• 대한치과보철학회지
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• 제38권5호
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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.

• Restorative Dentistry and Endodontics
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• 제16권2호
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• pp.174-181
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• 1991

A model system was used which enabled the same root canal system to be measured before and after coronal flaring of 51 extracted mandibular molars. The concavity of the distal surface of the mesial root was measured and the amount of reduction was compared after coronal flaring using step-back flared preparation, Gates-Glidden dirll or ultrasonic system(Quick-$\varepsilon$) at the furcation and apical 3mm from the furcation. The results were as follows: 1. The mean concavity of mesial root of manchbular molar was $0.73{\pm}0.27mm$ at the bifurcation and $0.65{\pm}0.23mm$ at the 3.0mm apical from the bifurcation. 2. The thickness of the root canal wall of the mesiobuccal canal was $1.08{\pm}0.26mm$ at the bifurcation and $1.00{\pm}0.23mm$ at the 3.0mm apical from the bifurcation. 3. The thickness of the root canal wall of the mesiolingual was $1.09{\pm}0.21mm$ at the bifurcation and $0.98{\pm}0.29mm$ at the 3.0mm apical from the bifurcation. 4. In the amount of reduction at the furcation and at the 3.0mm apical from the furcation there was no statistically significant difference between the step-back preparation and Gates-Glidden drill preparation, and ultrasonic preparation(P>0.05).

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.537-549
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• 1998

본 연구의 목적은 미세치근단 수술법에서 사용되는 치근단 절제방법 및 역충전와동 술식을 종래의 치근단 수술법에서 사용해 온 술식 및 방법과 치근단 미세누출의 측면에서 비교, 연구하고자 함이다. 치근단 절제방법 및 역충전와동 형성 방법에 따른 치근단 누출을 평가하기 위해서는 최근에 발거된 상악 중절치, 측절치 및 견치 71개를 절제 각도 및 와동 형성방법에 따라 5개의 군으로 분류하여 실험하였으며, 근관협부 처리에 따른 치근단 누출을 평가하기 위해서는 최근 발거된 상악 제 1대구치의 근심협측 치근 44개를 근관협부의 처리 유무에 따라 2개군으로 분류하여 실험하였다. 각 시편치아에서 근관을 형성하고 측방가압법으로 충전한 후 각 군에 따라 저속 다이아몬드 절단기를 이용하여 치근단 3 mm를 절제하였으며 저속 round bur와 초음파 스테인레스 스틸 기구를 이용하여 역충전와동을 형성하고 IRM으로 역충전하였다. 시편을 2% methylene blue 용액에 7일간 침잠시킨 후 35% 질산 용액에서 용해시킨 다음, 원심분리한 상층액을 비색계를 이용하여 누출 색소의 홉광도를 측정하였다. 결과치는 이원변량분석법과 Duncan's Multiple Range Test를 이용하여 분석하였으며, 다음과 같은 결과를 얻었다. ${\cdot}$ 사면을 부여하지 않고 치아 장축에 대해 직각이 되게 치근단을 절제하고 치아 장축에 평행하게 역충전와동을 형성한 경우, 초음파기구를 이용한 군과 저속 round bur를 이용한 군사이에는 미세누출에 있어서 유의한 차이가 나타나지 않았다(p>0.05). ${\cdot}$ 사면을 부여하면서 치근단을 절제하고 치아 장축에 평행하게 역충전와동을 형성한 경우, 초음파기구를 이용한 군은 저속 round bur를 이용한 군에 비해 유의하게 적은 치근단 누출을 보였다(p<0.0001). ${\cdot}$ 초음파기구를 이용하여 역충전와동을 형성한 경우에는, 치근단 절제시 사면의 부여에 관계없이 치근단 누출에 유의한 차이가 나타나지 않았으나(p>0.05), 저속 round bur를 이용한 경우에는, 사변을 형성하지 않은 군이 사면을 형성한 군에 비해 유의하게 적은 미세누출을 나타내었다(p<0.0001). ${\cdot}$ 치근단 절제시 사변을 부여한 경우에는, 저속 round bur로 치아 장축에 평행하게 역충전와동을 형성한 군은 치아 장축에 직각으로 역충전와동을 형성한 군에 비해 미세누출이 적게 나타났지만, 유의한 차이는 나타나지 않았다(p>0.05). ${\cdot}$ 초음파 기구를 이용하여 근관협부를 따라 역충전 와동을 형성한 군은 저속 round bur를 이용하여 근관협부를 따라 역충전 와동을 형성하지 못한 군에 비해 유의하게 적은 치근단 누출을 나타내었다(p<0.0001).

