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JIOS
10.5005/jp-journals-10021-1085
RESEARCH ARTICLE
Finite Element Analysis of Stress and Strain Distribution in the Bone around the Implants used for Orthodontic Anchorage
Finite Element Analysis of Stress and
Strain Distribution in the Bone around the
Implants used for Orthodontic Anchorage
1
PS Vijayalakshmi, 2AS Veereshi, 3Vijay P Jayade, 4MR Dinesh, 5Mukesh Kumar
ABSTRACT
Biomechanical influences on bone structure play an important role in the longevity of bone around an implant. The quantity and direction of
applied force influence the implant and cause deformation of the bone. FEA was used to analyze the changes in the bone on loading the implant
with orthodontic force in oblique and vertical directions and orthopedic force. The Mini-implants used in the present study efficiently resisted the
oblique loading. But their use, for the purpose of orthopedic loading is questionable. FE models showed the area with the highest stress and
strain to be around the neck of the implant and the surrounding bone at the cervical margin.
Keywords: Finite element analysis, Mini-implant, Stress, Strain, Cortical bone, Trabecular bone.
How to cite this article: Vijayalakshmi PS, Veereshi AS, Jayade VP, Dinesh MR, Kumar M. Finite Element Analysis of Stress and Strain
Distribution in the Bone around the Implants used for Orthodontic Anchorage. J Ind Orthod Soc 2012;46(4):175-182.
INTRODUCTION
Efficient attainment and control of anchorage is fundamental
to successful orthodontic and dentofacial orthopedic
treatment. Adequate anchorage to correct dental or skeletal
malocclusions is often a critical consideration in treatment
planning. Because of anchorage limitations, we may have to
settle for a compromised treatment alternative, or more
complicated treatment alternatives like extraoral traction
devices (which heavily depend on patient’s compliance) or
orthognathic surgery.1 Implants are an excellent alternative to
traditional orthodontic anchorage methodologies, and they are
a necessity when dental elements lack quantity or quality, when
extraoral devices are impractical, or when noncompliance
during treatment is likely.
In the last few years, implants of smaller sizes have been
specially designed for orthodontic anchorage. These miniimplants are small enough for placement at any surface of the
1
Reader, 2Associate Professor, 3Former Professor and Head, 4Professor
and Head, 5Professor
1,4
Department of Orthodontics, DAPM RV Dental College, Bengaluru
Karnataka, India
2,5
Department of Orthodontics, Rungta College of Dental Sciences
Bhilai, Chhattisgarh, India
3
Department of Orthodontics, SDM College of Dental Sciences, Dharwad
Karnataka, India
Corresponding Author: PS Vijayalakshmi, Reader, Department of
Orthodontics, DAPM RV Dental College, Bengaluru, Karnataka, India
e-mail: [email protected]
Received on: 20/12/11
Accepted after Revision: 20/6/12
alveolar process, even in the interdental areas. They are
relatively inexpensive, and techniques for their placement and
retrieval are simple.2 Several researchers have reported studies
related to the use of implants for orthodontic anchorage.3-25
When using any of the load bearing implants in the bone,
the stress and strain distribution in the bone around the implant
must be understood. Biomechanical influences on bone
structure play an important role in the longevity of bone
around an implant. The quantity and direction of applied force
influence the implants, and cause deformation of the bone.
Stress analyses of endosseous implants are necessary for
the investigation of bone turnover and maximum anchorage
possible. Incorrect loading or overloading may lead to
disturbed bone turnover and consequent implant loss.26 Since,
clinical determination of stress and strain distribution in the
bone is not possible, an alternative technique should be used.
The finite element method (FEM), which has been
successfully applied to the mechanical study of stresses and
strains in the field of engineering, makes it practicable to
elucidate stresses in the living structures caused by various
internal and external forces. Finite element analysis (FEA)
has become an increasingly useful tool for the prediction of
the effects of stress on the implant and its surrounding bone.
The key factor for the success or failure of dental implant is
the manner in which the stresses are transferred to the
surrounding bone. FEA allows predicting stress distribution
in the contact area of the implant with the cortical bone, and
around the apex of the implant in the trabecular bone.27
Numerous investigations28,29 have been conducted to
assess the stress and strain distribution that occurs around
larger/bulkier prosthodontic implants, but limited literature
is available regarding the same about mini-implants used for
The Journal of Indian Orthodontic Society, October-December 2012;46(4):175-182
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PS Vijayalakshmi et al
orthodontic anchorage. Also, the nature of loading of
prosthodontic implants would be different compared to those
used for orthodontic purposes. Hence, it was felt that there is
a need to explore the changes in the bone adjacent to the
implant following orthodontic loading. Therefore, the present
study was undertaken with the following aims and objectives:
1. To analyze, by applying the FEM the stress and strain
distribution patterns in the bone surrounding a miniimplant.
