Three-Dimensional Finite Element Analysis of
Stability in Proportion to Crown-to-Implant
Ratio in the Implant-supported Prostheses
Seung-Hwan Youn
The Graduate School
Yonsei University
Three-Dimensional Finite Element Analysis of
Stability in Proportion to Crown-to-Implant
Ratio in the Implant-supported Prostheses
A Dissertation Thesis
Submitted to the Department of Dental Science
and the Graduate School of Yonsei University
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy of Dental Science
Seung-Hwan Youn
This certifies that the dissertation thesis
of Seung-Hwan Youn is approved
Thesis Supervisor Jung-Kiu Chai
Kyoo-sung Cho
Seong-Ho Choi
Keun-Woo Lee
Han-Sung Kim
The Graduate School
Yonsei University
감사의
감사의
감사의
감사의 글
글
글
글
본 논문이 완성되기까지 부족한 저를 항상 격려해 주시고 사랑과 관심으로 이끌어 주신 채중규 교수님께 깊은 감사를 드립니다. 그리고, 많은 조언과 따뜻한 관심으로 지켜봐 주신 조규성 교수님, 최성호 교수님, 이근우 교수님, 김한성 교수님께 진심으로 감사 드립니다. 연구 내내 많은 도움을 주신 연세대 의공학부의 박원필 선생님과 관동대 치주과 윤정호 교수님, 연세대 구강생물학교실의 김희진 교수님, 연세대 보철과 심준성교수님, 치주과교실원 여러분들께 고마움을 전합니다. 힘들 때 도움이 되어준 친구들 강철구, 이광출, 이승문, 정호걸, 최정우에게도 감사의 마음을 전합니다. 그리고, 늘 아낌 없는 사랑과 헌신적인 도움으로 든든하고 따뜻한 버팀목이 되어준 사랑하는 아내 초영이와 개구쟁이 아들들 태건이와 효재에게 사랑의 마음을 전합니다. 마지막으로, 믿음과 사랑으로 이해해 주시고 항상 곁에서 든든하게 후원해주신 부모님께도 감사의 마음을 담아 이 논문을 드립니다. 2007년 5월 저자 씀i
Table of Contents
Abstract (English)
iii
I. Introduction
1
II. Materials and Methods
5
III. Results
11
IV. Discussion
14
V. Conclusion
19
References
20
Figures
27
Abstract (Korean)
33
ii
List of Figures
Figure 1. Finite Element model(Example in case of C/I ratio 1.0,6.5mm bone level). 7
Figure 2. Classification of models according to cancellous bone quantity. 8
Figure 3. Crown-to-implant ratios in atrophic maxillary bone (Example in case of
cancellous bone height : 5mm).
8
Figure 4. Values and distribution of loads applied to finite element model. 10
Figure 5. Distribution of stresses in all locations with centric vertical loads(outer
cortical : 0.5mm). 27
Figure 6. Distribution of stresses in all locations with lateral vertical loads(outer
cortical : 0.5mm). 28
Figure 7. Distribution of stresses in all locations with oblique loads(outer cortical :
0.5mm). 29
Figure 8. Distribution of stresses in all locations with centric vertical loads(outer
cortical : 1.0mm). 30
Figure 9. Distribution of stresses in all locations with lateral vertical loads(outer
cortical : 1.0mm). 31
Figure 10. Distribution of stresses in all locations with oblique loads(outer cortical :
1.0mm). 32
Figure 11. Von Mises stress value around implant in atrophic maxillar bone. 32
List of Tables
Table 1. Elastic properties of materials modeled. 9
Table 2.
Maximum von Mises stress values with centric vertical loads, lateral vertical loads and oblique loads in 0.5mm outer cortical thickness.
12
Table 3.
Maximum von Mises stress values with centric vertical loads, lateral vertical loads and oblique loads in 1.0mm outer cortical thickness.
iii
Abstract
Three-Dimensional Finite Element Analysis of
Stability in Proportion to Crown-to-Implant Ratio in the
Implant-supported Prostheses
The three dimensional finite element analysis(3-D FEA) is considered an appropriate method for investigation of the stress distribution throughout a 3-D structure. The purpose of this study was to determine the implant stability in proportion to crown-to-implant ratio in various condition with different bone quality and quantity of the atrophic posterior maxilla using finite element analysis. A 3-D finite element model of a maxillary bone section with a missing second premolar was used in this study. We classified models into 3 groups according to the cancellous bone quantity. First group has over 12mm cancellous bone, second has 5mm height of cancellous bone and third has grafted bone. In addition, we further classified the third group in two sub-groups considering the difference of bone quality in grafted bone. A vertical load was applied at the palatal cusp (200 N) and central (200 N) area, and oblique load was applied at the palatal cusp (200 N) area.
iv
Mises stresses according to crown-to-implant ratio. But in oblique loads, there were in direct proportion to crown-to-implant ratio.
In normal maxillary bone, von Mises stress value of 2.0 crown-to-implant ratio is three times greater than that of 0.5 crown-to-implant ratio.
In conclusion, in cases of centric vertical loading and lateral vertical loading on implant, there were no progression of von Mises stress values according to crown-to-implant ratio and in case of oblique loading on implants, von Mises stress increased in proportion to the crown-to-implant ratio. The maximum stress was localized on the palatal cortex for all levels of bone.
Key Words: crown-implant ratio, finite element analysis, implant-supported
THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF
STABILITY IN PROPORTION TO CROWN-TO-IMPLANT
RATIO IN THE IMPLANT-SUPPORTED PROSTHESES
Seung-Hwan Youn, D.D.S. , M.S.D.
Department of Dental Science
Graduate School, Yonsei University
(Directed by Prof. Jung-Kiu Chai, D.D.S., M.S.D., PhD.)
I. INTRODUCTION
The therapeutic regimen for treating patients with missing teeth has been significantly expanded by modern implant methods. The prosthesis supported by implants has become an important part of restorative therapy for both completely and partially edentulous patients(Jemt and Lekholm 1993; Zarb and Schmitt 1993). However, a prerequisite for successful oral implants is sufficient bone height(Knabe and Hoffmeister 1998). Longer implants provide greater surface area for direct bone contact, thereby the reducing localized stress in bone that can develop in crestal region due to transverse force components.
