UNIVERSIDADE ESTADUAL PAULISTA
“JÚLIO DE MESQUITA FILHO”
Instituto de Ciência e Tecnologia
Campus de São José dos Campos
ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2024.e4234
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Braz Dent Sci 2024 Apr/June;27 (2): e4234
This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron sputtering
Deposição de polímero de poliéter cetona cetona em titânio comercial puro com superfície estruturada a laser usando
pulverização catódica por magnetron
Aseel Mohammed AL-KHAFAJI1 , Moamin I. ISSA1 , Fatimah J. ISMAEL2 , Thekra Ismael HAMAD1 , Hikmat J. ALJUDY1
1 - University of Baghdad, College of Dentistry, Department of Prosthodontics. Baghdad, Iraq.
2 - University of Baghdad, College of Dentistry, Department of Oral Diagnosis. Baghdad, Iraq.
How to cite: Al-Khafaji AM, Issa MI, Ismael FJ, Hamad TI, Aljudy HJ. Poly ether keton keton polymer deposition on laser surface structured
commercial pure titanium using magnetron sputtering. Braz Dent Sci. 2024;27(2):e4234. https://doi.org/10.4322/bds.2024.e4234
ABSTRACT
Objective: This study aimed to evaluate the effect of coating titanium (Ti) dental implant with polyether ketone
ketone (PEKK) polymer using magnetron sputtering on osseointegration, trying to overcome some of the problems
associated with Ti alloys. Material and Methods: Implants were prepared from grade (II) commercially pure
titanium (CP Ti), then laser was used to induce roughness on the surface of Ti. PEKK was deposited on the
surface of Ti implants by radiofrequency (RF) magnetron sputtering technique. The implants were divided in
to three groups: without coating (Ls), with PEKK coating using argon (Ar) as sputtering gas (Ls-PEKK-Ar), and
with PEKK coating using nitrogen (N) as sputtering gas (Ls-PEKK-N). All the implants were implanted in the
femoral bones of rabbits. After three different healing periods (2, 6, and 12 weeks) the rabbits were sacriced
for a mechanical examination (removal torque) and for histological examination. Results: The results revealed a
signicant increase in the removal torque mean values when using PEKK coating on Ti implants, with the highest
value recorded by Ls-PEKK-N group. Histologically, the study demonstrated the progression of osteogenesis during
all the research periods. It was observed that the Ls-PEKK-N group had the highest percentage of new bone
formation in all healing periods. Conclusion: The use of PEKK as coating material on the surface of Ti implants
by RF- magnetron sputtering results in an increase in the torque required to remove implants and enhance bony
tissue formation around the implants especially when using nitrogen as a sputtering gas.
KEYWORDS
Dental implant; Magnetron sputtering; Osseointegration; PEKK; Titanium.
RESUMO
Objetivo: Este estudo teve como objetivo avaliar o efeito do revestimento de implante dentário de titânio (Ti)
com polímero de poliéter cetona cetona (PEKK) usando pulverização catódica por magnetron na osseointegração,
tentando superar alguns dos problemas associados às ligas de Ti. Material e Métodos: Os implantes foram
preparados a partir de titânio comercialmente puro grau (II) (CP Ti), em seguida o laser foi utilizado para
induzir rugosidade na superfície do Ti. PEKK foi depositado na superfície de implantes de Ti pela técnica de
pulverização catódica por radiofrequência (RF). Os implantes foram divididos em três grupos: sem revestimento
(Ls), com revestimento de PEKK utilizando argônio (Ar) como gás de pulverização catódica (Ls-PEKK-Ar) e com
revestimento de PEKK utilizando nitrogênio (N) como gás de pulverização catódica (Ls-PEKK -N). Todos os
implantes foram implantados em ossos femorais de coelhos. Após três períodos de cicatrização diferentes (2, 6
e 12 semanas), os coelhos foram sacricados para exame mecânico (torque de remoção) e exame histológico.
Resultados: Os resultados revelaram um aumento signicativo nos valores médios do torque de remoção quando
se utilizou o revestimento de PEKK em implantes de Ti, sendo o maior valor registrado pelo grupo Ls-PEKK-N.
Histologicamente, o estudo demonstrou a progressão da osteogênese durante todos os períodos da pesquisa.