2. To investigate the deformation of the bone around an
implant in response to forces of different magnitudes and
applied in different directions.
3. To derive clinical implications, which may aid in
optimization of implant design and its usage.
MATERIALS AND METHODS
The study was done in two parts as follows:
1. Data collection
2. FEM analysis
Data Collection
Data collection involved four steps:
a. In the first step, a case was selected for the placement of
the mini-implants.
• A patient, who presented with severe bimaxillary
dentoalveolar protrusion and had critical anchorage
requirements (needing complete utilization of the
extraction spaces for retraction) was selected- an ideal
case indicated for placing mini-implants for
anchorage.29
• The implants were fixed using the following surgical
procedure (as recommended by the authors)30 in the
interdental region between the 2nd premolar and the 1st
molar (Figs 1A and B) and the insertion site chosen was
measured from a guide bar on the bite-wing X-ray.
•
To avoid any damage to the roots, the screws were
implanted at a 60° angle between the teeth to the
occlusal plane. 29 At the same time, the implants
maintained an angle of approximately 30 to 40° to the
long axis of the maxillary teeth and 10 to 20° to the
mandibular teeth, to ensure optimum retention by
augmenting the area of contact between the implant
and adjacent bone (Figs 1A and B).
b. The second step of the study was to evaluate the implant
to bone integration.
• After 3 weeks of healing period, before loading the
implants, the Dentascan (Figs 2A and B) was taken to
ascertain the implant to bone integration.
• The data was also used to measure the thickness and
depth of the cortical and trabecular bone around the
implant.
c. The third step was to determine the dimensions of the
implant, so that these measurements could be used for
modeling the implant.
• The dimensions of the implant were measured directly
using a micrometer (to measure the pitch of the screw)
and Vernier calipers (to measure the vertical and
horizontal dimensions)
• Using the micrometer (0.25 range), the diameter at
the tip, diameter at the first pitch, and the diameter at
the tip of the implant were measured.
• The Vernier calipers of 8" were used to measure the
vertical and horizontal dimensions.
• Along with the micrometer, a threading pitch gauge
was also used to measure the pitch of the screw.
d. Finally, the thickness of the bone surrounding the implant
was measured using the implant assessment algorithm
provided in the resident Dentascan software.
• As per the Dentascan, cortical bone thickness was 2.6
mm and cancellous bone thickness was 2.4 mm.
Figs 1A and B: Mini-implants placed in the interdental region between the second premolar and the
first molar region in a patient having critical anchorage requirement
176
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Finite Element Analysis of Stress and Strain Distribution in the Bone around the Implants used for Orthodontic Anchorage
Figs 3A and B: Models of implant and implant-cortical-trabecular
bone in hypermesh FE modeling package
Assigning the material properties: In this study, the
assumption was made that the materials were homogenous and
linear and that they had elastic material behavior characterized
by 2 material constants viz. Young’s modulus and Poisson’s
ratio.
Boundary conditions: Since the implant was assumed to be
rigidly anchored in the bone, the entire outer surface of the
bone was restrained from translation along all three axes, and
restrained from rotations around all three axes.
Figs 2A and B: Dentascan of the same patient, which was used to
evaluate the implant to bone integration and to measure the thickness of
the cortical and trabecular bone
Finite Element Analysis
Software
The initial modeling was done using hypermesh FE modeling
package and AutoCAD mechanical. The finite element analysis
was done using MSC Patran version 3 as the pre- and postprocessor and MSC Nastran solver for Windows XP
professional.
Modeling the Mini-implant and the Surrounding Bone
•
•
•
•
•
•
The modeling was done using the software, Hypermesh
FE modeling package.
Once the dimensions of the bone and the implant were
obtained, these values were fed as input in both X and Y
dimensions into the modeling software.
These points were joined by lines to create the 2D
crossection of the implant and the bone.
Then, this crossection was revolved 360° to get 3D model
(Figs 3A and B).
The completed 3D model was then converted into a MSC
Nastran input file (dat format) and imported into MSC
Patran.
