1

Mechanical Behaviour of Dental Implants

Pedro Miguel Vitorino Borges Bicudo

Mechanical Engineering Department, Instituto Superior Técnico, University of Lisbon, Avenida Rovisco Pais,

1049-001 Lisboa, Portugal

Abstract

Dental implants are majority made of titanium, since this material promotes a stable and functional connection between the bone and

the surface of the implant. Efforts produced during the chewing cycles may interfere with this union, affecting the process of

osseointegration and eventually compromising the stability of the implant.

Given the difficulty in working with bone in vivo, in the present study two implant systems were inserted in polymer samples, known

as Sawbones, which simulate the structure of trabecular bone. On the experimental side, the performance of the implants was

evaluated through fatigue tests. The qualitative analysis of the damage in the structure of the samples was performed using scanning

electron microscope images. The study was complemented with the determination and comparison of stress fields and deformations

at the Sawbone-implant interface using an analytical model of indentation and the finite element method.

The experimental results showed that the performance of the Morse taper implant is greater than the external hexagonal implant

when both are tested cyclically in samples of different densities. It was proven that the diameter, length, density and type of implant-

abutment interface are design variables that affect the behavior of the implants. The numerical results of indentation model are very

similar to those obtained by the analytical model. The results of the penetration FEM model have the same tendency as the

experimental values and the FEM models and analytical indentation with increasing density of the polymer foam. It can be

concluded that, as in foams, the increase of the bone density will induce an increased stability to the implants

Keywords: Dental Implant; Sawbone; Fatigue Tests; Finite Element Method (FEM); Scanning Electron Microscopy (SEM)

1. Introduction

Nowadays, dental implants are the ideal solution for lack of

dentition, being considered the best alternative after natural

teeth. However, in spite of the latest advances recorded in

the dentistry field, implants are still likely to fail.

Complications at the implant-bone interface level, such as

bone loss, occurrence of micromovements and concentration

of tensions at the surface of the bone and the implant, are

very common phenomena, which reveal the need of solution

that keep the stability of the implant and the process of

osteointegration.

A weak primary stability is one of the major causes

contributing to the defect of the implants [1]. Therefore a

high primary stability assures a high resistance of the implant

to micromovements, which is very important for a successful

osteointegration, since the implant shall not be subject to

micromevements higher than 150 μm [1].

The factors that influence the primary stability are bone

density, the type of surface and the surgical technique used.

When an implant is placed, the primary stability will depend

firstly on the quatity and quality of cortical and trabecular

bone available for the fixation of the implant [1]. Thus, bone

desnsity is, amongst all, the most related influencing factor

of primary stability, hence its influence on the mechanical

behavior of the implants.

The literature reveals different studies [2], for a correlation

between the insertion torque values and the bone mineral

density. Friberg studies on bone resistance, allowed the

relation between the level of bone density and the value of

the applied torque inserted. The study reveal: i) low density

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– insertion torque smaller than 30 Ncm; ii) medium density -

insertion torque between 30 and 40 Ncm; iii) high density -

insertion torque values higher than 40 Ncm.

The research in biomechanics is one of the major factors to

achieve long-term success of the dental implants. To

evaluate different types of implants available in the market,

mechanical tests are fundamental, for it is through them that

is possible to analyze the performance of the tested material,

when submitted to different loadings, in different substrates.

Amongst the different possible mechanical tests to a dental

implant, fatigue tests take an important role in the

mechanical characterization of the implants. Throughout

time, the implants will be subject to different types of

loadings, product of the chewing cycles of one individual,

reason why it is of the highest importance to submit them to

these types of tests, under different levels of loading, with

the goal of predicting its life on fatigue.

From a biomechanical prespective, a well-succeeded

osteointegration depends on how the tensions and

deformations are transmitted to the bone and its involving

tissues, being key-factors for the success or defect of a dental

implant. Many variables affect the way tensions and

deformations are transmitted to the bone, such as the type of

loading applied, the length and diameter of the implant, its

geometry and surface, the bone-implant surface, and the

quality and quantity of involving bone. MEF allows to

analyze the influence of each one of the mentioned variables,

and for that reason it has become the most useful and used

tool to locate and predict flaws in any mechanical system.

Moreover, when a structural analysis is applied, it is possible

to determine what are the effects of the deformations and

tensions caused by structural loadings applied on the implant

and surrounding bone.

