art-2-1-21

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                    DENTAL MATERIALS
                    BIOSURFACE PROCESSING WITH ROLE IN IMPROVING
Original Articles
                    THE OSSEOINTEGRATION OF THE ORAL IMPLANT
                    Vlad Gabriel Vasilescu1a           , Elisabeta Vasilescu2b*       , Valentin Sîrbu3c       , Lucian Toma Ciocan1d
                    1
                     Department of Prosthesis Technology and Dental Materials, Faculty of Dental Medicine, “Carol Davila” University of Medicine and Pharmacy Bucharest,
                    Bucharest, Romania
                    2
                     Department of Materials and Environment, Faculty of Engineering, “Dunărea de Jos” University of Galați, Galați, Romania
                    3
                     Implant-Prosthetic Therapy Department, Faculty of Dental Medicine, “Carol Davila” University of Medicine and Pharmacy Bucharest, Bucharest, Romania

                    a
                      DDS, PhD, Assistant Professor; e-mail: vlad.vasilescu@umfcd.ro; ORCIDiD: https://orcid.org/0000-0001-6251-833X
                    b
                      Eng, PhD, Professor; e-mail: elisabeta.vasilescu@ugal.ro; ORCIDiD: https://orcid.org/0000-0002-6794-7368
                    c
                     DDS, PhD, Assistant Professor; e-mail: dr.sirbu@yahoo.com; ORCIDiD: https://orcid.org/0000-0002-6267-2406
                    d
                      DDS, PhD, Associate Professor; e-mail: lucian.ciocan@umfcd.ro; ORCIDiD: https://orcid.org/0000-0002-0329-5102


                    ABSTRACT                                                                                https://doi.org/10.25241/stomaeduj.2021.8(1).art. 2

                    Introduction The osseointegration of the oral implant involves a close contact between the bone and the
                    implant, an important feature that allows the optimal transfer of stresses from the implant to the bone.
                    Achieving and maintaining tissue integration is ensured by a biosurface design with a role in reducing the
                    effect of shear forces on the interface, which can stimulate osteogenesis and facilitate tissue remodelling.
                    Numerous specialized studies describe the method of modifying the biosurface area generated by a certain
                    topography, among them are those that attest to the role of roughness in increasing the number of cells that
                    will adhere to a biosurface with a larger area.
                    Methodology Research was performed in order to establish the influence of mechanical processing on
                    the micro-roughness of the surface of the samples from the experimental bioalloy Ti10Zr. Atomic force
                    microscopy (AFM), scanning electron microscopy (SEM) and fluorescence microscopy were used to evaluate
                    the experimental results.
                    Results The study presents the results on the micro-roughness profile and the values of the parameters that
                    characterize the micro-roughness profile groups (2D and 3D) of the biosurfaces processed by grinding and
                    very fine polishing. Aspects regarding the modification of biosurface morphology, compared to mechanical
                    processing, acid corrosion and anodic oxidation, as well as the results regarding cellular behaviour (e.g.
                    adhesion of osteoblasts) to experimentally processed biosurfaces are also presented.
                    Conclusions The results of this experimental study together with those previously presented in “Controlled
                    Changing of Implantable Bioinert Materials Biosurface “scientific paper compile a synthesis of information
                    on the ability to modify the microtopography of the biosurface of the Ti10Zr alloy, by different ways in order
                    to improve implant osseointegration.
                    KEYWORDS
                    Bioalloy; Experimentally Processed Surface; Micro-roughness; Atomic Force Microscopy; Cell Adhesion.


                    1. INTRODUCTION                                                                  implantation. Bone healing in the post-implantation
                                                                                                     period involves a series of cellular and extracellular
                    The direct and lasting connection between living                                 biological processes at the bone-implant interface,
                    and reshaped bone that defines the osseointegration                              completed with the formation of new bone
                    of the implant [1,2,3] is determined by the tissue                               [4,5,6]. The first reactions result in the formation
                    compatibility that influences the healing process                                of a clot interface, the biological processes being
                    of recovery and remodelling, immediately after                                   further controlled by growth and differentiation



                                  OPEN ACCESS This is an Open Access article under the CC BY-NC 4.0 license.
                                  Peer-Reviewed Article
                        Citation: Vasilescu VG, Vasilescu E, Sîrbu V, Ciocan LT. Biosurface processing with role in improving the osseointegration of the oral implant.
                        Stoma Edu J. 2021;8(1):18-25
                        Received: January 21, 2021; Revised: February 12, 2021; Accepted: February 15, 2021; Published: February 17, 2021
                        *Corresponding author: Prof. Dr. Eng. Elisabeta Vasilescu, Department of Materials and Environment, Faculty of Engineering, “Dunărea de Jos”
                        University of Galați, Str. Domnească, nr.111, Galaţi, RO-800201 Romania
                        Tel: 0040 236 130 208; Fax: 0040 236 314 463; e-mail: elisabeta.vasilescu@ugal.ro, elisabeta.vasilescu@yahoo.com
                        Copyright: © 2021 the Editorial Council for the Stomatology Edu Journal.




