Figure 12. Equivalent stresses at (a) the neck and (b) the tip of the implant.
Figure 12. Equivalent stresses at (a) the neck and (b) the tip of the implant.
Figure 11. The distribution of equivalent stress (MPa) around the first molar.
Figure 11. The distribution of equivalent stress (MPa) around the first molar.
Figure 10. Displacement in the inferior-superior direction (z-axis). (a) The contact model and (b) the fixation model.
Figure 10. Displacement in the inferior-superior direction (z-axis). (a) The contact model and (b) the fixation model.
Figure 9. Displacement in the mesiodistal direction (y-axis). (a) The contact model and (b) the fixation model.
Figure 9. Displacement in the mesiodistal direction (y-axis). (a) The contact model and (b) the fixation model.
Figure 8. Displacement in the buccolingual direction (x-axis). (a) The contact model and (b) the fixation model.
Figure 8. Displacement in the buccolingual direction (x-axis). (a) The contact model and (b) the fixation model.
Figure 7. The displacement of the three implants. (M) Mesial side, (D) Distal side, (B) Buccal side, and (L) Lingual side are shown.
Figure 7. The displacement of the three implants. (M) Mesial side, (D) Distal side, (B) Buccal side, and (L) Lingual side are shown.
Figure 6. Implant displacement under loading conditions.
Figure 6. Implant displacement under loading conditions.
Figure 5. An FEA model. (a) Buccal loading, (b) central loading, and (c) lingual loading are shown.
Figure 5. An FEA model. (a) Buccal loading, (b) central loading, and (c) lingual loading are shown.
Figure 4. An experimental model loading test.
Figure 4. An experimental model loading test.
Figure 3. An experimental model. (a) Buccal loading, (b) central loading, and (c) lingual loading are shown.
Figure 3. An experimental model. (a) Buccal loading, (b) central loading, and (c) lingual loading are shown.
Figure 2. Three implants were embedded in an artificial mandible.
Figure 2. Three implants were embedded in an artificial mandible.
Figure 1. An artificial mandible.
Figure 1. An artificial mandible.
Model
Loading points
Buccal loading
Central loading
Lingual loading
Average
The neck of the implant
Contact model
No. 34
9.62
...
Source
Sum of squares
df
Mean squared
F
value
p
value
The neck of the implant
A: Boundary conditions
64.725
1
...
Source
Sum of squares
df
Mean squared
F
value
p
value
Contact model
A: Observed area
22.324
1
22.324
...
Source
Sum of squares
df
Mean squared
F
value
p
value
Contact model
A: Observed area
116.630
1
116.63...
Source
Sum of squares
df
Mean squared
F
value
p
value
Contact model
A: Observed area
16.346
1
16.346
...
Model
Loading
Average
Buccal loading
Central loading
Lingual loading
Experimental model
2.49
4.76
4.90
4.05
...
Material
Young’s modulus (MPa)
Poisson ratio
Artificial cancellous bone
628
0.3
Artificial cortical bone
1,373
...
Omori, M., Sato, Y., Kitagawa, N. et al. A biomechanical investigation of mandibular molar implants: reproducibility and validity of a finite element analysis model.
Int J Implant Dent 1, 10 (2015). https://doi.org/10.1186/s40729-015-0011-5
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Received: 07 January 2015
Accepted: 24 March 2015
Published: 28 April 2015
DOI: https://doi.org/10.1186/s40729-015-...
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and in...
Miyuki Omori, Yuji Sato, Noboru Kitagawa, Yuta Shimura and Manabu Ito declare that they have no competing interests.
MO drafted the manuscript. YS contributed advice regarding the manuscript. All authors have read and approved the final manuscript.
Department of Geriatric Dentistry, Showa University, School of Dentistry, 2-1-1 Kitasenzoku, Ota-ku, Tokyo, 145-8515, Japan
Miyuki Omori, Yuji Sato, Noboru Kitagawa, Yuta Shimura & Manabu Ito
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The authors would like to express their deep appreciation to the teaching staff of the Geriatric Dentistry course at Showa University Dental Hospital for their help and cooperation. This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology (Showa University Grant-in-Aid for Scientific Research (C)) (Grant Number 2546...