In using osseointegrated dental implants for partially edentulous patients, clinicians are frequently confronted with insufficient bone, especially in maxillar.
Thus, the implant placement in the maxilla can be difficult for many reasons, including inadequate posterior alveolus, increased pneumatization of maxillary sinus, and close approximation of sinus floor to crestal bone. The thickness of bone beneath
the maxillary sinus correlates with the degree of pneumatization. Sinus pneumatization may minimize or completely eliminate the amount of vertical bone available(Misch 1987). In addition to the problem of a compromised alveolar ridge, the maxillary sinus can vary in size and shape, making implant placement impossible without surgical modification(Winter, Pollack et al. 2002).
Several techniques and a variety of materials have been reported to increase posterior maxillary bone height to permit successful dental implant placement(Boyne and James 1980; Tatum 1986). But these are very difficult methods and an additional surgery is needed.
For residual ridge with minimal bone height but adequate bone width, the use of short and wide implants may offer a simple and predictable treatment alternative in posterior area(Ferrigno, Laureti et al. 2002; Griffin and Cheung 2004; Nedir, Bischof et al. 2004).
The reasons are that the majority of the stress is concentrated at the level of the first few threads to the crestal cortical bone when an implant is loaded. (Geng, Tan et al. 2001; Meyer, Vollmer et al. 2001; Iplikcioglu and Akca 2002; Griffin and Cheung 2004; Himmlova, Dostalova et al. 2004; Koca, Eskitascioglu et al. 2005).
But in short implants, length of crown is important factor.(Simion, Fontana et al. 2004) As crown’s length is longer, bending moment is greater. Moreover stress under oblique loading were approximately 10 times greater than under axial loading(Papavasiliou, Kamposiora et al. 1996; Lin, Shi et al. 2000).
Treatment planning for conventional fixed prosthodontic restorations using natural teeth as abutments requires consideration of the crown-to-root (C/R) ratio of these abutments(Penny and Kraal 1979). In addition Ante’s law(Ante 1926) dictates that
the combined peri-cemental area of all of the abutment teeth should be equal to or greater than the peri-cemental area of the teeth to be replaced. Both the C/R ratio and peri-cemental area influence the degree of stress within the attachment mechanism. In the case of teeth, the mechanism of attachment is the periodontal ligament. Because this suspensory ligament is highly reactive to occlusal overload, it is generally recommended that a ratio of 2 lengths root structure embedded in healthy bone be used for 1 length of crown (ie, C/R ratio = 1:2 or 0.5). If this is not possible, an increased number of abutment teeth should be used. When the original Bränemark System implant was introduced, long implant fixtures were needed to avoid excessively high stress to crestal bone. Therefore small crown-to-implant ratio (ie, about 0.5) became the norm in implants (van Steenberghe, Lekholm et al. 1990; Wyatt and Zarb 1998; Misch 1999; Weiss CM 2001; Naert, Koutsikakis et al. 2002; Weng, Jacobson et al. 2003).
The distribution of forces in peri-implant bone has been investigated by finite element analysis in several studies. Recently, the stress distribution in bone correlated with implant-supported prosthesis design has been investigated primarily by means of 2-dimensional (2-D) and 3-dimensional (3-D) finite element analyses (FEAs). Studies comparing the accuracy of these analyses showed that, if detailed stress information is required, then 3-D modeling is necessary. The 3-D FEA is considered an appropriate method for investigation of the stress distribution throughout a 3-D structure. Therefore in the present study, this method was selected for the evaluation of stress distribution when bone and implants are loaded.
The purpose of this study was to determine the implant stability in proportion to crown-to-implant ratio in various condition with different bone quality and quantity
of the atrophic posterior maxilla using finite element analysis. The hypothesis tested was that the stress of implant fixture increases in proportion to the crown-to-implant ratio in the implant-supported prostheses.
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Ⅱ. Materials & methods
A 3-D finite element model of a maxillary bone section with a missing second premolar was used in this study. After taking 2D CT images using Skyscan 1076 Micro-CT(Skyscan Co., Kontich, Belgium) of maxillary edentulous bone and implant fixture, we reconstructed 2D CT images to 3D CAD Model using BIONIX 3.3(CANTIBio Co., Suwon, Korea). Therefore, different bone dimensions were generated to perform nonlinear calculations. The implant was placed into normal maxilla, an atrophic maxilla with crestal bone heights of 6.5mm, 5.75mm and an atrophic maxilla with grafted bone. Cancellous bone was modeled as a solid structure in cortical bone (Matsushita, Kitoh et al. 1990; Holmes and Loftus 1997) and classified by bone quantity.
A single-piece, 4.0 X 10mm screw-shaped dental implant system (Mk III implant, Bränemark; Nobel Biocare, Göteborg, Sweden) was selected for this study. Cobalt-Chromium (Wiron 99; Bego, Bremen, Germany) was simulated as a crown framework material, and feldspathic porcelain was used for the occlusal surface. Finite Element Model consist of 3-D 8-Node Structural Solid Element was made of 3D CAD model with Hyper Mesh 7.0(Altair Engineering, U.S.A.). The metal thickness used in this study was 1.0 mm. Cement thickness layer was not modeled(Matsushita, Kitoh et al. 1990). All materials were presumed to be linear elastic, homogenous, and isotropic(Papavasiliou, Kamposiora et al. 1996; Holmes and Loftus 1997; Papavasiliou, Kamposiora et al. 1997; Meyer, Vollmer et al. 2001; Tada, Stegaroiu et al. 2003). Figure 1 displays the FE-model.
First group has over 12mm cancellous bone, second has 5mm height of cancellous bone and third has grafted bone(Fig. 2).
In addition, we further classified the third group in two sub-groups considering the difference of bone quality in grafted bone.
