• Restorative Dentistry and Endodontics
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• v.23 no.2
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• pp.537-549
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• 1998

The purpose of this study was to evaluate the influence of root resection and retrograde cavity preparation methods on the apical leakage in endodontic surgery. To investigate the effect of various root resection and retrograde cavity preparation methods on the apical leakage, 71 roots of extracted human maxillary anterior teeth and 44 mesiobuccal roots of extracted human maxillary first molars were used. Root canals of the all the specimens were prepared with step-back technique and filled with gutta-percha by lateral condensation method. Three millimeters of each root was resected at a 45 degree angle or perpendicular to the long axis of the tooth according to the groups. Retrograde cavities were prepared with ultrasonic instruments or a slow-speed round bur, and occlusal access cavities were filled with zinc oxide eugenol cement. Three coats of clear nail polish were placed on the lateral and coronal surfaces of the specimens except the apical cut one millimeter. All the specimens were immerged in 2% methylene blue solution for 7 days in an incubator at $37^{\circ}C$. The teeth were dissolved in 14 ml of 35% nitric acid solution and the dye present within the root canal system was returned to solution. The leakage of dye was quantitatively measured via spectrophotometric method. The obtained data were analysed statistically using two-way ANOVA and Duncans Multiple Range Test. The results were as follows: 1. No statistically significant difference was observed between ultrasonic retrograde cavity preparation method and slow-speed round bur technique, without apical bevel (p>0.05). 2. Ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, with bevel (p<0.0001). 3. No statistically significant difference was found between beveled resected root surface and non-beveled resected root surface, with ultrasonic technique (p>0.05). 4. Non-beveled resected root surface showed significantly less apical leakage than beveled resected root surface, with slow-speed round bur technique (p<0.0001). 5. No statistically significant difference in apical leakage was found between the group of retrograde cavity prepared parallel to the long axis of the tooth and the group of one prepared perpendicular to the long axis of the tooth (p>0.05). 6. Regarding isthmus preparation, ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, in the mesiobuccal root of maxillary molar, without bevel (p<0.0001).

• Journal of dental hygiene science
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• v.11 no.3
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• pp.155-161
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• 2011

The purpose of this study was to obtain data necessary for guiding students in the future by grasping which rate of error is made how much depending on a shooting technique in the filming of periapical radiograph. 14,402 films, which were instructed targeting students for the Department of Dental Hygiene at D Health College and S Health College, were analyzed. The following results were obtained by conducting questionnaire survey targeting 263 students who completed the shooting practice lesson of bisecting angle technique and paralleling technique. 1. In case of having shot with bisecting angle technique, the ratio of error was the highest in both maxillary and mandibular first molar. 2. In case of having shot with paralleling technique, the ratio of error was the highest in the maxillary bicuspid and the mandibular first molar. 3. As for ratio of error in light of a shooting technique, both bisecting angle technique and paralleling technique were indicated to be the highest in inaccuracy of film position. The bisecting angle technique was indicated to have the higher ratio of error compared to the paralleling technique. 4. As for ratio of error in light of the processing technique, both bisecting angle technique and paralleling technique were indicated to be the highest in dark image and light image. The bisecting angle technique was indicated to have the higher ratio of error compared to the paralleling technique. 5. Students were indicated to feel it to be most difficult for grasping the processing level in the film-developing process. As the above results, to reduce ratio of error given the periapical radiography, a method of reducing ratio of error given the periapical radiography is considered to be what correctly understands the morphological and anatomical structure inside the mouth and what acquires the shooting technique by filming several times with having enough time.

• The korean journal of orthodontics
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• v.38 no.4
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• pp.240-251
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• 2008

Objective: The purpose of this study was to evaluate the effect of head position changes on the root parallelism between adjacent teeth on panoramic radiographs. Methods: A model with normal occlusion was constructed in the SolidWorks program, then RP (rapid protyping) model was fabricated. The model was repeatedly imaged and repositioned five times at each of the following nine positions: ideal head position, $5^{\circ}$ up, $10^{\circ}$ up, $5^{\circ}$ down, $10^{\circ}$ down, $5^{\circ}$, right, $10^{\circ}$, up, and $5^{\circ}$ right rotation, $10^{\circ}$ right rotation. Panoramic radiographs were taken by Planmeca ProMax and the angle between the long axes of adjacent teeth was directly measured in the monitor. Results: Axes of adjacent teeth tended to converge toward the occlusal plane when the head tilted up and converged in the opposite direction to the occlusal plane when the head tilted down. Anterior teeth showed the most notable differences. When one side of the head tilted up $5^{\circ}$ and $10^{\circ}$ along the anteroposterior axis (Y axis), tooth axes of the same side tended to converge toward the occlusal plane and tooth axes of the opposite side tended to converge in the opposite direction to the occlusal plane. When the head rotated to one side along the vertical axis (Z axis), the canine and lateral incisor of the same side converged in the opposite direction to the occlusal plane and the canine and lateral incisor of the other side converged toward the occlusal plane. Conclusions: When assessing the root parallelism on panoramic radiographs, the occlusal plane cant (anteroposterior or lateral) or asymmetry of the dental arch should be considered because these can cause distortion of tooth axes on panoramic radiographs.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.371-379
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• 1994