Tada S, Stegaroiu R, Kitamura E, Miyakawa O, Kusakari H. Influence of implant design and bone quality on stress/strain distribution in bone around implants: a 3-dimensional finite element analysis. Int J Oral Maxillofac Implants. 2003;18:357–68.
Sevimay M, Turhan F, Kilicarslan MA, Eskitascioglu G. Three-dimensional finite element analysis of the effect of different bone quality on stress distr...
Matsunaga S, Ide Y. Morphological characteristics of peri-implant trabecular bone using μ-CT and its mechanical evaluation. BONE. 2009;23:289–92 [in Japanese].
Yokoyama M. Modeling techniques and stress analysis in finite element methods. Tokyo: Yokendo; 2007. p. 1–22 [in Japanese].
Sato Y, Shindoi N, Hosokawa R, Tsuga K, Akagawa Y. A biomechanical effect of wide implant placement and offse...
Morita Y, Qian L, Todo M, Matsushita Y, Arakawa K, Koyano K. Stress and strain distribution analyses of porcine mandibular periodontium by experimental mechanics and finite element analysis. Jpn J Clin Biomech. 2009;30:7–13 [in Japanese].
Taira S. Modern material mechanics. Tokyo: Ohmsha; 2011. p. 235–8 [in Japanese].
Morita Y. Experimental study on displacement and strain distributions arou...
Frost HM. Wolff’s Law and bone’s structural adaptations to mechanical usage: an overview for clinicians. Angle Orthod. 1994;64:175–88.
Duyck J, Rønold HJ, Van Oosterwyck H, Naert I, Vander Sloten J, Ellingsen JE. The influence of static and dynamic loading on marginal bone reactions around osseointegrated implants: an animal experimental study. Clin Oral Implants Res. 2001;12:207–18.
Qu...
finite element analysis
computed tomography
coefficient of variation
computer-aided design/computer-aided manufacturing
analysis of variance
With the objective of verifying the reproducibility and validity of three-dimensional finite element models, we fabricated finite element models and multiple models in which implants were embedded in artificial mandibles and compared implant displacements under various loading conditions; the results obtained produced the following conclusions:
The CVs as calculated from the amount of displacemen...
The equivalent stress values of the contact model were higher at the implant neck than the tip, and the stress generation range was also broader. However, in the fixation model, the implant neck and tip had substantially equivalent values and the stress generation range was also narrower than that of the contact model. This shows that under immediate loading conditions, there is a high likelihood ...
It has been reported that when micromovement of an implant occurs, an ingrowth of soft tissue occurs after the implant is embedded; therefore, it is difficult to achieve osseointegration [32-34]. Brunski et al. [35] reported that when immediate loading or early loading is carried out, micromovements of the implant should be controlled to 100 μm or less and excessive movement of the implant not o...
In the experimental and contact models, the absolute values of displacement under loading were different, but aspects of the displacement under loading conditions caused by differences in the loading points were similar and showed similar tendencies. The correlation coefficient of the two was 0.925, representing a significant and strong correlation (p
In the experimental model, an implant cavity 3.0 mm in diameter was formed prior to embedding an implant 3.75 mm in diameter. In theory, the threads were completely mechanically fitted to the artificial mandibular bone. It does not osseointegrate, but does represent the circumstances of immediate loading in a state of full contact with the bone. The contact model reproduced the state of contact ...
When a three-dimensional FEA is used to analyze the mechanics of peri-implant bone, it is ideal to construct an FEA model that approximates the material properties and structures of an actual mandible. Moreover, the results should be compared with the behavior of an implant in an actual mandible. However, in an actual oral cavity, individual differences exist resulting from bone morphology and phy...
Central loading resulted in the lowest equivalent stress value, while buccal and lingual loading showed substantially similar values (Figure 12b). In the bone surrounding the implant tip, the loading point was a significant factor for the equivalent stress value (p
At all three loading sites, no. 36 had the greatest displacement; the more mesial the implant, the less the displacement, and the distal portions showed a sinking displacement (Figure 10). Central loading resulted in the least displacement; buccal and lingual loading showed substantially similar displacements. Compared with the contact model, the fixation model demonstrated less displacement, but...