The final model had 67660 hexahedral elements and 67934
nodes.
The FE Model
Two types of FE models of the implant–bone complex were
generated (Figs 3A and B)
• Type I: Implant being surrounding completely by cortical
bone.
• Type II: Implant being surrounded 3/4th by cortical bone
and the tip being embedded in the trabecular bone.
Implant Loading
The effects of 2 different static loading conditions were
planned to be examined. These loads were to be applied to
simulate the following clinical situations:
• Orthodontic loading:
– Intrusion and retraction/Oblique
– Vertical force
• Orthopedic loading ( as in protraction of maxilla).
Magnitudes of Force
Following force values were applied:
• Orthodontic loading:
– Intrusion and retraction/Oblique: 150, 200 and
250 gm.
– Vertical force: 45, 60, 75 and 90 gm
• Orthopedic loading (as in protraction of maxilla): 400,
500 and 600 gm.
The displacements produced by each of the force sets, and
the stresses generated in the implant and in the surrounding
The Journal of Indian Orthodontic Society, October-December 2012;46(4):175-182
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PS Vijayalakshmi et al
bone were studied. Maximum and minimum principal stresses
produced in each of the said structures were tabulated. Along
with these, the maximum and minimum principal strain was
also tabulated.
A current measure for small strain values is  strain µeps,
where a strain of 1 means a deformation of 100%. Thus, for
example, a strain of 100 µeps coincides with a strain of 0.0001
or 0.001% ( = 10–6). These values obtained were then
correlated with Frost’s Mechanostat theory (1994)30 given in
the table below.
The compressive stresses were greater than the tensile
stresses. These compressive and tensile stresses gradually
reduced toward the tip of the implant.
b. Distribution of stresses in the bone: Bone experienced a
similar pattern of stress distribution, tensile stresses on
RESULTS
Interpretation of Results
The results obtained are discussed under three headings:
1. Distribution of maximum and minimum principal stresses
in the implant and bone.
2. Displacement of the implant and bone
3. Distribution of maximum and minimum principal strain in
the implant-bone junction and bone.
These parameters are analyzed for both types I and II
FE models, under 3 different loading conditions. Figures 6
to 9 are graphical representation of the results obtained.
Fig. 5: Distribution of maximum principal (compressive) strain in the
cortical bone, on application of an orthopedic load of 400 gm to the type I
FE model
OBLIQUE LOADING OF THE IMPLANT FOR
INTRUSION AND RETRACTION
Implant in Cortical Bone: Type I FE Model
The oblique force, when applied to the implant, caused the
following stress distribution pattern:
a. Distribution of stresses in the implant:
Compressive stresses were seen on the mesial surface of
the implant, with the maximum compressive stress being
concentrated at the neck of the implant (Fig. 4).The tensile
stresses were distributed on the opposite side of force
application, i.e. on the distal surface. The maximum tensile
stresses were concentrated at the point of force application.
Fig. 4: Distribution of maximum principal stresses in the implant, on
application of an oblique force of 250 gm to the type I FE model
178
Fig. 6: Maximum and minimum principal stresses at the implantcortical bone junction for both type I and type II FE models
Fig. 7: Maximum and minimum principal stresses experienced by the
implant for both type I and type II FE models
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Finite Element Analysis of Stress and Strain Distribution in the Bone around the Implants used for Orthodontic Anchorage
The maximum principal strain further increased as the
magnitude of force was increased. These strain values were
correlated with the Frost mechanostat theory (1994).29 On
comparison, it was found that the strain values at implant-bone
interface were in the range required for physiologic bone
maintenance. In the deeper layers of the bone, these strain
values decreased significantly.
Implant in Cortical and Trabecular Bone:
Type II FE Model
Fig. 8: Maximum and minimum principal strains at the implant-cortical
bone junction for both type I and type II FE models
Fig. 9: Maximum and minimum principal strains in the cortical bone
for both type I and type II FE models
the distal aspect and compressive stresses on the mesial
surface. The cortical bone around the implant revealed that
the cervical margin and the bone around the first thread of
the implant were the most stressed areas.
c. Distribution of stresses at the implant-bone interface: At
the junction of the implant and bone, maximum
compressive stresses were seen. The 1st thread of the
implant had maximum compressive stress. The stresses
gradually reduced from the 1st ring to the 5th ring. The
pattern of stress distribution was similar for application
of 150, 200 and 250 gm loads.