Given the difficulties inherent to working with trabecular

bone, synthetic polyurethane foams are widely used as

alternative materials to this type of bone in several

biomechanical tests, due to the fact that these materials

present a similar cellular structure and consistent mechanical

characteristics, found in the same order as the ones of the

trabecular bone [3]. Amongst the different possible tests, the

measurement of micromovements in the bone-implant

system when exposed to cyclic loadings is one of the most

important pre-clinical tests to determine whether the

performance of the in vivo implant is possible, and to

evaluate its stability. In the present work, a set of fatigue

tests was performed, according to the ISO 14801 norm, in

which the implants were inserted in polymeric samples, with

different densities, simulating different bone types, with the

intuit of assessing the stability of the implants and evaluate

de deformations level in the bone-implant system. This study

was complemented with an analytical analysis and of finite

elements, where similar geometries to the test specimens

were generated, through which it was possible to determine

deformation fields and bone-implant interface tension, and

finally, compare these results to the medical reality.

2. Materials and methods

2.1. Preparation of test specimens

The insertion material used consists of rigid polyurethane

(PU) foams known as Sawbones. Three types of theses

foams were selected, with the purpose of covering a certain

range of densities. Of the three selected types, the Sawbone

10 is of lower density, Sawbone 12 of higher density and

Sawbone 11 of intermediate density. It is important to

establish a relation between the density of each Sawbone and

the bone density. According to the Misch classification for

bone density, can assume that the Sawbone with lower

density aims to simulate a bone of type D3, which is, a thin

trabecular bone (less dense) and a thin cortical part. The

Sawbone 12, the denser used in the test performed,

represents the characteristics simulated of a bone of type D1,

which corresponds to a dense cortical part with a trabecular

part less dense, and finally, the intermediate density

Sawbone 11, associated to the type D2 bone. In order to

simulate the cortical part of the bone, an epoxy resin was

used to replicate the cortical properties of the bone. Table 1

presents the correspondence between the different Sawbone

types and the bone density according to Misch.

Table 1 - Sawbones and bone density according to Misch

Sawbone Classificação Misch Densidade

10 D3 Baixa

11 D2 Intermédia

12 D1 Alta

For the experimental tests of fatigue, two types of implants

were tested: the external hexagon and the Morse taper with

the respective abutments, represented in figure 1.

The identification of the type of material was made through

the technique of EDS, which allowed identifying the

chemical spectrum of the implants. The results of such

analysis showed that the implants are produced with titanium

commercially pure (Ticp) degree 4.

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Figure 1 –Implants tested

The preparation of the test specimens was made based on the

surgical protocol and the drilling sequence recommended by

the manufacturer. The implants were inserted to a depth of

8,5 mm for the external hexagon and 9 mm for the Morse

taper, given that, to conduct the tests according to the ISO

14801 worse scenario, the implants must be 3 mm above the

test specimen, instead of totally inserted [4]. The implant

insertion was conducted with resource to a dental torque

wrench, where the reading of the applied torque was

possible, as shown in figure 2.

Figure 2 – Preparation of test specimens

The average force applied to the test specimens corresponds

to the lower and upper limits of the average chewing force of

an individual. The lower average force, between 70 and 80

N, corresponding to the lower limit of the average chewing

force and a higher average force, 150 N, corresponding to

the upper limit of the average chewing force. All the tests

had a duration of 120000 cycles, and were conducted at 3 Hz

and R = 0,1. The results were handled through displacement

– number of cycle graphs, with the identification of the

defect site made through SEM images.

2.2. Analytical model for indentation

Several physic problems in the real world involve some sort

of mechanical contact. The mechanical contact problems can

be experimentally study, numerically or through theoretical

models. It was sought on literature a model that aims the

analysis of the behavior of the Sawbone structure, with the

purpose of predicting the deformations that occur when it is

externally solicited by a force. The proposed model is one of

indentation for elastic materials. This seeks, based on the

mechanical theory of contact, to describe the deformation

occurring on the Sawbone, resultant of the contact action

from the implant. The elastic tension fields generated by an

indenter be it of spherical geometry, cylindrical or

pyramidal, although complex, are well defined on the

literature [5]. For a cylindrical indenter, for r<=a, this is, for

a radial distance, r, smaller than the contact radius, a, the

contact pressure distribution is:

(

)

(1)

Below the indenter, uz, is the depth below the original free

surface of the indenter and is obtained by:

(2)

For a cylindrical indenter, the radial tension of the indented

surface is given by:

( )

{ (

)

}

(

)

(3)

The radial displacements at the indented surface are given

by:

( )( )

{ (

)

} (4)

In the expressions 1, 2, 3 and 4, E and v correspond to the

Young's modulus and Poisson coefficient of the indented

sample. For the analytic calculations, a relation of 0,5 for r/a

was chosen, to evaluate deformations and tensions at the

Sawbone structure.

