Assessment of a chair-side argon-based non-thermal plasma treatment on the surface characteristics and integration of dental implants with textured surfaces Teixeira et al. surface
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/jmbbmShort communicationAssessment of a chair-side argon-based non-thermal plasmatreatment on the surface characteristics and integration ofdental implants with textured surfacesHellen 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 aa Department of Biomaterials and Biomimetics, New York University, New York, NY, USAb Department of Dentistry, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazilc Department of Prosthodontics, New York University, New York, NY, USAd École Nationale Vétérinaire d’Alfort, Maisons-Alfort, Val-de-Marne, Francee Department of Epidemiology and Health Promotion, New York University, New York, NY, USAA R T I C L E I N F O A B S T R A C TArticle history: The biomechanical effects of a non-thermal plasma (NTP) treatment, suitable for use in aReceived 31 May 2011 dental ofﬁce, on the surface character and integration of a textured dental implant surfaceReceived 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 experimentalAccepted 14 January 2012 treatments, in which the same AB/AE surface also received NTP treatment for a periodPublished 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 opticalKeywords: interferometry, and surface energy and surface chemistry were determined prior to andImplant surface treatment after plasma treatment. Two implants of each type were then placed at six bilateralArgon plasma locations in 6 dogs, and allowed to heal for 2 or 4 weeks. Following sacriﬁce, removalSurface modiﬁcation torque was evaluated as a function of animal, implant surface and time in vivo in aOsseointegration mixed model ANOVA. Compared to the CONTROL group, PLASMA 200 and 600 groupsin 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 (CoelhoThe 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 9989214; fax: +1 212 998 9214. E-mail address: email@example.com (H.S. Teixeira).1751-6161/$ - see front matter c 2012 Elsevier Ltd. All rights reserved.doi:10.1016/j.jmbbm.2012.01.012
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) 45–49surfaces) and surface chemistry (Ca–P based coatings over average high deviation), Sq (root mean square), Sds (density ofnon-coated surfaces) favor the early host-to-implant re- summits), and Sdr (developed surface ratio) parameters weresponse (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, ethyleneprocesses and not available for the dental community. An glycol, and diiodomethane were deposited on the surfaceeconomically viable, chair side, operator (dental surgeon) of each implant with a micro-pipette (OCA 30, Data Physicscontrolled surface treatment that enhances the host response Instruments GmbH, Filderstadt, Germany). Images wereto any implant surface would provide better treatment to captured and analyzed using SCA30 software (version 3.4.6more 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 thewith 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 byunder 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 transferred1988). By contrast, non-thermal plasmas (NTPs) deploy under vacuum to a Kratos Axis 165 multitechnique XPSmost 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 radiusat room temperatures (Barker, 2005). Unlike previous concentric hemispherical analyzer operated at constant passradiofrequency technology that required low pressures (Liu energy of 160 eV for survey and 80 eV for high resolutionet 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 atallow 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 Vétérinairemay 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 comprisedwas to evaluate the biomechanical effects of an Ar-based NTP an intra-muscular (IM) administration of atropine sulfatetreatment, 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 ofand integration of a dental implant with a textured surface, ketamine chlorate (15 mg/kg). Following hair shaving, skinin 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 placedlength. The implants provided by the manufacturer presented into each limb. The right and left limbs received implantsan alumina-blasted and acid-etched (AB/AE) surface (Duo that remained for periods of 2 and 4 weeks in vivo (twoSystem, Signo Vinces, Brazil). distinct surgical procedures were performed), respectively. The control treatment used implant specimens as- The implants were alternately placed from proximal to distalsupplied, while two experimental groups used these same at distances of 1 cm from each other along the central regionimplants and treated them with either 20 or 60 s of non- of the bone, and the start surface site (CONTROL, PLASMAthermal plasma (NTP) per quadrant (PLASMA 200 , PLASMA 200 , AND PLASMA 600 ) was alternated between animals. The600 ). The plasma was applied with a KinPenTM device (INP- implant distribution resulted in an equal number of implantsGreifswald, 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 atagain prior to implantation in the in vivo component of this 1200 rpm and was followed with burs of 2.5 mm and 3.2 mmstudy. 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 woundvoltage 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) foredges (three measurements per implant). Sa (arithmetic a period of 48 h post-operatively. The euthanasia was
