• 대한치과보철학회지
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• 제34권2호
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.

• 대한치과보철학회지
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• 제31권1호
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• pp.87-99
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• 1993

Many studies have been reported on the successful replacement of missing teeth with osseointegrated dental Implants. However, little research has been carried out on the bio-mechanical aspect of the stress on the surrounding bone of the free-standing type of dental implant prostheses. This experimental study was aimed to analyze the stress distribution pattern on the supporting tissues depending upon the position of osseointegrated implants supporting fixed bridges. In the cases of unilateral partially edentulous mandible (the 2nd premolar and the 1st and 2nd molars missing), two osseointegrated implants were placed at the 2nd premolar and 2nd molar sites (Model A) , the 1st and 2nd molar sites (Model B, Anterior cantilevered type), the 2nd premolar and 1st molar sites (Model C, Posterior cantilevered type). Chewing forces of dentate patients and denture wearer were applied vertically on the 2nd premolar, the 1st molar, and the 2nd molar of each model. A 3-Unit fixed partial denture was constructed at each model and cantilevered extension parts were involved in Model B and Model C. Two dimensional finite element analysis was undertaken. The commercial software (Super SAP) for IBM 16 bit personal computer was utilized. The results were as follows : 1. The magnitude of applied load influenced on the total value of stresses, but did not in-fluence on the pattern of stress distribution. 2. The magnitude of stress developed from the supporting tissues were in order of Model C,Model A,Model B. 3. High stresses were concentrated on the cervical and apical portion of the implant/bone interface. 4. A difference of the stress magnitude on the implant/bone interface between mesial and distal implant was most prominant in Model C and in order of Model A and Model B. 5. The stresses developed in Model A were evenly distributed throughout both implants. 6. The stresses concentrated on the cervical portion of cantilevered side were higher in the posterior cantilevered type than in the anterior cantilevered type.

• 대한치과보철학회지
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• 제31권1호
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• pp.129-150
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• 1993

Since the restoration or masticatory function is the most important aim of implants, it should be substituted for the role of natural teeth and deliver the stress to the bone under the continous load during function. In natural teeth, stress distribution can be obtained through enamel, dentin and cementum and the elasticity of the periodontal ligament play a role of buffering action. In contrast, implant prosthesis has a very unique characteristics that it delvers the load directly to bone through the implant and superstructure. This fact arise the needs to evaluate the stress distribution of the implant in the mechnical aspects, which has a similar role of natural teeth but different pathway of stress. With 3 kinds of implant in prevalent use, 2 types of experimental PEA implant models were made, axisymmetric and 2-dimensional type. In axisymmetric model, the stiffness of the part including the prosthesis and implant which extrude out of bony surface could be calculated with displacement of the superstructure un er 100N vertical load and then damping effects could be determined through this stiffness. In axisymmetric FEA model, load to the bone could be deduced by evaluation the stress distribution of the designed surface under the 100N vertical force and in 2-dimensional model, 100N eccentric vertical load and 20N horizontal loda. The result are as follows. 1. In every implant, stress to the bone tends to be concenturated on the cortical bone. 2. Though the stress of the cancellous bone is larger at the apex of implants, it is less compared with cortical bone. 3. Under 20N horizontal load, stress of the left and right sides of implant shows a symmetrical pattern. But under 100N eccentric vertical load, loaded side shows much larger stress value. 4. In the 1mm interface, stress distribution among implants tend to have a similar pattern. But under 20N horizontal load apposite side of being loaded shows less stress in IMZ. 5. In the case of screw type implant, stress tends to vary along with screw shape. 6. According to the result determined with microstrain, cancellous bone id generally under the condition of overload, while cortical bone is usually within the limitation of physiologic load. 7. In the Branemark implant, maximum stress to the cortical bone is larger than any other implant except for the condition of 20N horizontal force and 0.05mm interface. 8. Damping effects of implants is maximum in IMZ.

