• 대한치과보철학회지
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• 제43권1호
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• pp.105-119
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• 2005

Statement of problem. As the effects of the various diameters of fixture and abutment screw on stress distribution was not yet examined, this study focused on the different design of single implant restoration using three dimensional finite element analysis. Purpose. This study was to compare five different fixture-abutment combinations for single implant supported restorations with different fixture and abutment screw diameters. Material of methods. The five kinds of finite element models were designed by 3 diameter fixtures ($\oslash$3.3, 3.75, 5.0 mm) with 3 different abutment screws $\oslash$1.5, 1.7, 2.0 mm). The crown for mandibular first molar was made using UCLA abutment according to Wheeler's anatomy. 244 N was applied at the central fossa with two different loading directions, vertically and obliquely (30$^{\circ}$) and at the buccal cusp vertically. Maximum von Mises stresses were recorded and compared in the supporting bone, crowns, fixtures, and abutment screws. Results. 1. The stresses in supporting bone and implant-abutment structure under oblique loading were greater than those under vertical or offset loading. The stresses under vertical loading were the least among 3 loading conditions regardless of the implant and abutment screw diameters. 2. The stresses in the narrow implants were greater than the wider implants. The narrow implant with narrow abutment screw showed highest stresses in the lingual crest, but the narrow implant with standard abutment screw showed highest stress in abutment screw. 3. The stresses of abutment screws were influenced by the diameter of fixtures and loading conditions. The wide implants showed least difference between two different abutment screw diameters. Conclusions. The wide implants showed lesser stresses than the narrow implants and affected least by the different abutment screw diameters. The narrow implants with standard abutment screw showed highest stresses in the lingual bony crest under oblique loading.

• Journal of Oral Medicine and Pain
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• 제32권3호
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• pp.263-272
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• 2007

본 연구의 목적은 발치 및 임프란트 수술 이후 발생하는 지각이상을 분석하여 추후 지각이상의 평가 및 처치시 예측 가능한 지침을 확립하기 위함이다. 발치 및 임프란트 수술 이후 지각이상의 경험여부를 묻는 설문조사에 응답한 276명의 치과의사를 대상으로, 지각이상이 발생한 환자의 연령 및 성별, 지각이상이 발생한 위치, 동반증상, 회복율 및 회복기간에 대한 분석을 시행하여 다음과 같은 결론을 얻었다. 1. 지각이상은 환자의 성별, 연령과 상관성이 없었다. 2. 지각마비의 발생부위는 하악 구치부에서 가장 많이 발생되었으며 이는 발치 및 임프란트 시술시 지각마비가 발생한 경우에 모두 적용되었다(발치군: 93.2%, 임프란트군: 100%). 3. 가장 많이 동반된 증상은 동통으로, 발치의 경우 46.5%, 임프란트의 경우 44.8%로 지각마비 이후 통증을 호소하고 있었다. 4. 회복율은 발치의 경우 72.3%, 임프란트 수술 후 71.8%로 보고되었다. 대부분의 경우 지각이상이 6개월 이내에 해소되었다. 결론적으로, 발치 및 임프란트 수술 후 발생한 대부분의 지각이상은 발병 후 약 1년내에 해소된다고 볼 수 있다. 그러나 영구적인 지각이상의 발생가능성 또한 무시할 수 없다. 따라서 임상가는 환자에게 신경손상의 가능성을 미리 고지하고, 동의서 양식에 이에 대한 내용을 포함하도록 해야 한다. 또한 지각이상이 발생한 후, 객관적으로 예후를 평가하기 위하여 다양한 방법을 통해 지각이상의 경과를 기록할 수 있어야 하며, 보다 효과적이고 비침습적인 처치를 위하여 조기에 구강안면통증 전문가에게 의뢰하는 것을 고려해 보아야 할 것이다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.232-239
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• 2005

The objective of this study is to evaluate the simulated effects of axial and off-axial vertical loads at the implant/bone interface and the stress distribution according to the bone density of a single-unit dental implant in the cylinder and square thread implants by 3D FEA The implants were placed in the mandibular model with 25mm in height, 15mm in width and 20mm in length; then the mandibular bone density was classified into the bone type : I, II III and IV. In addition, the force were applied into 0mm, 2mm, 4mm away from the center of the implants.