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                                                                                                                                         Original Articles
 Figure 1. SEM view of trabecular bone (left) and Trabecular Metal Material (right) [18]


factors released by blood cells. They undergo                                   implant [15,16,17]; It has been shown, especially in
morphological and biochemical changes as an effect                              low-density bone structures, that implant stability is
of contact with the biosurface [7,8,9]. Achieving                               influenced by implant design and that a combination
implant osseointegration, but also maintaining                                  of microscopic and macroscopic surface topography
tissue integration are ensured by the presence of a                             modification techniques can create a stable bone-
high biocompatible material [10] and a design that                              implant interface.
stimulates osteogenesis and helps reduce the effect                             In the case of titanium alloys, research on the
of shear forces on the interface, such as surface                               application of techniques to improve cell interaction
roughness and shape characteristics [11,12]. The                                and cell development at the interface by intensifying
role of implant surface roughness in stimulating                                protein adsorption processes has been carried out in
and improving bone growth to implant surface                                    order to determine whether bone apposition could
in low bone density structures is highlighted in                                be enhanced by a microrough surface obtained
many specialized studies, which indicated higher                                by processing techniques such as blasting, acid
post-load failure rates for implants with relatively                            attack, or combinations thereof. In vitro research of
smooth surfaces compared to implants with low                                   the titanium implant with different surface micro-
bone density rough surface [13]; Also relevant are                              topographies has shown the differentiation of bone
the results of comparative studies on the roughness                             and mineralization cells, dependent on roughness.
of biosurfaces, obtained by different processing                                Rough surfaces favour osteointegration of the
methods, those oxidized with increased roughness                                implant through the attachment and subsequent
have shown a shorter post-implantation healing                                  proliferation of osteoblasts and the size of the
period due to improved cellular interaction at                                  implant-bone contact area; Notable results regarding
the bone-implant interface [14]. In summary, the                                the modification of the biosurface parameters
conclusions of the studies on the effect of micro-                              of the titanium implant and titanium alloys were
rough biosurfaces on the osseointegration process                               obtained by surface treatment with hydroxyapatite
clearly show the indication for the use of titanium                             (HA), achieved by various physical, chemical,
“microrough” implants obtained by titanium plasma                               electrochemical methods such as: Plasma spray,
spraying, or by techniques such as Al2O3 particle                               Pulsed Laser Deposition, Chemical Vapor Deposition,
blasting, TiO2 blasting and acid etching. The effects                           Physical Vapor Deposition, HA Blast Coating, etc.,
of microrough surfaces, such as faster integration,                             noting that regardless of the process applied, metal
a larger bone-to-implant contact area compared                                  surfaces are prepared by sandblasting, abrasion or
to titanium implants with a polished or machined                                chemical corrosion.
surface, have been confirmed by in vitro cell response                          The diversification of the biosurface processing
studies, demonstrating that osteoblasts are sensitive                           methods but also the advances registered in the
to changes in the roughness of biosurfaces. The                                 design of the oral implant resulted in implants with
clinical benefits mentioned by the authors in recent                            differentially processed surfaces and well adapted
clinical situations are related to the shortening                               clinically by the positioning mode and the placement
of the healing period for these implants to 6-8                                 area; The implant can have a portion obtained by
weeks instead of 12 weeks. The treatment of the                                 mechanical surface finishing operations (e.g. by
implant surface by mechanical, physical or chemical                             grinding), an engraved portion and a sandblasted
methods but also the differentiated treatment                                   portion at high temperatures with an ideal
led to a faster healing and a better stability of the                           roughness of osseointegration, which ensures the



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                    Vasilescu VG, et al.
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Original Articles    (a)                                                 (b)                                                (c)




                     Figure 2. Microscopic aspects of the surface of the Ti10Zr samples experimentally processed through: casting + machining + grinding (a), acid corrosion
                    (b), anodic oxidation (c).