Figure 6 and Table 2 show the results for implant displacement under 100 N of vertical loading at each loading point and in each model.
The implant displacement under loading conditions in the experimental model and the two FEA models showed a tendency to exhibit the smallest values under central loading; substantially similar values were exhibited in buccal and lingual loading. Buccal loading...
Regarding displacement under loading, a one-way analysis of variance (ANOVA) was used to investigate statistically significant differences between the loading sites. A three-way ANOVA was used to investigate statistically significant differences in three-dimensional implant displacements under loading conditions. The assessment site, dental formula, and loading point were used as intra-subject par...
Implant displacement measurements under loading conditions were measured using an Instron-type universal testing machine (Instron‐5500R®, Instron Japan, Kanagawa, Japan) for the experimental model. The experimental models were placed on the worktable of an Instron-type universal testing machine, and compression tests were performed using a conical jig. A vertical load was applied at a rate of 0...
The experimental models were fixed in a micro-CT scanner (inspeXio SMX-90CT, SHIMADZU, Kyoto, Japan) and scanned under the following imaging conditions: tube voltage, 90 kV; tube current, 109 nA; and slice thickness, 100 μm. FEA software (Mechanical Finder®, Research Center of Computational Mechanics, Tokyo, Japan) was used to construct three-dimensional FEA models from the resulting computed...
An artificial mandibular bone (P9-X.1135, Nissin Dental Products, Kyoto, Japan) with free-end edentulism of the left mandibular first premolar (no. 34), second premolar (no. 35), and first molar (no. 36) was used (Figure 1). The model is composed of a two-layer structure of artificial cortical bone (urethane resin) and artificial cancellous bone (urethane resin foam).
Using the anatomical crown ...
With the purpose of verifying the reproducibility and validity of a three-dimensional finite element model, the displacements of implants embedded in an experimental model and in three-dimensional FEA models constructed from the experimental model were compared under various loading conditions.
Bone remodeling to maintain osseointegration between bone and implant is absolutely essential to ensure favorable results and long-term stability in implant treatment [1,2]. Bone remodeling requires that various stresses generated around the bone caused by the occlusal load applied to the implant be within an appropriate range. Concentrations of stress at the bone-implant interface, which are caus...
Three-dimensional finite element analysis (FEA) is effective in analyzing stress distributions around dental implants. However, FEA of living tissue involves many conditions, and the structures and behaviors are complex; thus, it is difficult to ensure the validity of the results. To verify reproducibility and validity, we embedded implants in experimental models and constructed FEA models; implan...
Fig. 15. Load supporting area in the superstructures
Fig. 15. Load supporting area in the superstructures
Fig. 14. The distribution of equivalent stress around the no. 36 implant in the finite element analysis (FEA) models
Fig. 14. The distribution of equivalent stress around the no. 36 implant in the finite element analysis (FEA) models
Fig. 13. The distribution of equivalent stress around the peri-implant bone in the finite element analysis (FEA) models
Fig. 13. The distribution of equivalent stress around the peri-implant bone in the finite element analysis (FEA) models
Fig. 12. The strain around the no. 36 implant in the finite element analysis (FEA) models
Fig. 12. The strain around the no. 36 implant in the finite element analysis (FEA) models
Fig. 11. The strain around the no. 36 implant in the experimental models
Fig. 11. The strain around the no. 36 implant in the experimental models
Fig. 10. The displacement of the three implants
Fig. 10. The displacement of the three implants
Fig. 9. The displacement of the implants under loading in finite element analysis (FEA) models
Fig. 9. The displacement of the implants under loading in finite element analysis (FEA) models
Fig. 8. The displacement of the implants under loading in experimental models
Fig. 8. The displacement of the implants under loading in experimental models
Fig. 7. A finite element analysis (FEA) model. (a) Buccal load, (b) central load, and (c) lingual load
Fig. 7. A finite element analysis (FEA) model. (a) Buccal load, (b) central load, and (c) lingual load
Fig. 6. Loading test in the experimental model
Fig. 6. Loading test in the experimental model
Fig. 5. Application of strain gauges
Fig. 5. Application of strain gauges
Fig. 4. Experimental model. (a) Buccal load, (b) central load, and (c) lingual load
Fig. 4. Experimental model. (a) Buccal load, (b) central load, and (c) lingual load
Fig. 3. Three different models with different placements
Fig. 3. Three different models with different placements
Models
Mean difference
P value
Straight
B-offset
−58.94
...