Moreover we classified models according to Crown-to-implant ratio in atrophic maxillar. Crown-to-Implant ratio were 0.5, 1.0, 1.5 and 2.0(Fig. 3).
And Cortical bone thickness used in this study was an inner thickness of 0.5 mm and 0.25 mm and outer thickness of 1.0 mm and 0.5 mm beneath the maxillary sinus for all bone levels.
The corresponding elastic properties such as Young’s modulus (E) and Poisson ratio (m) were determined from the literature(Papavasiliou, Kamposiora et al. 1997; Geng, Tan et al. 2001) and are summarized in Table I. Model consist of elements and nodes(data not shown). A fixed bond between the bone and the implant along the interface was presumed. An occlusal force of 200 N was used. A vertical load was applied at the palatal cusp (200 N) and central (200 N) area, and oblique load was applied at the palatal cusp (200 N) area (Fig. 4)(Geng, Tan et al. 2001; Sutpideler, Eckert et al. 2004).
The final element on the x, y, z -axis for each design was assumed to be fixed, which defined the boundary condition. The applied forces were static. Stress levels were calculated using von Mises stresses(Timoshenko S 1968) values. The von Mises stresses are the most commonly reported in FEA studies to summarize the overall stress state at a point.(Papavasiliou, Kamposiora et al. 1996; Holmes and Loftus 1997; Meyer, Vollmer et al. 2001; Tada, Stegaroiu et al. 2003) The analyses were performed on a computer (Intel Core2Duo E6600 ; Intel P965 Chipset) using
software (ANSYS, version 10.0; ANSYS Corp, U.S.A.). Boundary conditions, loading, and mathematical models were prepared with finite element software. The outputs were transferred to the ANSYS program to display stress values and distributions. Data for stresses were produced numerically and color-coded.
a. Porcelain crown b. Outer cortical bone(1mm) c. Cancellous bone(5mm) d. Inner cortical bone(0.5mm) e. Grafted bone
a. Normal maxillary bone b. Atrophic maxillary bone c. Atrophic maxillary bone with bone graft Figure 2. Classification of models according to cancellous bone quantity.
a. C/I ratio=0.5 b. C/I ratio=1 c. C/I ratio=1.5 d. C/I ratio=2 Figure 3. Crown-to-implant ratios in atrophic maxillary bone ( Example in case of cancellous bone height : 5mm, length of fixture : 10mm ).
Table 1. Elastic properties of materials modeled.
Materials Modulus of elasticity, E (MPa) Poisson's ratio,v Porcelain (Lewinstein, Banks-Sills et al. 1995) 68900 0.28 Cr-co alloy(Craig 1989) 218000 0.33 Titanium(Koca, Eskitascioglu et al. 2005) 110000 0.35 Cortical bone(Cook, Klawitter et al. 1982) 13400 0.30 Cancellous bone(Farah, Craig et al. 1989) 1370 0.30
Grafted bone (Brodt, Swan et al. 1998)
Good : 690 Bad : 100
Good : 0.30 Bad : 0.20
Centric vertical loads Lateral vertical loads Oblique loads
a. Porcelain crown b. Outer cortical bone c. Cancellous bone d. Inner cortical bone e. Grafted bone
III. Results
Table 2 represents maximum von Mises stress values by centric vertical loads, lateral vertical loads and oblique loads in 0.5mm outer cortical thickness in various maxillary bone condition. For all bone levels, maximum von Mises stress values of 19.2 to 253.6 MPa were observed.
In centric vertical loads and lateral vertical loads, there are no progression of von Mises stresses according to crown-to-implant ratio. But in oblique loads, there are in direct proportion to crown-to-implant ratio.
In normal maxillary bone with oblique loads, von Mises stress value of 2.0 crown-to-implant ratio is three times greater than that of 0.5 crown-to-crown-to-implant ratio.
Table 3 represents maximum von Mises stress values by centric vertical loads, lateral vertical loads and oblique loads in 1.0mm outer cortical thickness in various maxillary bone condition. For all bone levels, maximum von Mises stress values of 17.5 to 202.2 MPa were observed.
There are similar pattern of maximum von Mises stress values between 0.5mm outer cortical thickness and 1.0mm outer cortical thickness.
Figure 5-10 represent the stress distribution within bone structure.
The maximum von Mises stress value was observed at the atrophic maxillary bone in the 0.5mm outer cortical thickness and the lowest stress value was observed at the normal maxillary bone in the outer cortical thickness 1.0mm.
Figure 11. represents von Mises stress values around implant. Maximum stess values are on the maxillar cortex.
Table 2. Maximum von Mises stress values with centric vertical loads, lateral vertical loads and oblique loads in 0.5mm outer cortical thickness.
Crown-to-Implant ratio Normal maxillary bone Atrophic maxillary bone Grafted bone (good) Grafted bone (bad) 0.5 22.181 68.326 35.958 58.536 1 21.406 68.602 39.014 61.142 1.5 19.374 69.495 37.303 57.832 Centric vertical loads 2 19.234 68.118 36.573 59.633 0.5 44.833 70.702 51.616 55.361 1 42.183 69.56 48.883 57.166 1.5 41.632 67.712 50.894 56.663 Lateral vertical loads 2 43.141 66.252 48.88 54.888 0.5 59.693 142.623 53.863 123.563 1 100.405 179.565 91.611 142.626 1.5 140.49 221.17 130.853 170.346 Oblique loads 2 181.281 253.59 173.954 194.333 0 50 100 150 200 250 300 0.5 1 1.5 2 0.5 1 1.5 2 0.5 1 1.5 2 Centric vertical loads Lateral vertical loads Oblique loads
S tr e s s ( M P a )
Normal maxillary bone Atrophic maxillary bone Grafted bone(good) Grafted bone(bad)
Table 3. Maximum von Mises stress values with centric vertical loads, lateral vertical loads and oblique loads in 1.0mm outer cortical thickness.