• 구강회복응용과학지
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• 제23권1호
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• pp.31-42
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• 2007

The purpose of this study was to compare the stress distribution according to the splinting condition and non-splinting conditions on the finite element models of the two units implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on the mandibular 1st and 2nd molars. A cemented abutment and gold screw were used for superstructures. A FEA models assumed a state of optimal osseointegration, as the bone quality, inner cancellous bone and outer 2 mm compact bone was designed. This concluded that the cortical and trabecular bone were assumed to be perfectly bonded to the implant. Splinting condition had 2 mm contact surface and non-splinting condition had $8{\mu}m$ gap between two implant prosthesis. Two group (Splinting and non-splinting) were loaded with 200 N magnitude in vertical axis direction and were divided with subdivision group. Subdivision group was composed of three loading point; Center of central fossa, the 2 mm and 4 mm buccal offset point from the central fossa. Von Mises stress value were recorded and compared in the fixture-bone interface and bucco-lingual sections. The results were as follows; 1. In the vertical loading condition of central fossa, splinting condition had shown a different von Mises stress pattern compared to the non-splinting condition, while the maximum von Mises stress was similar. 2. Stresses around abutment screw were more concentrated in the splinting condition than the non-splinting condition. As the distance from central fossa increased, the stress concentration increased around abutment screw. 3. The magnitude of the stress in the cortical bone, fixture, abutment and gold screw were greater with the 4 mm buccal offset loading of the vertical axis than with the central loading.

• The Journal of Advanced Prosthodontics
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• 제5권3호
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• pp.312-318
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• 2013

PURPOSE. The aim of this study was to compare the passivity of implant superstructures by assessing the strain development around the internal tapered connection implants with strain gauges. MATERIALS AND METHODS. A polyurethane resin block in which two implants were embedded served as a measurement model. Two groups of implant restorations utilized cement-retained design and internal surface of the first group was adjusted until premature contact between the restoration and the abutment completely disappeared. In the second group, only nodules detectable to the naked eye were removed. The third group employed screw-retained design and specimens were generated by computer-aided design/computer-aided manufacturing system (n=10). Four strain gauges were fixed on the measurement model mesially and distally to the implants. The strains developed in each strain gauge were recorded during fixation of specimens. To compare the difference among groups, repeated measures 2-factor analysis was performed at a level of significance of ${\alpha}$=.05. RESULTS. The absolute strain values were measured to analyze the magnitude of strain. The mean absolute strain value ranged from 29.53 to 412.94 ${\mu}m/m$ at the different strain gauge locations. According to the result of overall comparison, the cement-retained prosthesis groups exhibited significant difference. No significant difference was detected between milled screw-retained prostheses group and cement-retained prosthesis groups. CONCLUSION. Within the limitations of the study, it was concluded that the cement-retained designs do not always exhibit lower levels of stress than screw-retained designs. The internal adjustment of a cement-retained implant restoration is essential to achieve passive fit.

• 대한치과보철학회지
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• 제55권4호
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• pp.419-426
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• 2017

임플란트는 자각증상을 느끼기 어렵고, 완충역이 없으므로 응력 분포를 고려하지 않는 경우 기계적 실패를 야기할 수 있다. 다수의 상악 전치부 임플란트 수복의 경우 하악의 기능 운동 시 유도를 담당함으로써, 임플란트에 가해지는 측방력의 분산에 중요한 역할을 하므로, 적절한 가이드의 설정이 중요하다. T-scan system을 이용하는 방법은 교합지나 shimstock을 사용하는 기존의 정성적인 방법에 비해, 시간에 따른 교합의 변화와 기능 운동시 접촉되는 치아의 기여정도 및 육안으로 관찰하기 어려운 후방 구치나 반대편 치아의 접촉을 파악하는 등 동적인 교합평가에 유리하다. 본 논문에서는 다수의 상악 임플란트 보철물에 조화로운 전방유도를 부여하기 위하여 T-scan 분석을 활용하는 방법에 관하여 증례를 통해 살펴보고자 한다.

• 대한치과기공학회지
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• 제42권2호
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• pp.99-105
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• 2020

Purpose: A study analysed the stress distribution of abutment screw and supporting bone of fixture by the tightening torque force of the abutment screw within clinical treatment situation for the stability of the dental implant prosthesis. Methods: The finite element analysis was targeted to the mandibular molar crown model, and the implant was internal type 4.0 mm diameter, 10.0 mm length fixture and abutment screw and supporting bone. The occlusal surface was modeled in 4 cusps and loaded 100 N to the buccal cusps. The connection between the abutment and the fixture was achieved by combining three abutment tightening torque forces of 20, 25, and 30 Ncm. Results: The results showed that the maximum stress value of the supporting bone was found in the buccal cortical bone region of the fixture in all models. The von Mises stress value of each model showed 184.5 MPa at the 20 Ncm model, 195.3 MPa in the 25 Ncm model, and 216.5 MPa in the 30 Ncm model. The contact stress between the abutment and the abutment screw showed the stress value in the 20 Ncm model was 201.2 MPa, and the 245.5 MPa in the 25 Ncm model and 314.0 MPa in the 30 Ncm model. Conclusion: The increase of tightening force within the clinical range of the abutment screw of the implant dental prosthesis was found to have no problem with the stability of the supporting bone and the abutment screw.