2.3. Finite element method (FEM)

The generation of the finite element model was initiated with

the modulation of two distinct geometries for the implants,

one smooth and other threaded by the SolidWorks 2015

program, as shown in figure 3.

Figure 3 – Smooth and threaded geometries

The generation of the smooth geometry has the purpose of

simplifying the model, which means it was used in a

primarily analysis for the study of tensions and deformations

that occur at the set implant-Sawbone. Sawbone and epoxy

4

geometries were also created, to which the two types of

implants were assembled.

Both geometries were imported to ANSYS Workbench 14.5

commercial code. The analysis were made imposing a

convergence to the von Mises tension of 7% for both

modulated geometries, for which at the smooth geometry the

element SOLID186 was used, and for the threaded geometry

the SOLID187, a tetrahedral element, as shown in figure 4.

Some simplifications were made for the simulations. Firstly,

all materials were considered homogeneous, isotropic and

linearly elastic [6, 7]. The mechanical properties of the

materials, namely the Young’s modulus, E, Poisson

coefficient, v, density, ρ and the yeld strength, σy, are the

represented in table 2.

Figure 4 - Implants computational meshes

Table 2 – Material properties

E [MPa] ν Ρ [g/cm3] σy[MPa]

Sawbone 10 23 0,3 0,16 2,3

Sawbone 10 47,5 0,3 0,20 3,9

Sawbone 12 137 0,3 0,32 5,4

Epóxi 16700 0,26 1,64 157

Implant 120000 0,37 4,55 400

Also was assumed that de implants are 100%

osteointegrated. For that, the bonded contact type was used

to simulate the contact between the different surfaces, for

according to this model, there is no separation or slip

between the faces and edges at the contact surfaces. For the

boundary conditions, the lateral faces of the epoxy and all of

the Sawbone faces are constraint to the three directions, x, y

and z. The intensity of loading used corresponds to the two

limit values of average chewing force of an individual,

which means, analysis were made for the different types of

Sawbone applying a statical loading of 70 N and 150 N,

applied at the top of the implant, according to a 30º angle

with the axial axis of the implant, simulating the loading

conditions of of ISO 14081 norm.

A numerical study was also conducted to validate the

equations presented in subchapter 2.2. A representative

geometry, shown in figure 5, was generated for the

indentation model, were the tested sample is a cubical block

with a 15 mm edge, representative of the Sawbone, and the

indenter is the implant of smooth geometry. The

convergence criterion of the mesh was 5% for the von Mises

tension. The boundary conditions are the same as describe

before for the total constraint of the Sawbone walls and of its

base. The loading applied to the indenter axis is of

compressive character, therefore the intensity of the force

used on the indention simulations corresponds to the vertical

component of the resultant force.

Figure 5 – Indenter geometry

3. Results

3.1. Results of fatigue tests

The test results for the two systems used, implant external

hexagon and Morse taper, are arranged according to the type

of Sawbone in which were inserted, as shown in figures 5, 6

and 7. The test curves reveal clear that in a first stage and for

a low number of cycles the materials response is essentially

linear elastic. There is a rapid accumulation of deformation

caused by the bending and stretching of the cell walls. After

this stage, the yield point is where the first cell collapse

occurs. Then, after overcoming this peak, there is a slight

decrease of deformation, a result of the softening of the

material, registering lower deformation values temporarily.

At the end of this phase, it starts a level where the increase

value of the deformation in the material is negligible with

increase of the number of cycles. It is during this phase that

occurs the plastic collapse phenomenon, with formation of

plasticity on the membrane connection nodes of the cellular

material due to the fact that have exceeded the threshold

value of the total plastic moment when applying a normal

force to the cell walls [8].

