• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.321-327
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• 2018

PURPOSE. The purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly. MATERIALS AND METHODS. The Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within $50{\mu}m$ radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (${\alpha}=.05$). RESULTS. There was a significant difference in RMS only in SLA and SLS of 2D section (P<.05). In CMP mean, CMP 4 ($-5.3{\pm}46.7{\mu}m$) had a value closest to 0, while CMP 6 ($20.1{\pm}42.4{\mu}m$) and CMP 1 ($-89.2{\pm}61.4{\mu}m$) had the greatest positive value and the greatest negative value, respectively. CONCLUSION. Since the errors obtained from the study do not exceed the clinically acceptable values, the lamination method and the cutting method can be used clinically.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제31권2호
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• pp.116-126
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• 2009

The use of short implants has been accepted risky from biomechanical point of view. However, short implants appear to be a long term viable solution according to recent clinical reports. The purpose of this study was to investigate the effect of different diameter and length of implant size to the different type of bone on the load distribution pattern. Stress analysis was performed using 3-dimensional finite element analysis(3D-FEA). A three-dimensional linear elastic model was generated. All implants modeled were of the various diameter(${\phi}4.0$, 4.5, 5.0 and 6.0 mm) and varied in length, at 7.0, 8.5 and 10.0 mm. Each implant was modeled with a titanium abutment screw and abutment. The implants were seated in a supporting D2 and D4 bone structure consisting of cortical and cancellous bone. An amount of 100 N occlusal load of vertical and $30^{\circ}$ angle to axis of implant and to buccolingual plane were applied. As a result, the maximum equivalent stress of D2 and D4 bones has been concentrated upper region of cortical bone. As the width of implant is increased, the equivalent stress is decreased in cancellous bone and stress was more homogeneously distributed along the implants in all types of bone. The short implant of diameter 5.0mm, 6.0mm showed effective stress distribution in D2 and D4 bone. The oblique force of 100N generated more concentrated stress on the D2 cortical bone. Within the limitations of this study, the use of short implant may offer a predictable treatment method in the vertically restricted sites.

• 대한치과기공학회지
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• 제44권3호
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• pp.67-75
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• 2022

Purpose: This study aimed to comparatively evaluate the stress distribution of bones surrounding the implant system to which both titanium and polyetheretherketone (PEEK) abutments are applied using a three-dimensional finite element analysis. Methods: The three-dimensional implant system was designed by the computer-aided design program (CATIA; Dassault Systemes). The discretization process for setting nodes and elements was conducted using the HyperMesh program (Altair), after finishing the design of each structure for the customized abutment implant system. The results of the stress analysis were drawn from the Abaqus program (Dassault Systèmes). This study applied 200 N of vertical load and 100 N of oblique load to the occlusal surface of a mandibular first molar. Results: Under external load application, the PEEK-modeled dental implant showed the highest von Mises stress (VMS). The lowest VMS was observed in the Ti-modeled abutment screws. In all groups, the VMS was observed in the crestal regions or necks of implants. Conclusion: The bones surrounding the implant system to which the PEEK abutment was applied, such as the cortical and trabecular bones, showed stress distribution similar to that of the titanium implant system. This finding suggests that the difference in the abutment materials had no effect on the stress distribution of the bones surrounding implants. However, the PEEK abutments require mechanical and physical properties improved for clinical application, and the clinical application is thought to be limited.

