Copyright © 2020 University of Bucharest Rom Biotechnol Lett.

2020; 25(4): 1802-1809

Printed in Romania. All rights reserved doi: 10.25083/rbl/25.4/1802.1809
ISSN print: 1224-5984
ISSN online: 2248-3942

Received for publication, October, 2, 2019

Accepted, January, 2, 2020

Original paper
Biomechanical Interest of Artificial Periodontal
Ligament in Dental Implantology: A Finite Element
Study
ALI BENAISSA1, ALI MERDJI1,2, IYAD MUSLIH AL-SARTAWI3, MIRCEA
STETIU4,*, MSOMI VELAPHI5, RAJSHREE HILLSTROM6, SANDIPAN ROY7,
PERK LIN CHONG8, MOHAMED EL-AMINE DJEGHLAL9, BEL-ABBÈS BACHIR
BOUIADJRA2, ANDREEA ANGELA STETIU4 , OSAMA MUKDADI10
1
Faculty of Science and Technology, Mascara University, Algeria
2
Laboratory of Mechanics and Materials Physics (LMPM), Mechanical Engineering Department, University of Sidi
Bel-Abbes, Algeria
3
Energy Services Center, Amman, Jordan
4
Lucian Blaga University, Sibiu, Romania
5
Faculty of Engineering and the Built Environmment (FEBE), Cape Peninsula University of Technology, Bellville,
Cape Town, South Africa
6
Department of Bioengineering, Tandon School of Engineering, New York University, USA
7
Department of Mechanical Engineering, SRM Institute of Science and Technology, Chennai-603203, India
8
Engineering Processes Research Group, School of Computing, Engineering & Digital Technologies, Teesside
University, Middlesbrough, UK
9
Department of Mechanical Engineering, National Polytechnic School, Algiers, Algeria
10
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506, USA

Abstract Finite element method (FEM) is an important tool used in our days even in medicine
was the relationship between the human body and artificial structure can be predicted.
This work presents a numerical study performed with FEM of new dental implant system.
A conventional dental implant system was redesigned and an artificial periodontal
ligament was interposed between the implant and the alveolar bone. The aim was to
attenuate the stress in the bone surrounding the implant. The new system was assessed
and the interface stresses compared with the ones provoked by the conventional implant.
In general, the novel dental implant provoked lower interface stresses due to the stress
shielding effect of the artificial periodontal ligament.

Keywords Dental implant, periodontal ligament, stress, finite element method.

To cite this article: BENAISSA A, MERDJI A, AL-SARTAWI IM, STETIU M, VELAPHI M,

HILLSTROM R, ROY S, CHONG PL, DJEGHLAL ME-A, BOUIADJRA B-AB, STETIU AA,
MUKDADI O. Biomechanical Interest of Artificial Periodontal Ligament in Dental Implantology: A Finite
Element Study. Rom Biotechnol Lett. 2020; 25(4): 1802-1809. DOI: 10.25083/rbl/25.4/1802.1809

*Corresponding author: MIRCEA STETIU, Lucian Blaga University, Bd-ul Victoriei, Nr. 10, Sibiu, 550024,
Tel.: 0269 218 165, Romania
E-mail: stetium@yahoo.com
 Biomechanical Interest of Artificial Periodontal Ligament in Dental Implantology: A Finite Element Study