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Braz Dent Sci 2024 Apr/June;27 (2): e4234
Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
INTRODUCTION
Dental implants have emerged as a secure
and dependable therapeutic approach for those
experiencing diminished dentition [1]. Titanium
and its alloys are the materials that can be considered
to be the most widely used for endosseous implants
in dentistry, this could be due to their favorable
mechanical characteristics, superior biological
compatibility, and improved durability against
corrosion [2]. Despite its widespread use, the use
of titanium and its alloys as dental implants may
be associated with a few drawbacks. One such
disadvantage is the discrepancy in elastic moduli
between the titanium implant and the adjacent bony
tissue. This phenomenon has the ability to elevate
the likelihood of mechanical stressing of the bone,
hence resulting in detrimental effects on the adjacent
bone and subsequent bone loss [3,4]. The success
rate of dental implants depends primarily on their
ability to osseointegrate and maintain surrounding
bone [5,6]. The process of osseointegration can be
inuenced by various variables, such as the material
characteristics, surface topography, and geometry
of the implant. Consequently, the optimization of
osseointegration in dental implants is consistently
sought after in order to get favorable outcomes in
clinical practice [7]. Surface alteration of dental
implants, particularly through topographical
means, is well recognized as an effective approach
for enhancing the biological activity of these
implants [8,9]. Laser surface treatment of implants
has been shown to improve osseointegration by
changing titanium roughness; by formation of
microscopical surface structures, increasing water
absorption, and enhancement of oxide layer [10].
In addition to employing modified approaches
for inducing modification on the surface of the
implant, certain additive methods are also utilized
like implant surface coatings [11,12]. Polymers
represent important dental materials that have
favorable physical, mechanical, and biocompatibility
characteristics [13]. PEKK is an innovative polymer
that has piqued the interest of the researchers due to
its outstanding characteristics that can be employed
in a wide range of applications. In the last few
years, PEKK has been progressively employed as a
biomaterial due to the inherent characteristics, such
as excellent biocompatibility, sufcient resistance
to fracture, suitable compressive, tensile, and
exural strength, modulus of elasticity comparable
to that of bone, that render it appropriate for
many dental and medical applications. These may
include applications in orthopedics, spinal, oral, and
maxillofacial surgeries, prosthodontics, and dental
implants [6,14-17]. Magnetron sputtering is one of
the methods that are used for coating process. It is
a physical technique for vapor deposition in which
electrically charged particles strike a desired target’s
surface under the inuence of both magnetic and
electrical fields [18,19]. Several studies were
conducted to implement various coating materials
like calcium phosphate, hydroxyapatite, dicalcium
pyrophosphate , boron nitride using magnetron
sputtering technique, on the surface of dental and
medical implants to exert a topographical change
in an attempt to improve the osseointegration of
the implants [20-24].This study aimed to assess the
mechanical and histological effects of depositing
PEKK material by magnetron sputtering on laser
surface textured CPTi implant screws. The null
hypothesis is that the coating of laser surface
textured CPTi implants with PEKK polymer doesn’t
affect the required torque to remove implant from
the bone nor the histology of the bone in the
implantation site.
MATERIALS AND METHODS
Sample preparation
A commercially pure titanium (CP Ti) grade
(II) (Orotig Srl EU Company, Italy) was utilized
in the form of annealed rods of 1,000 mm in
length and 6 mm in diameter. These rods were
Observou-se que o grupo Ls-PEKK-N apresentou maior percentual de neoformação óssea em todos os períodos
de cicatrização. Conclusão: O uso de PEKK como material de revestimento na superfície de implantes de Ti por
pulverização catódica RF-magnetron resulta em um aumento no torque necessário para remover os implantes e
melhorar a formação de tecido ósseo ao redor dos implantes, especialmente quando se utiliza nitrogênio como
gás de pulverização catódica.
PALAVRAS-CHAVE
Implante dentário; Pulverização catódica por magnetron; Osseointegração; PEKK; Titânio.
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Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
employed to fabricate 180 implant screws.
A turning machine was used to create a screw-
shaped specimen (implants) with dimensions of
3 mm diameter and 5 mm length. The specimens
underwent an ultrasonic cleaning process with
ethanol followed by distilled water then air dried.
The sample size was determined by using G power
3.1.9.7 (Program written by Franz-Faul, University
of Kiel, Germany) with power of study=85%,
alpha error of probability=0.05 two sided, assume
effect size of F is 0.4 (large effect size), and nine
groups (3 groups with three different periods)
thus sample size is about 90 implants (10 implants
for each group in each healing period).This
calculation applied for the removal torque test,
and applied separately for the histological test
(in which also 90 implants required). Therefore,
a total of 180 implants were used [25, 26].
