1. J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 9 (2012) 45–49
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/jmbbm
Short communication
Assessment of a chair-side argon-based non-thermal plasma
treatment on the surface characteristics and integration of
dental implants with textured surfaces
Hellen S. Teixeira a,⇤ , Charles Marin b , Lukasz Witek a , Amilcar Freitas Jr. a ,
Nelson R.F. Silva c , Thomas Lilin d , Nick Tovar a , Malvin N. Janal e , Paulo G. Coelho a
a Department of Biomaterials and Biomimetics, New York University, New York, NY, USA
b Department of Dentistry, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
c Department of Prosthodontics, New York University, New York, NY, USA
d École Nationale Vétérinaire d’Alfort, Maisons-Alfort, Val-de-Marne, France
e Department of Epidemiology and Health Promotion, New York University, New York, NY, USA
A R T I C L E I N F O A B S T R A C T
Article history: The biomechanical effects of a non-thermal plasma (NTP) treatment, suitable for use in a
Received 31 May 2011 dental office, on the surface character and integration of a textured dental implant surface
Received in revised form in a beagle dog model were evaluated. The experiment compared a control treatment,
9 January 2012 which presented an alumina-blasted/acid-etched (AB/AE) surface, to two experimental
Accepted 14 January 2012 treatments, in which the same AB/AE surface also received NTP treatment for a period
Published online 31 January 2012 of 20 or 60 s per implant quadrant (PLASMA 200 and PLASMA 600 groups, respectively).
The surface of each specimen was characterized by electron microscopy and optical
Keywords: interferometry, and surface energy and surface chemistry were determined prior to and
Implant surface treatment after plasma treatment. Two implants of each type were then placed at six bilateral
Argon plasma locations in 6 dogs, and allowed to heal for 2 or 4 weeks. Following sacrifice, removal
Surface modification torque was evaluated as a function of animal, implant surface and time in vivo in a
Osseointegration mixed model ANOVA. Compared to the CONTROL group, PLASMA 200 and 600 groups
in vivo presented substantially higher surface energy levels, lower amounts of adsorbed C species
and significantly higher torque levels (p = .001). Result indicated that the NTP treatment
increased the surface energy and the biomechanical fixation of textured-surface dental
implants at early times in vivo.
c 2012 Elsevier Ltd. All rights reserved.
1. Introduction events that leads to bone healing and intimate interaction
with the device (Jimbo et al., 2007). Several reviews (Coelho
The rationale for surface modification focuses on implant et al., 2009; Dohan Ehrenfest et al., 2010) lead to a gen-
interaction with biofluids positively altering the cascade of eral consensus that both rough surfaces (over smooth turned
⇤ Correspondence to: New York University College of Dentistry, 345 E 24th Street, room 813a, New York, NY 10010, USA. Tel.: +1 212 998
9214; fax: +1 212 998 9214.
E-mail address: hst228@nyu.edu (H.S. Teixeira).
1751-6161/$ - see front matter c 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jmbbm.2012.01.012

2. 46 J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 9 (2012) 45–49
surfaces) and surface chemistry (Ca–P based coatings over average high deviation), Sq (root mean square), Sds (density of
non-coated surfaces) favor the early host-to-implant re- summits), and Sdr (developed surface ratio) parameters were
sponse (Albrektsson and Wennerberg, 2004a,b; Coelho et al., determined. A filter size of 250 µm ⇥ 250 µm was utilized.
2009). Surface energy (SE) was determined using the Owens–
However, in most cases, combinations of texture and Wendt–Rabel–Kaelble (OWRK) method (Owens and Wendt,
chemistry known to hasten osseointegration are proprietary 1969). Briefly, 500 µl droplets of distilled water, ethylene
processes and not available for the dental community. An glycol, and diiodomethane were deposited on the surface
economically viable, chair side, operator (dental surgeon) of each implant with a micro-pipette (OCA 30, Data Physics
controlled surface treatment that enhances the host response Instruments GmbH, Filderstadt, Germany). Images were
to any implant surface would provide better treatment to captured and analyzed using SCA30 software (version 3.4.6
more patients. build 79). The relationship between the contact angle and SE
While prior attempts to modify surface characteristics D P D
was calculated as L = L + L , where L is the SE, L is the
with thermal or radio-frequency plasma devices were disperse component and L P is the polar component.