• 대한치과보철학회지
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• 제41권5호
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• pp.582-595
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• 2003

Statement of problem : Most posts are metallic, but in response to the need for a post that possesses optical properties compatible with an all-ceramic crown. an esthetic post has been developed. Although there have been many studies about the esthetic post materials, 3-dimensional finite element studies about the stress distribution of them are in rare. Purpose : The purpose of this study is to investigate comparatively the distribution of stresses of the restored, endodontically treated maxillary incisors with the esthetic post materials and the displacement on the cement layer on simulated occlusal loading by using a 3-dimensional finite element analysis model. Material and method : Four 3-dimensional finite element models were constructed in a view of a maxillary central incisor, a post, a core, and the supporting tissues to investigate the stresses in various esthetic posts and cores and the displacement on the cement layer (Model 1 ; Cast gold post and core, Model 2 ; Glass fiber post with composite core, Model 3 ; Zirconia post with composite core. Model 4 ; Zirconia post with ceramic core). Force of 300N was applied to the incisal edge and the cingulum (centric stop point) with the angle of 135-degree to the long axis of the tooth. Results : 1. The stresses and displacement on the incisal edge were higher than on the cingulum 2. The stresses in dentin were the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. 3. The stresses in post and core were the highest in Model 4 (Zirconia post with ceramic core), and the second was Model 1, the third Model 3, and the lowest Model 2. 4. The displacement on the cement layer was the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. Conclusion : When a functional maximum bite force was applied, the distribution of stresses or the esthetic post and core materials and the displacement on the cement layer were a little different. It seems that restoring extensively damaged incisors with esthetic post and core materials would be decided according to the remaining tooth structure.

• 대한치과보철학회지
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• 제41권5호
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• pp.674-688
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• 2003

Statement of Problem : With increasing demand of the implant-supported prosthesis, it is advantageous to use the different platform width of the fixture according to bone quantity and quality of the patients. Purpose : The purpose of this study was to assess the loading distributing characteristics of two implant designs according to each platform width of fixture, under vertical and inclined loading using finite element analysis. Material and method : The two kinds of finite element models were designed according to each platform width of future (4.1mm restorative component x 11.5mm length, 5.0mm wide-diameter restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction, 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction and 200N at the buccal cusp in a 300 transverse direction individually Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. Results : The stresses were concentrated mainly at the cortex in both vertical and oblique load ing but the stresses in the cancellous bone were low in both vertical and oblique loading. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading. Increasing the platform width of the implant fixture decreased the stress in the supporting bone, future and abutment screw. Increased the platform width of fixture decreased the stress in the crown and platform. Conclusion : Conclusively, this investigation provides evidence that the platform width of the implant fixture directly affects periimplant stress. By increasing the platform width of the implant fixture, it showed tendency to decreased the supporting bone, future and screw. But, further clinical studies are necessary to determine the ideal protocol for the successful placement of wide platform implants.

• 대한치과보철학회지
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• 제32권2호
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• pp.327-353
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• 1994

This study was performed to evaluate the effects of number and alignment of implant fixture and various bar designs on the retention of denture and the stress distribution. Six kinds of photoelastic mandibular models and nine kinds of overdenture specimens were designed. A unilateral vertical load was gradually applied on the right first molar to calculate the maximal dislodgement load of each specimen. A unilateral vertical load of 17 Kgf was applied on the right first molar and a vertical load of 10 Kgf was applied on the interincisal edge region. The stress pattern which developed in each photoelastic model was analyzed by the reflection polariscope. The results obtained were as follows: 1. The maximal dislodgement load reversely increased with the distance from the loading point to the implant fixture, while it linearly increased with that from the most posterior implant fixture to the mesial clip. The maximal dislodgement load also increased with the use of a cantilever bar. 2. Under the posterior vertical load, the stress to the supporting tissue of the denture base increased with the distance from the loading point to the implant future. The stress concentration on the apical area of the implant future reversely increased with the distance from the loading point to the implant future. 3. In the overdentures supported by two implant fixtures under the posterior vertical load. the specimen implanted on lateral incisor areas with a cantilever bar exhibited more favorable stress distribution than that without a cantilever bar. The specimen implanted on the canine areas without a cantilever bar, however, exhibited more favorable stress distribution. 4. In the overdentures supported by three implant fixtures. the specimen implanted ell the midline and canine areas exhibited more favorable stress distribution than that implanted oil the midline and the first premolar areas. 5. In the overdentures supported by four implant fixtures. the specimen implanted with two adjacent implant fixtures exhibited more favorable stress distribution than that implanted at equal distance under the posterior vertical load. 6. Under the anterior vertical load, the overdentures supported by three implant fixtures exhibited stress concentration on the supporting structure of the middle implant future. In overdentures supported by two or four implant futures, no significant difference was noted in stress distribution between the types of bars. These results indicate that the greater the number of implant fixtures, the better the stress distribution is. A favorable stress distribution may be obtained in the overdentures supported by two or three implant fixtures, if the location and the design of the bar are appropriate.