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 47performed by anesthesia overdose 4 weeks and 2 weeks after 4. Discussionthe 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 ofthe soft tissue was removed by surgical blades. For the matter, characterized by the presence of positive (sometimetorque testing, the radius was adapted to an electronic also negative) ions and negatively charged electrons in atorque 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 electricaltooling was adapted to each implant internal connection and energy) to a volume containing gases, so that a certainthe bone block was carefully positioned to avoid specimen fraction of free electrons and ions are generated from themisalignment during testing. The implants were torqued in neutral constituents. In technical plasma devices, the plasmathe counter clockwise direction at a rate of ⇠0.196 rad/min, is generally generated using electrical discharges (Liebermanand a torque versus displacement curve were recorded for and Lichtenberg, 1994). To date, implant surfaces have beeneach specimen. both cleaned and/or sterilized by radiofrequency plasma Preliminary evaluation showed heterogeneous variances devices or plasma coated with bioactive ceramics with highin 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 specializedthan the other conditions. Variances were homogenized by equipment environment was required, NTPs can drivetransforming the data to ranks. A mixed model ANOVA was “high-temperature” chemistry at ambient temperatures atthen used to compare rank torque by time and treatment. atmospheric pressure (Barker, 2005). Thus, depending onStatistical signiﬁcance was set to ↵ = 0.05. Thus, while plasma set up and chemistry, a wide range of implantthe raw torque data are presented, in order to maximize surface alterations are achievable and may be utilized atinterpretation, analysis considered only the ranked data, the operating room immediately prior to implant placementwhich better satisﬁed the assumptions of this statistical under atmospheric conditions (these units may be fabricatedmodel. 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 otherThe scanning electron micrographs of the implant surfaces commercially available products (Coelho et al., 2009). Therevealed a textured microstructure (Fig. 1(a)). There were surface energy assessment prior and after NTP applicationno particles evident from the alumina-blasting procedure.An example of the three-dimensional reconstruction of the showed a substantial increase in surface energy (in bothsurface is presented in Fig. 1(b) along with the Sa, Sq, polar and disperse components). The XPS results showed thatSds, and Sdr roughness parameters. The surface energy (SE) surface elemental chemistry was modiﬁed by the 20 s andwas substantially greater than the CONTROL group in both 60 s Ar-based NTP treatment, and that this change resulted inPLASMA 200 and PLASMA 600 groups (Fig. 1(c)). This general higher degree of exposure of the surface chemical elementsincrease arose from both polar and disperses components. mainly at the expense of the removal of adsorbed C speciesThe surface chemistry assessment of the CONTROL surface (Coelho and Lemons, 2009). The higher degree of surfaceshowed 36% C, 44% O, 16% Ti, and 2% N, and traces of Si and energy observed for the CaP-Plasma is likely related to theP. 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 surfacecarbon was present primarily as a hydrocarbon (C–C, C–H) on chemistry where plasma treated groups showed lowerall surfaces. amounts of adsorbed species relative to the CONTROL The surgical procedures and follow-up demonstrated no group likely accounted for the signiﬁcantly higher levelscomplications or other clinical concerns, and no implant of biomechanical ﬁxation observed at early implantationwas excluded due to clinical instability (determined after times in the in vivo laboratory model. The lack of differenceeuthanization). The raw torque values in each group and time between both plasma treated groups was possible due toin vivo (mean ± SD) are presented in Fig. 2. In general, there the remarkably similar SE and XPS results, depicting thatappears to be substantially increased interfacial strength in exposure times as short as 20 s is sufﬁcient to hasten the earlyeach of the two plasma conditions and somewhat greater host-to-implant response, as surface energy and wettabilitystrength in 4 than 2 week implantations. The ANOVA of of biomaterials are properties that are known to enhanceranked 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 thatconﬁdence intervals are presented in Fig. 3 as a function increasing the surface energy of a grit-blasted implant surfaceof surface treatment and time in vivo, where signiﬁcantly by means of proprietary cleaning and storage in isotonichigher torque was detected for both PLASMA 200 and PLASMA solution hastened osseointegration of dental implants at600 relative to the CONTROL. While a slight increase in torque early implantation times relative to controls presenting thewas detected from 2 to 4 weeks in vivo, this difference was same surface roughness proﬁle but lower surface energynot signiﬁcant. levels (Buser et al., 2004). In contrast to NTP treatment, where
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 DFig. 1 – (a) Scanning electron micrograph and (b) IFM three-dimensional reconstruction of the AB/AE surface used in thepresent study. (c) Surface energy assessment showed that increases in both the polar and disperse components of bothplasma treated surfaces accounted for the overall higher surface energy values of those groups relative to the CONTROLgroup. (d) The surface chemistry assessment of the CONTROL surface showed 36% C, 44% O, 16% Ti, and 2% N, and traces ofSi and P. Remarkably similar surface chemistry proﬁles were obtained for both plasma treated groups, where a decreasedamount 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. Conclusiongroups 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 priorto placement, the implant is stored in isotonic solution until friendly device, produced substantial improvements inimmediately 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 observedwhen NTPs were used in biomedical applications (Aronsson Acknowledgmentet al., 1997), the utilization of low temperature, atmosphericpressure Ar-plasma on surface alterations may be a promisingtechnique to improve the efﬁciency of implant osseointegra- The present study was partially supported by Signo Vinces,tion and biomechanical ﬁxation. Brazil.