Models
Mean difference
P value
Straight
B-offset
−402.94
...
Models
Loading
Strain (με)
Strain M
Strain B
Strain D
...
Models
Mean difference
P value
Straight
B-offset
−25.14
...
Models
Mean difference
P value
Straight
B-offset
1524.82
...
Models
Loading
Strain (με)
Strain M
Strain B
Strain D
...
Models
Displacement (μm)
Buccal loading
Central loading
Lingual loading
Buccal offse...
Models
Displacement (μm)
Buccal loading
Central loading
Lingual loading
Buccal offse...
Material
Young’s modulus (MPa)
Poisson’s ratio
Artificial cancellous bone
6.29
0.3
Artificial cortical bone
13.73
0.3
Implant and superstructure
108,000
0.3
Table 1 Mechanical properties of materials used in the FEA models
Shimura, Y., Sato, Y., Kitagawa, N. et al. Biomechanical effects of offset placement of dental implants in the edentulous posterior mandible. Int J Implant Dent 2, 17 (2016). https://doi.org/10.1186/s40729-016-0050-6
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Received: 18 January 2016
Accepted: 13 June 2016
Published: 17 June 2016
DOI: https://doi.org/10.1186/s40729-016-0050-6
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were m...
Yuta Shimura, Yuji Sato, Noboru Kitagawa, and Miyuki Omori declare that they have no competing interests.
YS drafted the manuscript. YS, NK, and MO contributed advice for the manuscript. All authors read and approved the final manuscript.
Department of Geriatric Dentistry, Showa University, 2-1-1 Kitasenzoku, Ota-ku, Tokyo, 145-8515, Japan
Yuta Shimura, Yuji Sato, Noboru Kitagawa & Miyuki Omori
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We are sincerely grateful for the assistance we received from the teaching staff of the Geriatric Dentistry course at Showa University Dental Hospital; Professor Takashi Miyazaki and the late Akihiro Fujishima of the Department of Conservative Dentistry, Division of Oral Biomaterials and Engineering; Professor Masanori Nakamura of the Department of Oral Anatomy and Developmental Biology; and Profe...
Yoshino A. Effects of ratio of superstructure length to fixture length on the strain of the bone surfaces surrounding the implant. J Jpn Soc Oral Implantol. 2001;14:398–413. in Japanese.
Rangert B, Jemt T, Jörneus L. Forces and moments on Branemark implants. Int J Oral Maxillofac Implants. 1989;4:241–7.
Sato Y. Discussion of offset arrangement in implants. Quintessence Dent Implantol. 2000;...
Nishioka RS, de Vasconcellos LG, de Melo Nishioka LN. External hexagon and internal hexagon in straight and offset implant placement: strain gauge analysis. Implant Dent. 2009;18:512–20.
Nishioka RS, de Vasconcellos LG, de Melo Nishioka GN. Comparative strain gauge analysis of external and internal hexagon, Morse taper, and influence of straight and offset implant configuration. Implant Dent. 2...
Frost HM. Wolff’s Law and bone’s structural adaptations to mechanical usage: an overview for clinicians. Angle Orthod. 1994;64:175–88.
Duyck J, Rønold HJ, Van Oosterwyck H, Naert I, Vander Sloten J, Ellingsen JE. The influence of static and dynamic loading on marginal bone reactions around osseointegrated implants: an animal experimental study. Clin Oral Implants Res. 2001;12:207–18.
Qu...