successful, they operated either at high temperatures or Surface specific chemical assessment was performed by
under low pressures. As well, because the equipment was X-ray photoelectron spectroscopy (XPS). The implants (n = 3,
expensive and unreliable, these processes fell from favor each group) were inserted in a vacuum transfer chamber and
(Aronsson et al., 1997; Baier, 1986, 1987; Baier and Meyer, degassed to 10 7 torr. The samples were then transferred
1988). By contrast, non-thermal plasmas (NTPs) deploy under vacuum to a Kratos Axis 165 multitechnique XPS
most of their energy to drive “high-temperature” chemistry, spectrometer (Kratos Analytical Inc., Chestnut Ridge, NY,
allowing surface activation/modification while operating USA). Spectra were obtained using a 165 mm mean radius
at room temperatures (Barker, 2005). Unlike previous concentric hemispherical analyzer operated at constant pass
radiofrequency technology that required low pressures (Liu
energy of 160 eV for survey and 80 eV for high resolution
et al., in press), recent innovation, has scaled microplasma
scans. The take off angle was 90 and a spot size of 150 µm ⇥
NTP generators to dimensions that are small enough to
150 µm was used. The implant surfaces were evaluated at
allow safe and portable operation in the clinical setting at
various locations.
atmospheric pressure, while providing sufficient energy to
The in vivo study included 6 adult male beagle dogs,
generate meaningful increases in surface energy.
approximately 1.5 years of age. The experimental protocol
The incorporation of reactive species and surface cleaning
received the approval of the École Nationale Vétérinaire
may result in increased levels of surface reactivity and energy
d’Alfort (Maisons-Alfort, Val-de-Marne, France).
that could improve the integration of commercially available
All surgical procedures were performed under gen-
implant surfaces. The objective of the present investigation
eral anesthesia. The pre-anesthetic procedure comprised
was to evaluate the biomechanical effects of an Ar-based NTP
an intra-muscular (IM) administration of atropine sulfate
treatment, suitable for use in the dental office and applied
(0.044 mg/kg) and xylazine chlorate (8 mg/kg). General anes-
immediately prior to implantation, on the surface character
thesia was then obtained following an IM injection of
and integration of a dental implant with a textured surface,
ketamine chlorate (15 mg/kg). Following hair shaving, skin
in a beagle dog model.
exposure, and antiseptic cleaning with iodine solution at the
surgical and surrounding area, a 5 cm incision at the skin level
was performed. Then, a flap was reflected and the radius dia-
2. Materials and methods
physis exposed.
This study utilized screw root form endosseous grade IV The surgical region was the center of the radius diaphysis,
titanium alloy implants of 3.8 mm in diameter by 8.5 mm in where three implants (one of each treatment) were placed
length. The implants provided by the manufacturer presented into each limb. The right and left limbs received implants
an alumina-blasted and acid-etched (AB/AE) surface (Duo that remained for periods of 2 and 4 weeks in vivo (two
System, Signo Vinces, Brazil). distinct surgical procedures were performed), respectively.
The control treatment used implant specimens as- The implants were alternately placed from proximal to distal
supplied, while two experimental groups used these same at distances of 1 cm from each other along the central region
implants and treated them with either 20 or 60 s of non- of the bone, and the start surface site (CONTROL, PLASMA
thermal plasma (NTP) per quadrant (PLASMA 200 , PLASMA 200 , AND PLASMA 600 ) was alternated between animals. The
600 ). The plasma was applied with a KinPenTM device (INP- implant distribution resulted in an equal number of implants
Greifswald, Germany). The plasma treatment was applied for the 2 and 4 weeks comparison for both surfaces.
immediately prior to any characterization assessment and Drilling started with a 2 mm diameter pilot drill at
again prior to implantation in the in vivo component of this 1200 rpm and was followed with burs of 2.5 mm and 3.2 mm
study. at 800 rpm, all under saline irrigation. The implants were then
SEM (Philips XL 30, Eindhoven, The Netherlands) was placed into the drilled sites by means of a torque wrench.
