured (n=10, per type). To evaluate reproducibility, the impressions were rotated by $10-20^{\circ}$ on the table and scanned. These data were compared to the first STL data and the error sizes were measured (n=5, per type). One-way analysis of variance was used to assess the repeatability and reproducibility of the 3 types of teeth, and Tukey honest significant differences (HSD) multiple comparison test was used for post hoc comparisons (${\alpha}=.05$). RESULTS. The differences with regard to repeatability were 4.5, 2.7, and $3.1{\mu}m$ for the canine, premolar, and molar, indicating the poorest repeatability for the canine (P<.001). For reproducibility, the differences were 6.6, 5.8, and $11.0{\mu}m$ indicating the poorest reproducibility for the molar (P=.007). CONCLUSION. Our results indicated that impressions of individual abutment teeth, digitized with a blue light scanner, had good repeatability and reproducibility.

• 대한소아치과학회지
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• 제44권1호
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• pp.116-121
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• 2017

상악 제2유구치의 부가치근은 드물게 관찰된다. 본 증례보고에서는 두 증례를 통해 상악 제2유구치의 부가치근과 하방 영구 계승치의 변위 및 회전이 연관되었을 가능성에 대해 논의하였다. 상악 제2유구치의 치관 형태를 관찰함으로써 부가치근의 존재 가능성을 의심할 수 있으며, 부가치근이 존재하는 경우 영구 계승치의 맹출 양상을 주의 깊게 관찰해야 할 필요가 있을 것으로 사료된다. 만약 소구치 치배가 비정상적인 맹출 양상을 보인다면 선행 유치의 조기 발거 및 공간유지가 보존적인 치료법이 될 수 있다.

• 비파괴검사학회지
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• 제25권4호
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• pp.254-261
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• 2005

지금까지 한국인의 치아 통계는 매우 부족한 상태이고, 대부분 치아형태의 정보를 얻기 위해 방사선학적 방법을 이용하거나, 치아를 절단하는 등의 방법으로 연구를 해왔다. 이와 같은 방법은 오랜 시험 기간을 필요로 하고 정밀도가 낮고 파괴적인 방법을 주로 이용한 것이므로, 이제는 한국인의 표준 치아에 대한 정밀한 데이터를 얻기 위해 새로운 비파괴적인 시험이 필요하다. 이를 위하여 각각의 하악 제1소구치를 미세단층촬영기(Micro-CT, SkyScan, Belgium)를 이용하여 $21.31{\mu}m$의 해상도로 교합면에 대한 수평면으로 0.022mm 로 Scan을 하였다. 이를 통하여 내 외부 형태학적 중요부위를 측정하였으며, 영구 치아의 평균 치수표로 사용했었던 G. V. Black(1836-1915)에 의해 제시된 수치와 비교하였다.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.339-352
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• 1996

Many dentists have been taken an interest in restoration of severly damaged teeth after endodontic treatment and it is a true that there are lots of studies about it. In these days, although we have used Para-Post, pins, threaded steel post, cast gold post and core, and so on, as a method of restoration frequently, it has been in controversy with the effects of them on the teeth and surrounding periodontal tissue. In this study, we assume that the crown of the upper 1st premolar was severly damaged, and after the root canal therapy, two most common types of restoration were carried out ; 1) coronal-radicular amalgam restoration, 2) after setting up the Para-Post, restore with amalgam core and gold crown. After restoration, in order to present the concentration of stress at internal portion of the tooth and the surrounding periodontal tissue, we doveloped a 2-dimensional finite element model of labiopalatal section, then loaded forces from 2 long perpendicular to the lingual incline of buccal ridge an the middle point, parallel to the long direction axis of tooth at the fossa-were applied. The analyzed results were as follows : 1. Stress of the normal first premolar was concentrated on the most weakest anatomical structure, that is, cervical area, and no stress on the bifurcated area of the canal. 2. Crown restoration after root canal therapy causes large stress concentration on the bifurcated area of the canal. This stress concentration has larger value in case of lateral movement of mandible, and there are decrease in the stress concentration compared with natural tooth. 3. Coronal-radicular amalgam restoration method transports more stress to the tooth structure than restoration using Para-Post. 4. There are more stress concentration around Para-Post in the case of lateral movement, and we have more favo rable result when restored with Para-Post. 5. Generally, stress in the lateral movement is larger than stress in the perpendicular load.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권4호
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• pp.368-372
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• 2010