On oblique loading, the implant in the type II model
experienced the same magnitude of stress as the type I model.
The concentration of the stresses was seen at the neck of the
implant, with the maximum tensile stress at the point of force
application. The cortical bone experienced lower compressive
and tensile stresses as compared to the type I model. However,
unlike in model I, there were no significant differences
between the tensile and the compressive stresses in the bone.
The trabecular bone experienced lower stresses when
compared to the cortical bone. But in contrast to the cortical
bone, compressive stresses were slightly greater than the
tensile stresses. Within the trabecular bone, maximum stress
concentration of both tensile and compressive stresses was
seen at the corticotrabecular junction. Implant-cortical bone
junction experienced greater stresses when compared to the
implant-trabecular bone junction. At both the interfaces, tensile
stresses were greater than the compressive stresses.
The implant in the type II model experienced a greater
displacement when compared to the type I model. The
magnitude of displacement increased in all the areas with the
increase in the load applied.
On loading the implant, the maximum strain was found at
the implant-cortical bone junction, near the point of force
application. Overall, the bone experienced greater tensile
strain than compressive strain, which reduced gradually to the
last layer of bone to a negligible amount. These strain values
were correlated with the Frost’s mechanostat Table 1, similar
to the type I model. The correlation revealed that the strain
values at implant-cortical bone interface and in the cortical
bone were well within the optimum range for bone
maintenance. The strain values in the trabecular bone and the
implant-trabecular bone interface were significantly lower.
According to the Frost’s theory, such low strain values are
not conducive for bone maintenance.
Displacement of the Implant and the Bone
On application of oblique force to the implant, the implant
showed a very negligible amount of displacement. The implant
tended to tip toward the direction of force applied. This
displacement was in the range of 0.000215 to 0.000729 mm.
Distribution of Strain
On application of force on the implant, it created an area of
maximum strain at the junction of the implant and the bone.
Table 1: Frost’s mechanostat values
Factor
Peak load in microstrain (E)
Mechanical
Disuse atrophy
Bone maintenance
Physiologic hypertrophy
Pathologic overload
<200
200 to 2500
2500 to 4000
> 4000
1 micron () = 10–6
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PS Vijayalakshmi et al
VERTICAL LOADING OF THE
IMPLANT FOR INTRUSION
Implant in Cortical Bone: Type I Model
The vertical force, applied to the implant to cause intrusion,
created areas of greater tensile stresses than compressive
stresses. The implant, cortical bone and the junction between
implant and bone experienced greater tensile than compressive
stresses,unlike the oblique loading, where the implant
experienced greater compressive stresses than tensile stresses.
On application of vertical force to the implant, the implant
showed a very negligible amount of displacement. This
displacement was very minimal in the range of 0.000109 to
0.000218 mm.
Vertical loading of the implant created an area of maximum
strain at the junction of the implant and the bone, concentrating
at the point of force application. The maximum principal strain
further increased as the magnitude of force was increased.
The strain values gradually decreased in the deeper layers of
the bone (Table 1).
Implant in Cortical and
Trabecular Bone: Type II Model
The implant experienced the same magnitude of stresses as
the type I model. The concentration of the stresses was seen
at the neck of the implant, with maximum tensile stress at the
point of force application. At the junction of implant and
cortical bone, the stresses were slightly lower than the type I
model. The cortical bone experienced similar compressive
and tensile stresses when compared to the type I model, with
tensile stresses were greater than the compressive stresses.
Highest tensile stresses were concentrated at the implantcortical bone junction. The trabecular bone experienced lower
stresses when compared to the cortical bone. Both the tensile
and the compressive stresses were in the same range. Greater
concentration of both tensile and compressive stresses was
seen at the corticotrabecular junction. The implant in the
Type II model displaced to the same extent as the Type I model.
The cortical bone showed displacement slightly greater than
the Type I model in the range of 0.0000261 to 0.000522 mm
with maximum displacement at the implant-cortical
junction.The trabecular bone displaced to a negligible amount
in the range of 0.00000115 to 0.00000219 mm.
On loading the implant, the maximum strain was found at
the implant-cortical bone interface, similar to the type I model.
Overall, the bone experienced greater tensile strain than
compressive strain, which reduced gradually to the last layer
of bone.
ORTHOPEDIC LOADING OF THE IMPLANT
Relatively heavy forces (400, 500 and 600 gm) were applied
on the implant in a mesial (sagittal) direction simulating the
orthopedic force in maxillary protraction.