• 대한치과교정학회지
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• 제34권1호
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• pp.33-45
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• 2004

제 1소구치가 발치된 증례에서 bull loop를 견치 직후방에 제작한 후 gable bend를 어느 정도 부여할 때 전치부의 효과적인 치축조절과 후방 이동량을 극대화 할 수 있는지를 입체적으로 확인하는 것이 본 연구의 목적이다. 제 1소구치가 제거된 상악우측 인공 치조골부에 중절치부터 제 2대구치까지 실험용 치아들을 식립하였다. 그 후 bull-loop가 형성된 반쪽 호선에 $10^{\circ},\;20^{\circ},\;30^{\circ}$의 gable bend를 부여한 후 3전치를 후방 견인하여 발치공간을 폐쇄시켰고 이러한 실험과정을 각 군마다 3회씩 반복 실험하였다. 발치공간이 폐쇄된 후 실험전, 후의 교합방사선 사진상에 촬영된 전치부와 구치부의 시상면과 교합면 상에서의 각 군별 치아이동 양상을 일요인 분산분석(ANOVA)과 Scheffe 검정으로 평가한 결과 아래와 같은 결론을 얻었다. 1. Gable bend의 양이 증가할수록 전치부의 치축은 치체이동 양상을 보였으며 후방 이동량도 증가하였다. 2. Gablebend의 양이 증가할수록 구치부의 전방 이동량은 감소하였으나 수직적 압하량 및 협측 이동량은 증가하였다(p<0.001). 3. 발치공간에 인접한 견치의 원심회전과 제 2소구치의 근심회전에 의해 악궁의 조화가 이루어졌다(p<0.001).

• 대한치과보철학회지
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• 제29권3호
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• pp.141-170
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• 1991

This study was to analyze the displacement and the magnitude and mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment teeth and the mandibular supporting bone when various abutment designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. The models of overdenture and mandibe with the canine and the second premolar remaining, were fabricated. In the first design, a 1 mm space was prepared between the denture and the dome abutment with the height of 2 mm(OS). In the second design, a contact between the denture and the occlusal third of the dome abutment with the hight of 2 mm was prepared(OC). In the third design, a 0.5 mm space was prepared between the denture and 8 degree tapered cylindrical abutments with the height of 7 mm(TS). In the fourth design, a contact between the denture and the occlusal two thirds of the conical abutments with the height of 7 mm was prepared(TC). In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 Kgs on the first molar region (P1) and 7 Kgs on the central incisor region (P2) in a vertical direction. The force of 10 Kgs was then applied distributively from the first premolar to the second molar of each motel in a vertical direction (P3). The results were as follows: 1. The vertical load on the central incisor region(P2) produced the higher displacement and stress concentration than that on the posterior region(P1, P3). 2. The case of space between abutment and denture base produced higher displacement than that of contact, and the case of long abutment produced higher displacement than that of short abutment because of low rigidity of denture base. 3. The magnitude of the torque and vertical force to the abutment teeth and the stress distribution to the denture base was higher in the telescope coping than in the overdenture coping. 4. The vertical load on the central incisor region(P2) produced higher equivalent stress in the mandible than that on the posterior region(P1, P3). 5. The case of space between abutment and denture base produced better stress distribution to the farther abutment from the loading point than that of contact. 6. In case of sound abutment teeth, the type of telescope coping can be used, hilt in case of weak abutment, the type of overdenture coping is considered to be favorable generally.

• The Journal of Advanced Prosthodontics
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• 제4권2호
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• pp.97-102
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• 2012

Study was conducted to determine and assess the effect of different type of denture adhesives on the incisal bite force of complete denture wearers until the dislodgement of upper denture, using pressure transducer. MATERIALS AND METHODS. 30 patients out of 100 were included in the study. Based on the Kapur's method of scoring denture retention and stability, these patients were divided into 3 groups-Group A - Clinically good dentures; Group B - Clinically fair dentures; and Group C - Clinically poor dentures. A custom made occlusal force meter was constructed based on the load cell type of pressure transducers. Different adhesives (powder, paste and adhesive strips) were used in the study. Complete denture wearers were asked to bite on the load cell and the readings of incisal bite force were recorded. The readings of incisal bite force were subjected to statistical analysis using Repeated measures ANOVA followed by post-hoc bonferroni test. RESULTS. The result suggests that denture adhesives improved the incisal bite force of complete denture wearers significantly The incisal bite force (in kg) in Group A without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 2.48 (${\pm}0.16$), 3.43 (${\pm}0.11$), 6.01 (${\pm}0.11$), 3.22 (${\pm}0.09$) respectively. The incisal bite force (in kg) in Group B without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.87 (${\pm}0.18$), 3.35 (${\pm}0.14$), 5.34 (${\pm}0.18$), 3.21 (${\pm}0.12$) respectively. The incisal bite force (in kg) in Group C without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.00 (${\pm}0.17$), 3.07 (${\pm}0.14$), 4.37 (${\pm}0.26$), 2.99 (${\pm}0.14$) respectively. CONCLUSION. Within the limitations of the study, it was concluded that the use of denture adhesive was found to be significantly effective in improving the incisal bite force of complete dentures until the dislodgement of upper denture. Fittydent paste adhesive was found to be more effective than the powder and strips adhesives. The improvement in incisal bite force was found to be higher in Group C in comparison to that of Group A and Group B.

