Biomechanical Effects of Various Bone-Implant Interfaces ...downloads.hindawi.com/journals/jhe/2017/7495606.pdf · Research Article Biomechanical Effects of Various Bone-Implant Interfaces

Research ArticleBiomechanical Effects of Various Bone-Implant Interfaces on theStability of Orthodontic Miniscrews: A Finite Element Study

Fabing Tan,1 Chao Wang,1,2 Chongshi Yang,3 Yuanding Huang,1,2 and Yubo Fan1

1College of Stomatology, Chongqing Medical University, Chongqing, China2Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences, Chongqing, China3Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing, China

Correspondence should be addressed to Chao Wang; [email protected]

Received 9 February 2017; Revised 26 April 2017; Accepted 3 May 2017; Published 19 June 2017

Academic Editor: Wei Yao

Copyright © 2017 Chao Wang et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction. Osseointegration is required for prosthetic implant, but the various bone-implant interfaces of orthodonticminiscrews would be a great interest for the orthodontist. There is no clear consensus regarding the minimum amount of bone-implant osseointegration required for a stable miniscrew. The objective of this study was to investigate the influence of differentbone-implant interfaces on the miniscrew and its surrounding tissue. Methods. Using finite element analysis, an advancedapproach representing the bone-implant interface is adopted herein, and different degrees of bone-implant osseointegrationwere implemented in the FE models. A total of 26 different FE analyses were performed. The stress/strain patterns werecalculated and compared, and the displacement of miniscrews was also evaluated. Results. The stress/strain distributions arechanging with the various bone-implant interfaces. In the scenario of 0% osseointegration, a rather homogeneous distributionwas predicted. After 15% osseointegration, the stress/strains were gradually concentrated on the cortical bone region. Theminiscrew experienced the largest displacement under the no osseointegra condition. The maximum displacement decreasessharply from 0% to 3% and tends to become stable. Conclusion. From a biomechanical perspective, it can be suggested thatorthodontic loading could be applied on miniscrews after about 15% osseointegration without any loss of stability.

1. Introduction

Miniscrew has been extensively applied in orthodontic treat-ment as a temporary anchorage device because of its ease ofplacement, low cost, minimal anatomic limitations, andenhanced patient comfort. The existing evidence suggests asuccess rate of more than 80% for miniscrews [1]. Likewise,Albogha and Takahashi have stated a success rate rangingfrom 77.7% to 93.43% in their study [2]. However, the failureof miniscrew may have dramatic consequences and remaindifficult to be anticipated by orthodontists [3]. Since thefailure of miniscrew necessitates additional surgical inter-ventions and prolonged treatment time, investigating themechanical stability of miniscrew becomes imperative.

The biomechanical properties of bone to implant inter-face are the key determinants for miniscrew stability. Ini-tially, when the miniscrew is placed into bone, the retention

of the implant is provided by mechanical locking. Later, withthe progression of bone formation around the implant,bioactive retention can be achieved via physicochemicalbonding. It is clinically evident that full osseointegration isa prerequisite for successful prosthetic (or dental) implants[4, 5]. Nevertheless, some fibrous tissue formation at thebone-implant interface would be acceptable because ortho-dontic loading has to be applied as early as possible and alsothe miniscrew at the end of treatment must be easily remov-able [3]. That is to say, partial bone-implant osseointegrationof the miniscrew might be permitted for orthodontic treat-ment. Therefore, the effect of the different degrees of bone-implant osseointegration on the stability will be of greatinterest from the orthodontist’s point of view.

The objective of this study was to investigate the influ-ence of the different implant-bone interface conditions onthe biomechanics of an orthodontic miniscrew and its

HindawiJournal of Healthcare EngineeringVolume 2017, Article ID 7495606, 10 pageshttps://doi.org/10.1155/2017/7495606

https://doi.org/10.1155/2017/7495606

surrounding tissue with the use of finite element analysis(FEA). FEA is particularly suitable for a biological structureanalysis as it allows great flexibility in dealing with geometriccomplex domains composed of multiple materials [2, 6–8].In the present study, an advanced approach representingthe bone implant interfaces was adopted wherein [9] differ-ent percentages of bone-implant osseointegration wereimplemented in the FEmodels and the biomechanical behav-ior of miniscrew and the supporting tissue with the variousbone-implant interfaces was predicted and compared.