Surface structuring by laser
The laser was utilized to induce surface
roughening on titanium. The surfaces of titanium
specimens underwent structuring under ambient
conditions using a pulse mode CNC ber laser
device. (Jinan JinQiang 20W laser--- China)
having an output laser power of 20-Watt with an
emission wavelength of 1064 nm and maximum
scanning speed of 7000 mm/sec. The sample-
laser source distance was 20 cm. The dot design
was utilized to structure the entire surface of
the specimen, with 0.01 mm space among each
neighboring dot in every direction.
PEKK coating
The deposition of PEKK coatings on Ti screws
was carried out using radiofrequency reactive
magnetron sputtering technique and device (Torr
International Inc., United States) (Figure 1),
employing PEKK as the sputtering target.
The sputtering target (PEKK disc) which
has (50mm) diameter and (4mm) thickness,
was attached to the anode (positive charge) of
system and the specimens (titanium implants)
were mounted on the custom-made holder and
attached to cathode (negative charge) rotating
disc. The specimens to target distance has been
set at 5 cm. The cathode disc was rotated at a
constant velocity to provide uniform distribution of
PEKK material across all surfaces of the implants.
The vacuum process was initiated to remove
air from the chamber of the device, ultimately
achieving a base pressure of 5.5 x 10-6 mbar, and
the space inside was lled with either argon gas
or nitrogen gas. A preliminary sputtering process
was conducted at an operating pressure of 1.5 x
10-3 mbar to cleanse the surface of the target and
establish stable sputtering circumstances.
After setting the specimens’ temperature
to 60C for one hour, and the operational power
equaled 50 watt a thin coating of PEKK was
produced (Figure 2).
The implant screws preparation workow is
shown in (Figure 3).
Figure 1 - Magnetron sputtering device, (A) The entire apparatus; (B) Sputtering chamber.
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Braz Dent Sci 2024 Apr/June;27 (2): e4234
Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
Elemental analysis with EDX
Energy dispersive X-ray analysis (EDX)
was performed to determine the composition
information and elemental identication of the
implant surface. This was accomplished by using
eld-emission scanning electron microscope with
EDX system attachment (MIRA3, TESCAN, Czech
Republic).
Sterilization of the specimens
All the specimens (implants) were sterilized
using autoclave due to the PEKK materials’
ability to endure elevated temperatures and their
compatibility with steam sterilization [27,28].
Sample grouping
According to the type of surface modication
the titanium screws were divided into 3 groups:
Ls: CP Ti screws with laser structuring and
without coating;
Ls-PEKK-Ar: CP Ti screws with laser
structuring and PEKK coating using argon gas in
RF-magnetron sputtering;
Ls-PEKK-N: CP Ti screws with laser
structuring and PEKK coating using nitrogen
gas in RF-magnetron sputtering.
These groups were tested mechanically
(removal torque) and histologically
(histomorphometric analysis) on three different
healing periods (2, 6, and 12 weeks). A total of
180 implant screws were used, with 10 screws
being given to each group for each test during
each healing period.
A diagrammatic flowchart of sample
preparation and the entire workow is shown
in (Figure 4).
Animal experiment (in vivo study)
This study was approved by the Research
Ethics Committee of the College of Dentistry,
University of Baghdad (ref. number 244, project
number 244221 at 10.2.2021). A total of sixty
healthy New Zealand white rabbits aged 10 to
12 months and weighing 2–2.5 kg, without any
apparent illnesses, were chosen for the study.
The animals were maintained in a controlled
Figure 2 - Schematic illustration of magnetron sputtering process.
Figure 3 - Ti implant screws preparation workflow, (A) Before
surface structuring by laser; (B) After laser structuring; (C) After
PEKK coating.
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Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
environment, conforming to conventional
parameters, with a regulated temperature range
of 23°C–25°C., as well as dietary needs supplies.