Botryoid odontogenic cyst (BOC) is considered a rare multilocular variant of the lateral periodontal cyst. In this report, a 67-year-old male visited with chief complaint of severe mobility on mandibular incisors. Multilocular radiolucent lesion was seen from the right premolar to the left premolar area, involving almost the whole mandible. Histologically, the botryoid odontogenic cyst showed focal nodular thickening of the lining epithelium. These thickening often showed swirling appearance of the cells. Cyst enucleation and bone graft on mandible anterior and both body area were performed under general anesthesia, and postoperative healing was favorable without recurrence.

• 대한치과교정학회지
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• 제32권3호
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• pp.155-163
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• 2002

치조성 양악 전돌 증례에서 컴퓨터 시뮬레이션을 이용한 연조직 측모의 치료 결과 예측의 객관적 정확성을 상, 하악 제 1소구치 발거를 통해 교정치료를 받은 21명의 성인 여성을 대상으로 $Quick\;Ceph\;Image\;Pro^{TM}\;&\;Quick Eeph\;2000^{TM}$ 을 이용하여 조사, 평가하였다. 치료 전 측모 두부방사선 규격사진 투사도에서 경조직 이동량을 계측하고 Quick Ceph system 상에서 경조직을 동일한 양 이동시켜 컴퓨터시뮬레이 션을 위한 기준으로 삼았다. 이후 프로그램을 통해 연조직 변화를 시뮬레이션하고, 이 자료와 실제 치료 결과로 얻어진 연조직 계측 값을 측정하여 비교해 봄으로써 치료 결과 예측에 대한 정확도를 확인하고 임상에의 적용시 고려할 사항을 알아보았다. 시뮬레이션 결과 계측 항목의 수평 성분은 실제 치료 결과보다 작게, 수직 성분은 치료 결과보다 크게 예측하는 것으로 나타났으며 치료시 의 후방 견인은 실제보다 확대되어 나타나는 경 향을 보였다. 상악에서는 항목간 예측 오차의 방향이 일정하여 예측치가 실제보다 더 후방 이동되어 나타났으나, 하악에서는 증례간 차이가 컸다 Upper Lip Length는 짧게, Upper Vermilion Length는 길게 예측하여 시뮬레이션시 상순이 말려 보이는(rolling)효과를 확인할 수 있었으며 하순에서도 유사한 성향이 나타났으나 상순에 비해서 약하게 나타났다.

• 대한치과교정학회지
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• 제47권2호
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• pp.100-107
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• 2017

Objective: To analyze the long-term changes in maxillary arch widths and buccal corridor ratios in orthodontic patients treated with and without premolar extractions. Methods: The study included 53 patients who were divided into the extraction (n = 28) and nonextraction (n = 25) groups. These patients had complete orthodontic records from the pretreatment (T1), posttreatment (T2), and postretention (T3) periods. Their mean retention and postretention times were 4 years 2 months and 17 years 8 months, respectively. Dental models and smiling photographs from all three periods were digitized to compare the changes in three dental arch width measurements and three buccal corridor ratios over time between the extraction and nonextraction groups. Data were analyzed using analysis of variance tests. Post-hoc multiple comparisons were made using Bonferroni correction. Results: Soft-tissue extension during smiling increased with age in both groups. The maximum dental width to smile width ratio (MDW/SW) also showed a favorable increase with treatment in both groups (p < 0.05), and remained virtually stable at T3 (p > 0.05). According to the MDW/SW ratio, the mean difference in the buccal corridor space of the two groups was $2.4{\pm}0.2%$ at T3. Additionally, no significant group ${\times}$ time interaction was found for any of the buccal corridor ratios studied. Conclusions: Premolar extractions did not negatively affect transverse maxillary arch widths and buccal corridor ratios. The long-term outcome of orthodontic treatment was comparable between the study groups.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제29권2호
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• pp.79-85
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• 2003