In the present study, which aimed to verify the biomechanical effects of offset placement on peri-implant bone, we created multiple finite element models and models where implants were actually placed. We compared the compressed displacement as well as the strain and stress distribution in the peri-implant bone between both kinds of models, and the results can be summarized as follows:
Central lo...
Concentration of stress in the loading-side peri-implant bone was observed in all placements and for both the experimental and the FEA models. Considerable stress was also found to be concentrated in the no. 36 peri-implant bone in buccal loading with buccal offset and lingual loading with lingual offset. Similar to the strain results, stress was observed in a large range under conditions where th...
Similar trends were observed in the direction and magnitude of displacement between placements. Buccal loading exhibited considerable motion towards the buccal rotation/tilting of the implant bodies, and lingual loading exhibited little motion towards lingual displacement. This corresponds to the fact that there was more compressed displacement during buccal loading than during lingual loading.
I...
Moreover, considering the possibility of error while using an implant placement guide, we created many FEA models for each placement to compare the accuracy between the same placement models used with different FEA models.
Most studies verifying the usefulness of offset placement used a single technique for analysis [8–19]. Therefore, the results regarding the usefulness of offset placement var...
Reported studies verifying the effects of offset placement include ones where implant bodies were embedded in rectangular experimental models [11–14], ones where rectangular bone models were constructed with FEA models [15, 16], and ones where FEA models were constructed from CT data on human mandibles [17, 18]. The artificial mandible models used in the present study were type II in the Lekholm...
Figure 11 and Table 4 show the strain, by loading site, in the implant part corresponding to the first molar in the experimental models during the application of a 100-N vertical load.
Considerable compressive strain was observed with the load-side strain gauges in all placements, and similar trends were observed between placements. As much as about 4500 με of compressive strain was observed...
Figures 8 and 9 and Tables 2 and 3 show the results for the compressed displacement of the implants, by loading site, during the application of a 100-N vertical load in each of the models.
In all placements, the compressed displacement in the experimental models and FEA models was greatest with buccal loading and smallest with central loading at the three loading points. For both the experiment...
The places on the experimental models where the strain gauges were applied were represented as coordinate points on the FEA models, and the strain in the FEA models was calculated by dividing the change in length between before and after loading by the length of the strain gauges.
An equivalent stress occurring in the peri-implant bone during loading was observed and assessed in a buccolingual cr...
Implant displacement under loading conditions was measured using an Instron-type universal testing machine (Instron-5500R®, Instron Japan, Kanagawa, Japan) for the experimental model. The experimental models were placed on the worktable of an Instron-type universal testing machine, and compression tests were performed using a conical jig. A vertical load was applied at a rate of 0.5 mm/s on the ...
Four two-wire strain gauges (KFR-02N-120-C1-11, Kyowa Electronic Instruments, Tokyo, Japan) were applied to the no. 36 peri-implant bone surface [21]. The surface of the measurement site was polished with no. 320 sandpaper and then wiped clean with acetone, following which they were adhered with a special adhesive (CC-33A, Kyowa Electronic Instruments, Tokyo, Japan). The strain gauges were applied...
An artificial mandibular bone (P9-X.1135, Nissin Dental Products, Kyoto, Japan) with free-end edentulism of the left mandibular first premolar (no. 34), second premolar (no. 35), and first molar (no. 36) was used (Fig. 1). The model was composed of a two-layer structure of artificial cortical bone (urethane resin) and artificial cancellous bone (urethane resin foam).
Using the anatomical crown w...
Bone remodeling to maintain osseointegration between the bone and implant is absolutely essential to ensure favorable results and long-term stability in implant treatment [1, 2]. Bone remodeling requires that various stresses generated around the bone caused by the occlusal load applied to the implant be within an appropriate range. The concentration of stress at the bone-implant interface, caused...
Offset placement may not necessarily be more biomechanically effective than straight placement in edentulous posterior mandibles.
Proper implant placement is very important for long-term implant stability. Recently, numerous biomechanical studies have been conducted to clarify the relationship between implant placement and peri-implant stress. The placement of multiple implants in the edentulous posterior mandible has been studied by geometric analysis, three-dimensional finite element analysis (FEA), model experimentation, ...