                    optimal anchoring of the implant. Also, the control of                        mechanical processing + polishing / polishing to
                    the properties of the tissue-implant interface is well                        mirror gloss, of some samples from the experimental
                    possible in the case of the titanium implant obtained                         bioalloy TI10Zr.
                    by sintering (LST- Laser Sintered Titanium, 2009) which                       The research represents the continuation of the study
                    has a rough surface with micropores of 2-200 µm                               and the completion of the information previously
                    and a prescribed geometry from the design stage.                              presented in the works "Controlled Changing of
                    The healing process begins with the insertion of the                          Implantable Bioinert Materials Biosurface" [19] and
                    implant as this surface stimulates and accelerates                            "In Vitro Testing of Materials Biocompatibility with
                    the healing of bone tissue, which makes it possible                           Controlled Chemical Composition" [20], in order to
                    to immediately load the implant into bone of density                          establish the optimal and efficient way to modify
                    I, II, III, in much safer conditions. Research in recent                      biosurface area, and in this way of improving the
                    years in interdisciplinary fields such as engineering                         osseointegration of the oral implant from Ti10Zr,
                    and medicine has led to remarkable results for                                between the mechanical, chemical (acid attack)
                    obtaining biomaterials with high biocompatibility                             and electrochemical (anodic oxidation) processing
                    and the promotion of advanced surface processing                              processes.
                    technologies. Some of these resulted in a porous
                    biomaterial made of TiZrTa alloy with structure and                           2. METHODOLOGY
                    elasticity close to those of bone.
                    The modern design introduced by the “Trabecular                               In the experiments, samples from the experimental
                    Metal” implant (Fig.1) conceptually revolutionized                            bioalloy with titanium base were used (Ti10Zr / Patent
                    the theory of osseointegration and introduced                                 no. 132079/2019). The samples were taken from
                    the notion of osseoincorporation (growth of bone                              the molded semi-finished product subsequently
                    tissue including in the structure of the implant).                            subjected to mechanical processing (casting process
                    Considered the newest discovery in the field of                               + mechanical processing by grinding and casting +
                    dental implantology, it is the only implant with                              mirror gloss polishing).
                    three-dimensional structure (3D) that mimics bone                             The analysis of the sample surface was performed
                    cell architecture (80% porosity) and systematic                               by scanning electron microscopy (SEM), atomic
                    nanotextured topography of superficial areas. The                             force microscopy (AFM / EasyScan2 Model), and the
                    trabecular structure of the implant causes the bone to                        investigation and evaluation of the interactions at
                    form inside it, resulting in a common body between                            the interface was performed by in vitro analysis by
                    the implant and the human bone. The implants have                             exposing G292 osteoblasts to these surfaces, under
                    a treated surface of SLA type (Sandblasting with                              the same conditions with samples from the same
                    Large grit followed by Acid etching), chemically                              bioalloy but treated on the surface by acid attack
                    modified and moderately rough which increases                                 and anodic oxidation (previously published results)
                    the bone-implant contact surface ensuring a period                            [19,20].
                    of osseointegration twice less than other implant
                    systems [18].                                                                 3. RESULTS
                    The paper presents the experimental research
                    conducted in order to study the influence of changes                          The results of the scanning electron microscopy
                    in the microtopography of biosurfaces processed                               analysis (Fig. 2) highlighted the changes in the mor-
                    by casting + mechanical processing and casting +                              phology of the experimental biosurface modified by



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A. Samples taken from cast semi-finished products and subsequently subjected to mechanical processing




                                                                                                                                    Original Articles
(grinding).
a.1. 2D images




a.2. 3D images




 Figure 3. Parameters that characterize the roughness profile.
Ra = 125,62nm, Rq = 147,75nm, Ry = 525,97nm, Rp = 266,18nm, Rv = - 259,79nm, Rm = - 3,628fm.

mechanical processing, compared to those obtained                          surface through atomic force microscopy analysis
by corrosion (acid attack) and anodic oxidation, and                       (AFM) provided useful information on the roughness
the results of atomic force microscopy analysis (Fig.                      profile and the values of the parameters that
3 and Fig. 4) illustrates the roughness profile (2D and                    characterize the roughness profile groups. The
3D images) and shows the measured values of the                            roughness corresponds in value to surfaces with
parameters that characterize the roughness profile                         very fine processing. There are isolated peaks of high
groups by mechanical sample processing. Figure 5                           roughness, with a rounded shape, characteristic of
shows the aspects regarding the in vitro evaluation                        the surface obtained from mechanical processing
of the adhesion of osteoblasts on the surface of the                       (Fig. 4).
investigated samples.                                                      The investigation and evaluation of the response
                                                                           of experimentally processed biosurfaces to in vitro
Remarks:                                                                   cellular behaviour were carried out by exposing
The anodic oxidation method allows the develop-                            G292 osteoblasts to Ti10Zr samples, with surface
ment of an oxide layer on the surface of the material                      morphological characteristics conferred by mecha-
with a role in improving the adhesion and fixation                         nical processing described above, under the same
properties.                                                                conditions as samples processed by casting, acid
The Ti10Zr alloy samples thus processed provide a                          corrosion and anodizing.
special surface configuration, as shown in electron                        G292 osteoblasts were seeded in 6-well plates at a
scanning microscopy images (Fig. 2c). The oxide film                       density of 5 x 104 cells/cm2 in the presence of Ti10Zr
is a basis for the formation of the osteoinductive                         samples with differently processed surfaces; At
matrix. Micro-topographic analysis of the sample                           the same time, cells were cultured in vessels but in