본 연구는 비규격화시켜 촬영한 두장의 방사선 사진을 일반 영상처리 프로그램으로 기하학적 보정을 하여 디지탈 공제 촬영술을 시행한 결과를 개인별로 제작된 필름유지장치를 이용하여 규격화 시켜 촬영한 두장의 방사선사진을 디지탈 공제 촬영술을 시행한 결과와 비교하여 일반 영상처리 프로그램의 임상적 유용성을 평가해보고자 시행하였다. 19명의 자원자를 대상으로 하여, 각 환자에서 4매의 하악구치부 치근단 사진을 촬영하였다. 그중 2매는 XCP 필름 유지장치만으로 평행촬영법으로 촬영하였고, 나머지 2매는 교합제에 인상재를 부가하여 개인별로 제작된 XCP필름 유지장치를 이용하여 표준화시켜 역시 평행촬영법으로 촬영하였다. 기하학적 보정은 "Adobe Photoshop"과 "NIH Image" 프로그램으로 시행하였다. 특히 "Adobe Photoshop"의 임의영상회전 기능과 "IH Image"의 공제시술시 중첩된 사진을 투명하게 보여주는 기능, 병진기능을 활용하였다. 두 사진의 유사성을 측정하기 위해 공제된 사진의 계조도의 표준편차를 구하였다. 표준화군의 평균 표준편차가 기하학적 보정군의 평균 표준편차보다 약간 낮았으나, 통계적으로 유의성이 있는 차이를 보이지는 않았다. 위의 결과로 미루어보아, 하악구치부 에서 XCP필름 유지장치로 평행촬영한 비표준화방사선사진을 "Adobe Photoshop"과 "NIH Image" 프로그램을 이용하여 기하학적 보정을 할 수 있으리라 사료된다.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.219-237
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• 1999

This study was designed to evaluate the frequency and the severity of root resorption of the permanent teeth before orthodontic treatment by means of radiograph in the malocclusion patients. In this study the author analysed the frequency and the severity of root resorption in individual teeth, the relationships of the frequency and the severity of root resorption and age, sex, Angle's classification, overjet, overbite, and maxillary and mandibular incisor inclination, and the relationships of the frequency of root resorption and the characteristics of malocclusion and marked occlusal attrition showed in individual teeth. The results were as follows. 1. All of the persons examined showed some evidence of root resorption in one or more of the permanent teeth, $35.84\%$ of the teeth examined and more frequent in female group than male group(p<0.01). 2. On the susceptibility of the root resorption in individual teeth in this study, the author found the mandibular incisors and the maxillary incisors, in the order named, to be most susceptible in all affected teeth, but maxillary central incisors, maxillary first bicuspids, and maxillary lateral incisors, in the order named, were more susceptible to marked root resolution. 3. The more proclined maxillary Incisors the more affected root resorption in four maxillary incisors and the more proclined mandibular incisors the more affected root resorption in four mandibular incisors. 4. Overbite more affected root resorption than overjet, and the higher tender to openbite the more frequent was root resorption. 5. On the characteristics of malocclusion showed in individual teeth, the openbite teeth combined with crossbite, were most frequent in root resolution.

• The korean journal of orthodontics
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• v.31 no.4 s.87
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• pp.425-438
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• 2001

The delivery of optimal orthodontic treatment is greatly influenced by clinician's ability to predict and control tooth movement by applying well-known force system to dentition. It is very important to determine the location of the centers of resistance of a tooth or teeth in order to have better understanding the nature of displacement characteristics under various force levels. In this study, three dimensional finite element analysis was used to measure the initial displacement of the consolidated teeth under loading. The purpose of this study was to define the location of the centers of resistance at the upper six anterior segment. To observe the changes of six anterior segment, 200gm, 250gm, 300gm, and 350gm forces at right and left hand side each were imposed toward lingual direction. For this study, two cases, six anterior teeth and six anterior teeth after corticotomy, were reviewed. In addition, it was reviewed the effects of changes on the location of the center of resistance in both cases based on different degree of forces aforementioned. The results were that : 1. The instantaneous center of resistance for the six anterior teeth was vertically located between level 4 and level 5, which is, at 6.76mm, $44.32\%$ apical to the cementoenamel junction level. 2. The instantaneous center of resistance for the six anterior teeth after corticotomy was located vertically between level 4 and level 5, that is, at 7.09mm $46.38\%$ apical to the cementoenamel junction level. 3. Changes of force showed little effect on the location of the center of resistance in each case. 4. It was observed that the location of the instantaneous center of resistance for the six anterior teeth after corticotomy was changed more than the six anterior teeth without corticotomy to the apical part, and the displacement of the consolidated anterior teeth moved further in case of the consolidated teeth after corticotomy.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.233-238
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• 2014

