STATEMENT OF PROBLEM: There are many studies focused on the effect of shape of fixtures on stress distribution in the mandibular bone. However, there are no studies focused on the effect of the abutment types on stress distribution in mandibular bone. PURPOSE: The purpose of this study is to investigate the effect of three different abutment types on the stress distributions in the mandibular bone due to various loads by performing finite element analysis. Material and method : Three different implant systems produced by Warantec (Seoul, Korea) were modeled to study the effect of abutment types on the stress distribution in the mandibular bone. The three implant systems are classified into oneplant (Oneplant, OP-TH-S11.5), internal implant (Inplant, IO-S11.5) and external implant (Hexplant, EH-S11.5). All abutments were made of titanium grade ELI, and all fixtures were made of titanium grade IV. The mandibular bone used in this study is constituted of compact and spongeous bone assumed to be homogeneous, isotropic and linearly elastic. A comparative study of stress distributions in the mandibular bone with three different types of abutment was conducted. RESULTS: It was found that the types of abutments have significant influence on the stress distribution in the mandibular bone. It was due to difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the mandibular bone was increased with the increase of inclination angle of load. CONCLUSION: It was concluded that the maximum effective stress in the bone by the internal implant was the lowest among the maximum effective stresses by other two types.
Finite Element Analysis ; Titanium

There are three designs of thread form in screw type implants: V-thread, Reverse buttress thread and Square thread. The purpose of this study was to find out how thread form designs have an influence on the equivalent stress, equivalent strain, maximum shear stress and maximum shear strain and which design of thread form generates more maximum equivalent stress and strain. 3-D finite element analysis was used to evaluate the stress and strain patterns of three tread types. The results of this study were as follow. 1. Under the 200N of axial load, the value of maximum equivalent stress is smallest in square thread and there is no significant difference between that of V thread and reverse buttress thread. 2. Under the 200N of axial load, the value of maximum equivalent strain is largest in V thread and smallest in square thread. 3. Under the 200N of axial load, the value of maximum shear stress is smallest in square thread and there is no significant difference between that of V thread and reverse buttress thread. 4. Under the 200N of axial load, the value of maximum equivalent strain is largest in V thread and there is no significant difference between that of square thread and reverse buttress thread. 5. Above results show that the square thread has special advantages in stress and strain compared with other thread types, especially in shear stess which is most determinant to implant-bone interface. Considering the superior biomechanical properties of square form implant, we presume that square form implant has better clinical results than the other types of implants in the same clinical conditions.
Finite Element Analysis*

Cortical support is an important factor, as the engagement of the fixture in strong compact bone offers an increased load-carrying capacity and initial stability. Because of the poor bone quality in the posterior mandible and other anatomic considerations, it has been suggested that implant fixtures be placed in these locations with apical engagement of the lingual cortical plate for so-called bicortication. The purpose of this investigation was to determine the effect of cortical engagements and in addtion polyoxymethylene (POM) intramobile connector(IMC) of IMZ implant on implant load transfer in edentulous posterior segment of mandible, using three-dimensional(3D) finite element analysis models composed of cortical and trabecular bone involving single implant. Variables such as (1) the crestal peri-implant defect, (2) the apical engagement of lingual cortical plate, (3) the occlusal contact position (a vertical load at central fossa or buccal cusp tip), and (4) POM IMC were investigated. Stress patterns were compared and interfacial stresses along the bone-implant interface were monitored specially. Within the scope of this study, the following observations were made. 1) Offset load and angulation of fixture led to increase the local interfacial stresses. 2) Stresses were concentrated toward the cortical bones, but the crestal peri-implant defect increased the interfacial stresses in trabecular bone. 3) For the model with bicortication, it was noticed that the crestal cortical bone provided more resistance to the bending moment and the lingual cortical plate provided more support for the vertical load. But Angulaton problem of the fixture from the lingual cortical engagement caused the local interfacial stress concentrations. 4) It was not clear that POM IMC had the effect on stress distribution under the present experimental conditions, expecially for the cases of crestal peri-implant defect.
Finite Element Analysis* ; Mandible*