performed at various magnifications under an acceleration Standard layered suture techniques were utilized for wound
voltage of 15 kV. Surface roughness was evaluated in three closure (4-0 vicryl—internal layers, 4-0 nylon—the skin).
control implants by optical interferometry (IFM) (Phase View Post-surgical medication included antibiotics (penicillin,
2.5, Palaiseau, France) at the flat region of the implant cutting 20.000 UI/kg) and analgesics (ketoprophen, 1 ml/5 kg) for
edges (three measurements per implant). Sa (arithmetic a period of 48 h post-operatively. The euthanasia was

3. J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 9 (2012) 45–49 47
performed by anesthesia overdose 4 weeks and 2 weeks after 4. Discussion
the first and second surgical procedures, respectively.
At necropsy, the limbs were retrieved by sharp dissection; The plasma state is often referred to as the 4th state of
the soft tissue was removed by surgical blades. For the matter, characterized by the presence of positive (sometime
torque testing, the radius was adapted to an electronic also negative) ions and negatively charged electrons in a
torque machine equipped with a 200 Ncm torque load cell neutral background gas (Lieberman and Lichtenberg, 1994).
(Test Resources, Minneapolis, MN, USA). Custom machine Plasmas are created by supplying energy (often electrical
tooling was adapted to each implant internal connection and energy) to a volume containing gases, so that a certain
the bone block was carefully positioned to avoid specimen fraction of free electrons and ions are generated from the
misalignment during testing. The implants were torqued in neutral constituents. In technical plasma devices, the plasma
the counter clockwise direction at a rate of ⇠0.196 rad/min, is generally generated using electrical discharges (Lieberman
and a torque versus displacement curve were recorded for and Lichtenberg, 1994). To date, implant surfaces have been
each specimen. both cleaned and/or sterilized by radiofrequency plasma
Preliminary evaluation showed heterogeneous variances devices or plasma coated with bioactive ceramics with high
in the torque measure between groups; the control treatment temperature plasma sources (Coelho and Lemons, 2009).
at 4 weeks in vivo time was notably (more, less) variable Unlike previous plasma technology, where specialized
than the other conditions. Variances were homogenized by equipment environment was required, NTPs can drive
transforming the data to ranks. A mixed model ANOVA was “high-temperature” chemistry at ambient temperatures at
then used to compare rank torque by time and treatment. atmospheric pressure (Barker, 2005). Thus, depending on
Statistical significance was set to ↵ = 0.05. Thus, while
plasma set up and chemistry, a wide range of implant
the raw torque data are presented, in order to maximize
surface alterations are achievable and may be utilized at
interpretation, analysis considered only the ranked data,
the operating room immediately prior to implant placement
which better satisfied the assumptions of this statistical
under atmospheric conditions (these units may be fabricated
model.
in portable sizes). The present study characterized surface
energy and chemistry in AB/AE surfaces and its effect on
biomechanical fixation at early implantation times in vivo.
3. Results
The SEM and IFM assessment showed that the roughness
of these implant surfaces were similar to that of several other
The scanning electron micrographs of the implant surfaces
commercially available products (Coelho et al., 2009). The
revealed a textured microstructure (Fig. 1(a)). There were
surface energy assessment prior and after NTP application
no particles evident from the alumina-blasting procedure.
An example of the three-dimensional reconstruction of the showed a substantial increase in surface energy (in both
surface is presented in Fig. 1(b) along with the Sa, Sq, polar and disperse components). The XPS results showed that
Sds, and Sdr roughness parameters. The surface energy (SE) surface elemental chemistry was modified by the 20 s and
was substantially greater than the CONTROL group in both 60 s Ar-based NTP treatment, and that this change resulted in
PLASMA 200 and PLASMA 600 groups (Fig. 1(c)). This general higher degree of exposure of the surface chemical elements
increase arose from both polar and disperses components. mainly at the expense of the removal of adsorbed C species
The surface chemistry assessment of the CONTROL surface (Coelho and Lemons, 2009). The higher degree of surface
showed 36% C, 44% O, 16% Ti, and 2% N, and traces of Si and energy observed for the CaP-Plasma is likely related to the
P. Relative to the CONTROL group, both plasma treated groups removal of the adsorbed C species from the surface (Baier,
evidence a decreased level of C and increased levels of Ti and 1986, 1987; Baier and Meyer, 1988).