The study’s rabbits were divided randomly into
three groups based on healing period: 2 weeks,
6 weeks, and 12 weeks. A simple randomization
method was used. The rabbits and the samples
were randomly coded and numbered (to allow
later data interpretation after data analysis), and
the rabbits were randomly distributed all over the
three healing periods for the mechanical (removal
torque) and histological tests. However, for
organization purposes and to facilitate later data
interpretation three implants were implanted in
the femoral bones in each rabbit (the right femur
received 1 implant from Ls group, while the left
femur received 2 implants 1 from Ls-PEKK-Ar
group and 1 from Ls-PEKK-N group, ensuring
1cm distance between the two implants which
allow independency of each implant and implant
site). Each primary group has 20 animals; 10 had
to be sacriced for histological examination and
10 for mechanical testing using a removal torque
test, and this was applied for each healing period.
Surgical procedure
The surgical procedure was conducted
using a meticulous and extremely sterile aseptic
method. The rabbits were anaesthetized with an
intramuscular injection of ketamine hydrochloride
50 mg at a dosage of 1 ml/ kg, along with
xylocaine 2% at a dosage of 1 ml /kg of body
weight. After surgery, 0.05 mg/kg buprenorphine
was injected intramuscularly to alleviate pain.
Continuous monitoring of the animal’s body
temperature and oxygen levels was performed
throughout the surgical procedure. The operative
site was prepared through the removal of fur and
subsequent disinfection of the skin using 70%
ethanol and chlorhexidine then surgical towels
and iodine-ethanol wash were applied.
The lateral side of the femoral bone was
exposed by making approximately a 3cm incision
then a flap and skin were carefully reflected
after gaining access to the bone a guiding drill
was used, the initial holes (1.8 mm in diameter,
5 mm in depth, and 1 cm apart from each other)
were made using an implant operation engine and
drills (Dentium F28D104 112,Korea) . The drilling
speed was 800 rpm, and the torque was 20 N
accompanied with saline irrigation. The implant
bed was gradually enlarged in a stepwise manner
up to a diameter of 2.8 mm. Afterwards, the implant
bed was thoroughly washed of drilling debris
utilizing a solution of normal saline. Following
this, the sterilized implant was taken from its
packaging and then screwed into the designated
site employing a screwdriver then torqued using
torque meter to 10 N.cm [29,30]. The surgical
wound was stitched and disinfected using iodine
and treated with a local oxytetracycline spray then
covered with sterile gauze, which was changed on a
daily basis. Additionally, a systemic oxytetracycline
injection at a dosage of 20% and 0.5ml /kg was
administered each day for a duration of ve days.
After surgery, rabbits and the surgical site
are regularly checked for infections and concerns.
Figure 4 - A diagrammatic flowchart of the entire workflow.
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Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
The animals were subjected to supervision for
durations of 2 weeks, 6 weeks, and 12 weeks.
Removal torque test
For each healing interval (2, 6, and 12 weeks),
ten rabbits were employed for removal torque
mechanical testing. The rabbits were subjected
to anesthesia, following which an incision in the
lateral side of the rabbit femur was made then the
muscles and fascia were retracted to reveal the
implants. The digital torque meter (Hitachi
Maxwell LTD./174, Japan) was utilized to
engage the slit in the implant head, enabling the
recording of the maximal peak torque required
for loosening the implant from the bony site.
The removal torque was measured in units of
Newton-centimeters.
Histology and histomorphometry
Tissue sample for histological evaluation
was collected by the utilization of a disc cutter
connected to a slow-speed rotation handpiece,
which was accompanied with robust freezing.
To facilitate humane euthanasia, a surplus
quantity of anesthetic solution was administered
to the rabbits. The excised tissue samples were
promptly immersed in a solution of 10% buffered
formalin and allowed to undergo xation for a
duration of 24 hours. Subsequently, the tissues
were immersed in a solution of 10% formic acid to
facilitate the process of decalcication. The tissue
samples were subjected to a two-week period of
xation, after which the screws were removed,
rendering the specimens suitable for histological
investigation.
The tissue samples underwent paraffin
embedding, formalin xation, and hematoxylin
and eosin staining. Specically, the Olympus CH
model light microscope was used to examine
the dyed slides. A modified adaptor called
Labcam, made in the United States, was used in
conjunction with an iPhone camera to capture a
series of images at different magnications.
A histomorphometric analysis was performed
with the software program Image J Version 1.52.
The newly formed bone’s area was calculated by
software using pixels. The diameter of the circular
image was measured using the integrated ruler
of the microscope and the Picture J program on
a desktop computer to transform the pixel values
into millimeter measurements (Image J analyze
set scale Pixels in mm). A precise scale factor
and the magnication power used to take all the
photos were calculated for the microscope.