Crown-to-Implant ratio Normal maxillary bone Atrophic maxillary bone Grafted bone (good) Grafted bone (bad) 0.5 19.598 58.952 34.608 48.14 1 17.575 58.357 34.487 48.065 1.5 17.487 58.799 34.568 48.206 Centric vertical loads 2 19.927 58.405 34.368 47.649 0.5 35.688 63.384 40.841 55.399 1 34.16 63.493 37.382 53.854 1.5 31.175 59.837 36.415 52.54 Lateral vertical loads 2 31.63 63.524 36.189 53.14 0.5 41.26 118.733 36.81 101.132 1 73.744 142.807 70.089 112.737 1.5 107.813 175.219 105.199 132.817 Oblique loads 2 143.482 202.178 138.4 152.819 0 50 100 150 200 250 0.5 1 1.5 2 0.5 1 1.5 2 0.5 1 1.5 2 Centric vertical loads Lateral vertical loads Oblique loads
S tr e s s ( M P a )
Normal maxillary bone Atrophic maxillary bone Grafted bone(good) Grafted bone(bad)
IV. DISCUSSION
In the past two decades, finite element analysis(FEA) has been one of the most frequently used methods for the prediction of the effects of stress on the implant and surrounding bone. Vertical and oblique loads from mastication induce axial forces and bending moments, and result in stress gradients in the implants, as well as in the bone. A important factor for the success of a dental implant is the manner in which stresses are transferred to surrounding bone.
FEA allows investigators to predict stress distribution in the contact area of implants with cortical bone and around the apex of implants in spongy bone(Geng, Tan et al. 2001).
In the model used in the present study, we made several hypotheses regarding the simulated structures. All structures in the model were assumed to be homogeneous, isotropic, and to possess linear elasticity. Different properties of materials were in the model of this study. Additionally, a implant-bone interface with 100% contact ratio was simulated, which does not necessarily simulate clinical situations(Brunski, Puleo et al. 2000). Also, it is important to note that the stress distribution patterns may be different depending on the materials and properties assigned to each layer of the model used in the experiments. Furthermore, the cement layer in prosthesis was not modeled. Thus, the inherent limitations in this study should be considered.
When applying FEA to dental implants, it is important to consider not only axial loads and horizontal forces (moment-causing loads) but also a combined load (oblique occlusal force), because the latter represents more realistic occlusal load pattern (Holmgren, Seckinger et al. 1998).
pattern. In the present study, the area of the loading force was specifically applied to cusp tip and central fossa. However, the geometric form of the tooth surface can produce a pattern of stress distribution that is specific for the modeled form. The pattern could be different with even moderate changes to the occlusal surface of the crown. Although this occlusal form exists for this model, the same form would not represent all premolar teeth.
It was reported that the stress is concentrated in the neck of implant and is probably due to the rigid connection between the implant and bone. The elastic modulus of cortical bone is higher than spongy bone, and for this reason cortical bone is stronger and more resistant to deformation(Ichikawa, Kanitani et al. 1997; Stegaroiu, Sato et al. 1998; Gross and Nissan 2001).
As a result of 3-D finite element analysis, there was no difference according to crown-to-root ratio in case that vertical loading was on palatal cusp and central fossa. There were small variations according to crown-to-implant ratio. However, in case of oblique loading on palatal cusp von Mises stress value increase directly in proportion to crown-to-implant ratio. For this result, it is thought that in vertical loading of central fossa and palatal cusp the quantity of bending moment is smaller than that of oblique loading. And the greater the crown’s length is, the bigger bending moment in oblique loading is.
Bending moment could cause tensile forces that is thought to be harmful to implants. This is in agreement with the findings of Mische et al. (Misch 1999) who stated that the greater the crown height, the greater the moment force or lever arm with any lateral force and as the crown-implant ratio increases, the number of implants and/or wider implants should be inserted to counteract the increase in stress.
This also corroborated the findings of papavasiliou et al., (Papavasiliou, Kamposiora et al. 1996) who found the highest stresses were concentrated in the cortical bone and stresses under oblique loading were approximately 10 times greater than under axial loading. The present findings support the theoretical analysis by Rangert et al.(Rangert, Jemt et al. 1989) of forces and moments on implants. It suggested that the axial force was more favorable, because it distributed stress more evenly throughout the implant. This spported the findings of Block et al.,(Block, Finger et al. 1989) who demonstrated that the amount of bone directly in contact with the apical surface of a loaded implants was much less than that surrounding the remainder of the implant.
In addition, according to bone quantities, the difference in stress value appeared to be great.
In model with 0.5mm outer cortical bone, average stress value is 20.5MPa when vertical loading on central fossa of crown in normal maxillary bone. In atrophic maxillary bone with 5mm cancellous bone, average stress value is 68.6MPa which is three times as great as normal maxillary bone. In grafted bone, average stress value are 37.2MPa when grafted bone quality is good. However, in case of bad quality, it’s value is 59.3MPa.
This corroborated the statement of Smet et al.(De Smet, van Steenberghe et al. 2001) that significant marginal bone loss is observed around implants (Branemark system) when excessive load is present. Moreover, Quirynen et al.(Quirynen, Naert et al. 1992) observed a clear correlation between excessive marginal bone loss (> 1 mm) after the first year of load and implant loss with occlusal overload, but not with marginal gingivitis.
Meyer et al.(Meyer, Vollmer et al. 2001) stated that implant-transmitted overloading to bone seems to depend mainly on bone quality. The amount of crestal height plays another but more minor role in the effects of stress and strains under mechanical loading.
In comparing the stress values between 1.0mm and 0.5 mm thickness of outer cortical bone, von Mises stress values generally are high in 0.5mm thickness. Moreover, the smaller crown-to-implant ratio is, the greater influences in stresses are.
In case of oblique loading, the stress value of grafted bone of atrophic maxillar is lower than that of normal maxillary bone. It is thought to be due to double cortical layer effect that inner cortical layer supports implants once more if grafted bone quality is not bad.
On the contrary, if grafted bone quality is bad, high von Mises stress value could exist. Even though grafted bone quality is bad, it’s stress value is lower than that of atrophic maxillary bone.
