Elemental Analysis of the Surface Residues on Dental Implants by fanzhongqing

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									                                                                  Elemental Analysis of the Surface Residues on Dental Implants    Thesis




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           Elemental Analysis of the Surface Residues on Dental Implants


   Taeil Kim2, Kyoo-Ok Choi2, Tae-Gwan Eom2, Tae-Hee Byun2, Jae-Ho Kim1
   Bio-Top Biomaterial/Implant Center, and College of Dentistry, Seoul National University, Seoul, Korea

   1Department of Molecular Science and Technology, Ajou University, Suwon, 442-749, Korea
   2Osstem Implant Technical Center, Busan, Korea, 611-073, Korea (Received November 3, 2003/Accepted December 1, 2003)




       T
            itanium has been widely used for the raw materials for various biomaterial and biomechanical applications, especially in
            the areas of dental and orthopaedic fields. Successful osseointergration of Ti has been attributed to the surface
       cleanness as delivered state . 7 different dental implant systems were analyzed to assess the presence, type and amount of
       surface contaminants of them by X-ray photoelectron spectroscopy (XPS). It has been reported that the majority of the
       elemental contamination are the organic carbon and trace amounts of N, Ca, P, Cl, S, Na and Si. In this study, samples of
       AVANA Implants show smaller relative concentration of C and other elements, whereas higher concentration of Ti and O.
       Therefore, this indicates that the surface of AVANA samples contains the least amount of surface contaminants. Also, the
       surface roughness and the surface morphology of 7 implant systems were measured.

       Key words : Titanium, Osseointergration, Dental Implant, Contamination,




Introduction

   Implants are manufactured with commercially pure(c.p) titanium and oxidized to create a layer of titanium oxide (TiO2)[1].
Titanium has been widely used for the raw materials for various biomaterial and biomechanical applications, especially in the areas
of dental and orthopaedic fields. A number of studies have investigated different aspects of surface quality for a better
understanding of the interplay between living tissue and an implant surface. Investigations have concerned the surface energy, the
oxide layer, the surface roughness and the chemical compositions[5]. The condition of the oxide layer, namely its chemical purity
and surface cleanliness, is of paramount importance for the biologic outcome of osseointergration [6-7].
   Titanium-interacts with biologic fluids through its stable oxide layer, which forms the basis for its exceptional bio-
compatibility[8]. Depending on the implantation site, the demands may differ with respect to surface quality. On the one hand,


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    When penetrating into the oral cavity a rough surface will collect much more bacteria than a smooth one. On the other hand,
    several authors have stressed the importance of a rough surface for hard tissue implants[9-10].Mechanical interlocking may be
    enhanced by increase of the surface roughness and the stress distribution can be improved[11]
         It has been in a controversy how the composition of the surface of implants has influenced on the interaction of bone during the
    osseointegration process. Successful osseointergration of Ti has been attributed to the surface cleanness "as delivered state".
    During the manufacturing process including surface treatment steps, the implants exposed to many chemicals under different
    physical states. It has been reported that the majority of the elemental contamination are the organic carbon and trace amounts of
    N, Ca, P, Cl, S, Na and Si[1-2]. For instance, it has been reported that a small amount of fluorine contamination can dramatically
    alter the surface oxide of Ti implants during autoclaving and it has been suggested that single monolayer of contaminations from
    the environment or bulk material can invalidate the utility of implants[12]. It is, therefore, possible that some early implant failures
    may be caused by the presence of contaminations on the implant surface, whereas some late losses could be due to progressive
    dissolution of Ti over time[13].
         The objective of this study is to assess the presence, type and amount of surface contaminants of implants from 7 different
    implant systems by X-ray photoelectron spectroscopy (XPS). Among many different surface analytical tools, auger spectroscopy
    and XPS, also known as ESCA (Electron Spectroscopy for Chemical Analysis) are considered as the most widely used for the
    qualitative and quantitative analysis of the elements on the material surface[14-18]. However, in this study we presented data
    obtained by XPS.


    EXPERIMENTAL

    (1) Materials


         The total number of implants used in this study were 60 manufactured by 7 different implant systems;
         AVANA (Korea, 30ea.): surface blasted with hydroxyapatite
         1) A(USA, 5ea): Partial surface treatment product
         2) B(Sweden, 5ea): Electrochemical oxide formed surface
         3) C(Switzerland, 5ea): surface blasted with Al2O3 and etched
         4) AVANA(Korea, 30ea): surface blasted with hydroxyapa-tite
         5) D(Korea, 5ea): surface blasted with TiO2 and etched
         6) E(Korea, 5ea): surface blasted with hydroxyapatite
         7) F(Korea, 5 ea): Surface blasted with Al2O3 and etched


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                                                                Elemental Analysis of the Surface Residues on Dental Implants         Thesis




   Fig. 1 is the photograph of samples. All of the samples were fully packaged and sterkle, and packages were opened just before
analysis. Based on the previously documented analytical procedure, the composition of the surface was characterized.