The percentage of new bone formation
area (NBFA) for each experimental group and at
different points during the healing process was
calculated using the formula used in this study.
The calculation of the new bone formation area
as a percentage of the total tissue area, denoted
as NBFA%, yields a value of 100%. This approach
yielded a quantication of the extent of new bone
formation surrounding the implant site.
Statistical analysis
Statistical analysis of the data was carried
out using Prism 8 (GraphPad Software, USA)
(RRID:SCR_002798). The results were visually
represented using bar charts, where the mean
values were positioned within the vertical bars and
the standard deviation was indicated above the
bars. To determine statistical signicance across
groups, one-way analysis of variance (ANOVA)
was used, and for multiple comparisons, Tukey’s
HSD (honestly signicant difference) post-hoc
test was used at a level of signicance of 0.05.
RESULTS
Elemental analysis with EDX
The EDX spectrum and elemental analysis of
all groups are presented in (Figure 5). The EDX
spectrum obtained from the Ls group showed
titanium (Ti) with energy at 4.5 keV and oxygen
(O) with energy at 0.51 keV. While the spectrum
from Ls-PEKK-Ar group showed carbon (C) with
energy at 0.25 KeV in addition to both (Ti) and
(O). Furthermore, the spectrum from Ls-PEKK-N
group showed titanium, oxygen, carbon and
nitrogen (N) with energy at 0.39 keV.
Removal torque test
The results were visually represented using
a bar chart, where the torque mean values were
positioned within the vertical bars and the
standard deviation was indicated above the bars
(Figure 6). During the three healing periods (2,
6, and 12 weeks) statistical analysis using one
way ANOVA showed a signicant difference in
torque required to remove the implant among the
groups (
P
˂0.0001). Multiple comparisons using
the Tukey’s HSD test among the groups of each
healing period showed a signicant differences
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Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
among them (
P
˂0.0001), except for the 2 weeks
period where there was non-signicant difference
between Ls-PEKK-Ar group and Ls-PEKK-N group
(
P
=0.1857).The highest torque mean value
recorded by Ls-PEKK-N group in all periods,
for 2 weeks (20.13±1.31) while for 6 weeks
(42.98±0.95) and for 12 weeks (65.25±0.78)
(Figure 6). So, the outcomes of the removal
torque test were recorded an increase in the
torque required for implant removal with the use
of PEKK as coating.
Histology and histomorphometry
Histological analysis conducted at different
stages of the healing process revealed the
progression of osteogenesis in the experimental
cohorts as shown in (Figure 7).
The Ls group had minimal new bone
formation after a 2-week period, presented as
dispersed immature bone trabeculae surrounding
the implant space as depicted in Figure 8A,
with an estimated area of 2.18%. On the other
hand, it was observed that the Ls-PEKK-N
group had the highest percentage of new bone
formation (2.91%) during this period, whereas
the Ls-PEKK-AR group showed a greater level of
new bone development (2.63%). The histological
sections revealed woven bone trabeculae that
were encircled by osteoblasts that were actively
functioning. Figure 8B, C.
At the 6-week time point, it can be observed
that all groups had a greater extent of new bone
formation, this was characterized by the presence
Figure 5 - EDX results of (A) Ls implant; (B) Ls-PEKK-Ar implant, and (C) Ls-PEKK-N implant.
Figure 6 - Removal torque mean values with standard deviation, and
the level of significance between the groups in at 2,6 and 12-week
healing intervals (ns: non-significant, ** : significant difference).
Figure 7 - NBFA with standard deviation, and the level of significance
between the groups in at 2,6 and 12 week healing intervals (ns: non-
significant, ** : significant difference).
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Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
of more developed woven bone trabeculae, as
well as prominent functioning osteoblastic rim
and osteocytes inside the lacunae as shown
in Figure 8D, E, F. Among the groups, it was
observed that the Ls-PEKK-N group had the
highest percentage of new bone production,
measuring at 8.74% and the most mature looking
bone trabeculae.
After a duration of 12 weeks, it was seen
that all groups exhibited notable enhancements
in bone formation and maturation, as shown in
Figure 8G, H, I. The Ls group had a substantial
increase in new bone formation (13.02%),
accompanied by a considerable presence of
osteoblasts and osteocytes, as well as the
development of Haversian networks. The PEKK-AR
group had a comparatively elevated rate of
new bone formation at 15.24%. Conversely,
the PEKK-N group, characterized by advanced
maturity, well-structured Haversian systems,
and significant lamellar bone organization,
demonstrated the highest rate of new bone
formation at 16.88%.