Von Mises stress values in proportion to crown-to-root ratio of atrophic maxillary bone without bone graft of which outer cortical bone thickness is 1.0mm, and inner cortical bone thickness is 0.5mm are higher than that of atrophic maxillary bone with sinus bone graft that outer cortical bone thickness is 0.5mm and inner cortical bone thickness is 0.25mm. It is thought that the case of bad cortical bone quality with sinus bone graft was better than that of not bad cortical bone quality without sinus bone graft.
In this respect, it is thought that bad cortical bone quality with sinus graft could be better in clinical situation than not-bad cortical bone quality without bone graft. In present study, we classified model into two sub group according to grafted bone
qualities. Moreover, because a variety of bone quality , we refered to Brodt et al.(Brodt, Swan et al. 1998) and assumed two grafted bone qualities.
The stress was concentrated in the neck of implant as shown in Figure XI. Koca et al.(Koca, Eskitascioglu et al. 2005) stated that it was probably due to the rigid connection between the implant and bone. According to the results of the present study, it is suggested that crown-to-implant ratio is directly in proportion to stress of cortical crestal regions.
Hereafter, further research what the variations of fixture length cause in relation to crown-to-root ratio and in case of severe bone resorption, the analysis that onlay bone graft or not for altering crown-to-root ratio are thought to be needed.
How we apply this crown-to-root ratio to clinical situation such as implant surgery and prosthesis is thought to be important. In addition to crown-to-root ratio, the surface area of implants should be considered important factor. Thus further research about relationship between crown-to-root ratio and implant design is need to be thought.
V. Conclusion
Within the limitations of this study, the following conclusions were drawn:
1. In cases of centric vertical loading and lateral vertical loading on implant, there were normal maxillary bone grouop, grafed bone(good) group, grafted bone(bad) group and atrophic maxillary bone group in low stress value order. And there were no progression of von Mises stress values according to crown-to-implant ratio.
2. In cases of oblique loading on implant, there were grafted bone(good) group, normal maxillary bone group, grafted bone(bad) group and atrophic maxillary bone group in low stress value order. Grafted bone(good) group showed lower von Mises stress values than normal maxillary bone group. And von Mises stress values increased in proportion to the crown-to-implant ratio.
3. Von Mises stress values in oblique loading showed three times to nine times higher than that in central loading.
4. Regardless of cortical bone thickness, there are similar patterns of maximum von Mises stress values between 0.5 outer cortical thickness and 1.0mm outer cortical thickness.
5. The maximum von Mises stress value was localized on the palatal cortex. In conclusion, in cases of centric vertical loading and lateral vertical loading on implant, there were no progression of von Mises stress values according to crown-to-implant ratio and in case of oblique loading on crown-to-implants, von Mises stress increased in proportion to the crown-to-implant ratio. The maximum stress was localized on the palatal cortex for all levels of bone.
VI. References
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Figures
1 MN MX 0 2.46 5 4 .929 7.394 9.858 12.32 3 14 .787 17.252 19.716 22.1 81 JAN 30 2007 16:05:04 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.011937 SMX =22.181 1 MN MX 0 2.37 8 4 .757 7.135 9.514 11.89 2 14 .271 16.649 19.027 21.4 06 JAN 30 2007 17:13:47 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.011421 SMX =21.406 1 MN MX 0 2.15 3 4 .305 6.458 8.611 10.76 3 12 .916 15.069 17.221 19.3 74 JAN 30 2007 17:57:17 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.011338 SMX =19.374 1 MN MX 0 2.13 7 4 .274 6.411 8.548 10.68 5 12 .823 14.96 17.097 19.2 34 JAN 30 2007 20:22:36 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013125 SMX =19.234 1 MN MX 0 7.592 15.184 22.775 30.367 37.959 45.551 53.143 60.735 68.326 JAN 25 2007 17:17:14 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020725 SMX =68.326 1 MN MX 0 7.622 15.245 22.867 30.49 38.112 45.735 53.357 60.98 68.602 JAN 25 2007 17:41:21 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020206 SMX =68.602 1 MN MX 0 7.722 15.443 23.165 30.886 38.608 46.33 54.051 61.773 69.495 JAN 25 2007 18:36:02 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020125 SMX =69.495 1 MN MX 0 7.569 15.137 22.706 30.275 37.843 45.412 52.981 60.549 68.118 JAN 30 2007 14:55:01 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020006 SMX =68.118 1 MN MX 0 3.995 7.991 11.986 15.981 19.977 23.972 27.968 31.963 35.958 JAN 30 2007 21:00:26 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.015814 SMX =35.958 1 MN MX 0 4.335 8.67 13.005 17.339 21.674 26.009 30.344 34.679 39.014 JAN 30 2007 21:30:11 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.017105 SMX =39.014 1 MN MX 0 4.145 8.289 12.434 16.579 20.724 24.868 29.013 33.158 37.303 JAN 30 2007 22:06:49 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016782 SMX =37.303 1 MN MX 0 4.064 8.127 12.191 16.255 20.318 24.382 28.446 32.509 36.573 JAN 30 2007 23:01:26 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.015591 SMX =36.573 1 MN MX 0 6.504 13.008 19.512 26.016 32.52 39.024 45.528 52.032 58.536 FEB 1 2007 16:05:39 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019738 SMX =58.536 1 MN MX 0 6.794 13.587 20.381 27.174 33.968 40.761 47.555 54.348 61.142 FEB 1 2007 16:35:53 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.021299 SMX =61.142 1 MN MX 0 6.426 12.851 19.277 25.703 32.129 38.554 44.98 51.406 57.832 FEB 1 2007 17:13:20 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.021271 SMX =57.832 1 MN MX 0 6.626 13.252 19.878 26.504 33.13 39.756 46.382 53.008 59.633 FEB 1 2007 20:13:49 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020202 SMX =59.633Figure 5. Distribution of stresses in all locations with centric vertical loads(outer cortical : 0.5mm).