Models
Mean difference
P value
Straight
B-offset
−58.94
0.855
Straight
L-offset
270.67
0.061
B-offset
L-offset
329.61
0.020
Models
Mean difference
P value
Straight
B-offset
−402.94
0.007
Straight
L-offset
−323.79
0.029
B-offset
L-offset
79.16
0.772
Table 7 Means and standard deviations (SD) of strain around the no. 36 implant (με) in the finite element analysis (FEA) models
Models
Loading
Strain (με)
Strain M
Strain B
Strain D
Strain L
Buccal offset
Buccal loading
−222.34 ± 158.56
−934.84 ± 76.82
252.11 ± 103.72
−98.32 95.94
Central loading
−336.26 ± 94.27
−477.17 ±...
Table 6 Tukey’s test for strain L in the experimental models
Models
Mean difference
P value
Straight
B-offset
−25.14
0.999
Straight
L-offset
168.04
0.948
B-offset
L-offset
193.18
0.932
Table 5 Tukey’s test for strain B in the experimental models
Models
Mean difference
P value
Straight
B-offset
1524.82
0.044
Straight
L-offset
−503.40
0.670
B-offset
L-offset
−2028.22
0.007
Table 4 Means and standard deviations (SD) of strain around the no. 36 implant (με) in the experimental models
Models
Loading
Strain (με)
Strain M
Strain B
Strain D
Strain L
Buccal offset
Buccal loading
−599.33 ± 595.46
−4507.35 ± 1192.62
1164.77 ± 169.94
−148.09 ± 174.19
Central loading
−697.29 ± 651.92
−2526.69 ± 5...
Models
Displacement (μm)
Buccal loading
Central loading
Lingual loading
Buccal offset
72.24 ± 1.43
28.24 ± 1.86
28.02 ± 1.41
Straight
68.49 ± 5.24
31.43 ± 1.23
40.18 ± 1.29
Lingual offset
49.63 ± 2.03
26.39 ± 0.37
38.44 ± 1.46
Table 2 Means and standard deviations (SD) of displacement of the implants (μm) under loading in experimental models
Models
Displacement (μm)
Buccal loading
Central loading
Lingual loading
Buccal offset
54.60 ± 8.53
37.39 ± 5.53
40.22 ± 4.24
Straight
80.66 ± 7.47
52.92 ± 1.07
63.03 ± 3.69
Lingual offset
53.11 ± 4.35
40....
Table 1 Mechanical properties of materials used in the FEA models
Material
Young’s modulus (MPa)
Poisson’s ratio
Artificial cancellous bone
6.29
0.3
Artificial cortical bone
13.73
0.3
Implant and superstructure
108,000
0.3
Figure 15. Load supporting area in the superstructures
Figure 14. The distribution of equivalent stress around the no. 36 implant in the finite element analysis (FEA) models
Figure 13. The distribution of equivalent stress around the peri-implant bone in the finite element analysis (FEA) models
Figure 12. The strain around the no. 36 implant in the finite element analysis (FEA) models
Figure 11. The strain around the no. 36 implant in the experimental models
Figure 9. The displacement of the implants under loading in finite element analysis (FEA) models
Figure 8. The displacement of the implants under loading in experimental models
Figure 7. A finite element analysis (FEA) model. (a) Buccal load, (b) central load, and (c) lingual load
Figure 7. A finite element analysis (FEA) model. (a) Buccal load, (b) central load, and (c) lingual load
Figure 6. Loading test in the experimental model
Figure 5. Application of strain gauges
Figure 4. Experimental model. (a) Buccal load, (b) central load, and (c) lingual load
Figure 3. Three different models with different placements
Figure 2. Three implants were embedded in an artificial mandible
Figure 1. An artificial mandible
References
Frost HM. Wolff’s Law and bone’s structural adaptations to mechanical usage: an overview for clinicians. Angle Orthod. 1994;64:175–88.
Duyck J, Rønold HJ, Van Oosterwyck H, Naert I, Vander Sloten J, Ellingsen JE. The influence of static and dynamic loading on marginal bone reactions around osseointegrated implants: an animal experimental study. Clin Oral Implants Res. 200...