180
Implant in Cortical Bone: Type I FE Model
On loading the implant with orthopedic forces (Fig. 5), the
implant experienced greater tensile and compressive stresses
when compared to the previous two orthodontic loadings.
These stresses were concentrated at the point of force
application. In contrast, the minimum principal compressive
stresses were greater than the maximum principal tensile
stresses.
The bone experienced greater compressive and tensile
stresses compared to the orthodontic loading. The maximum
principal tensile stress was greater than the minimum principal
compressive stress.The interface experienced greater stresses
compared to the previous two orthodontic loadings. Here, the
compressive stresses were greater than the tensile stresses in
contrast to the overall stress distribution in the bone.
Displacement of the implant: On application of orthopedic
force to the implant, the implant showed a greater amount of
displacement when compared to the previous two orthodontic
loadings. This displacement was in the range of 0.000708 to
0.000285 mm.
On application of orthopedic force to the implant, the bone
experienced maximum compressive and tensile strain. The
junction between the implant and the cortical bone experienced
greater strain compared to the deeper layers of bone. Similar
to all the previous loads, these strain values were compared
with the Frost’s mechanostat Table 1, which revealed that all
the three orthopedic loads resulted in strain in the range of
physiologic bone maintenance.
Implant in Cortical and Trabecular
Bone: Type II FE Model
The implant experienced greater tensile and compressive
stresses compared to the type I implant.
i. The cortical bone also experienced greater tensile and
compressive stresses when compared to the type I model.
Similar to the previous model, the tensile stresses were
greater than the compressive stresses.
ii. The trabecular bone experienced lower stresses compared
to the cortical bone. Implant-cortical bone junction
experienced greater stresses when compared to the
implant-trabecular bone junction.
Displacement of the implant: The implant displaced to a
greater extent than the type I implant. This displacement was
in the range of 0.00114 to 0.00171 mm. The strain values
were comparatively higher than the type I model. Similar to
all the previous loads, the values obtained were compared with
the Frost’s mechanostat Table 1. Strain values in the cortical
bone and implant-cortical bone interface were sufficient for
bone maintenance, while the strain values in trabecular bone
and implant-trabecular interface were significantly less, which
would probably result in atrophy of bone according to Frost’s
mechanostat theory.
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Finite Element Analysis of Stress and Strain Distribution in the Bone around the Implants used for Orthodontic Anchorage
DISCUSSION
Biomechanical influences on bone structure play an important
role in the longevity of bone around implants.3 Bone tissue is
known to remodel its structure in response to mechanical
stress. Low stress levels around an implant may result in poor
connection with bone or bone atrophy. On the other hand,
abnormally high stress concentrations in the supporting tissues
can result in pressure necrosis and subsequently in implant
failure. 3 The present study was aimed at analyzing the
deformation of bone surrounding a mini-implant in response
to different force magnitudes.
2.
COMPARISON WITH OTHER STUDIES
Melsen and Verna (2005)21 evaluated the load transfer from
the Aarhus miniscrew on the bone, and the influence of
different cortical bone thicknesses and the underlying
trabecular bone density, on applying a mesially directed force
of 50 gm. The results obtained from our study matched with
their study. The primary component of the load transfer was
seen at the first revolution of the miniscrew thread within the
cortex. Authors found that on decreasing the thickness of the
cortical bone, the peak strain values reached the pathological
overload window (Frost’s mechanostat theory). But in our
study, the thickness of the cortical bone was kept constant
with the larger part of the implant being surrounded by the
cortical bone. Hence, the cortical bone experienced greater
strain values than the underlying trabecular bone. At this
thickness of the cortical bone, the peak strain values were in
the optimal range of bone maintenance.
Chen, Esterle and Roberts (1999) 31 investigated the
mechanical environment of cortical bone adjacent to
retromolar endosseous implants used for orthodontic
anchorage in a coordinated histomorphometric and finite
element study. The authors studied the change in the stress
pattern in the bone before and after placement of implants.
They noticed a strong change in the stress pattern in the bone
after implantation, wherein the stresses increased by 2 to
4 times on orthodontic loading. It was observed that on loading
the implant by an anterior force, compressive stresses were
found on the buccal and distal sides, and tensile stresses were
found on the lingual and mesial sides. The results obtained in
our study were similar to the above study. Their coordinated
histomorphometric study revealed that the high areas of stress
were associated with high remodeling activity of the bone.