1 MN MX 0 4.9819.963 14.94419.926 24.90729.888 34.8739.851 44.833 JAN 24 2007 17:35:21 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013893 SMX =44.833 1 MN MX 0 4.6879.374 14.06118.748 23.43528.122 32.80937.496 42.183 JAN 23 2007 21:38:23 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013439 SMX =42.183 1 MN MX 0 4.6269.252 13.87718.503 23.12927.755 32.38137.007 41.632 JAN 23 2007 22:32:05 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013223 SMX =41.632 1 MN MX 0 4.7939.587 14.3819.174 23.96728.761 33.55438.348 43.141 JAN 23 2007 23:21:54 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013288 SMX =43.141 1 MN MX 0 7.59215.184 22.77530.367 37.95945.551 53.14360.735 68.326 JAN 25 2007 17:17:14 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020725 SMX =68.326 1 MN MX 0 7.62215.245 22.86730.49 38.11245.735 53.35760.98 68.602 JAN 25 2007 17:41:21 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020206 SMX =68.602 1 MN MX 0 7.72215.443 23.16530.886 38.60846.33 54.05161.773 69.495 JAN 25 2007 18:36:02 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020125 SMX =69.495 1 MN MX 0 7.56915.137 22.70630.275 37.84345.412 52.98160.549 68.118 JAN 30 2007 14:55:01 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020006 SMX =68.118 1 MN MX 0 5.73511.47 17.20522.94 28.67634.411 40.14645.881 51.616 JAN 24 2007 15:26:55 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016953 SMX =51.616 1 MN MX 0 5.43110.863 16.29421.726 27.15732.589 38.0243.452 48.883 JAN 24 2007 16:10:39 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016105 SMX =48.883 1 MN MX 0 5.65511.31 16.96522.62 28.27533.93 39.58545.239 50.894 JAN 24 2007 17:07:09 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.017366 SMX =50.894 1 MN MX 0 5.43110.862 16.29321.725 27.15632.587 38.01843.449 48.88 JAN 25 2007 13:59:56 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016921 SMX =48.88 1 MN MX 0 6.15112.302 18.45424.605 30.75636.907 43.05849.21 55.361 JAN 25 2007 14:30:16 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019861 SMX =55.361 1 MN MX 0 6.35212.703 19.05525.407 31.75938.11 44.46250.814 57.166 JAN 25 2007 15:00:53 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020655 SMX =57.166 1 MN MX 0 6.29612.592 18.88825.184 31.4837.775 44.07150.367 56.663 JAN 25 2007 15:38:24 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019283 SMX =56.663 1 MN MX 0 6.09912.197 18.29624.395 30.49336.592 42.69148.789 54.888 JAN 25 2007 16:34:07 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020057 SMX =54.888
Figure 6. Distribution of stresses in all locations with lateral vertical loads(outer cortical : 0.5mm).
1 MN MX 0 7.277 14.553 21.83 29.107 36.383 43.66 50.936 58.213 65.49 FEB 5 2007 14:24:54 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.06135 SMX =65.49 1 MN MX 0 11.156 22.312 33.468 44.624 55.781 66.937 78.093 89.249 100.405 FEB 5 2007 15:27:40 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.07277 SMX =100.405 1 MN MX 0 15.61 31.22 46.83 62.44 78.05 93.66 109.27 124.88 140.49 FEB 5 2007 16:04:47 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.087519 SMX =140.49 1 MN MX 0 20.14240.285 60.42780.569 100.712120.854 140.996161.139 181.281 FEB 5 2007 23:43:26 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.108556 SMX =181.281 1 MN MX 0 15.84731.694 47.54163.388 79.23595.082 110.929126.776 142.623 FEB 5 2007 10:43:46 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.073147 SMX =142.623 1 MN MX 0 19.95239.903 59.85579.807 99.758119.71 139.662159.613 179.565 FEB 5 2007 11:09:12 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.089749 SMX =179.565 1 MN MX 0 24.57449.149 73.72398.298 122.872147.447 172.021196.596 221.17 FEB 5 2007 11:56:04 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.105913 SMX =221.17 1 MN MX 0 28.17756.353 84.53112.707 140.883169.06 197.237225.413 253.59 FEB 5 2007 13:17:40 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.114899 SMX =253.59 1 MN MX 0 9.204 18.408 27.613 36.817 46.021 55.225 64.43 73.634 82.838 FEB 5 2007 22:52:40 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.072177 SMX =82.838 1 MN MX 0 10.534 21.068 31.602 42.136 52.67 63.204 73.739 84.273 94.807 FEB 6 2007 20:13:20 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.087176 SMX =94.807 1 MN MX 0 14.539 29.078 43.618 58.157 72.696 87.235 101.774 116.313 130.853 FEB 6 2007 20:52:37 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.099733 SMX =130.853 1 MN MX 0 19.32838.656 57.98577.313 96.641115.969 135.297154.626 173.954 FEB 7 2007 18:02:54 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.1141 SMX =173.954 1 MN MX 0 13.729 27.458 41.188 54.917 68.646 82.375 96.104 109.833 123.563 FEB 6 2007 22:14:55 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.082639 SMX =123.563 1 MN MX 0 15.847 31.695 47.542 63.389 79.237 95.084 110.931 126.779 142.626 FEB 6 2007 23:20:10 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.094199 SMX =142.626 1 MN MX 0 18.927 37.855 56.782 75.709 94.637 113.564 132.492 151.419 170.346 FEB 7 2007 14:00:06 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.106766 SMX =170.346 1 MN MX 0 21.59343.185 64.77886.37 107.963129.555 151.148172.74 194.333 FEB 7 2007 20:10:29 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.120869 SMX =194.333
Figure 7. Distribution of stresses in all locations with oblique loads(outer cortical : 0.5mm).
