• 대한소아치과학회지
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• 제36권2호
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• pp.288-292
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• 2009

치관-치근 파절(crown-root fracture)은 법랑질, 상아질, 백악질에 파급된 파절이며 치수노출을 수반하는 것과 수반하지 않는 것이 있다. 치근부위만 파절된 경우와 달리 치관-치근 파절의 경우 치수와 치주조직을 통해 세균감염이 발생하기 때문에 치유를 기대하기 힘들다. 파절은 치근을 따라 다양한 부위에서 일어나기 때문에 치료방법은 파절 정도에 따라 결정된다. 치근의 파절선이 치관부에 근접 한 경우 느슨한 치아 파절편을 제거 한 후, long junctional epithelium이 형성되도록 치은을 노출된 상아질에 맞게 적합시키거나, 외과적으로 파절 부위를 노출시키거나, 교정적 또는 외과적으로 치아를 정출시키는 방법 등을 고려해 볼 수 있지만 파절선이 깊은 경우 발치가 일반적이다. 그러나 최근 논문에서 수직 치관-치근 파절된 치아에 대해 발치대신 레진으로 파절선을 수복한 후 재식하여 성공한 사례가 발표되었다. 이 방법으로 치아를 보존할 수 있으며 이러한 방법이 전치 부에서는 예후가 좋다고 보고되었다. 본 증례에서는 외상으로 인하여 상악중절치의 치관-치근 파절이 발생한 10세 환아에서 해당 치아를 발치하여 레진으로 파절부위를 재부착한 후 재식하였다. 그러나 18개월간 주기적으로 관찰한 결과 문헌에서와 같은 좋은 결과를 나타내지는 않았다.

• 대한소아치과학회지
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• 제30권4호
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• pp.576-580
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• 2003

7세 남아가 맹출 중인 상악 영구 중절치의 외상을 주소로 내원하였다. 환아의 우측 중절치는 아탈구와 치근 파절을 보였고, 좌측 중절치는 함입성 탈구와 치근 파절을 보였다. 두 치아는 정복 후 선부자에 의해 고정하였다. 이후 주기적인 검진을 시행하였다. 4년이 지난 현재, 우측 중절치는 방사선 사진에서 파절편 사이에 방사선 투과성이 보이지 않고 정상적인 치조백선을 보여 경조직으로 치유되는 양상을 보였다. 좌측 중절치는 파절편이 분리되어있고 근관이 점차 폐쇄되는 소견을 보이고 있어 골과 결합조직의 개입에 의한 치유 양상을 보이고 있다. 임상 검사에서 정상적인 동요도와 타진 반응을 보였고, 전기치수검사에 양성 반응을 보였다. 외상을 받은 치아의 예후는 외상의 유형, 환자의 연령, 치근의 발육단계, 변위의 정도 등에 의해 영향을 받는다. 본 증례는 개방근관을 가진 치아가 외상 후 우측 중절치는 석회화 조직으로 치유, 좌측 중절치는 골과 결합조직의 개입으로 치유되고 있는 양상을 보이고 있어 이를 보고하는 바이다.

• Journal of Welding and Joining
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• 제2권2호
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• pp.62-69
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• 1984

In this study, cold crack susceptibility of high strength steel (ABS EH32 Steel) welded zone with shielded metal are welding was investigated by tensile restraint cracking test method. Effects of diffusible hydrogen content on root cracking, lower critical stress, crack initiation and fracture mode, hardness value distribution of welded zone and fractograph were mainly investigated. Following conclusions are made: 1. In the view of the lower critical stress level, wet electrode, containing much diffusible hydrogen content shows lower value than dried electrode. 2. Hardness value(Hv 5kg) in Heat Affected Zone of wet electrode is higher than that of dried electrode caused by hydrogen embrittlement. 3. In the case of wet electrode, root crack is initiated and propagated in Heat Affected Zone and then propagated to weld metal, but using of dried electrode, root crack is initiated in Heat Affected Zone and propagated to weld metal without propagating in HAZ. 4. For wet electrode, quasi-cleavage fracture mode is majorly observed on the fracture surface of HAZ and partially of weld metal due to hydrogen embrittlement.

• Journal of Welding and Joining
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• 제19권3호
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• pp.298-304
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• 2001

Turbine blade is subject to force of three types ; the torsional force by torsional mount, the centrifugal force by the rotation of rotor and the cyclic bending force by steam pressure. The cyclic bending force was a main factor on fatigue strength. SEM fractography in root of turbine blade showed micro-clack width was not dependent on stress intensity factor range. Especially, fatigue did not exist on SEM photograph in root of turbine blade. To clear out the fracture mechanism of turbine blade, nanofractography was needed on 3-dimensional crack initiation and crack growth with high magnification. Fatigue striation partially existed on AFM photograph in root of turbine blade. Therefore, to find a fracture mechanism of the torsion-mounted blade in nuclear power plant, the relation between stress intensity factor range and surface roughness measured by AFM was estimated, and then the load amplitude ΔP applied to turbine blade was predicted exactly by root mean square roughness.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1-6
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• 2004

In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structure with notch.