O (Fig. 1(d)). High-resolution spectral evaluation showed that The increase in surface energy and differences in surface
carbon was present primarily as a hydrocarbon (C–C, C–H) on chemistry where plasma treated groups showed lower
all surfaces. amounts of adsorbed species relative to the CONTROL
The surgical procedures and follow-up demonstrated no group likely accounted for the significantly higher levels
complications or other clinical concerns, and no implant of biomechanical fixation observed at early implantation
was excluded due to clinical instability (determined after times in the in vivo laboratory model. The lack of difference
euthanization). The raw torque values in each group and time between both plasma treated groups was possible due to
in vivo (mean ± SD) are presented in Fig. 2. In general, there the remarkably similar SE and XPS results, depicting that
appears to be substantially increased interfacial strength in exposure times as short as 20 s is sufficient to hasten the early
each of the two plasma conditions and somewhat greater host-to-implant response, as surface energy and wettability
strength in 4 than 2 week implantations. The ANOVA of of biomaterials are properties that are known to enhance
ranked data showed an effect of implant surface treatment adhesion, proliferation, and mineralization of osteoblasts
(p = 0.001), but not time in vivo (p = 0.47), or the interaction (Lai et al., 2010; Lim et al., 2004, 2008; Sista et al., 2011).
of these factors (p = 0.37). The mean torque rank and 95% For instance, Buser et al. (2004) have demonstrated that
confidence intervals are presented in Fig. 3 as a function increasing the surface energy of a grit-blasted implant surface
of surface treatment and time in vivo, where significantly by means of proprietary cleaning and storage in isotonic
higher torque was detected for both PLASMA 200 and PLASMA solution hastened osseointegration of dental implants at
600 relative to the CONTROL. While a slight increase in torque early implantation times relative to controls presenting the
was detected from 2 to 4 weeks in vivo, this difference was same surface roughness profile but lower surface energy
not significant. levels (Buser et al., 2004). In contrast to NTP treatment, where

4. 48 J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 9 (2012) 45–49
A B
C D
Fig. 1 – (a) Scanning electron micrograph and (b) IFM three-dimensional reconstruction of the AB/AE surface used in the
present study. (c) Surface energy assessment showed that increases in both the polar and disperse components of both
plasma treated surfaces accounted for the overall higher surface energy values of those groups relative to the CONTROL
group. (d) The surface chemistry assessment of the CONTROL surface showed 36% C, 44% O, 16% Ti, and 2% N, and traces of
Si and P. Remarkably similar surface chemistry profiles were obtained for both plasma treated groups, where a decreased
amount of C along with increases in Ti and O contents were observed compared to the CONTROL group.
Fig. 3 – Rank torque data (mean ± 95% confidence interval)
as a function of surface treatment and time in vivo. A like
number of asterisks depict statistically homogeneous
groups.
Fig. 2 – Raw torque data (mean ± standard error) for all 5. Conclusion
groups at both implantation times in vivo.
Treatment of dental implants with textured surfaces with
room temperature plasma and delivered by a practitioner-
any given implant surface may be treated immediately prior
to placement, the implant is stored in isotonic solution until friendly device, produced substantial improvements in
immediately prior to placement so that the gain in surface biomechanical fixation at early implantation times.
energy is maintained.
Considering the favorable effects that have been observed
when NTPs were used in biomedical applications (Aronsson
Acknowledgment
et al., 1997), the utilization of low temperature, atmospheric
pressure Ar-plasma on surface alterations may be a promising
technique to improve the efficiency of implant osseointegra- The present study was partially supported by Signo Vinces,
tion and biomechanical fixation. Brazil.

5. J O U R N A L O F T H E M E C H A N I C A L B E H AV I O R O F B I O M E D I C A L M AT E R I A L S 9 (2012) 45–49 49
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