The purpose of this study is to observe histopathologic changes in the bilateral craniomandibular joints after allowing 6 weeks of consolidation by varying the amount of distraction in rabbit mandible. Eight rabbits weighing about 2 to 3 kg were used. After corticotomy was performed on the left mandibular body between the first premolar and the second premolar region, a unilateral fixation device was placed. Then, a 7-day period was allowed without distraction of the device. The mandible was lengthened 0.5 mm/day. Corticotomy and lengthening of mandible were not performed in control group. After the completion of the lengthening process, a 6-week-consolidation period was allowed. Then, the rabbits were sacrificed, and histologic examination of the craniomandibular joints was performed. Proliferative changes were observed in the craniomandibular joints in all groups. With the increasing amount of distraction, hypertrophy of the cartilage layer became more severe, bone formed was dense and enchondral ossification was clearly shown in subchondral bone. Hypertrophy of the cartilage layer was also seen in the non-distracted side as the distracted side in the experimental group. These results indicate that when physical force is applied constantly to joints, the proliferation of articular cartilage and bone formation are present. When more than 6 weeks of consolidation period is allowed at the time of performing distraction for more than 5 mm, articular changes, especially, in the contralateral side should also be noted.

• Imaging Science in Dentistry
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• 제42권1호
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• pp.5-12
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• 2012

Purpose : This study was performed to evaluate possible variations in maxillary and mandibular bone texture of normal population using the fractal analysis, particles count, and area fraction in intraoral radiographs. Materials and Methods : Periapical radiographs of patients who had full mouth intraoral radiographs were collected. Regions of interest ($100{\times}100$ pixels) were located between the teeth of the maxillary anterior, premolar, and molar area, as well as the mandibular anterior, premolar, and molar areas. The fractal dimension (FD) was calculated by using the box counting method. The particle count (PC) and area fraction (AF) analyses were also performed. Results : There was no significant difference in the FD values among the different groups of age, gender, upper, and lower jaws. The mean FD value was $1.49{\pm}0.01$. The mean PC ranged from 44 to 54, and the mean AF ranged from 10.92 to 11.85. The values of FD, PC, and AF were significantly correlated with each other except for the upper molar area. Conclusion : According to the results, patients with normal trabecular pattern showed a FD of approximately 1.5. Based on these results, further investigation would be recommended if the FD value of patient significantly differenct from this number, since the alteration of this value indicates microstructural modification of trabecular pattern of the jaws. Additionally, with periapical radiographs, simple and cost-effective, PC and AF could be used to assess the deviation from the normal.

• Journal of Periodontal and Implant Science
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• 제43권6호
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• pp.315-322
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• 2013

Purpose: In this study, we investigated the effect of silk scaffolds on one-wall periodontal intrabony defects. We conjugated nano-hydroxyapatite (nHA) onto a silk scaffold and then seeded periodontal ligament cells (PDLCs) or dental pulp cells (DPCs) onto the scaffold. Methods: Five dogs were used in this study. Bilateral 4 mm${\times}$2 mm (depth${\times}$mesiodistal width), one-wall intrabony periodontal defects were surgically created on the distal side of the mandibular second premolar and the mesial side of the mandibular fourth premolar. In each dog, four of the defects were separately and randomly assigned to the following groups: the PDLCcultured scaffold transplantation group (PDLC group), the DPC-cultured scaffold transplantation group (DPC group), the normal saline-soaked scaffold transplantation group, and the control group. The animals were euthanized following an 8-week healing interval for clinical, scanning electron microscopy (SEM), and histologic evaluations. Results: There was no sign of inflammation or other clinical signs of postoperative complications. The examination of cellseeded constructs by SEM provided visual confirmation of the favorable characteristics of nHA-coated silk scaffolds for tissue engineering. The scaffolds exhibited a firm connective porous structure in cross section, and after PDLCs and DPCs were seeded onto the scaffolds and cultured for 3 weeks, the attachment of well-spread cells and the formation of extracellular matrix (ECM) were observed. The histologic analysis revealed that a well-maintained grafted volume was present at all experimental sites for 8 weeks. Small amounts of inflammatory cells were seen within the scaffolds. The PDLC and DPC groups did not have remarkably different histologic appearances. Conclusions: These observations indicate that nHA-coated silk scaffolds can be considered to be potentially useful biomaterials for periodontal regeneration.