2. Materials and Methods

The geometry of the partial maxilla, including both premolarand molar, was obtained from the dental hospital, and com-puted tomography images captured at 0.5 mm intervals weredisposed with Mimics software (Materialise NV, Leuven,Belgium) and Geomagic Studio software (Geomagic Com-pany, NC, USA). Maxillary trabecular bone was modeledas a solid structure in the cortical bone with an averagethickness of 2mm based on the CT images. Likewise, theperiodontal ligament (PDL) was modeled based on the exter-nal geometry of teeth roots with a thickness of 0.20mm. Theimplant was structured as a threaded endosseous miniscrew(8mm length, 1.3mm diameter, 0.1mm thread ridge, 60degrees screw top angle, and 0.5mm thread pitch) by usinga commercial CAD software SolidWorks (SolidWorks Corp.,Dassault Systemes, Concord, MA, USA). The miniscrew wasinserted into maxillary bone between the premolar andmolar at a distance of 3mm from the alveolar crest, asshown in Figure 1.

The entiremodel was imported to the finite element pack-age ANSYS Workbench (Swanson Analysis System Co.,Houston, TX, USA). The finite element model was meshedusing 10-node solid tetrahedral elements (Figure 2(a)). Fol-lowing a convergence test [7], 0.5mm was determined to bethe appropriate element mesh size for bone and tooth, andeven a miniature size (0.2mm) was selected to accommodatethe small feature in the model (e.g., PDL andminiscrew). Thedetailed element assignment is listed in Table 1. The contactsamong the tooth, the related bones, tissue, and ligaments aredefined in Table 2.

For the realistic presentation, different amounts of bone-implant osseointegration were implemented, ranging from0% to 100% (Figure 3). In the existing studies, it was foundthat there should be a small gap between the implant andperi-implant bone [9, 10]. To evaluate the effect of differentbone implant interfaces, a simulation method has alreadybeen developed by Lian et al. [9], which was used in thepresent study. Hence, based on the histological image(Figure 2(c)) [11], it can be suggested that 0.1mm (100μm)thick mixed tissue exists around the miniscrew, constitutinga blend of bony tissue and soft tissue to simulate varyingbone-implant contact (Figure 2(b)). An ad hoc APDL(ANSYS Parametric Design Language) routine was devel-oped to set the different bone-implant osseointegration. Asshown in Figure 3, a certain percentage of mixed tissue ele-ments were selected randomly and assigned the propertiesof bony tissue. The remaining elements within the mixed

tissue were designated as soft tissue. In this study, a total of13 different percentages of bone-implant osseointegrationwere considered (0%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%,25%, 50%, 75%, and 100%).

Mesial and superior maxillary bone surfaces were fixed inall directions as the boundary conditions (Figure 1(b)). Toconsider the loading effect of different clinical applications[9, 12], two different kinds of orthodontic load (traction forceand revolving torque) were applied at the head of the screw(Figures 1(c) and 1(d)). The direction of the traction forceapplied was 30 degrees declination to the occlusal plane(Figure 1(c)), and the revolving torque was applied in theclockwise direction (Figure 1(d)).

Fully anisotropic elastic components were used for bothcortical and trabecular bones [13, 14], as listed in Table 3. Anonlinear elastic stress-strain behavior of PDL was employedand inputted into FE models, following the approach pro-posed by Toms et al. [14]. Miniscrew and dentin were consid-ered homogeneous, isotropic, and linearly elastic (Table 4).

3. Results

In the present study, a total of 26 analyses were performed,including the 13 different degrees (from 0% to 100%) ofbone-implant osseointegration models with two differentkinds of orthodontic load applications (traction force andrevolving torque).

The FE simulated results for the force and torque load inthe peri-implant tissue (mixed tissue region) are shown inFigures 4 and 5, respectively. For the ease of observation,equivalent stresses/strains in the cross section of the FEmodels are displayed. As shown in the figures, the stressand strain distributions in the mixed tissue are changing withthe various bone-implant interfaces. Initially, in the scenarioof 0% osseointegration, a rather homogeneous equivalentstress/strain distribution was predicted. And then, remark-able stress/strain concentrations could be seen in the peri-implant tissue with the 1% osseointegration interface. Afterthe 15% osseointegration, the stress and strains were gradu-ally concentrated on the cortical bone region rather than inthe trabecular bone region. It is worth noting that, whateverkind of the orthodontic loads are subjected, there is a signif-icant change in the first 7 degrees (0%~10%), but the varia-tion range reduced obviously after the 15% osseointegration.