1 MN MX 0 2.178 4.355 6.533 8.71 10.888 13.066 15.243 17.421 19.598 FEB 8 2007 20:48:48 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.011989 SMX =19.598 1 MN MX 0 1.953 3.906 5.858 7.811 9.764 11.717 13.67 15.623 17.575 FEB 8 2007 21:39:49 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.010889 SMX =17.575 1 MN MX 0 1.94 3 3 .886 5.829 7.772 9.715 11 .658 13.601 15.544 17.4 87 FEB 9 2007 23:20:24 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.010972 SMX =17.487 1 MN MX 0 2.2144.428 6.6428.856 11.07113.285 15.49917.713 19.927 FEB 10 2007 12:17:47 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.01402 SMX =19.927 1 MN MX 0 6.55 1 3.1 19.65126.201 32.75 139 .301 45.85252.402 58.9 52 FEB 8 2007 16:19:50 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020205 SMX =58.952 1 MN MX 0 6.48412.968 19.45225.936 32.4238.904 45.38851.872 58.357 FEB 8 2007 16:50:57 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020671 SMX =58.357 1 MN MX 0 6.53313.067 19.626.133 32.66639.2 45.73352.266 58.799 FEB 8 2007 17:23:29 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020477 SMX =58.799 1 MN MX 0 6.48912.979 19.46825.958 32.44738.937 45.42651.916 58.405 FEB 8 2007 18:02:17 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019776 SMX =58.405 1 MN MX 0 3.8457.691 11.53615.381 19.22723.072 26.91830.763 34.608 FEB 9 2007 14:40:56 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.017779 SMX =34.608 1 MN MX 0 3.8327.664 11.49615.328 19.15922.991 26.82330.655 34.487 FEB 9 2007 15:21:16 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.017414 SMX =34.487 1 MN MX 0 3.84 17 .682 11.52315.364 19.20 423 .045 26.88630.727 34.5 68 FEB 9 2007 16:52:37 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016517 SMX =34.568 1 MN MX 0 3.81 97 .637 11.45615.275 19.09 322 .912 26.73130.549 34.3 68 FEB 9 2007 17:54:08 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016579 SMX =34.368 1 MN MX 0 5.34910.698 16.04721.395 26.74432.093 37.44242.791 48.14 FEB 9 2007 16:26:22 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020865 SMX =48.14 1 MN MX 0 5.34110.681 16.02221.362 26.70332.043 37.38442.724 48.065 FEB 9 2007 16:58:21 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019037 SMX =48.065 1 MN MX 0 5.35 61 0.712 16.06921.425 26.78 132 .137 37.49442.85 48.2 06 FEB 9 2007 21:13:36 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019486 SMX =48.206 1 MN MX 0 5.29 41 0.589 15.88321.177 26.47 231 .766 37.0642.355 47.6 49 FEB 9 2007 22:16:21 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.021029 SMX =47.649
Figure 8. Distribution of stresses in all locations with centric vertical loads(outer cortical : 1.0mm).
1 MN MX 0 3.965 7.931 11.896 15.861 19.827 23.792 27.757 31.723 35.688 FEB 7 2007 17:54:30 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.012926 SMX =35.688 1 MN MX 0 3.796 7.591 11.387 15.182 18.978 22.773 26.569 30.364 34.16 FEB 7 2007 18:43:51 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.01319 SMX =34.16 1 MN MX 0 3.4646.928 10.39213.855 17.31920.783 24.24727.711 31.175 FEB 8 2007 16:15:14 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.013513 SMX =31.175 1 MN MX 0 3.5147.029 10.54314.058 17.57221.086 24.60128.115 31.63 FEB 8 2007 17:19:00 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.012482 SMX =31.63 1 MN MX 0 7.04314.085 21.12828.171 35.21342.256 49.29956.342 63.384 FEB 7 2007 15:17:12 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.018911 SMX =63.384 1 MN MX 0 7.05514.11 21.16428.219 35.27442.329 49.38456.438 63.493 FEB 7 2007 15:42:46 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019773 SMX =63.493 1 MN MX 0 6.64913.297 19.94626.594 33.24339.891 46.5453.188 59.837 FEB 7 2007 16:16:48 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.018652 SMX =59.837 1 MN MX 0 7.05814.117 21.17528.233 35.29142.35 49.40856.466 63.524 FEB 7 2007 17:07:47 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.020875 SMX =63.524 1 MN MX 0 4.538 9.076 13.614 18.152 22.689 27.227 31.765 36.303 40.841 FEB 8 2007 00:41:11 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.016453 SMX =40.841 1 MN MX 0 4.154 8.307 12.461 16.614 20.768 24.921 29.075 33.229 37.382 FEB 8 2007 14:32:36 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.01617 SMX =37.382 1 MN MX 0 4.0468.092 12.13816.184 20.23124.277 28.32332.369 36.415 FEB 8 2007 21:11:38 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.017094 SMX =36.415 1 MN MX 0 4.0218.042 12.06316.084 20.10524.126 28.14732.168 36.189 FEB 9 2007 14:11:58 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.018823 SMX =36.189 1 MN MX 0 6.155 12.311 18.466 24.622 30.777 36.933 43.088 49.244 55.399 FEB 8 2007 15:03:52 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019515 SMX =55.399 1 MN MX 0 5.984 11.968 17.951 23.935 29.919 35.903 41.886 47.87 53.854 FEB 8 2007 15:53:46 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.018128 SMX =53.854 1 MN MX 0 5.83811.675 17.51323.351 29.18935.026 40.86446.702 52.54 FEB 9 2007 15:11:58 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019835 SMX =52.54 1 MN MX 0 5.90411.809 17.71323.618 29.52235.427 41.33147.236 53.14 FEB 9 2007 18:42:03 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.019613 SMX =53.14
Figure 9. Distribution of stresses in all locations with lateral vertical loads(outer cortical : 1.0mm).