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a) b)

Figure 6 - Experimental results for Sawbone 10: a) external hexagonal implant; b) Morse taper implant

a) b)

Figure 7 - Experimental results for Sawbone 11 a) external hexagonal implant; b) Morse taper implant

a) b)

Figure 8 - Experimental results for Sawbone 12 a) external hexagonal implant; b) Morse taper implant

The results shown in Figure 5, regarding the Sawbone 10,

show that for the external hexagonal implant there is a clear

difference in the progress of the two curves. In the green

curve, representing the test performed at an average force of

75 N, is not recorded, in the plastic collapse phase, which

starts at around 10000 cycles, an increase in the deformation

amount with the increased number of cycles. Regarding the

red curve, increased to twice the value of the average of the

test force promoted early a sudden increase of deformation

for a low number of cycles, a behavior which tends reduce

during the plastic collapse phase of the material, which is

clearly visible that the gradual increase in the number of

cycles promotes a decrease in strain rate of Sawbone. In the

case of the Morse taper implant the progress of the two

curves is substantially the same, verifying a sudden increase

in the elastic deformation zone until the yield point of the

material and about 20000 cycles starts the plastic collapse

phase, where the variation in deformation value in the

Sawbone is not significant with increasing number of cycles.

Against the behaviour of the external hexagon implant, the

increase of the average strength intensity from 75 to 150 N,

did not cause a change in the material behavior during the

phase of plastic collapse. This means that the structure of

Sawbone was able to accommodate the movements of the

implant when it is subjected to a cyclic load of greater

intensity.

In the external hexagonal implant, the results for the tests

with the Sawbone 11 show, for the corresponding curve of

80 N, an equivalent behavior that was previously registered.

After exceeding the elastic range and the slight softening

material, there has been an increase in the value of the

deformation in Sawbone until the conclusion of the test. For

the test conducted, at an average force of 150 N, it is found

that for about 20000 cycles occurs a gradual increase in

Sawbone deformation. In the Morse taper implant, the results

also show a very similar behavior of the two curves, and for

both specimens, as from the plastic collapse phase begins, it

was found a slight variation of deformation in advance the

number of cycles. Comparatively to the previous recorded

results for Sawbone 10, the deformation values are

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significantly inferior in this case, being possible to verify a

small variation on the values derived from the increment of

strenght.

Finally, in tests performed with the denser Sawbone, the

results of the external hexagonal implant are the ones

expected. Again, for the loading of lower intensity, there is a

long plateau where the progress of deformation is

substantially constant. When the intensity of the applied

average force passes to 150 N, the deformation rate in

Sawbone also gradually increases. For the Morse taper

implant, once again it is clear that the behavior of the two

curves is almost the same, recording from the plastic

collapse phase and for the two curves shown, the Sawbone

strain rate is practically constant, having no abrupt increase

in strain values up to completion of the test.

Figure 9 – Insertion torque external hexagonal implant

Figure 10 - Insertion torque Morse taper implant

In all tests the values of the insertion torque were recorded,

hence why it is now possible to analyze how this parameter

varies with the density of the foams. Clearly increased the

Sawbone density, leads to an increase of the respective

implant insertion torque. This increase in the torque value

can be explained based on the structure of the cells.

3.2. Results of FEM penetration simulations

The distributions of stress and strain are presented in figures

4.11 to 4.14, manilly, maximum stress values in the implant

and deformations in Sawbone. These are represented in a

color scale, that is, closer to the red, higher the value of the

stress / strain. Amongst the results presented for the smooth

geometry, there was a gradual decrease in the value of stress,

such as deformation, which with the type of Sawbone, and

that this situation happens for both strength intensities used.

Firstly it is noted that in all simulated cases, either the

implant or the Sawbone-epoxy set have not reached the limit

value of the yield stress of its material, meaning, all

components support the loading imposed without deform

plastically. From the point of view of stress analysis, it can

be said that the most favorable situation occurs when using

the higher density Sawbone, beacuse the stress values are

minimized. Taking this into account, it can be seen that for

both strength intensities, there is a 20.45% decrease of the

stress for the less dense Sawbone, and 14.20% for the

Sawbone intermediate density, when compared with

Sawbone of high density, respectively. Regarding

deformations on Sawbone, it is in the less dense than the

highest values occur, and there as the value of density

increases, the amount of deformation decreases, behavior

similar to stress. Given the nature of the applied compressive

force and bending moment generated on the implant, the

maximum deformation occurs at the contact interface

between the implant base and Sawbone, a situation which

occurs for all values of density and intensity strength tested.

a) b) c)

Figure 11 – Deformations in Sawbone of smooth geometry: a) Sawbone 10; b) Sawbone 11; c) Sawbone 12

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a) b) c)

Figure 12 - Stress in Sawbone of smooth geometry: a) Sawbone 10; b) Sawbone 11; c) Sawbone 12

a) b) c)

Figure 13 - Deformations in Sawbone of threaded geometry: a) Sawbone 10; b) Sawbone 11; c) Sawbone 12

a) b) c)

Figure 14 - Stress in Sawbone of threaded geometry: a) Sawbone 10; b) Sawbone 11; c) Sawbone 12

On the results of the threaded geometry, these are very

similar to those previously found for the smooth geometry. It

was found that there is a reduction of the values of stress, as

for the deformation, when there is a increase of density on

the Sawbone. It is for the denser Sawbone that both values

are minimized, a situation which occurs for both strength

intensities. For all the conditions simulated, the materials

don’t deform plastically.