(2) X-ray photoelectron spectroscopy


   The main analytical technique employed in this study was scanning
XPS(VG Escalab 250, Surface Science, UK) for the analysis of the
surface composition. Based on the previously documented analytical
procedure, the composition of the surface was characterized. Aluminum
Ka radiation was used for the radiation source. The sampling area of                 A        B       C       AV.     D         E        F
each sample was maintained as 3 x 3 mm in diameter. The base                      [Fig. 1] The photograph of implant samples used for analysis
                                                                                  Parenthesis Indicate the manufacturing country of each
pressures of these equipments were typically in the low 10-9 torr range           sample. A: (USA); B: (Sweden); C: (Switzerland); D: (Korea);
                                                                                  E: (Korea); F: (Korea), and AV: (Korea). AV is an AVANA
during analysis. Quantification of the XPS spectra was achieved by                implant sample manufactured by Osstem Implant System.
measuring the relative peak areas after correcting with atomic sensitivity
factors and the ionization cross-sections. The relative surface
concentration for each element was listed as indicated in the Table 1.
The relative total concentration of the surface contaminants was estimated by summation of the peak areas of all contaminants of
each sample. The total concentration indicated in the last column of Table 1 is the ratio of total surface concentration of the
elements of each implant system to that of AVANA implant.


(3) Scanning Electron Microscopic Analysis


   Randomly, one chosen implant out of each sample was observed the morphological surface cleanliness condition using a S-
4300 scanning electron microscope(SEM)(Hitach, Japan). The accelerating voltage was maintained 30kV. The base pressure of
these equipments was typically in the low 2 x 10-7 Pa range during analysis.


(4) Surface roughness measurement


   With a profilometer (SV-3000S4, Japan), The average roughness(Ra) were measured and recorded at a traverse speed of
0.5mm/s with diamond-tipped stylus running parallel to the Apex chip pocket(excluding ITI productions). The transverse length
was 1.6mm, the cutoff length was 0.08mm , the stylus radius was 2 um(which conforms to the JIS1994), and Gaussian filter was


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    used. All surface roughness values measured with 3samples of 7 different implants were average.




     [Table 1] Elemental Analysis of the Surface Residues on 7 Dental Implants

                    ELE      Na        N        C      Zn       P        Cl        Si         Ti        Ca      O        Al      Cu       Con.

        SPL                                                                                                                               ratio

                        A    0        0.00    30.42    0       0         0.0       0      20.1         0       49.44    0       0         0.34

      Abroad            B    0        0.00    22.19    0       8.73      0.0       0      14.59        0.4     54.49    0       0         0.31

                        C    0        1.57     31.64   0       0         0.0       0.92   19.23        0       46.64    0       0         0.30

                  AVANA      0        1.36    20.80    0       1.97      0.0       1.02   19.83        0.41    54.62    0       0         0.26

                        D    1.12     0.64     41.00   0.4     0         1.4       2.8    09.9         2.6     40.10    0       0         0.51
       Home
                        E    0        1.60    24.00    0       1.8       0.0       0.5    17.4         0       51.60    2.8     0.3       0.31

                        F    0        1.00    26.98    0       0         0.0       9.39   12.03        0       49.42    1.19    0         0.39




    RESULTS AND DISCUSSION

    (1) X-ray photoelectron spectroscopy


         Photographs of the samples used in this study are shown in fig.1, which are consisted of three foreign products and four
    domestic products. As described in the experimental section, the surface treatment procedure of those samples was different. Five
    samples from each implant system were used in the analysis. Fig. 2 shows a typical survey spectrum (a) and high resolution XPS
    spectra (b, c, d) of AVANA implant systems. Spectra from 7 implant systems is most often dominated from Ti, O, C, N. The
    dominance of the Ti and O signals shows that the surface consists mainly of a titanium oxide layer[2].
         The relatively strong C1s peak around 285 eV observed from all measured samples can be assigned to C-C and C-H bonded
    carbon(hydrocarbons) by contacted chemicals during the manufacturing process and by air-exposure. The presence of hydroxides
    is indicated by the shape of the O1s peak for these surfaces, which frequently shows spectral components between                  531 and
    533 eV which may be assigned to OH and H2O. O1s peak can be assigned to oxygen present in the surface C=O and C-OH[2, 20].
    The Ti2p peak spectrum is dominated by a doublet peak at around              459 eV and        464.8, which can be assigned to TiO2 . These
    two major peaks in each sample were attributed to the tetravalent titanium form; Ti4+2p3/2 and Ti+2p1/2, respectively.
         Generally, the peak positions and line shapes come to an agreement with those observed for TiO2[19].