• 대한소아치과학회지
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• 제47권1호
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• pp.25-35
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• 2020

이 연구의 목적은 CBCT를 사용하여 유구치 치근 및 근관의 형태학적 특징을 평가하는 것이다. 과잉치 발거를 위해 전남대학교 치과병원 소아치과에 내원하여 CBCT를 촬영한 만 4 - 5세 환자 총 68명의 영상으로 연구를 진행하였다. 치근 흡수가 되지 않은 상악 제1유구치, 상악 제2유구치, 하악 제1유구치, 하악 제2유구치로 구분하여 분석하였다. 치근 및 근관의 수, 치근 및 근관의 길이와 각도 등의 다양한 변수들이 분석되었다. 상악 유구치는 모두 3개의 치근을 가졌고 원심 협측 치근과 구개 치근은 단일 근관을 가졌다. 한 치근에 2개의 근관이 있는 경우는 오직 상악 제2유구치의 근심 협측 치근에서 발견되었다. 하악 유구치는 대부분 근심과 원심 2개의 치근을 가졌다. 하악의 근심 치근은 대부분 2개의 근관을 가졌다. 치근의 길이와 관련하여, 상악의 구개 치근의 길이가 가장 긴 반면, 원심 협측 치근의 길이는 가장 짧은 것으로 밝혀졌다. 하악 유구치는 근심의 치근이 더 길었다. 상악 유구치에서는 구개 치근의 각도가 가장 컸으나 하악은 근심의 각도가 더 작았다. 상악 유구치의 치근 및 근관이 곡선형이 많은 반면 하악 유구치는 직선형을 더 많이 볼 수 있었다.

• 대한치과의사협회지
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• 제55권10호
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• pp.688-694
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• 2017

Objectives: This preliminary study compared the effects of glide path establishing instruments prior to substantial root canal preparation. Materials and Methods: Glide path was established by enlargement of the 2nd mesiobuccal root canal of Dentalike by using three kinds of glide path preparation nickel-titanium file; PathFile, One G and ProGlider. The pre- and post-instrumented Dentalikes were weighed in the resolution of 1 / 10mg. In addition, after glide path preparation, torque generated during shaping using the WavoOne file was measured. The data were analyzed by one-way ANOVA and Tukey post-hoc test at a significance level of 95%. Results: The ProGlider had the significantly larger amount of reduced weight than other instrument groups (p < 0.05). There was no significant difference between group of glide path preparation with ProGlider and without glide path preparation in maximum torque and total stress generation during the shaping with WaveOne. Conclusions: Glide path preparation instruments may have different efficiency according to their geometries. The Dentalike artificial teeth were revealed to have discrepancies in the size of root canals by microCT examination. It is impossible to make a meaningful judgment of the results due to the reliability or resolution problem of the root canal size of the artificial tooth selected as the standardized tooth.