• 대한치과보철학회지
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• 제48권3호
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• pp.215-223
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• 2010

연구 목적: 이 연구는 임플란트 식립 시 미세나사가 변연골에 발생시키는 스트레인을 조사하여, 변연골의 골유착에 장애를 줄 수 있는 골의 과부하 영역 이 미세나사에 의해 확장되는 양태를 평가하였다. 연구 재료 및 방법: 3종의 임플란트 식립 모델을 삼차원적 유한 요소분석으로 실험하였다. 대조 모델은 미세나사가 없이 주나사만 있는 $4.1{\times}10$ mm 임플란트 (Submerged model, Dentis Co, Daegu, Korea), type I은 미세나사가 있는 straight body, type II는 미세나사가 있는 7% tapered body로 설정하였다. 임플란트가 치밀골을 통과하는 3,600 단계의 식립 과정이 모사되었다. 유한요소 해석에는PC용으로 출시된DEFORM$^{TM}$ 3D (ver 5, SFTC, Columbus, OH, USA)가 사용되었다 결과:임플란트 외벽으로부터 1 mm 이내의 변연골 스트레인 영역은 대조모델에서의 4000 ${\mu}$-strain 보다 높았다. Type I 임플란트의 경우 임플란트 외벽으로부터 1-1.5 mm 영역 이내의 인접골이 과부하 영역에 속하였고, type II 임플란트의 경우에는 2 mm 이상이었다. 결론: 미세나사의 유무와 몸체의 테이퍼 유무에 따라 변연골 스트레인은 직접적인 영향을 받았고 대조모델에 비해 경부 미세나사가 있는 type I 및 type II 임플란트의 식립 시 변연골의 과부하 영역이 월등히 컸다.

• 대한치과교정학회지
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• 제14권1호
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• pp.75-92
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• 1984

This study attempted to analyze the distribution of stress, to examine the bending effect in the mandible according to the pulling directions and determine on which pulling directions are adequate when an orthopedic force was applied to the mandible. An orthopedic force, 500gm, was applied to the gnathion, one point of the chin area, in three directions. The three directions were ; high puli' from gnathion to the center of condyle head, and vertical pull, from gnathion to a parallel line with the posterior border of the ramus, and medium pull, from the gnathion to a parallel line with the lower border of mandible. The distribution of principal stress, bending moment and amount of displacement within the mandible was analyzed by a 3-dimensional finite element method and that of the various portions of mandible were computed and compared according to the pulling directions. The results were as follows : 1. The bending moment of each part of a mandible has been found to be markedly larger in case of vertical pull than in case of either high pull or medium pull. In vertical pull the bending moment turned out to largest at the condyle head and neck portion, the gonial angle portion, the coronoid portion and the ascending ramus portion, respectively, while comparatively large at the cuspid and bicuspid portion and the first molar portion. In case of high pull it was largest at the gonial angle portion and becoming smaller at the coronoid portion, the ascending ramus portion, the condyle head and neck portion, and the cuspid and bicuspid portion, in that order. In case of medium pull, however, the bending moment was largest at the condyle head and neck portion, becoming smaller at the first molar portion, the ascending ramus portion, the coronoid portion, the cuspid and bicuspid portion, and gonial angle portion, in that order. 2. As for the bending effect it was calculated to be mostly oriented downward at the mandibular body and backward at the mandibular ramus in both high pull and vertical pull. In case of medium pull it was oriented upward at the mandibular body and forward at the mandibular ramus. 3. The bending effect also turned out to be mostly oriented outward in case of high pull and medium pull, and inward in vertical pull. 4. At the mandibular body and ramus, the bending effect in the upward-downward direction and that in the forward-backward direction were found to be larger than in the inward-outward direction. 5. If and when we expect any correcting effect on the mandibular protrusion by means of the chin cup appliance, we can say sure as conclusion that high pull and vertical pull are more effective than medium pull.