Purpose: A method detecting change of jaw or alveolar bone density may be helpful in periodontal care, implant dentistry and evaluation of bone density of whole body. Materials and methods: In this study, bone density of intraoral periapical radiography using phantom-integrated XCP is compared with that of quantitative computed tomography (QCT). Results: Bone density of intraoral periapical radiography and the one measured by QCT showed high correlation (correlation coefficient = 0.92, P<.001) in alveolar bone, and relatively high correlation (0.73, P<.001) in cancellous bone. Conclusion: This study revealed possibility of scoring of bone density by intraoral periapical radiography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.1
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• pp.19-25
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• 1993

The purpose of this study was to evaluate the prevalence and distribution of additonal root in the mandibular 1st molars and premolars by means of the analysis of the full mouth periapical radiographs in 6,082 patients visited the Dental Infirmary of Kyungpook National University Hospital from March 1989 to February 1993. The results were as follows: 1. The incidence of additional root in the mandibular 1st molars was revealed to be 9.32% in total examined patients, and there was a higher prevalence in males(I1.35%) than in females(7.46%). And bilateral occurrence was revealed to be 4.26%. 2. The incidence of additional root in the mandibular premolars was to be 3.57% in total examined patients, and there was a higher prevalence in males(4.28%) than in females(2.91%). And bilateral occurrence in the 1st premolars was revealed to be 1.53%.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.543-549
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• 2000

Gutta-percha와 근관sealer를 사용한 근관 충전은 가장 많이 이용되고 성공률이 높은 방법이지만, 현재 사용되는 모든 근관sealer는 미세누출을 나타낸다. 따라서 더 효과적인 근관 폐쇄를 이루기 위한 재료 및 방법들이 연구되어왔다. 이중 상아질 접착제는 근관 충전재와 함께 사용되어 미세누출을 감소시키지만, 근관 내에 사용하기에 술식이 복잡하고 기술이 요구된다. 본 연구의 목적은 gutta-percha와 레진계 근관 sealer로 충전한 근관에서 self-etching primer를 미리 도포한 경우와 도포하지 않은 경우의 치근단 미세누출을 비교하고, self-etching primer를 도포함에 있어 근관 내에 적용하는 방법에 따른 미세누출을 비교하는 것이다. 또한 근관sealer와 상아질 계면을 주사전자현미경으로 관찰하여, 이 결과를 미세누출과 관련시켜보고자 하였다. 36개의 발거된 사람의 단근치에서 치관부를 절단, 제거하고 ProFile로 근관 형성한 후, 무작위로 선택하여 4개의 군으로 분류하였다. 1군에서는 주사기와 30게이지 주사 바늘로 self-etching primer를 근관 내에 적용하였고, 2군에서는 self-etching primer를 paper point에 적셔 근관 내에 적용하였다. 3군에서는 self-etching primer를 적용하지 않았다. 1, 2, 3군의 치아를 gutta-percha와 AH26 sealer를 사용하여 continuous wave 충전법으로 충전한 후 치근단공 주위 3mm를 제외한 치근변에 nail polish를 2회 도포하였고, 4군(음성 대조군)은 치근면 전체에 도포하였다. 1군과 2군에서 각각 2개의 치아는 주사전자현미경적 관찰을 위해 준비하였다. 모든 치아를 Methylene Blue 수용액에 48시간동안 침적, 수세한 후 치아 장축에 평행하게 양분하여 10배의 실물확대현미경 하에서 치근단 색소 침투를 관찰하였다. Self-etching primer를 도포한 군과 도포하지 않은 군 사이에는 평균 미세누출량에 유의한 차이가 없었다. 주사 바늘로 적용한 군과 paper point로 적용한 군 사이에도 평균 미세누출량에 유의한 차이가 없었다. 상아질과 근관 sealer계면의 주사전자현미경 관찰 결과 일부분에서 긴밀한 접착 관계를 나타내었고, 다른 부분에서는 간극을 나타내었다.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.535-549
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• 1999

The Purposes of this study were to investigate the initial tissue changes on the teeth and surrounding tissues under contraction and intrusive force by contraction UTA. A control and experimental dogs, 10-months in age, were studied. Contraction and intrusive force(60gm) were applied at upper four incisors by contraction UTA. Experimental dogs were sacrificed at 2 weeks and 4 weeks after force application, respectively. In this study, 2 experimental groups were designed by the duration of force applied(E1, E2). The specimens were taken around the upper first and second incisor in each groups and were prepared for the H-E and MT stain for light microscopic observation. From the results of the study, the following conclusions may be drown. : 1. In control group, the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third, oblique in middle third and apical third. In alveolar bond, smooth appearance was shown with osteoblast. 2. In experimental group 1, in proportion to force was concentrated at labial middle third and apical third of root of the upper first and second incisors, root of these tooth tipped labially and intruded at a time. 3. In experimental group 2, periodontal ligament width and arrangement was similar to control and observed strong calcified response at the labial middle third of root. But, alveolar bond resorption and cementum resorption were as before seen at labial middle third and apical third of root that force was concentrated.