Our study also showed similar areas of high stresses
distribution around the first few threads of implant.
CLINICAL IMPLICATIONS
From the results of the present study, following clinical
implications could be derived:
1. The mini-implants would efficiently resist oblique loading,
simulating anterior intrusion and retraction. The loads of
3.
4.
5.
200 and 250 gm produced strain in the optimal range of
bone maintenance. These devices would serve as a reliable
means of ‘absolute anchorage’ as per the initial stress
pattern.
The use of these mini-implants for the purpose of
orthopedic loading is questionable, since the stress values
experienced by the implant are quite high. Even though
the strain values experienced by the bone were in the range
of optimal maintenance, the site of placement of the
implants and the timing become crucial factors in deciding
the usage of these implants for orthopedic loading. The
ideal time for orthopedic protraction of maxilla is during
the mixed dentition phase. The miniscrew can loosen, even
after having been initially fixed, if an adjacent deciduous
tooth is exfoliating. There can also be a risk of injuring
the underlying permanent tooth bud.
In the implant, the most critical area is its neck, where
there is maximum stress concentration, and the marginal
bone (cervical margin) which surrounds it. Thus, this area
should be preserved clinically in order to maintain the
bone-implant interface structurally and functionally.
It was seen in our study that the implant tipped to a very
negligible amount in the direction of the load applied, like
a tooth tipping on application of load. But the displacement
seen was very negligible and clinically insignificant.
Based on the experience from our study, the following
suggestions can be made for optimization of the implant
design:
a. The neck of the implant must be long enough to project
away from the soft tissues, so that any attachments
placed on the implants do not impinge the mucosa. The
inflammation of the overlying soft tissue and/or the
marginal bone resorption can jeopardize the stability
of the implant.
b. The neck of the implant must be sturdy enough, since
the maximum stress concentration occurs at the neck
of the implant. If the implant is not strong in this
region, it may affect the integrity of the implant.
c. When using these mini-implants for orthodontic
loading, it is advisable to take all the necessary
precautions to place the implant as much in the cortical
bone as possible. The reason is that the stress and strain
values in the trabecular bone were very low, which
would result in atrophy of the surrounding bone (as
postulated in Frost’s mechanostat principle).
CONCLUSION
From this study, it can be concluded that:
1. The mini-implants used in the present study efficiently
resisted the oblique loading, which simulated intrusion and
retraction of the anterior teeth. The loads of 200 and 250
gm produced strains in the optimal range of bone
maintenance.
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PS Vijayalakshmi et al
2. The use of these mini-implants for the purpose of
orthopedic loading is questionable.
3. The implant tipped on loading in all the three clinical
situations simulated in the present study. But this
displacement was to a negligible amount and was clinically
insignificant.
4. Both the types of FE models showed the area with the
highest stress and strain to be around the neck of the
implant and the surrounding bone at the cervical margin.
This finding is clinically important in order to preserve
the bone-implant interface functionally and structurally
in this area.
5. To obtain an optimal biomechanical response, the implant
should preferably be placed entirely in the cortical bone
(however, this may not always be feasible clinically). The
neck of the implant should be sturdy enough, and the head
of the implant should not produce any kind of irritation to
the overlying mucosa.
REFERENCES
1. Roberts WE, Helm FR, Marshall KJ, Gongloff RK. Rigid
endosseous implants for orthodontic and orthopedic anchorage.
Angle Orthod 1989;59(4):247-56.
2. Cheng SJ, Tseng IY, Lee JJ, Kok SH. A prospective study of the
risk factors associated with failure of mini-implants used for
orthodontic anchorage. Int J Oral Maxillofac Implants 2004;19:10006.
3. Gainesforth BL, Higley LB. A study of orthodontic anchorage
possibilities in basal bone. Am J Orthod Oral Surg 1945;31:
406-17.
4. Linkow L. Implanto-orthodontics. J Clin Orthod 1970;4:685-705.
5. Creekmore TD, Eklund MK. The possibility of skeletal anchorage.
J Clin Orthod 1983;17(4):266-71.
6. Roberts WE, Marshall KJ, Mozsary PG. Rigid endosseous implant
utilized as anchorage to protract molars and close an atropic
extraction site. Angle Orthod 1990;60:135-52.
7. Roberts WE, Nelson CL, Goodacre CJ. Rigid implant anchorage
to close a mandibular first molar extraction site. J Clin Orthod
1994;38:693-704.