• 대한치과보철학회지
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• 제42권4호
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• pp.356-372
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• 2004

Statement of problom: In the internal connection system the loading transfer mechanism within the inner surface of the implant and also the stress distribution occuring to the mandible can be changed according to the abutment form. Therefore it is thought to be imperative to study the difference of the stress distribution occuring at the mandible according to the abutment form. Purpose: The purpose of this study was to assess the loading distributing characteristics of 3 implant systems with internal connection under vertical and inclined loading using finite element analysis. Material and method: Three finite element models were designed according to the type of internal connection of ITI(model 1), Friadent(model 2), and Bicon(model 3) respectively. This study simulated loads of 200N in a vertical direction (A), a $15^{\circ}$ inward inclined direction (B), and a $30^{\circ}$ outward inclined direction (C). Result: The following results have been made based on this numeric simulations. 1. The greatest stress showed in the loading condition C of the inclined load with outside point from the centric cusp tip. 2. Without regard to the loading condition, the magnitudes of the stresses taken at the supporting bone, the implant fixture, and the abutment were greater in the order of model 2, model 1, and model 3. 3. Without regard to the loading condition, greater stress was concentrated at the cortical bone contacting the upper part of the implant fixture, and lower stress was taken at the cancellous bone. 4. The stress of the implant fixture was usually widely distributed along the inner surface of the implant fixture contacting the abutment post. 5. The stress distribution pattern of the abutment showed that the great stress was usually concentrated at the neck of the abutment and the abutment post, and the stress was also distributed toward the lower part of the abutment post in case of the loading condition B, C of the inclined load. 6. In case of the loading condition B, C of the inclined load, the maximum von Misess stress at the whole was taken at the implant fixture both in the model 1 and model 2, and at the abutment in the model 3. 7. The stress was inclined to be distributed from abutment post to fixture in case of the internal connection system. Conclusion: The internal connection system of the implant and the abutment connection methods, the stress-induced pattern at the supporting bone, the implant fixture, and the abutment according to the abutment connection form had differenence among them, and the stress distribution pattern usually had a widely distributed tendency along the inner surface of the implant fixture contacting the a butment post.

• 대한치과보철학회지
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• 제42권4호
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• pp.425-442
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• 2004

Statement of problem: A difficulty in achieving a passive-fitting prosthesis can be overcome by individual crown restoation of multiple implants. But individualized crown has another difficulty in control of contact tightness and stress distribution. Purpose: This in vitro study is to evaluate the stress distribution and the magnitude in the supporting tissues around Endopore implants with different crown lengths, interproximal contact tightness, and the splinting effects. Material & methods: Three Endopore implants($4.1{\times}9mm$) were placed in the mandibular posterior edentulous area distal to the canine and photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA). Restorations were fabricated in two crown lengths: 9, 13 mm. For non-splinted restorations, individual crowns were fabricated on three custom-milled titanium abutments. After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m$), and heavy($80{\mu}m$). For splinted restorations, 3-unit fixed partial dentures were fabricated. This study was examined under simulated non-loaded and loaded conditions(6.8 kg). Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure. Results: 1. When restorations were not splinted, the more interproximal contact tightness was increased among the three implants, the more stress was shown in the cervical region of each implant. When crown length was increased, stresses tended to increase in the apex of implants but there were little differences in stress fringes. 2. When nonsplinted restorations were loaded on the first or third implant, stresses were increased in the apex and cervical region of loaded implant. Regardless of interproximal contact tightness level, stresses were not distributed among the three implants. But with tighter interproximal contact, stresses were increased in the cervical region of loaded first or third implant. 3. When the nonsplinted restorations were not loaded, there were little stresses on the supporting structure of implants, but low level stresses were shown in the splinted restorations even after sectioning and soldering. 4. With splinted restorations, there were little differences in stresses between different crown lengths. When splinted restorations were loaded, stresses were increased slightly on the loaded implant, but relatively even stress distribution occurred among the three implants. Conclusions: Splinting the crowns of adjacent implants is recommended for Endopore implants under the overloading situation.