Now comparing the results between the two tested

geometries, the thread geometry provides a reduction in

terms of the stresses anda deformation in the Sawbone. For

the less dense Sawbone, the introduction of threads on the

implant body leads to a reduction of 17.52% in the value of

the stress at the interface, in addition to the value of the

maximum deformation decreases Sawbone 1.92%. For

Sawbone 11, reducing stresses is also evident, dropping the

value of the maximum stress of 15.79% and 4.80%

deformation. Finally, for Sawbone with higher density

tension in the threaded implant compared to smooth implant,

decreases 11.74% while the deformation decreases 4.79%.

The decrease in tension between the two geometries is

justified because increasing the contact area on the interface

contact between the implant and the Sawbone-epoxy set,

maintaining the same degree of loading, an increase in the

area promotes a reduction in the amount of tension.

3.3. Results of indentation simulations

The results of numerical simulations, such as analytical

calculations showed that the deformation values decrease as

the mechanical properties of Sawbone increase, as shown in

tables 3 and 4. The finite element model valid the equations

for the displacement, having experienced a 8.28% error

between analytical and numerical values. Regarding stress

analysis, it appears that the value of the resultant doesn't vary

in function of the Sawbone. The finite element model also

validates the stress equations, having been an error between

the two values of 5.23%.

Table 3 – Numerial results of indentation

Deformation (mm) Tension (MPa)

Force (N) 60,62 129,90 60,62 129,90

Sawbone 10 0,551 1,180 1,180 7,292

Sawbone 11 0,267 0,571 0,571 7,293

Sawbone 12 0,092 0,198 0,198 7,298

Table 4 – Analytical results of indentation

Deformation (mm) Tension (MPa)

Force (N) 60,62 129,90 60,62 129,90

Sawbone 10 0,600 1,286 3,592 7,697

Sawbone 11 0,291 0,623 3,592 7,697

Sawbone 12 0,101 0,216 3,592 7,697

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In figure 15, it can be seen an example of indentation stress

fields and deformation.

Figure 15 – Example of indentation stress fields and

deformation

4. Discussion

There were several differences for the two tested implant

systems. For both, the external hexagonal implant, as for the

Morse taper implant, it was found that the deformation value

decreases as the Sawbone density increases. The SEM

images, shown in figure 16, verify this, once the results were

analyzed, it is observed that the number of collapsed cells

within the affected area is larger for the less dense structure.

Figure 16 – SEM images: Sawbone 10 and 12, respectively

Although this situation occurs for both implants, the

variation range of values for the displacement is smaller for

the Morse taper implant, that is, this type of implant is less

sensitive to load variation when it is tested in the same cell

structure, as shown in figure 17.

From the point of view of the bone structure, a bone-type

D1, being denser and mechanically stronger, is less sensitive

to the variation of masticatory forces.

Another interesting result is found for the case of the less

dense Sawbone, that is, when both the implants were tested

in the worst design condition. For the external hexagonal

system it was found that the plastic collapse phase starts

earlier at about 10000 cycles, and that the curve behavior for

the greater force intensity displays significant differences

compared to the Morse taper implant curve. The difference

of the values recorded can be reflected in the fact that for the

external hexagonal implant, the Sawbone structure doesn’t

accommodate the movements suffered by the implant when

it is loaded cyclically. To make an analogy between the

experimental results and the world of dentistry, this result

may lead to a lower adhesion of bone cells around the

implant, contributing to a delay of osseointegration time,

compromising the long-term success of the implant.

Numerical studies show that the effect of diameter and

length of the implants has an influence on stress distribution

at the bone-implant interface [6, 7]. The increase in diameter

of the implant promotes a reduction in the normal and shear

stresses along the implant-bone interface, promoting a better

distribution of loads to the tissue. In other words, the

increase of the lateral area and implant section reduces the

tensions generated in the cortical bone, stresses arising from

compressive forces, tensile, bending and torsion, wherein the

diameter of the implant have a greater influence compared

with the length [9]. The shape of the Morse taper implant

also helps to explain the better performance during the test,

since the introduction of microthreads in the implant neck

region, as shown in figure 1, helps to minimize the amount

of tension along the zone, resulting in a decrease of bone loss

after the placement of the implant [1].