8. Southard TE, Buckley MJ, Spivey JD, Krizan KE, Casko JS.
Intrusion anchorage potential of teeth versus rigid endosseous
implants: A clinical and radiographic evaluation. Am J Orthod
Dentofacial Orthop 1995;107:115-20.
9. Block MS, Hoffman DR. A new device for absolute anchorage
for orthodontics. Am J Orthod Dentofacial Orthop
1995;107(3):251-58.
10. Hoffman DR. Implants and orthodontics. In: Block MS, Kent JN
(Eds). Endosseous implants for maxillofacial reconstruction (1st
ed). Philadelphia: WB Saunders Co 1995:382-400.
11. Block MS. Orthodontic and orthopedic anchorage using
subperiosteal bone anchors. In: Higuchi KW (Ed). Orthodontic
applications of osseointegrated implants. Illinois, Quintessence
Publishing Co Inc 2000;109-19.
12. Janssens F, Swennen G, Dujardin T, Glineur R, Malevez C. Use
of an onplant as orthodontic anchorage. Am J Orthod Dentofacial
Orthop 2002;122(5):566-70.
182
13. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of
palatal implants for orthodontic anchorage. Design and clinical
application of the orthosystem. Clin Oral Implants Res
1996;7(4):410-16.
14. Umemori M, Sugawara J, Mitani H, Nagasaka H, Kawamura H.
Skeletal anchorage system for open bite correction. Am J Orthod
Dentofacial Orthop 1999;115(2):166-74.
15. Byloff FK, Karcher H, Clar E, Stoff F. An implant to eliminate
anchorage loss during molar distalization: A case report involving
the Graz implant-supported pendulum. Int J Adult Orthodon
Orthognath Surg 2000;15(2):129-37.
16. De Clerck H, Geerinckx V, Siciliano S. The zygoma anchorage
system. J Clin Orthod 2002;36(8):455-59.
17. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod
1997;31(11):763-67.
18. Bousquet F, Bousquet P, Mauran G, Parguel P. Use of an impacted
post for anchorage. J Clin Orthod 1996;30(5):261-65.
19. Costa A, Raffaini M, Melsen B. Miniscrews as orthodontic
anchorage: A preliminary report. Int J Adult Orthod Orthognath
Surg 1998;13:201-09.
20. Melsen B, Verna C. Miniscrew implants: The Aarhus anchorage
system. Semin Orthod 2005;11:24-31.
21. Park HS, Bae SM, Kyung HM, Sung JH. Micro-implant anchorage
for treatment of skeletal class I bialveolar protrusion. J Clin Orthod
2001;35(7):417-22.
22. Bae SM, Park HS, Kyung HM, Kwon OW, Sung JH. Clinical
application of micro-implant anchorage. J Clin Orthod
2002;36(5):298-302.
23. Park HS, Kyung HM, Kwon OW, Sung JH. A simple method of
molar uprighting with micro-implant anchorage. J Clin Orthod
2002;36(10):592-96.
24. Maino BG, Bednar J, Pagin P, Paola Mura. The spider screw for
skeletal anchorage. J Clin Orthod 2003;37(2):90-97.
25. Gedrange T, Bourauel C, Kobel C, Harzer W. Three-dimensional
analysis of endosseous palatal implants and bones after vertical,
horizontal, and diagonal force application. Eur J Orthod
2003;25:109-15.
26. Geng JP, Tan KBC, Liu GR. Application of finite element analysis
in implant dentistry: A review of literature. J Prosthet Dent
2001;85:585-98.
27. Rieger MR, Fareed K, Adams WK, Tanquist RA. Bone stress
distribution for three endosseous implants. J Prosthet Dent
1989;61:223-28.
28. Canay S, Hersek N, Irfan Akpinar, Asik Z. Comparison of stress
distribution around vertical and angled implants with finite-element
analysis. Quintessence Int 1996;27:591-98.
29. Roberts EW. Bone physiology, metabolism and biomechanics in
orthodontic practice. In: Graber TM, Vanarsdall RL (Eds).
Orthodontics—current principles and techniques (3rd ed). St Louis:
Mosby 2000:193-219.
30. Chen J, Esterle M, Roberts WE. Mechanical response to functional
loading around the threads of retromolar endosseous implants
utilized for orthodontic anchorage: Coordinated histomorphometric
and finite element analysis. Int J Oral Maxillofac Implants
1999;14:282-89.
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