• 대한치과교정학회지
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• 제25권5호
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• pp.543-555
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• 1995

골격성 부정교합에 대한 악정형 치료시, 바람직한 악정형 효과를 얻기 위해서는 악정형 장치의 역학 현상에 대한 분석이 필요하다. 상악의 저성장에 기인한 골격성 III급 부정교합의 치료를 위한 상악골의 전방견인시 바람직한 견인력 방향과 견인 위치를 알아보기 위해, 성인 두개골을 대상으로 3차원 유한 요소 모델을 제작하여, 제1소구치와 제1대구치에서 각각 교합평면에 평행 또는 $20^{\circ}$ 하방으로 500g의 전방 견인력을 주어 상악골체의 각 부분에서 응력과 변위를 분석하여 다음과 같은 결과를 얻었다. 1. 모든 경우 상악골이 반시계 방향으로 회전하는 양상을 보였다. 2. 견인력 방향에 따른 상악골의 회전은, $20^{\circ}$ 하방으로 견인하는 경우가 평행하게 견인하는 경우보다 더 적었다. 3. 견인 위치에 따른 상악골의 회전은, 평행하게 견인시에는 견인 위치가 제1대구치일 때가, $20^{\circ}$ 하방으로 견인시에는 제1소구치일 때가 더 적었다. 이상의 결과 견인력 작용선이 상악골체의 저항 중심점에 가장 근접하여 반시계 방향으로의 변위가 가장 적게 일어난 제1소구치에서 $20^{\circ}$ 하방으로 견인한 경우가 바람직한 견인력 방향과 견인 위치로 판단되었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제38권4호
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• pp.231-239
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• 2012

Objectives: This study sought to provide guidelines in order to decrease the incidence of nerve injury during mandibular ramus bone harvesting, and to improve understanding of the anatomical structure of the inferior alveolar canal (IAC) to include its distance from the exterior buccal cortex. Materials and Methods: In January and February 2009, 20 patients who visited the Wonkwang University Department of Oral and Maxillofacial Surgery reporting various conditions underwent cone beam computed tomography and were included in this study. Patients with missing left or right mandibular first molars or incisors, or who had jaw fracture or bone pathologies, were excluded. The reference point (R point) was defined as the point where the occlusal plane reached the anterior ramus of the mandible. The position of the IAC in relation to the R point, the buccal bone width (BW), the alveolar crest distance (ACD), the distance from the alveolar crest to the occlusal plane (COD), and the distance from the IAC to the sagittal plane (CS) were determined using proprietary image analysis software which produced cross-sectional coronal and axial images. Results: The distance medially from the R point to the IAC along the axial plane was $6.19{\pm}1.21mm$. The HD from the R point, posteriorly to IAC, in the lateral view was $13.07{\pm}2.45mm$, the VD from the R point was $14.24{\pm}2.41mm$, and the ND from the R point was $10.12{\pm}1.76mm$. The pathway of the IAC was positioned almost in a straight line along a sagittal plane within $0.56{\pm}0.70mm$. The distance from the buccal bone surface to the IAC increased anteriorly from the R point. Conclusion: Marking osteotomy lines in the retromolar area in procedures involving bone harvesting should be discouraged due to the risk of damage to IAC structures. Our measurements indicated that the area from the R point in the ramus of the mandible to 10 mm anterior can be safely harvested for bone grafting purposes.