A histological image in panoramic view for
the bone-implant space interface showing bone
formation in screw threads area using Lecia
inverted light microscope at 10X magnication
(Figure 9).
Figure 8 - Hematoxylin and eosin cross sectional histological view of new bone formation area surrounding implant space (4X), (A) control
group at 2-week; (B) Ls-PEKK-AR at 2-week; (C) Ls-PEKK-N group at 2-week; (D) control group at 6-weeks; (E) Ls-PEKK-AR at 6 weeks; (F)
Ls-PEKK-N group at 6 weeks; (G) control group at 12 weeks; (H) Ls-PEKK-AR at 12 weeks; (I) Ls-PEKK-N group at 12 weeks.
Figure 9 - A histological image in panoramic view for the bone-
implant space interface at 10X magnification.
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Braz Dent Sci 2024 Apr/June;27 (2): e4234
Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
DISCUSSION
Surface modification of dental implants,
particularly by alterations in topography and
chemical structures, has been recognized as a
highly successful approach for enhancing the
bioactivity of these implants [8,9,31]. In addition
to that stress distribution of occlusal load to the
peripheral bone surrounding dental implants is
crucial for implant longevity [32].
PEKK exhibits exceptional physical as
well as mechanical characteristics [17]. PEKK’s
durability, shock absorption, sufcient strength
(65 MPa), and fracture resistant features make
it a viable restorative material. When compared
to dentin, the PEKK has a similar compressive
strength but a lower modulus of elasticity. PEKK,
like polyetheretherketone (PEEK), has an elastic
modulus that is similar to that of bone. Therefore,
it can be concluded that PEKK possesses desirable
mechanical characteristics and excellent stress
distribution, making it a suitable biomaterial for
dental implants [33,34].
In the present study RF- magnetron sputtering
technique, was used for coating laser textured Ti
dental implants with PEKK material, in an attempt
to enhance the implant bioactivity and improve
osseointegration that was evaluated by measuring
the torque required to remove implants from bone
and by histological evaluation [35,36]. According
to the ndings of the current study, coating laser
textured Ti dental implants with PEKK polymer
resulted in an increase in removal torque and in
bone formation and maturation. Therefore, the
null hypothesis was rejected.
In this study the healing periods were selected
based on different studies. Different studies used
different periods (one or more) whether 2, 4, 6,
8, or 12 weeks. In this study we used 2 weeks as
the rst period which was the rst period used in
many studies [37-39] and it was noted that a new
bone formation surrounding the dental implant
was evident 2 weeks after implant insertion [37].
While in a study by Dhaliwal et al., 2017 rabbits
were sacriced after 6 weeks healing period [40].
Also, Gehrke and Marin, 2015 used 6 weeks as
the rst euthanasia period [41]. The 12 weeks
healing period was the longest used in most of the
studies [37,41,42], in which considerable direct
bone contact with the implant was observed after
12 weeks [37].
The results of this study showed that the
removal torque mean values for all the groups
were increased over time. This elevation in torque
mean value with time might be due to progressive
bone formation and the maturation of woven
bone to lamellar bone around the implants that
consequently improved osseointegration and the
mechanical capacity with time [43,44].
The results of this study showed that
coating Ti dental implant with PEKK results in
greater removal torque mean values. Although
laser surface treatment causes increase in
the osseointegration capability of the dental
implant, which might be due to increase in the
implant surface roughness [45,46]. However,
coating implant with PEKK resulted in stronger
osseointegration capability that could be
attributed to the greater surface roughness that
related to particle size of PEKK powder and
change of the surface chemistry.
Regarding chemistry and surface
microstructure, a research reported that PEKK has
a large number of ketone groups which enhance
the capacity for surface chemical modication that
can results in complicated surface topography,
increased surface area, and a microrough surface,
all of which can enhance cellular activity and
the process of osteointegration on the surface of
PEKK [47,48].