Figures 6 and 7 show the equivalent stress and strain onthe surrounding bone under the application of traction forceand revolving torque, respectively. As evident from Figure 6,under the application of traction force, the stress induced inthe cortical bone was much higher as compared to that inthe trabecular bone. With the change in bone-implantinterfaces, the stress distribution gradually concentratedon the bone around the neck of miniscrew. The strain dis-tribution also showed a trend similar to the stress. However,in the initial phase (0%~15%), the maximum strain waslocated in the trabecular bone rather than the cortical bone.Furthermore, the equivalent stress and strain distributionswith revolving torque application are shown in Figure 7.The changing trend of equivalent stress and strain is muchsimilar to that of traction force application. At the beginning

2 Journal of Healthcare Engineering

(0% osseointegration), the stress was longitudinally distrib-uted along the whole miniscrew. With the integration of thebone and implant, the stress was highly concentrated in theneck of the miniscrew. Similarly, the strain distribution wasconcentrated on the trabecular bone initially, which later onshifted towards the neck of the miniscrew with the changein bone-implant osseointegration percentages.

Figure 8 illustrates quantitatively the relationshipbetween the degree of bone-implant osseointegration andbiomechanical characteristics of bone-implant complex.Figures 8(a) and 8(b) represent the change in average equiv-alent stress and strain in the mixed (peri-implant) tissue,respectively. It is evident from Figure 8(a) that the stressincreases progressively before the 10% osseointegration,followed by a slight decrease, and then increases again. Asshown in Figure 8(b), the strain decreases significantly atthe beginning, and then tends towards stability until the100% osseointegration is achieved. From Figures 8(c)and8(d) , it can be seen that the equivalent stress changes withthe increase in the osseointegration degrees in the corticalbone and trabecular bone region, respectively. Besides, ini-tially the stress increases sharply, and then drops downfollowed by a gradual increase again after the 15% osseointe-gration. As shown in Figure 8(d), it can be seen that the graphexhibits similar patterns to those presented in Figure 8(c),but a turning point is not observed at the 15% osseointe-gration in the trabecular bone. Relative to the displace-ment (Figure 8(e)), the miniscrew experienced the largestdisplacement under the condition of no osseointegration(0%). The maximum displacement decreases sharply from

0% to 3% and tends to become stable after completion ofapproximately 3~4% osseointegration.

4. Discussion

In this study, finite element models were generated toinvestigate the effect of different implant-bone interfaceconditions on the mechanical stability of miniscrew. From0% to 100%, 13 different degrees of bone-implant inter-faces were simulated. The stress/strain patterns generatedby the miniscrews at the surrounding tissue were calcu-lated and compared, and the displacement of miniscrewwas also evaluated.

In dental biomechanics, almost all the FE models gener-ated currently simulated different bone to implant interfacesby employing frictional contact analysis [2]. In a typical FEmodel built by Yang and Xiang [15], three different contacttypes were used to represent the integration quality at theimplant-bone interface. The “bonded” type simulates a fullosseointegration; the “no separation” type indicates animperfect osseointegration, and the “frictionless” contactimplies no osseointegration. As a progressive technology ofsimulating partial contact, a random algorithm was devel-oped by Gracco et al. to set a part of the nodes localized atthe bone/implant interface as the tie constraint, and theremaining part of the interface was set as frictional contact[16]. However, although contact analyses with different fric-tional coefficients can be used to assess the biomechanicaleffects of many different implant-bone complex, the specificfrictional coefficients is still difficult to determine by an

(a)

Fixe

d bo

unda

ry

Fixed boundary

(b)

Force

(c)

Torque

(d)

Figure 1: (a) Microimplant. (b) Geometry models with fixed boundary conditions (buccal side). (c) The traction force and (d) revolvingtorque employed during orthodontic loading.