• 대한소아치과학회지
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• 제27권2호
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• pp.344-350
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• 2000

외상으로 인하여 치아가 받는 여러 가지 손상형태 중 치관-치근파절이 나타나는 빈도는 영구치에서 5%, 유치열에서는 2%라고 알려져 왔다. 치조정 하방에 파절선이 존재하고 치수노출을 동반한 치관-치근 파절에서는 크게 두가지의 보존적인 치료방법이 있다. 첫째, 교정력에 의해 정출시키는 방법과 둘째 치조와내에서 교합면 방향으로 재위치시키는 Intra-alveolar transplantation 등이 있다. 외과적 정출법은 1970년대에 소개된 이래로 교정적 정출법의 대안으로 많이 시행되고 있으며 높은 성공률을 가진 술식으로 여겨지고 있다. 본 증례는 외상으로 인해 상악 우측 중철치의 치수노출을 동반한 치관-치근 파절이 발생한 경우로 외과적 정출을 시행하기로 하였으나, 치근단 파절편의 길이가 짧아서 치아를 발거 후 회전시켜 재식하는 방법만으로는 파절선을 치조정 상방으로 위치시킬 수가 없었다. 따라서 치아를 발거한 후 파절편의 지지를 위해 치조와의 치근단부에 탈회냉동건조골을 이식한 후에 치근단 파절편을 노출한 후 suture splint를 시행하였다. 1년 3개월간의 관찰결과, 치조백선이 회복되고 정상적인 동요도를 보였으며, 염증성, 대체성 치근흡수 등과 같은 합병증은 발생되지 않았다.

• 대한치과보철학회지
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• 제40권1호
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• pp.68-78
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• 2002

The post core system has been used for reconstructon of severely damaged crown by caries or trauma. But problems such as crown exfoliation, post core fracture and root fracture have been reported. Ideal mechanical properies of the post require high fracture strength, high elastic limit and high resistance against fatigue and corrosion Modulus of elasticity of the post should be similar with that of dentine. Low hardness is also required for the convenience of post removal in failure. Furthermore, the post itself must be translucent for the esthetical purpose. Several types of the post have been developed to satisfy the criteria above mentioned. The purpose of this study was to find out the mechanical properties of quartz fiber post by comparing with those of gold post and zirconia post. The results of this study were as follows : 1. Maximal fracture strength and stiffness of quartz fiber post were similar with those of gold post and zirconia post. 2. Young's modulus and hardness of quartz fiber post were lower than those of gold post and zirconia post. Mechanical property of quartz fiber post against post fracture was similar with that of gold post and zirconia post. Mechanical property of quartz fiber post against root fracture was higher than that of gold post and zirconia post. Quartz fiber post could be removed easily due to low hardness.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.316-321
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• 2016

Although it is challenging, the early diagnosis of a vertical root fracture (VRF) is crucial in order to ensure tooth preservation. The purpose of this clinical case report was to describe reparative surgery performed to treat a tooth affected by an incomplete VRF. A 26 year old male patient was suspected to have a VRF in a maxillary left central incisor, and an exploratory flap was performed in order to confirm the diagnosis. After detecting the fracture, the lesion was surgically treated, the fracture and the infected root-end were removed, and a platelet-rich plasma membrane was used to cover the defect in order to prevent bacterial migration. A 24 month clinical and radiological follow-up examination showed that the tooth was asymptomatic and that the healing process was in progress. The surgical approach described here may be considered an effective treatment for a combined endodontic-periodontal lesion originating from an incomplete VRF and a recurrent periapical lesion.

• Archives of Plastic Surgery
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• 제40권5호
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• pp.546-552
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• 2013

Background The zygoma is a major portion of the midfacial contour. When deformity occurs in this area, a reduction should be conducted to correct it. If a sagittal fracture at the temporal root of the zygomatic arch occurs, this also requires reduction, but it is difficult to approach due to its anatomical location, and the possibility of fixation is also limited. Thus, the authors attempted the reduction of sagittal fracture by two- or three-point fixation and the Gillies approach without direct manipulation. The preoperative and postoperative results of the patients were evaluated. Follow-up was performed to establish a treatment guideline. Methods A retrospective study was done with 40 patients who had sagittal fractures at the temporal root of the zygomatic arch from March 2009 to June 2012. Only two- or three-point fixation was performed for the accompanying zygomatic-orbital-maxillary fracture. The Gillies approach was used for complex fractures of the zygomatic arch, while the temporal root of the zygomatic arch was only observed without reduction. Preoperative and postoperative computed tomography and X-ray scans were performed to examine the results. Results The result of the paired t-test on preoperative and postoperative bone gap differences, the depression level, and the degree of temporal protrusion showed a marked decrease in the mean difference at a 95% confidence interval. The results were acceptable. Conclusions In the treatment of sagittal fractures at the temporal root of the zygomatic arch, it is acceptable to use indirect reduction and non-fixation methods. This leads to a satisfactory aesthetic and functional outcome.

• Restorative Dentistry and Endodontics
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• 제44권2호
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• pp.15.1-15.8
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• 2019

Objectives: The aim of this study was to investigate whether the diameter and direction of the plunger and simulation of the periodontal ligament (PDL) affected the stress distribution in endodontically treated premolars. Methods: A fracture strength test was simulated via finite element analysis. A base model was set up, and the following parameters were modified: plunger diameter (3 mm vs. 6 mm), plunger direction (vertical vs. $135^{\circ}$ angular to the central fossa), and PDL simulation. The analysis was conducted using the CosmosWorks structural analysis program, and the results are presented in terms of von Mises stresses. Results: The smaller plunger increased the stresses at the contact area of the crown, but the plunger diameter had no effect on the stress distribution within the root. An angular plunger direction increased stresses within the root, as well as at the buccal cusp of the crown, compared with the vertical direction. Simulation of the PDL caused higher stress accumulation, especially in the cervical region of the root. Conclusions: The plunger diameter had no effect on the stress distribution in the roots, whereas the plunger direction and PDL simulation did affect the stress distribution. More stringent standards can be established by taking such parameters into account when performing fracture testing in future studies.