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 49REFERENCES Dohan Ehrenfest, D.M., Coelho, P.G., Kang, B.S., Sul, Y.T., Albrek- tsson, T., 2010. Classiﬁcation of osseointegrated implant sur- faces: materials, chemistry and topography. Trends Biotechnol.Albrektsson, T., Wennerberg, A., 2004a. Oral implant surfaces: part 28, 198–206. 1—review focusing on topographic and chemical properties Jimbo, R., Sawase, T., Shibata, Y., Hirata, K., Hishikawa, Y., of different surfaces and in vivo responses to them. Int. J. Tanaka, Y., Bessho, K., Ikeda, T., Atsuta, M., 2007. Enhanced Prosthodont. 17, 536–543. osseointegration by the chemotactic activity of plasmaAlbrektsson, T., Wennerberg, A., 2004b. Oral implant surfaces: part ﬁbronectin for cellular ﬁbronectin positive cells. Biomaterials 2—review focusing on clinical knowledge of different surfaces. 28, 3469–3477. Int. J. Prosthodont. 17, 544–564. Lai, H.C., Zhuang, L.F., Liu, X., Wieland, M., Zhang, Z.Y., 2010.Aronsson, B.O., Lausmaa, J., Kasemo, B., 1997. Glow discharge The inﬂuence of surface energy on early adherent events of plasma treatment for surface cleaning and modiﬁcation of osteoblast on titanium substrates. J. Biomed. Mater. Res. Part A metallic biomaterials. J. Biomed. Mater. Res. 35, 49–73. 93 (1), 289–296.Baier, R.E., 1986. Implant dentistry forefront ’85. Surface Lieberman, M.A., Lichtenberg, A.J., 1994. Principles of Plasma preparation. J. Oral Implantol. 12, 389–395. Discharges and Materials Processing. John Wiley & Sons, NewBaier, R.E., 1987. Selected methods of investigation for blood- York. contact surfaces. Ann. New York Acad. Sci. 516, 68–77. Lim, J.Y., Liu, X., Vogler, E.A., Donahue, H.J., 2004. Systematic vari-Baier, R.E., Meyer, A.E., 1988. Implant surface preparation. Int. J. ation in osteoblast adhesion and phenotype with substratum Oral Maxillofac. Implants 3, 9–20. surface characteristics. J. Biomed. Mater. Res. Part A 68 (3),Barker, R., 2005. Introduction and overview. In: Becker, K., 504–512. Kogelschatz, U., Schoenbach, K.H., Barker, R.J. (Eds.), Non- Lim, J.Y., Shaughnessy, M.C., Zhou, Z., Noh, H., Vogler, E.A., Equilibrium Air Plasmas at Atmospheric Pressure. IOP Donahue, H.J., 2008. Surface energy effects on osteoblast Publishing, Bristol. spatial growth and mineralization. Biomaterials 29 (12),Buser, D., Broggini, N., Wieland, M., Schenk, R.K., Denzer, A.J., 1776–1784. Cochran, D.L., Hoffmann, B., Lussi, A., Steinemann, S.G., 2004. Liu, F., Sun, P., Bai, N., Tian, Y., Zhou, H., Wei, S., Zhou, Y., Zhang, J., Enhanced bone apposition to a chemically modiﬁed SLA Zhu, W., Becker, K., Fang, J., 2009. Inactivation of bacteria in an titanium surface. J. Dent. Res. 83, 529–533. aqueous environment by a direct-current, cold atmospheric-Coelho, P.G., Granjeiro, J.M., Romanos, G.E., Suzuki, M., Silva, pressure air plasma microjet. Plasma Processes and Polymers N.R., Cardaropoli, G., Thompson, V.P., Lemons, J.E., 2009. (in press). Basic research methods and current trends of dental implant Owens, D.K., Wendt, R.C., 1969. Estimation of the surface free surfaces. J. Biomed. Mater. Res. Part B 88, 579–596. energy of polymers. J. Appl. Polym. Sci. 13, 1741–1747.Coelho, P.G., Lemons, J.E., 2009. Physico/chemical characterization Sista, S., Wen, C., Hodgson, P.D., Pande, G., 2011 The inﬂuence and in vivo evaluation of nanothickness bioceramic deposi- of surface energy of titanium–zirconium alloy on osteoblast tions on alumina-blasted/acid-etched Ti–6Al–4V implant sur- cell functions in vitro. J. Biomed. Mater. Res. Part A faces. J. Biomed. Mater. Res. Part A 90, 351–361. doi:10.1002/jbm.a.33013. [Epub ahead of print].