1 MN MX 0 5.82 11.641 17.46123.282 29.10234.922 40.74346.563 52.383 FEB 13 2007 22:20:58 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.054726 SMX =52.383 1 MN MX 0 8.19416.388 24.58132.775 40.96949.163 57.35665.55 73.744 FEB 13 2007 23:05:24 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.064036 SMX =73.744 1 MN MX 0 11.9 792 3.958 35.93847.917 59.89 671 .875 83.85495.833 107. 813 FEB 13 2007 23:26:08 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.083061 SMX =107.813 1 MN MX 0 15.9 423 1.885 47.82763.77 79.71 295 .655 111.597127.539 143. 482 FEB 14 2007 13:58:44 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.093705 SMX =143.482 1 MN MX 0 13.19326.385 39.57852.77 65.96379.155 92.348105.541 118.733 FEB 9 2007 17:49:51 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.079427 SMX =118.733 1 MN MX 0 15.86731.735 47.60263.47 79.33795.205 111.072126.939 142.807 FEB 9 2007 21:18:53 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.086257 SMX =142.807 1 MN MX 0 19.46938.938 58.40677.875 97.344116.813 136.282155.751 175.219 FEB 9 2007 21:53:38 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.101213 SMX =175.219 1 MN MX 0 22.4 644 4.928 67.39389.857 112.3 2113 4.785 157.249179.714 202. 178 FEB 14 2007 15:00:13 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.110781 SMX =202.178 1 MN MX 0 8.89 17.781 26.67135.561 44.45253.342 62.23271.122 80.013 FEB 13 2007 20:33:36 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.071781 SMX =80.013 1 MN MX 0 9.35 18.699 28.04937.398 46.74856.097 65.44774.796 84.146 FEB 13 2007 21:23:37 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.079677 SMX =84.146 1 MN MX 0 11.6 892 3.378 35.06646.755 58.44 470 .133 81.82193.51 105. 199 FEB 13 2007 20:34:35 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.095991 SMX =105.199 1 MN MX 0 15.3 783 0.755 46.13361.511 76.88 992 .266 107.644123.022 138. 4 FEB 13 2007 21:53:47 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.106323 SMX =138.4 1 MN MX 0 11.23722.474 33.71144.948 56.18567.421 78.65889.895 101.132 FEB 14 2007 00:03:14 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.077814 SMX =101.132 1 MN MX 0 12.52625.053 37.57950.105 62.63275.158 87.684100.211 112.737 FEB 14 2007 14:02:17 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.088783 SMX =112.737 1 MN MX 0 14.7 572 9.515 44.27259.03 73.78 788 .544 103.302118.059 132. 817 FEB 14 2007 16:07:58 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.095356 SMX =132.817 1 MN MX 0 16.9 83 3.96 50.9467.92 84.89 910 1.879 118.859135.839 152. 819 FEB 14 2007 17:20:39 NODAL SOLUTION STEP=1 SUB =1 TIME=1 SEQV (AVG) DMX =.1118 SMX =152.819
Figure 10. Distribution of stresses in all locations with oblique loads(outer cortical : 1.0mm).
국문요약 국문요약 국문요약 국문요약
임플란트
임플란트
임플란트
임플란트 보철물
보철물에서
보철물
보철물
에서
에서
에서 치관
치관
치관
치관 임플란트
임플란트 비에
임플란트
임플란트
비에
비에
비에 따른
따른
따른 안정성에
따른
안정성에
안정성에
안정성에
대한
대한
대한
대한 3
3
3
3
차원
차원 유한요소법적
차원
차원
유한요소법적
유한요소법적
유한요소법적 분석
분석
분석
분석
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기계가공면 임플란트에서 짧은 임플란트(10mm 이하)가 긴 임플란트(10mm 초과)보다 더 높은 실패율을 보였으나 최근에는 표면처리된 짧은 임플란트의 생존률이 긴 임플란트의 생존률과 유사하다는 임상결과가 보고되고 있다. 하지만 짧은 임플란트를 이용한 수복치료를 계획함에 있어 임플란트의 길이 뿐만 아니라 치관의 길이도 고려해야만 한다. 치관의 길이가 길고 치관-임플란트비가 불리할 경우에는 같은 측방력이 가해지더라도 더 큰 moment 를 유발하게 되어 임플란트의 예후가 나쁘게 된다. 그래서 짧은 임플란트의 예후를 예측함에 있어 임플란트와 보철물의 치관-임플란트비 역시 중요한 요소 중 하나라고 생각된다. 하지만 짧은 임플란트의 길이에 대한 보고들은 있었으나 치관-임플란트비를 구체적으로 고려한 연구는 미미한 상황이다. 이 연구는 여러 다른 골질에서 치관-임플란트비에 따라 임플란트의 안정성에 대해 3 차원 유한요소법을 이용하여 분석하였다. 상악피질골이 0.5mm 와 1.0mm 인 상악골 모델에서 해면골이 충분한 군, 해면골이 부족한 군, 골이식술을 시행한 군에서 골이식후의 골질에 따라 양호한 군과 양호하지 않은 4 가지
군으로 나누어 중심와에 수직으로 200N 의 힘과 구개측교두에 수직으로 200N 의 힘, 그리고 구개측 교두에 사선으로 200N 의 힘을 가하였다. 중심와와 구개측 교두에 수직으로 힘을 가했을 경우에는 치관-임플란트비에 따라 응력의 차이가 없었다. 구개측 교두에 사선으로 힘을 가했을 경우 치관-임플란트비에 비례하여 응력이 증가하는 것을 알수 있었다. 상악피질골이 0.5 인 모델에서 해면골이 충분한 군, 해면골이 부족한 군과 골이식한 이식골의 골질이 좋은 군에서는 각 치관-임플란트비가 0.5 증가함에 따라 약 40MPa 의 응력이 증가하였으며 이식골의 골질이 나쁜 군에서는 각 치관-임플란트비가 0.5 증가함에 따라 약 25MPa 의 응력이 증가하였다. 결론적으로 중심와와 구개측교두에 수직으로 힘을 가할 경우에는 치관-임플란트비에 따라 응력의 증가가 나타나지 않았으나 구개측교두에 사선으로 힘을 가할 경우에는 치관 임플란트비에 따라 응력의 증가가 정비례 관계를 나타냈으며 임플란트 주변골에서의 최고 응력은 임플란트목 주위의 구개측 피질골에서 나타났다. 핵심되는 핵심되는 핵심되는 핵심되는 말말말말: 치관-임플란트비, 유한요소분석법, 임플란트 고정성보철물,