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N(E)




                                                                   N(E)
                      BINDING ENERGY(eV)                                                BINDING ENERGY(eV)

                             (a)                                                                (b)




                                                                   N(E)
N(E)




                      BINDING ENERGY(eV)                                                  BINDING ENERGY(eV)


                             (c)                                                                (d)

[Fig. 2] XPS survey spectrum (a), high resolution spectra of AVANA implant (b) for carbon, (c) for oxygen, and (d) for titanium
N(E)




                                                                  N(E)




                      BINDING ENERGY(eV)                                                BINDING ENERGY(eV)

                             (a)                                                                (b)

[Fig. 3] High-resolution XPS spectra of the Ti 2p(a) and O 1s(b) of the samples from the seven implant implants systems



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         D implants had high amounts of surface carbon, while F
    implants had the highest amounts silicon. Although from all
    samples of AVANA implants (30 ea.), Ti, O, C, P and N
    were detected, Ca was detected only from 3 samples. The
    traces of Na, Zn, and Cl were observed only from samples
                                                                               (a) AVANA(x50)                              (b) A(x50)
    of D implant, whereas Cu was detected on E implant. fig. 3
    shows that Ti2p and O1s peak were observed all sample
    surfaces. In the case of not cleaned implant, no titanium was
    detected. Apparently, contaminating hydrocarbons
    completely covered the underlines the importance of
    cleaning procedures in the production of dental implants.
                                                                                  (c ) B(x50)                              (d) C(x50)
    For partially and completely cleaned implant, an increasing
    amount of titanium and a decreasing carbon/titanium ratio
    was more detected as cleaning became more complete. In
    the case of decontamination on implant surfaces, Ti2p and
    O1s peak intensity generally are extended more and more.
    Otherwise, In the case of C1s peak, the peak is smaller and                   (e) D(x50)                               (f) E(x50)

    smaller. As indicated in table 1, samples of AVANA
    Implants shows smaller relative concentration of C1s and
    other elements, whereas higher concentration of Ti2p and
    O1s. Therefore, this indicates that the surface of AVANA
    samples contains the least amount of surface contaminants.
                                                                                  (g) F(x50)
         On the basis of the theory, decontamination of implant
    was focused on titanium, O and C quantity. The maximum            [Fig. 4] The SEM images of seven different implant samples. Manufacturers of
                                                                      each sample are identical to those of samples in Figure 1
    theoretical amount titanium expected is 33% in the surface
    analysis of titanium and the rest surface composition is
    oxygen. Recently, it was identified as about 18% surface concentration of titanium is a reasonable value for cleaned titanium
    surfaces in the normal environment[17,18]. As shown table 1, the average titanium surface concentrations of AVANA, C, and A
    implant systems are estimated 19.83%, 19.23%, and 20.1% respectively, which are the highest among analyzed samples. The
    analytical data of I implant system shows that 50 % of surface concentration was from contaminants other than Ti, and O.




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(2) Scanning Electron Microscopic Analysis


   7 different dental implant systems were essentially free from macroscopic contamination. In previous study, different degrees of
organic resides, appearing mainly as dark stains, were detected on most of the retrieved thirteen[13] of samples. In the case of
implant maintained organic resides and appearing as dark stains, the surface appears to be covered by a greasy layer of
contaminants. This is apparently the result of working oils used in machining tools. In the cytotoxicity testing, the cell layer was
well developed and came into contact with partially and completely cleaned implants, significant cell depth was detected in the
case of the not cleaned twenty-one[21] of implants. In this study, fig. 4 shows that all completely cleaned implant surfaces were
discollar. An amount of White dots appear to E sample surfaces, unlike AVANA blasted with hydroxylapatite. It is not understood
what exactly it is.


(3) Surface roughness measurement


   In this study, the surface roughness values were measured and observed with cleaning effects on different modified implants.
Table 2 shows that the mean values of all samples were measured on 9 areas. Especially, the profile of AVANA implant surface
roughness was shown in fig. 5( others not shown). The surface roughness values(Ra) of AVANA, A, B, C, D, E, and F are
measured 1.8, 0.96, 1.5, 2.71, 1.21, 1.07, and 0.82um. Generally, in the case of increasing surface roughness, it is understood that
the cleaning is more difficult than less surface roughness. But it was observed that it is not important to clean implant surfaces.
XPS data apparently shows the results in the case of sample AVANA, B, and C. It is more important that how cleaning procedures
are carried out.

[Table 2] The mean values of surface roughness (Each implant sample was measured at 9 different sampling areas)

     Samples            AVANA                  A                  B                  C                  D             E                   F

     Ra(um)                1.8               0.96                1.5               2.71               1.21           1.07              0.82




(4) Conclusions


   The elemental analysis of the implant surfaces shows wide variety of elements and wide range of concentration, which may
attributes to manufacturing process and surface treatment condition. The surface composition of the carbon attributed to surface
contamination layer is found to vary depending on sample preparation and handling, and consists mainly of adsorbed organic
molecules(C-C and C-H bonded carbon[2]. Among 7 different implant systems, AVANA implant shows the largest concentration


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    of Ti, and O while the smallest concentration of other contaminating elements. This reflects that AVANA implant were produced
    under the optimal mechanical manufacturing process and surface treatment including final cleaning process. Recent literature
    includes some interesting studies on the effect of surface roughness on cell behavior with respect to in vitro study and evaluation of
    dental implants.


    (5) Acknowledgment


         This work was supported by the Ministry of Commerce, Industry and Energy.




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