• Restorative Dentistry and Endodontics
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• 제45권1호
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• pp.7.1-7.9
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• 2020

Objectives: This study was performed to assess the anatomy of mandibular first molars. Materials and Methods: In this in vivo study, cone-beam computed tomography (CBCT) volumes of 312 bilateral intact first mandibular molars from 156 patients (79 men and 77 women; average age, 35.6 ± 11.2 years) were investigated in terms of the direction of each canal's curvature in the buccolingual and mesiodistal dimensions (direction of the position of the apex in relation to the longitudinal axis of the root), the presence of an isthmus (a narrow, ribbon-shaped communication between 2 root canals) in 3 segments (0-2, 2-4, and 4-6 mm) from the apex), and the presence and number of accessory canals (smaller canals besides the main root canals, connecting the pulp to the periodontium). Data were analyzed statistically (α = 0.05). Results: Mesiolingual canals were mostly buccally and distally inclined, while mesiobuccal and distolingual canals were mostly distally curved. Isthmuses were more common in younger patients (χ² test, p < 0.05). The average numbers of accessory canals in the apical, middle, and coronal segments were 9.9 ± 4.2, 6.9 ± 2.9, and 9.3 ± 3.0 canals per segment, respectively (analysis of variance, p < 0.001). Age and sex were not associated with the number of accessory canals (p > 0.05). Conclusions: The complex anatomy of these teeth deserves attention during non-surgical or surgical endodontic treatment. Around the apex, isthmuses might be more prevalent in younger and female individuals.

• Restorative Dentistry and Endodontics
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• 제26권2호
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• pp.111-120
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• 2001

Calcium hydroxide pastes is widely used in conventional endodontics. Along with the expanded clinical use of calcium hydroxide, literatures suggest mixing calcium hydroxide with other substance. Among added substances the vehicle plays the most importance role in the overall process because it is directly related with the velocity of ionic dissociation of $Ca^{2+}$ and OH ion. In this study, we evalutated and compared periapical tissue response and root resorption after canal was filled with mixture of saline and calcium hydroxide(Junsei Chemical Co.. Japan) as a aqueous vehicle, Metapaste(Meta Co., Korea) as a viscous vehicle paste, Vitapex(Neo Dental, Japan) as a oily vehicle paste and IRM(Caulk Dentsply, USA) in replantation of rat molar. A total of 31 maxillary first molars of Sprague-Dawley female rats, 30 days old were used. The upper 1st molar was extracted and the mesiobuccal canal was filled with mixture of saline and calcium hydroxide, Metapaste, Vitapex. IRM and then replanted. Rats were sacrificed 3 weeks after replantation. the maxillae were removed. section of 4 micron were cut and stained with hematoxylin-eosin, Apical tissue response were observed under light microscope. The results were as follows: 1. Saline mixing group and Metapaste group were significant different in fibrous capsule width compared to Vitapex group and IRM group(P<0.05). 2. Saline mixing group. Metapaste group. Vitapex group and IRM group did not prevent root resorption and there were no statistical difference. 3. In saline mixing group and Metapaste group. loss of pastes were observed in all samples. From the results of our study. we observed loss of pastes in saline mixing group and Metapaste group because of water soluble property and assumed it was related to inflammation in apical area and sealing ability of material. So, we should study and develop calcium hydroxide vehicle which is easily removed and more stable and because of only 3 weeks observation we need more evaluation in long period.

• Restorative Dentistry and Endodontics
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• 제20권2호
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• pp.768-779
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• 1995