3Journal of Healthcare Engineering

existing biomechanical testing [17]. In order to overcome thelimitations of the existing methodologies, an alternativemethod was proposed by Lian et al. [9]. In this method, anassumption was made that a small part of tissue surroundingthe implant was constituted as a mix of hard and soft tissue.According to the observation of previous histological studies[18, 19], this assumption has been proved to be reasonable.Therefore, considering the progressive change of the

surrounding tissue around the miniscrew, this alternativemethod was advanced from a 2D simulation to 3D, to repro-duce the different bone-implant interfaces in our FE models.

Till date, the minimum level of bone-implant osseoin-tegration for clinical success in orthodontics has not beenclearly described. From the biomechanical viewpoint, theminimumamount of bone-implant osseointegration requiredcan be inferred from our analytical results. For the equivalentstress and strain (Figures 4–7), the implant-bone interfaceconditions significantly affected the stress/strain distributions

Molar premolar

Periodontal ligament(PDL)

Trabecular bone

Cortical bone

(a)

0.1 mm

Mixed tissue

(b)

Implant

Bone

100 �휇m

(c)

Figure 2: (a) Finite element models of cortical bone, trabecular bone, periodontal ligament (PDL), and premolar and molar (palatal side). (b)The 0.1mm (100 μm) thick mixed tissue around microimplant. (c) The histological image showing the bone-implant interface (courtesy ofProfessor Shicheng Wei).

Table 1: The number of nodes and elements of FE model.

Nodes Elements

Cortical bone 150,450 94,395

Trabecular bone 161,301 107,895

Microimplant 7563 4000

PDL 28,913 14,332

Teeth 16,793 9384

Mixed tissue 56,068 29,579

Total 421,088 259,585

Table 2: Contact types set in the FE models.

Contact bodies Contact type

Tooth Tooth Frictionless

Tooth PDL Bonded

PDL Bone Bonded

Microimplant Mixed tissue Bonded

Mixed issue Bone Bonded


on the surrounding tissue when the osseointegration was lessthan 15%. Further analysis (15%~100%) reveals that, eventhough the stress/strain concentration appears around theimplant neck region, the overall changes in the stress/straindistributions from 15% to 100% osseointegration can beneglected.Besides, according to theprogressivebiomechanicalcharacteristics of bone-implant complex (Figure 8), the mini-mum amount of bone-implant osseointegration may varybetween 2% and 10%. Some of the previous findings are alsoin support of our results. Deguchi et al. implied that implantswith as little as 5% bone osseointegration at the bone-implant interface can successfullywithstandorthodontic force[20], and also the study by Woods suggested that 2.2 percentBIC may be sufficient for light force [21]. However, duringthe low degrees of bone-implant osseointegration (0~15%),our results show that the presence of connective tissue(soft tissue) at the implant-bone interface might result inan increase of stress/strain magnitudes in the trabecularbone as compared with full osseointegration conditions.

Because of the occurrence of fibrous tissue, miniscrew can-not be tightly held by alveolar bone, leading to miniscrewinstability. The surrounding trabecular bone might be dam-aged due to the changing mechanical environment inducedby the miniscrew, and excessive implant displacement maycause loosening, dislocation, or even loss of the implant.Therefore, it can be inferred that orthodontic loading canbe applied over the miniscrew after completion of 15%osseointegration without a compromise of stability. That isto say, less than 15% osseointegration might be a risk factorin terms of implant stability, and hence should be avoided.

Now, a critical question arises, that is, what should be thelatency period to achieve the minimum percentage of bone-implant osseointegration during an orthodontic treatment?In reference to previous animal/ histological studies, severalinvestigations have been done on the healing time of ortho-donticminiscrew.However, no studyhas been conducted spe-cifically to solve this problem. Even more, the existing resultsare inconclusive about the proper timing of orthodonticforce application. A histological study done byRamazanzadehet al. concluded that healing time has no significant effecton miniscrew stability, but only a comparison of bone-implant contact between 4 weeks and 8 weeks was madein his study [22]. In an another study by Oltramari-Navarro et al., similar histomorphometric results wereobserved for the immediate and the delayed orthodonticloads groups, but it is important to note that the immediategroup presented higher failure rate (50%) than the delayedgroup [18]. Likewise, the results of an animal study byZhao et al. indicated that early loading may decrease theosseointegration of miniscrews, and the same investigators

Table 3: Anisotropy elastic coefficients for cortical and trabecular bonea.