dentistry (COCHRAN, 1999). This method can be used as

Introduction an ideal tool to investigate the functional responses of
Dental implant has been increasingly used to recover dental implants in different conditions. It allows the inves-
the masticatory function of lost tooth. It has been well tigation of the relative merits of different parameters,
known that the success of dental implant is heavily depen- shapes or designs as well as offering insight into the
dent on initial stability and long-term osseointegration internal state of stress in components or materials within
due to optimal stress distribution in the surrounding bones. the implant or at the implant–bone interface (ISHGAKI,
Stress and strain fields around osseointegrated dental 2002). In this study, artificial ligament was coated on
implants are affected by a number of biomechanical factors, Bränemark type dental implant for replacing the role of
including the type of loading, material properties of the intact periodontal ligament.
implant and the prosthesis, implant geometry, surface
structure, quality and quantity of the surrounding bone, and Material and Method
the nature of the bone–implant interface (KOCA, 2005; A. Geometrical Models
ŞTEŢIU, 2019). As far as implant shape is concerned, The modeling consists of using CAD software to
design parameters that primarily affect load transfer create three-dimensional models representing the implant
characteristics (the stress/strain distributions in the bone) systems were based on Brånemark system and mandibular
include implant diameter and the length of the bone– bone respectively. In this study two different types of
implant interface, as well as, in the case of threaded implant system were compared (Figure 1):
implants, thread pitch, shape, and depth. To increase the • The conventional implant system is composed
surface area for osseous integration, threaded implants primarily of four parts: (a) the crown, (b) the framework,
are generally preferred to smooth cylindrical ones (c) the abutment screw, (d) the Abutment, (d) and (e) the
(PAPAVASILIOU, 1996). Depending on bone quality, implant.
surface treatments and thread geometry can significantly • The new implant system is composed with the
influence implant effectiveness, in terms of both initial same parts of the conventional implant system and (f)
stability and the biomechanical nature of the bone–implant the artificial ligament was interposed between the bone
interface after the healing process (COCHRAN, 1999). and the implant.
The biomechanical behavior of dental implant is quite
different from natural teeth. One of the major reasons is that
for dental implants, there is a lack of function of periodontal
ligament. That is because material of periodontal ligament
is a soft tissue, and it could function as an intermediate
cushion element which absorbs the impact force and
uniformly transfers the occlusal forces into the surrounding
bone. However, the bio-structure of dental implant is
directly connected with bone. That would cause the
non-uniform stress pattern at bone and might induce
biomechanical overloading failures in implant and bone.
This overloading would cause the micro damage accumu-
lation at bone and results in primary marginal bone loss.
Then the bacterial invasion might occur in the area of
bone loss and cause serious progressive bone resorption
(HANSSON, 2003). This insufficient bone support is
dangerous for implant stability and might increase the risk of
implant fracture and bone failure (SPIEKERMANN, 1995).
For this reason biomechanical optimization is an
important objective in the design of dental implants several
concepts have been developed, and many implant types are
commercially available in different sizes, shapes, materials, Figure 1. Components of the models
and surfaces. To analyze the effectiveness and reliability of
endosseous implants, revealing possible risks of implant The mandibular bone the original 3D model of
failure, stress analysis of bone–implant mechanical interac- a mandibular bone section was constructed using com-
tions is important (GERAMY, 2004). The study for artificial puterized tomography (CT) scan technology (Fig. 2).
periodontal ligament has become an important issue in this The mandibular section was processed in Solidworks 3D
field. Thus, a new concept of coating an implant’s surface (CAD, Software-2012), on which the final 3D solid model
with a natural polymer membrane was introduced in order of the mandibular bone was created. The bone was mode-
to provide the viscoelastic characteristic of the periodontal led as a cancellous core surrounded by a cortical layer.
ligament to implant system. The width and height of cortical bone model were 15.8 mm
In recent years, the finite element method has been and 23.5 mm, respectively. The thickness of its upper part
used to investigate the stress distribution within implant was 2 mm (Fig. 3).
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B. Material properties
The material properties adopted were specified in
terms of Young’s modulus, Poisson’s ratio and density
for the implant and all associated components (Table 1).
All materials were assumed to exhibit linear, homoge-
neous elastic behavior (KAYABAŞ, 2006).
C. Boundary conditions
In order to define the boundary conditions, a 3D
coordinate system was defined by three dynamic loads
in the coronal–apical direction, lingual–buccal direction
and mesial–distal direction.
For the boundary conditions, 3 zones were
considered (Fig. 4):
• The inferior plane of the mandibular bone was
defined as having zero displacement.
• The central surface in the occlusale face of the
crown was subjected to a combined load of 17.1 N,
114.6 N and 23.4 N in a lingual–buccal, a coronal–
apical, and a distal–mesial direction, respectively.
The other surfaces were treated as free surfaces,
Figure 2. Computer Tomography (CT) scan of patient. i.e. zero loads.

Figure 3. Components of mandibular bone Figure 4. Boundary conditions

Table 1. Mechanical properties of investigated materials (KAYABAŞ, 2006)

Parts Materials Elastic modulus, Poisson’s Density

E [Gpa] ratio [kg/m3]
Crown Feldspathic 61.2 0.19 2300
porcelain
Framework Co–Cr alloy 218 0.33 8500
Abutment Titanium 110 0.32 4428.8
Implant Titanium 110 0.32 4428.8
Abutment Titanium 110 0.32 4428.8
screw
Ex = Ey = 11.5
Cortical bone Ez = 17 νxy = 0.48 1100
Mandibular Gxy = 3.6 νxz = νyz = 0.31
bone Gxz = Gyz = 3.3
Cancellous 3 0.29 270
bone
Artificial Silicone 0.006 0.49 2220
ligament

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 Biomechanical Interest of Artificial Periodontal Ligament in Dental Implantology: A Finite Element Study

For dynamic analysis, time dependent masticatory D. Finite Element Model

load is applied. Time history of the dynamic load com- The mesh of the components is simplistic and
ponents for 4 s is demonstrated in Figure 5. The solid model consisted of linear tetrahedron elements with four nodes
resulting from the intersection of implant and jaw bone (Fig. 6). Since the interface of bone–implant experiences
represents the assumption of complete osseointegration, the largest deformations under load, it is necessary to mesh
restricting any relative displacement between implant this boundary into small elements. The implant system and
and bone. the bone were meshed with increasingly larger elements as
the distance from the interface increases, with the size of
elements in contact with the interface being defined by
the elements of the boundary mesh.