No abstract available.
Finite Element Analysis*

STATEMENT OF PROBLEM: The researches on the influence of design variables on the stress distribution in cortical and trabecular bones and on optimal design for implant system were limited. PURPOSE: The purpose of this study is to identify the sensitivities of design parameters and to suggest the optimal parameters for designing the onebody type implant system. MATERIAL AND METHODS: Stresses arising in the implant system were obtained by finite element analysis using a three dimensional model. An onebody type implant system [Oneplant (Warrantec. Co. Ltd., Korea)]was considered in this study. Vertical load(150 N) was applied on the top of the abutment along the axial direction. The initial design variables set for sensitivity analysis were radius of fixture, numbers of micro thread, numbers of power thread, height of micro thread, fixture length, tapered angle of fixture, inclined angle of thread, width of micro thread and width of power thread. The statistical technique of Design of Experiments(DOE) was applied to the simulation model to deduce effective design parameters on stress distributions in bones. The deduced design parameters were incorporated into a fully automated design tool which is coupled with the finite element analysis and numerical optimization to determine the optimal design parameters. RESULTS: 1. The result of sensitivity analysis showed six design variables - radius of fixture, tapered angle of fixture, inclined angle of thread, numbers of power thread, numbers of micro thread and height of micro thread - were more influential than the others. 2. The optimal values of design variables can be deduced by coupling finite element analysis (FEA) and design optimization tool(DOT).
Finite Element Analysis ; Radius

No abstract available.
Finite Element Analysis*

No abstract available.
Finite Element Analysis*

The purpose of the present study is to evaluate the stress distribution on the length and diameter of the miniscrew and cortical bone width. Three dimensional finite element models were made of diameter 1.2mm, 1.6mm, 2.0mm and length 6.0mm, 8.0mm, 10.0mm, 12.0mm and cortical bone width 1.0mm. Also, another three dimensional finite element models were made of diameter 1.2mm, 1.6mm, 2.0mm and length 8.0mm and cortical bone width 1.0mm, 1.5mm, 2.0mm, 2.5mm. Two-hundred grams horizontal force were applied on the center of the miniscrew head and at that stress distribution and its magnitude had been analyzed by ANSYS, which is three dimensional finite element analysis program. The obtained results were as follows : 1. The comparison of the maximum von-Mises stress in the miniscrew showed that as the diameter increases from 1.2mm to 2.0mm stress has been decreased, while on the same diameter stress was not changed regardless of the length change. 2. The comparison of the maximum von-Mises stress in the cortical and cancellous bone showed that as the diameter increases from 1.2mm to 2.0mm stress has been decreased, while on the same diameter stress was not changed regardless of the length change. 3. In the analysis of the stress distribution in the cortical and cancellous bone, the most of the stress had been absorbed in the cortical bone, and did not transmitted much to the cancellous bone. 4. In the analysis of the maximum von-Mises stress according to the cortical bone width, the same diameter of the miniscrew showed a constant stress value regardless of the cortical bone width change. The above results suggest that the maintenance of the miniscrew is more reliable on diameter than length of the miniscrew.
Finite Element Analysis ; Head

The present study was performed to evaluate the stress distribution on the diameter of the mini-implant and insertion angle to the bone surface. To perform three dimensional finite element analysis, a hexadron of 15 x 15 x 20 mm3 was used, with a 1.0 mm width of cortical bone. Mini-implants of 8 mm length and 1.2 mm, 1.6 mm, and 2.0 mm in diameter were inserted at 90 degrees, 75 degrees, 60 degrees, 45 degrees, and 30 degrees to the bone surface. Two hundred grams of horizontal force was applied to the center of the mini-implant head and stress distribution and its magnitude were analyzed by ANSYS, a three dimensional finite element analysis program. The findings of this study showed that maximum von Mises stresses in the mini-implant and cortical and cancellous bone were decreased as the diameter increased from 1.2 mm to 2.0 mm with no relation to the insertion angle. Analysis of the stress distribution in the cortical and cancellous bone showed that the stress was absorbed mostly in the cortical bone, and little was transmitted to the cancellous bone. The contact area increased according to the increased diameter and decreased insertion angle to the bone surface, but maximum von Mises stress in cortical bone was more significantly related with the contact point of the mini-implant into the cortical bone surface than the insertion angle to the bone surface. The above results suggest that the maintenance of the mini-implant is more closely related with the diameter and contact point of the mini-implant into the cortical bone surface rather than the insertion angle.
Finite Element Analysis* ; Head

finite element analysis when under 100N vertical force and 20N horizontal force were simultaneously loaded on the following 6 different kinds of implant design and 4 different kinds of thread design. According to the results, the cylinder type or cylinder and tapered type is the most favorable design in the same diameter. To supplement the shortcoming of the tapered type and stepped cylinder type in the respect of design and project area, it is better to increase the diameter of the implants. The square and reverse threads are better than triangular and plateau thread in the respect of maximum equivalent stress and strain in the cortical and cancellous bone and project area.]]>
Finite Element Analysis