E1 E2 E3 G12 G13 G23 ν12 ν13 ν23

Cortical boneb 12.5 17.9 26.6 4.5 5.3 7.1 0.18 0.31 0.28

Trabecular bonec 0.21 1.148 1.148 0.068 0.068 0.434 0.055 0.055 0.322abcEi represents Young’s modulus (GPa); Gij represents shear modulus (GPa); νij represents Poisson’s ratio; the 1-direction is radial, the 2-direction is tangential(circumferential), and the 3-direction is axial (longitudinal); the 1-direction is inferosuperior (the axis of transverse isotropy symmetry with the smallest ofYoung’s modulus value), the 2-direction is mediolateral, and the 3-direction is anteroposterior.

0% 1% 2% 3% 4% 5%

So� tissueBony tissue

10% 15% 20% 25% 50% 75% 100%

Figure 3: Different degrees of the bone-implant osseointegration interfaces implemented in the FE models, varying from 0% to 100%.

Table 4: Material elastic modulus parameter employed in the FEmodels.

Elastic modulus(GPa)

Poisson’sratio

References

Tooth 22.0 0.31 Holberg et al., 2013

Microimplant 113.4 0.342 Alrbata et al., 2014

Bony tissue 2.4 0.3 Lian et al., 2010

Soft tissue 0.07 0.3 Lian et al., 2010


Equivalent stress

(MPa)

2.2 700 275 209 136.94 145 60 25 32 40 342317117.73.92.40.960.452.8e‒7

2720149.14.62.91.10.576.3e‒7

2216117.33.72.30.970.401.5e‒6

2418120.14.12.510.514.9e-6

3049

2516115.53.41.40.659.3e‒6

403020136.64.21.70.831.4e‒5

97.173.349.632.916.210.14.052.034.67e‒5

92.43069.4946.54234.10115.6599.78718.9751.96760.000e

14010570.245.945.914.96.243.120.00

18213792.962.131.323.215.27.60.00

46835223815577.148.239.39.640.00

508750

37925116679.849.9200.950.00

1.91.71.51.20.980.740.490.250.0083

(a)

Equivalent strain

4.4 5 3.3 1.9 1.2 0.90 0.3 0.11 0.00 0.066 0.057 0.016 0.00850.00570.00430.00390.0020.00090.00060.00020.00015.7e‒7

0.0110.00810.00550.00380.00180.00110.00040.00027.7e‒7

0.0510.00640.00560.00360.00190.00120.00040.00021.9e‒6

0.0440.0330.0220.0150.00730.00450.00150.00030.9e‒6

0.0540.040.0270.0130.00910.00570.00230.00111.5e‒5

0.0170.0500.0090.0260.0130.00830.00330.00172.3e‒5

0.20.150.10.0670.0340.0210.00850.00457.8e‒5

0.650.490.330.220.110.070.0250.0140.000

0.770.580.390.250.130.000.0320.0160.000

1.30.950.540.430.210.130.0540.0270.000

2.21.71.10.740.370.230.0930.0470.001

3.42.61.71.20.590.460.30.150.00

3.93.432.521.510.510.025

(mm/mm)

0% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%

(b)

Figure 5: Progressive alteration of (a) equivalent stress and (b) strain distributions in peri-implant tissue under the application ofrevolving torque.

(MPa)

Equivalent stress

0.26 64.2 46.3 46 31.6 17 13 11 11 9.18 8.45 7.23 7.153.950.7590.651

0.5420.4340.3250.217

0.1081.83e‒7

3.820.4060.348

0.290.232

0.1470.1160.0581

1.63e‒7

4.490.5280.4530.3770.3020.2260.1510.07541.51e‒

4.880.5740.4920.410.3280.2460.1640.08193.59e‒7

60.570.490.410.320.240.160.0816.6e‒7

5.60.660.570.470.380.28

0.190.0951.6e‒6

70.820.70.590.470.350.230.123.7e‒6

8.90.840.720.60.480.360.240.121e‒5

16.71.781.521.271.010.7610.5070.2541.81e‒5

24.32.592.221.851.481.110.740.371.7e‒5

24.62.892.482.071.651.240.8260.4134.92e‒5

33.93.613.092.582.061.551.030.5100.000

0.190.130.050.040.030.030.020.010.00

(a)