Histological and histomorphometric analysis
of this study revealed a signicant increase in
NBFA with highly organized bone trabeculae
surrounded by well-defined osteoblastic rim
around the implant site in all groups comparative
to Ls group and this result may be related to
many factors, the first one is the increase in
the implant roughness that led to increase
contact area, cell adhesion, proliferative abilities,
interlocking with the tissue that enhance implants
osseointegration [46,49,50]. The rough surfaces
had conrmed superior biomolecules adsorption
from biological uids, which has the probability
to modify the events cascade that leads to
intimate bone apposition and bone healing with
the implants [51,52].
Regarding the differences in the mean values of
torque removal between Ls-PEKK-N and Ls-PEKK-Ar
groups, although argon is the preferred operating
gas for magnetron sputtering procedures because
of its substantial atomic mass, unreactive nature,
and comparatively affordable price. Different gases
can be utilized for sputtering deposition, each
10
Braz Dent Sci 2024 Apr/June;27 (2): e4234
Al-Khafaji AM et al.
Poly ether keton keton polymer deposition on laser surface structured commercial pure titanium using magnetron sputtering
Al-Khafaji AM et al. Poly ether keton keton polymer deposition on laser surface
structured commercial pure titanium using magnetron
sputtering
with different mass properties. Consequently, the
momentum behavior varies when solid surfaces
are bombarded by ions, which in turn affects
the sputtering yield, particle implantation, and
inclusion of process gas into the formed coatings.
The gas incorporation in the coating is higher for
sputtering gases with lower atomic mass [53].
Due to the fact that nitrogen has a lower
atomic mass than argon, so this can explain
the result of EDX analysis which showed the
presence of nitrogen in the Ls-PEKK-N group
(Figure 5). Nitrogen-containing compounds have
the ability to inuence arginylglycylaspartic acid;
this is the primary integrin binding domain to
bronectin and a member of the adhesive protein
class. It has been proposed that extracellular
fibronectin and cell adhesion are strongly
linked. Therefore, functional groups that include
nitrogen (which presented on implant surface)
may have the ability to modulate the integrin-
mediated signaling cascade, which in turn
promotes adhesion, growth, and differentiation
of osteoblast cells [54]. In addition to that the
negative charge of osteoblast cells may interact
with the positive charge of the functional groups
that contain nitrogen facilitating cell adhesion
and promoting cell growth and the development
of bone tissue [55,56]. We Hypothesize that
these mechanisms may explain the higher mean
value of torque removal and the highly signicant
increase in NBFA and mature looking bone
trabeculae of Ls-PEKK-N group in comparison to
Ls-PEKK-Ar group.
CONCLUSION
Coating Ti dental implants with PEKK
polymer by RF-magnetron sputtering can result
in an improved stability of implants that can be
concluded from a higher torque required to remove
implant from bone and from histomorphometric
analysis which revealed an increase in NBFA and
mature-looking bone trabeculae, especially when
using nitrogen as sputtering gas. These ndings
open up new research avenues for utilizing these
new technologies to improve osteointegration
around the implant site.
Author’s Contributions
AMAK: Conceptualization, Methodology,
Investigation, Resources, Data Curation,
Supervision, Project Administration and Funding
Acquisition. MII: Conceptualization, Software,
Writing – Original Draft Preparation, Writing
– Review & Editing, Visualization and Funding
Acquisition. FJI: Methodology, Software,
Validation, Formal Analysis, Investigation,
Resources, Data Curation, Writing – Original Draft
Preparation. TIH: Conceptualization, Validation,
Formal Analysis, Visualization, Supervision,
Project Administration and Funding Acquisition.
HJA: Validation, Formal Analysis, Investigation,
Resources, Visualization, Supervision, Project
Administration and Funding Acquisition.
Conict of interest
The authors have no proprietary, nancial,
or other personal interest of any nature or kind
in any product, service, and/or company that is
presented in this article.
Funding
This research did not receive any specic
grant from funding agencies in the public,
commercial, or not-for-prot sectors.
Regulatory Statement
This study was conducted in accordance with
all the provisions of the local human subjects
oversight committee guidelines and policies of
the research ethics committee of the college of
dentistry, university of Baghdad. The approval
code for this study is (ref. number 244, project
number 244221 at 10.2.2021).
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Moamin I. Issa
(Corresponding address)
University of Baghdad, College of Dentistry, Department of
Prosthodontics, Baghdad, Iraq.
Email: moamin_alniama@codental.uobaghdad.edu.iq
Date submitted: 2024 Jan 17
Accept submission: 2024 May 30