This study was performed to investigate the effect of root canal shaping techniques on the change of the shape of prepared root canal. 40 mesiobuccal canals of recently extracted mandibular 1st and 2nd molars were divided into 4 groups and shaped by step-down/balanced force technique, step-down/step-back technique, step-back technique and conventional technique respectively. The change of the shape of root canal was traced by superimposing the radiographs obtained before and after shaping of each root canal. The results were as follows. 1. By the experimented techniques except conventional technique, the root canals were more shaped in convex side of apical area and in concave side of most curved and coronal area than in the other sides(P<0.05). By conventional technique, the root canals were more shaped in convex side than in convave side from apex to orifice(P<0.05). 2. By step-down/balanced force technique, the cancave sides at C and D points of proximal view and C point of clinical view were more shaped than the convex side(P<0.05). Through the entire canal, the concave side was more shaped than the convex side in proximal view(P<0.01). But there was no statistical difference between both sides in clinical view. 3. By step-down/step-back technique, the change of root canal shape was not statistically different in concave and convex sides at each point of both views(P>0.05). And through the entire canal in proximal view, there was no statistical difference in shaping percentage between both sides. But through the entire canal in clinical view, the concave side was more shaped than the convex side(P<0.1). 4. By step-back technique, the convex side at B point of clinical more shaped than the other sides(P<0.05). Through the entire canal in proximal and clinical views, there was no statistical difference in shaping percentage between both sides. 5. Comparing the total shaping percentage among techniques, that in conventional technique was the greatest numerically, and followed by the percentages in step-down/step-back, step-down/balanced force and step-back technique. But, in proximal view, shaping percentages were not statistically different among techniques(P>0.05, ANOVA test). In clinical view, shaping percentages in step-back and conventional techniques were statistically different(P<0.01, ANOVA test). * Proximal view: radiograph taken in mesiodistal direction. * Clincal view: radiograph taken in faciolingual direction. A point : 1mm point from radiographic apex B point : center point between A and C points C point : most curved point of root canal D point : center point between C point and canal oriffice.

• Imaging Science in Dentistry
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• 제46권3호
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• pp.179-184
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• 2016

Purpose: In the present study, we coined the term 'alveolar dome' and aimed to demonstrate the prevalence of alveolar domes through digital periapical radiographs. Materials and Methods: This study examined 800 digital periapical radiographs in regard to the presence of alveolar domes. The periapical radiographs were acquired by a digital system using a photostimulable phosphor (PSP) plate. The ${\chi}^2$ test, with a significance level of 5%, was used to compare the prevalence of alveolar domes in the maxillary posterior teeth and, considering the same teeth, to verify the difference in the prevalence of dome-shaped phenomena between the roots. Results: The prevalence of alveolar domes present in the first pre-molars was statistically lower as compared to the other maxillary posterior teeth (p<0.05). No statistically significant difference was observed in the prevalence of alveolar domes between the maxillary first and second molars. Considering the maxillary first and second molars, it was observed that the palatal root presented a lower prevalence of alveolar domes when compared to the distobuccal and mesiobuccal roots (p<0.05). Conclusion: The present study coined the term 'alveolar dome', referring to the anatomical projection of the root into the floor of the maxillary sinus. The maxillary first and second molars presented a greater prevalence of alveolar domes, especially in the buccal roots, followed by the third molars and second pre-molars. Although the periapical radiograph is a two-dimensional method, it can provide dentists with the auxiliary information necessary to identify alveolar domes, thus improving diagnosis, planning, and treatment.

• Restorative Dentistry and Endodontics
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• 제29권5호
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• pp.446-453
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• 2004

하악 대구치 근심치근의 danger zone에서 수종의 전동 니켈-티타늄 파일의 근관성형력을 근관성형 전후 치질 두께의 변화를 측정하여 평가하고자 하였다. 기구에 따라 총 40개의 하악 대구치를 10개씩 $Profile^{\circledR}$, GT Rotary file, Quantec 및 ProTaper 4개 군으로 나누고 각 치아당 2개의 근관을 straight up-and-down과 anticurvature 군으로 나누어 근단부 근관을 모두 30번 크기로 일정하게 확대하였다. 수정된 Bramante법을 사용하였으며 술전 및 술후의 근관 상아질 두께를 치수저 하방 1, 3 및 5 mm지점에서 측정, 이원변량분석법으로 통계분석하였다. 모든 군의 danger zone과 safe zone에서의 straight up-and-down 동작과 anticurvature 동작 사이에는 치근상아질 두께변화에 현저한 차이를 나타내지 않았다 (p > 0.05). ProTaper는 danger zone과 safe zone 모두에서 다른 기구에 비해 많은 량의 근관상아질 삭제를 보였으며 특히 분지부 3 mm 수준에서 현저하였다(p < 0.05).