0.52 0.8 0.26 0.15 0.11 0.1 0.041 0.034 0.011 0.0071 0.0037 0.003 0.00090.00080.00030.00018.8e‒57e‒55.3e‒53.5e‒51.8e‒51.2e‒7

0.00210.00120.00030.00020.00020.00010.00015.5e‒51.2e‒7

0.00260.00150.00030.00030.00020.00020.00016.5e‒52.2e‒7

0.005 0.0029 0.00070.00060.00050.00030.00020.00015.6e‒7

0.00780.00450.00120.0010.00080.00060.00040.00021.3e‒6

0.0240.0140.00390.00320.00260.00190.00130.00062.6e‒6

0.0290.0170.00440.00360.00290.00220.00150.00078.6e‒6

0.0730.0420.0120.00970.00780.00590.00390.0023.2e‒5

0.080.0460.0130.0110.00850.00640.00430.00223.4e‒5

0.110.0630.0170.0150.0120.00870.00580.00294e‒5

0.230.210.0320.0270.0210.0160.0110.0057e‒5

0.560.320.0850.0710.0570.0430.0290.0140.000

0.390.250.120.10.080.060.040.020.00

(mm/mm)

0% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%

Equivalent strain

(b)

Figure 4: Progressive alteration of (a) equivalent stress and (b) strain distributions in peri-implant tissue under the application oftraction force.


suggested that a 4-week healing time is recommendedbefore orthodontic loading [23]. Deguchi et al. also con-cluded that a minimal healing period of 3 weeks is requiredfor orthodontic loading [20]. Above all, the existing animal

experiments presented some useful conclusion; however,their results remain limited when it comes to understand-ing the various conditions of bone-implant interfaces play-ing a role in miniscrew stability.

Equivalent stress

0.40.360.310.270.220.180.130.0890.0443.5e‒7

(MPa)

5%

0%

15%

50%

100%

2.41.61.20.80.540.270.170.0680.0343.3e‒7

(MPa)

1.510.780.530.350.180.110.0460.0232.9e‒7

(MPa)

1.61.10.810.540.360.180.110.0430.0222.5e‒7

(MPa)

1.20.820.620.420.280.140.0880.0350.0182.4e‒7

(MPa)

(a)

Equivalent strain

0.000410.000370.000320.000270.000230.000180.000149.1e‒54.6e‒53e‒8

(mm/mm)

0.001

0.000160.000118e‒55.3e‒53.5e‒51.8e‒51.1e‒54.2e‒52.1e‒51.9e‒11

(mm/mm)

0.000117.1e‒55.3e‒53.5e‒52.3e‒51.2e‒57.4e‒63e‒61.5e‒61.6e‒11

(mm/mm)

8.3e‒55.6e‒54.2e‒52.8e‒51.9e‒59.6e‒66e‒62.4e‒61.2e‒61.6e‒11

(mm/mm)

0.00690.00520.00340.00230.00127.2e‒52.9e‒51.4e‒52.1e‒11

(mm/mm)

(b)

Figure 6: Progressive alteration of (a) equivalent stress and (b) strain distributions in the surrounding bone under the application oftraction force.


The research limitations and suggestions for futureresearch should be pointed out. Firstly, additional animalresearch is required to answer the above-mentioned ques-tion. If the exact time for achieving 15% osseointegration of

miniscrew could be confirmed, the appropriate time of min-iscrew loading can be effectively ensured for orthodontists.Secondly, the bone remodeling process was not consideredin the simulation. In fact, the bone remodeling occurs around

Equivalent stress

0%

1.110.880.760.630.50.380.250.131.8e‒7

5%

8.25.54.12.81.80.930.580.230.126.4e‒8

15%

4.83.22.41.61.10.540.330.130.0649.1e‒8

50%

6.24.23.12.11.40.690.430.170.0867.3e‒8

100%

6.14.13.121.40.690.430.170.0868.6e‒8

(a)

0.00140.00930.00070.000470.000310.000169.9e‒54e‒52e‒55.9e‒12

0.000350.000240.000180.000128e‒54e‒52.5e‒51e‒55e‒64.7e‒12

0.000380.000250.000190.000138.5e‒54.3e‒52.7e‒51.1e‒55.6e‒55.8e‒5

0.00270.00240.00210.00180.00150.00120.0080.0050.0031.2e‒1

0.00670.00450.00340.00230.00150.00074 0.000460.000199.3e‒54.2e‒12

Equivalent strain

(b)