In addition, there was not a significantly less strain site by offset placement. Anitua et al. have reported that offset placement did not affect marginal bone loss around the implant in the oral cavity of the living body. Overloading of the peri-implant bone has been reported to result in bone resorption, and the concentration of considerable stress in the load-side peri-implant bone observ...
Thus, compressed displacement exhibited the same trend in the experimental models and FEA models. The results of both models may be reliable. When the effects of offset placement are considered, there is the concept of the load-supporting area (Fig. 15) put forth by Sato. The load-supporting area is the area surrounded by the lines connecting the implant peripheries, and if a loading point falls w...
In previous studies verifying the usefulness of offset placement, one set of FEA models was created and analyzed by changing the conditions or settings. Few studies used different FEA models with the same placement models. In the present study, we carried out the same experiments with both the models to verify the validity of each analysis.
Moreover, considering the possibility of error while usi...
Strain in the FEA models also exhibited considerable compressive strain on the loading side, similar to the experimental models. In terms of quantitative data for comparison with the experimental models, the length of the places where the strain gauges were applied was measured on the FEA models and the strain was calculated from the length before and after loading and compared with the expe...
Discussion
Experimental models
Reported studies verifying the effects of offset placement include ones where implant bodies were embedded in rectangular experimental models, ones where rectangular bone models were constructed with FEA models, and ones where FEA models were constructed from CT data on human mandibles. The artificial mandible models used in the present study were type II in the ...
Strain on the peri-implant bone
Strain in the experimental models
Figure 11 and Table 4 show the strain, by loading site, in the implant part corresponding to the first molar in the experimental models during the application of a 100-N vertical load.
Considerable compressive strain was observed with the load-side strain gauges in all placements, and similar trends were observed between pl...
A strain gauge (2630-100, Instron Japan, Kanagawa, Japan) was attached between the worktable and jig, and the change in the distance between the worktable and jig was measured under the assumption that it would be the same as the implant displacements under loading conditions (Fig. 6). Measurements were taken five times at each loading site, and the mean of the five measurements was considered the...
FEA software (Mechanical Finder®, Research Center of Computational Mechanics, Tokyo, Japan) was used to construct three-dimensional FEA models from the resulting CT data. The mesh was constructed of tetrahedral elements, and the total numbers of nodes and elements were approximately 260,000 and 1,400,000, respectively. FEA models were prepared with appropriate physical properties (Table 1) determ...
Preparation of the superstructure
Using the anatomical crown width as a reference, it was determined that the occlusal surface view of the superstructure would be trapezoidal with a 7-mm buccolingual width in the mesial first premolar section, a 10-mm buccolingual width in the distal first molar section, and a 26-mm mesiodistal width (Fig. 4). The vertical dimension was 8 mm; the upper 4 mm was t...
Compressed displacement
Figures 8 and 9 and Tables 2 and 3 show the results for the compressed displacement of the implants, by loading site, during the application of a 100-N vertical load in each of the models.
In all placements, the compressed displacement in the experimental models and FEA models was greatest with buccal loading and smallest with central loading at the three loading points....
Methods
Fabrication of the experimental model
Artificial mandibular bone
An artificial mandibular bone (P9-X.1135, Nissin Dental Products, Kyoto, Japan) with free-end edentulism of the left mandibular first premolar (no. 34), second premolar (no. 35), and first molar (no. 36) was used (Fig. 1). The model was composed of a two-layer structure of artificial cortical bone (urethane resin) and ar...
Background
Bone remodeling to maintain osseointegration between the bone and implant is absolutely essential to ensure favorable results and long-term stability in implant treatment. Bone remodeling requires that various stresses generated around the bone caused by the occlusal load applied to the implant be within an appropriate range. The concentration of stress at the bone-implant interface,...
Biomechanical effects of offset placement of dental implants in the edentulous posterior mandible
Abstract
Background
Proper implant placement is very important for long-term implant stability. Recently, numerous biomechanical studies have been conducted to clarify the relationship between implant placement and peri-implant stress. The placement of multiple implants in the edentulous posterio...