• The Journal of Advanced Prosthodontics
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• 제13권1호
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• pp.55-64
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• 2021

PURPOSE. To investigate the biomechanical effect of marginal bone resorption (MBR) on the mandibular mini implant (MI)-retained overdenture (MI-OD) on the edentulous model. MATERIALS AND METHODS. The experimental mandibular edentulous model was modified from a commercial model with 2 mm thick artificial soft tissue under denture base. Two MIs (Φ2.6 mm × 10 mm) were bilaterally placed between the lateral incisor and the canine area and attached with magnetic attachments. Three groups were set up as follows: 1) alveolar bone around the MI without MBR (normal group), 2) with MBR to 1/2 the length of the implant (resorption group), and 3) complete denture (CD) without MI (CD group). Strain around the MI, pressure near the first molar area, and displacement of denture were simultaneously measured, loading up to 50 N under bilateral/unilateral loading. Statistical analysis was performed using independent-samples t test and one-way ANOVA (α=.05). RESULTS. The strain around the MI with MBR was approximately 1.5 times higher than that without MBR. The pressure in CD was higher than in MI-ODs (P<.05), while there was no statistical difference between the normal and resorption group (P>.05). Similarly, the CD demonstrated a greater displacement of the denture base than did the MI-ODs during bilateral and unilateral loadings (P<.05). CONCLUSION. The strain around the MI with MBR was approximately 1.5 times higher than that without MBR. The pressure on posterior alveolar ridge and denture displacement of MI-ODs significantly decreased compared to CDs, even when MBR occurs. Bilateral balanced occlusion was recommended for MI-ODs, especially when MBR occurred.

• 대한치과보철학회지
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• 제53권2호
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• pp.120-127
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• 2015

목적: 4종의 임플란트 나사산이 골유착 중간과정과 완료 이후 단계에서 보이는 응력분산 특성을 평가하고자 한다. 재료 및 방법: 실린더형 몸체(외경 4.1 mm 길이 10 mm)에 이전연구에서 식립 특성이 우수하게 평가되었던 V-자형 나사산과 다른 3종(buttress형, reverse buttress형, square형)의 나사산을 가진 4종의 임플란트가 악골에 매식된 복합체 모델을 CAD 프로그램으로 제작하였다. 지대주 상부에 100 N의 힘을 임플란트 장축과 30도 방향으로 부하하고 인접골 응력분포를 유한요소 해석하였다. 응력분산 특성이 골유착 진척 상태에 따라 달라질 수 있다는 가정하에 임플란트/골 계면을 골유착 미숙단계와 골유착 완료단계의 두 가지로 구분하여 분석하였다. 골유착 미숙단계는 임플란트/골 계면을 비선형 contact 조건(마찰계수 0.3)으로 모사하였고, 골유착이 완료된 단계에 대해서는 계면이 충분히 결합된 것으로 간주하여 접합(bonding) 조건을 부여하였다. 결과: 골유착 정도에 따라 임플란트의 응력분산 특성이 달라졌다. 골유착 미숙단계에서는 골응력과 나사산에 따른 응력 특성의 차이도 상대적으로 컸고 골유착 완료단계에서는 골응력의 절대값과 나사산간 차이가 모두 감소하였으며, V-자형 나사산의 응력분산 특성은 골유착 미숙 및 완료단계에서 모두 4종 나사산의 중간 정도였다. 이로부터 나사산 디자인의 차이는 임플란트 식립후 골유착이 진행되는 과정까지 영향을 미치며, 일단 골유착이 완료되면 나사산의 영향은 급격히 감소할 것임을 추론할 수 있었다. 결론: V-자형 나사산의 응력분산 특성은 골유착이 이루어지는 단계와 완료된 이후 단계 전기간 동안 4종 나사산의 중간 정도였다.

• 대한치과보철학회지
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• 제39권2호
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• pp.125-145
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• 2001

To compare the stress distribution patterns between cement-retained and screw-retained implant supported fixed prostheses according to four different abutment types, a three dimensional finite element analysis was performed. The hypothetical three unit fixed partial denture case was modelled on the three implants(10mm length and 3.75 diameter) in mandibular bone. Four angles of implantation(vertical, 10, 15 and 20 degree inclined mesially) were created and three different directions of force (vertical, oblique, horizontal) were applied at the center of the second premolar and distal end of the first molar for each cases. Within the limits of this study, the results were as follows, 1. In vertically installed cases, the more stress was concentrated at upper components, but mesially inclined cases, the more stress was concentrated at cortical bone. 2, The more inclined mesially the more stress was observed, especially at cortical bone. 3. The cement-retained models showed lower principal stress and more even stress distribution than the screw-retained models. 4. The similar stress distribution pattern was showed in model 1 and model 2, model 3 and model 4. 5. The more stress was observed when the loads were applied at the distal end of 1st molar than the center of 2nd premolar. 6 The fixture and the model as a whole, lesser stress values were observed when vertical loads were applied as compared to horizontal and oblique loads.