• 대한치과보철학회지
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• 제28권1호
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• pp.63-94
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• 1990

The purpose of this study was to analyze the displacement and the magnitude and the mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment tooth and the mandibular supporting bone when various denture base materials, such as acrylic resin and 0.5mm metal base, and various denture base designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. Mandibular arch models, with only canine remaining, were fabricated. In the first denture base design, a space, approximately 1mm thick, was prepared between the denture and the dome abutment. In the second denture base design, contact between the denture and the dome abutment was eliminated except the contact of the occlusal third of the abutment. In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle region, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 kgs on the first molar region(P1) and 7 kgs on the central incisal region (P2) in a vertical direction. Then the force of 10 kgs was applied distributively from the first premolar to the second molar of each model in a vertical direction(P3). The results were as follows. : 1. When the testing vertical loads were given to the selected points of the overdenture, the overdenture showed the rotatory phenomenon, as well as sinking and the displacements of alveolar ridge, abutment and lower border of mandible under the metal base overdenture were less than those under the acrylic resin overdenture. 2. The maximum principal stresses(the maximum tensile stresses) being considered, high tensile stresses occured at the buccal shelf area, the posterior region of the ridge crest and the anterior border region of the mandibular ramus. 3. The minimum principal stresses(the maximum compressive stresses) being considered, high compressive stresses occured at the inferior and posterior border region of the mandible, the mandibular angle and the posterior border region of the mandibular ramus. 4. The vertical load on the central incisal region(P2) produced higher equivalent stress in the mandible than that on any other region(P1, P3) because of the long lever arm distance from the fixed points to the loading point. 5. Higher equivalent stresses were distributed throughout the metal base overdenture than the resin base overdenture under the same loading condition. 6. The case of occlusal third contact of the abutment to the denture produced higher equivalent stresses in the abutment, the mandibular area around the abutment and the overdenture than the case of a 1mm space between the denture and the abutment. 7. Without regard to overdenture base materials and designs, the amounts and distribution patterns of equivalent stresses under the same loading condition were similar in the mucous membrane.

• 한국산학기술학회논문지
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• 제16권10호
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• pp.6611-6617
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• 2015

본 연구는 수작업으로 제작된 metal coping과 CAD/CAM(Computer Aided Design/Computer Aided Manufacturing)으로 제작된 지르코니아 coping을 제작하여 변연과 내면 적합도를 비교 분석하고자 하였다. 모형은 우레탄 모형재를 사용하여 knife, chamfer변연 두 종류의 지대치를 제작하였다. 수작업과 CAD/CAM으로 제작된 보철물의 변연 적합도를 실리콘 리플리카 테크닉방법을 사용하여 측정하였다. 적합도 측정은 현미경의 CCD카메라로 캡쳐하였다. 이때 지대치와 보철물의 거리는 이미지분석 소프트웨어에서 거리 조정이 된 상태에서 실시하였다. 측정부위는 marginal opening을 MO, marginal gap을 MG, internal gap을 IG, Axial gap을 AG, occlusal gap을 OG로 하였다. 제작법과 변연 형태에 따른 비교분석을 위해 이원배치분산분석을 실시하였으며 서로 다른 평균값들의 비교 분석을 위해서 일원배치분산분석과 Scheffe's 사후 검정을 실시하였다. 그 결과 CAD/CAM의 OG와 knife 변연의 MO을 제외하고는 < $120{\mu}m$ 적합도를 나타냈다. CAD/CAM으로 제작된 coping은 chamfer 변연 MO에서 높은 적합도를 보였으나 MG에서는 knife변연이 chamfer변연 보다 더 좋은 적합도를 보였다. AG의 내면 적합도는 가장 좋은 값을 나타내었다(< $38{\mu}m$).