Results
In this study, the distributions of the von Mises stress
in the bone surrounding the implant were investigated.
The von Mises stress is a scalar variable that is defined in
terms of all the individual stress components and, therefore,
is a good representative of the state of stresses. It has been
extensively used in biomechanical studies of bone and
dental prostheses (GENG, 2001).
The distributions of overall stress state for each
component in our model were shown under effect of axial
and horizontal loading in the coronal–apical, lingual–
buccal and distal–mesial. A qualitative and quantitative
analysis was performed, based on a progressive visual color
Figure 5. Dynamic loading in 4 s. scale, pre-defined by the software used, ranging from dark
blue to red (Fig. 7). The maximum stress values in each
component under different loading are shown in (Fig. 8).

Figure 6. Mesh using linear tetrahedron elements of: (a) the parts of the implant system and
(b) the mandibular bone and the final model.

In this section, the von Mises stresses were obtained used to plot the von Mises stresses variation. Along the
from the analysis, allowing the consideration of maximum paths shown in the same figure, graphics were generated
compressive and tensile stresses, as bone behavior under to make comparisons between both implant system geo-
tension and compression is essentially different. Figure 9 metries, displaying maximum and minimum von Mises
shows points distributed along the implant–bone interface stresses for both models under combined dynamic loads.
at a cervical, bucco-lingual and a pathmesio-distal section
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Figure 7. The distributions of overall stress ranging Figure 8. Histograms of comparison of von Mises stresses
from dark blue to red. for each component in both models.

Figure 9. Different paths of the bone-implant interface used for stress distribution.

Figures 10, 11 and 12 present a comparison of von direction, and sudden a slight ascends on the curves shows
Mises stress distribution along the cross-section of both the increase in stresses at the base of the implant on the
models for the three different types of loadings. The largest same side as those in cortical bone (Fig. 13). For the new
tensile stresses occurred in the cortical bone in one side implant system with artificial ligament in mesiodistal
loaded under the larger curvature region of the crown direction path (Fig. 11), the stress distribution was quali-
surface in the cervical area while the highest stresses tative similar with the conventional implant; however,
occurred on the cervical line (Fig. 10). there is a big difference in the cortical bone. A similar
The conventional implant under dynamic load was pattern occurred for buccolingual direction path (Fig. 12),
presented a high compressive peak stress concentration in although reaching different values.
one side of the cortical bone around the implant and a smo- In general, the curves show that the stress distribution
oth distribution along the body of cancellous bone (Fig. 11 at the interface in the bone of the model with an artificial
and 12). These stresses, decreased in the coronal–apical ligament was lower than for the conventional model.
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 Biomechanical Interest of Artificial Periodontal Ligament in Dental Implantology: A Finite Element Study

Figure 10. Comparison of stress distribution around Figure 11. Comparison of stress distribution around
bone/implant interface (Cervical path). bone/implant interface (Mesiodistal path).

Figure 12. Comparison of stress distribution around Figure 13. The stress contours of cancellous bone
bone/implant interface (Buccolingual path). for buccal side.

surface area between the implant and the cancellous bone.

Discussion In addition, the cortical bone is more than ten times stiffer
The aim of this study was to provide an analysis than the cancellous bone. These are the reasons due to the
between two different geometric configurations of implant high stress increments were found in the cortical bone.
systems, to find the pure effect upon the bone stresses of • The intimate contact at the cortical bone and
prosthesis materials, to know the influence of the artificial implant interface; the loading applied to the implant is
ligament on the load transfer to the bone and to compare directly transmitted to the cortical bone.
their biomechanical behavior. For this reason, it was This suggests that great importance is to be attached
assumed that all the parameters of both models were to the contact of the implant with the cortical layer of bone.
identical except the structural part of prosthetic design. In a number of radiologic long-term studies, loaded
In both models, the extreme stresses in the mandibular implants showed typical bone loss around the implant neck
bone occur in the layer of cortical bone adjacent to the neck (NATALI, 2006). This agrees well with the results of the
of the implants. These were due to: present finite element study, in which the highest stress
• The evidence of the surface area between the levels occurred in this very area. The cervical bone
implant and the cortical bone is much smaller than the resorption always occurs to accommodate the reformation
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ALI BENAISSA et al

of a ‘biological width’. Preservation of peri-implant bone • Stresses in the new implant system with artificial
height depends on the magnitude and concentration of ligament were in general lower than in the conventional
stress transmitted to the bone by the implant. There appears implant;
to be an optimal level of stress at which bone resorption is • In both geometries stress concentration occurred
balanced by apposition. The minimum required load for at one side of the neck;
avoidance of cortical bone loss appears to have been • High magnitudes stresses in mandibular bone
defined, but the upper limit of the physiological stress range were observed in the cortical area;
has not yet been fully investigated. • The cancellous bone presented low stress concen-
In order to improve osseointegration, recent studies tration for both geometries;
have focused on implant position, shape, and surface • The use of implant/bone interface with lower
characteristics (COOPER, 1998; VAN STEENBERGHE, stiffness was capable to diminish or to delay the loads
1995; LUMBIKANONDA, 2001). Stress around implants transmitted to the bone.
may lead to bone resorption and implant loss (TADA,
2003; KITAMURA, 2005; VAN OOSTERWYCK, 1998; References
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