The implant abutment connection also influences the results

obtained. The performance of the Morse taper system, when

compared with the behavior of the external hexagonal

implant has a higher success rate, meaning, for the same type

of loading the number of cycles to failure is higher thanks to

their locking mechanism, by wherein the clearance between

the implant and the abutment is reduced, eliminating

vibration and micromovements of the connecting srew [10].

The values of the measured insertion torque also show a

clear relationship with the density of Sawbone. There have

been higher torque values when the foam density is higher,

and this result is in line with some studies published. Given

that the three Sawbones are closed cell foams, the air that

lies within each cell has influence on the process. This means

that for larger cells the air which is inside it is at lower

pressure compared to larger cells [11]. Therefore the force

which is necessary to fix the implant in the less dense

Sawbone is lower compared with the densest Sawbone, that

is, the value of the torque is lower for lower densities and

higher for higher density foams.

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Figure 17 – Comparison of the experimental results

Figure 18 - Variation in the deformation values for different Sawbone

Figura 19 - Variation in the stress values for different Sawbone

Establishing a link between these results and bone density, it

was found that measured values haven't exceeded the

recommended maximum torque, this means that the bone

structure is not overloaded at the time of insertion of the

implants.

For the numerical results, it is noted that the maximum

magnitude of the deformation recorded in all the simulations

is in the range of microns, μm. According to the literature,

excessive micromovements between the implant and

surrounding bone can interfere with the process of

osseointegration, having been postulated that such

deformations must not exceed the value of 150 μm [1]. The

simulations results indicate that this threshold value is never

reached, and knowing that the Sawbones are a test material

used to simulate the conditions of trabecular bone, it can be

stated that for the Sawbones 10, 11 and 12, representative of

the type of bone D3, D2 and D1, respectively, the

corresponding micromovements of the implant relative to the

10

bone microstructure proved to be sufficiently low to avoid

the formation of fibrous tissue, favoring the long-term

osseointegration.

In order to compare the results of indentation, with the

penetration results, an analysis between displacement and

stress values for both situations was made and is shown in

figures 18 and 19. However, the fact that the simulations

made with the penetration model have been used the type of

contact bonded, makes that all the components of the

geometry behave as a single body. In order to overcome this

situation, the type of contact between the walls of Sawbone

and epoxy with the implant was changed, for no separation.

This type of contact also used in linear simulations is similar

to bonded, but is permitted a slight sliding between surfaces.

This sliding simulate better the penetration of the implant on

the surface of Sawbone, since the formulation of border

conditions of the indentation model only takes into account

the interactions between the base of the indenter and the

sample surface, non-accounting for the effect of the side

walls of the indenter as it penetrates into the sample. Based

on this analysis, it can be said that the numerical model

indentation validates the analytical equations. However, the

magnitude of strain and stress values, when compared with

the numerical value of the penetration FEM model, it isn’t of

the same order of magnitude, but it is noted the same trend as

the other models. Despite this, the evidenced behavior in the

three situations is the same, which justifies that despite the

analytical model not quantify a priori the value of deflection

and penetration stress, this allows us to understand the

implant behavior when inserted in a PU sample.

5. Conclusions

The analysis of the mechanical behavior of implants

subjected to fatigue tests on different substrates, completed

with an analytical and finite element analysis, revealed

different conclusions. The results of the tests showed that the

performance of the Morse taper implant is greater than the

external hexagonal implant when both are tested cyclically in

samples of different densities. This superior resistance

presented by Morse taper system explains the significantly

increased long-term stability of these implants in clinical

applications. It has been proven that the diameter, length,

density and type of implant-abutment interface are design

variables that affect the behavior of the implants. The

deformation and tension results obtained with the penetration

FEM model exhibit the same trend as the analytical results

and MEF indentation, so that part of a scale factor, the

analytical model of indentation can be a starting point for the

explanation of the experimental results. Obviously the

conditions are different, since experimental tests are dynmic

while simulations and analytical method reproduce static

indentation behaviours.

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[4]. UNE-EN ISO 14801. (2007). “Dentistry. implants.

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[5]. Fischer-Cripps, A. C. (2007). “Introduction to contact

mechanics - second edition”. Mechanical Engineering Series.

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