Figure 7: Progressive alteration of (a) equivalent stress and (b) strain distributions in the surrounding bone under the application ofrevolving torque.


the implant during the healing period. So the progressiveprocess of bone remodeling should be included in furthersimulation to investigate mechanical stability of orthodonticminiscrew. Finally, the material nonlinear properties of themixed tissue (hard and soft tissue) should be considered inthe FE analysis. Because large deformation can be observedduring this simulation, the incorporation of nonlinear prop-erties can provide more accurate and reliable results.

5. Conclusions

Within the limitation of this study, it can be suggested thatthe orthodontic force can be applied at the miniscrew aftercompletion of approximately 15% osseointegration which isthe more beneficial for the mechanical stability of the minis-crew. Under this condition, the miniscrew can be tightly heldin place by the surrounding tissue and employed as

0.16 1.2

1.11.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.000%

Percentage of osseointegration (%)

Ave

rage

equ

ival

ent s

tres

s und

er th

efo

rce

load

(MPa

)

Ave

rage

equ

ival

ent s

tres

s und

er th

em

omen

t loa

d (M

Pa)

1% 2% 3% 4% 5% 10% 15% 20%

Mixed tissue

25% 50% 75% 100%

(a)

0.081.75

1.50

1.25

1.00

0.75

0.50

0.25

0.00

‒0.25

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0.00

‒0.010% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%


Ave

rage

equi

vale

nt st

rain

und

er th

efo

rce l

oad

(mm

/mm

)

Ave

rage

equi

vale

nt st

rain

und

er th

em

omen

t loa

d (m

m/m

m)

Mixed tissue

(b)

4.012

10

8

6

4

2

0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0


Max

imum

equ

ival

ent s

tres

s und

er th

efo

rce

load

(MPa

)

Max

imum

equ

ival

ent s

tres

s und

er th

em

omen

t loa

d (M

Pa)

Cortical bone

0% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%

(c)

2.0 10

9

8

7

6

5

4

3

2

1

0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0


Max

imum

equ

ival

ent s

tres

s und

er th

efo

rce

load

(MPa

)

Max

imum

equ

ival

ent s

tres

s und

er th

em

omen

t loa

d (M

Pa)

Trabecular bone

0% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%

(d)

Force loadMoment load

0.060.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

0.05

0.04

0.03

0.02

0.01

0.00

‒0.01Max

imum

disp

lace

men

t str

ess u

nder

the

forc

e l o

ad (m

m)

Max

imum

disp

lace

men

t str

ess u

nder

the

mom

ent l

oad

(mm

)

Microimplant

Percentage of osseointegration (%)0% 1% 2% 3% 4% 5% 10% 15% 20% 25% 50% 75% 100%

(e)

Figure 8: Change in biomechanical characteristics of microimplant and supporting oral tissues with the different bone-implant osseointegrationinterfaces. (a) The average equivalent stress in the peri-implant mixed tissue. (b) The average equivalent strain in the peri-implant tissue. (c) Themaximum equivalent stress in cortical bone. (d) Themaximum equivalent stress in trabecular bone. (e) Themaximumdisplacement ofmicroimplant.


orthodontic anchorage without compromising implant sta-bility. For clinical application of the results simulated in ourstudy, a specifically designed study is required to confirmthe appropriate time of orthodontic loading in the future.

Conflicts of Interest

The authors declare that there is no conflict of interestregarding the publication of this paper.

Acknowledgments

The work was supported by the National Natural ScienceFoundation of China (Grant no. 11402042), the MedicalScientific Research Foundation of Health and Family Plan-ning Commission of Chongqing (major project, Grant no.20141012) and the Program for Innovation Team Buildingat Institutions of Higher Education in Chongqing in 2013.Special thanks are to Professor Shicheng Wei of PekingUniversity at Beijing for his assistance during this study.

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Biomechanical Effects of Various Bone-Implant Interfaces ...downloads.hindawi.com/journals/jhe/2017/7495606.pdf · Research Article Biomechanical Effects of Various Bone-Implant Interfaces