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                    B. Samples subjected to mechanical processing (grinding + polishing to mirror gloss).
Original Articles
                    b.1. 2D images




                    b.2. 3D images




                     Figure 4. Parameters that characterize the roughness profile.
                    Ra = 7,9282 nm, Rq = 9,1452nm, Ry = 43,537nm, Rp = 16,564nm, Rv = - 26,973nm, Rm = - 3,4725fm.

                    the absence of any material (control). At 24 and 48                         control. The experimental results demonstrate, for all
                    hours after incubation, medium was harvested from                           ways of processing the biosurface of Ti10Zr samples
                    each well and fluorescent labelling of cytoskeletal                         (acid attack, anodizing, mechanical processing), a
                    actin filaments and intracellular glutathione was                           good adhesion of osteoblasts, especially to oxidized
                    performed (Fig. 5).                                                         ones, which have cells with a well-organized actin
                    Examination by fluorescence microscopy of the                               cytoskeleton, interconnected and with cell densities
                    architecture of actin filaments revealed that the cells                     comparable to those of the control (in the absence
                    grew in a single layer, showed an osteoblast – like                         of sample material).
                    phenotype and there were no differences from the



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                                                                                                                                                          Original Articles
  24
   24              F-actin
                   F-actin               DAPI
                                         DAPI            Colocalization
                                                         Colocalization         48
                                                                                 48            F-actin
                                                                                               F-actin               DAPI
                                                                                                                     DAPI            Colocalization
                                                                                                                                     Colocalization
 hours
 hours                                                                         hours
                                                                               hours


Control
Control                                                                       Control
                                                                              Control




  TiZr
  TiZr                                                                         TiZr
                                                                               TiZr



 Figure 5. Highlighting the actin cytoskeleton by fluorescent labelling of F-actin with phalloidin-FITC (DAPI nucleus counter colouring) in osteoblasts
grown for 24 and 48 hours on the surface of the culture vessel/Control and Ti10Zr alloy [21].


4. DISCUSSIONS                                                               the biological processes at the implant-tissue
                                                                             interface in the immediate post-implantation period.
The study of the influence of the mechanical                                 The results of this experimental study together with
processing method on the micro-roughness profile                             those previously presented in “Controlled Changing
and the values of the micro-roughness parameters                             of Implantable Bioinert Materials Biosurface“
determines the cellular behaviour, tested by                                 provides useful information on the ability of the
evaluating the adhesion and the distribution of                              Ti10Zr bioalloy to modify its microtopography of
osteoblasts on surfaces thus processed.                                      the biosurface, by different ways to improve implant
In vitro testing of cellular behaviour, which                                osseointegration. The results of the research that
provides the information needed to understand                                aimed to establish the optimal way to modify the
the mechanism by which surface micro-roughness                               biosurface area through more ways of processing
controls the cellular response, proves that different                        are presented. The modification of the biosurface
changes in topography lead to differentiated                                 parameters (microroughness) was evaluated, as well
responses, at least in cell distribution mode.                               as their influence on the adhesion of osteoblasts and
Corroborating the results obtained in the mechanical                         the cell proliferation capacity on the experimentally
processing of the surface with those obtained in the                         processed surfaces.
chemical processing (corrosion or anodic oxidation)                          The conclusions of the research are that the increase
of the Ti10Zr bioalloy, differences were observed                            of the biosurface area by modifying the morphology
both in terms of the micro-roughness profile and the                         and/or micro-roughness either by corrosion, by
values of the micro-roughness parameters, but also                           oxidation or coarse either high-precision mechanical
in terms of the mode of cell spread on these surfaces.                       processing, has been demonstrated and denotes
Mechanically machined surfaces contribute to                                 the ability of Ti10Zr bioalloy to improve biosurface
the obtaining of microrough biosurfaces. The                                 characteristics. However, some observations of the
values characterizing the parameters of the micro-                           experimental study should be noted, which may
roughness profile are not the same for differently                           be of interest in selecting one or another of the
machined surfaces (with different micro-roughness                            experienced processing methods, as follows:
profile) and are significantly lower for surfaces                            a. considering any of the processes applied in
with fine machining (samples with almost smooth                              coatings to increase the bioactivity of the metal
surface, polished).                                                          surface, they require prior preparation by blasting,
Compared to the surfaces processed by corrosion                              abrasion or chemical corrosion.
or anodic oxidation, those obtained by mechanical                            b. the increase of the biosurface area by creating
processing (regardless of the processing method) in                          rough or microporous surfaces facilitates the cell
addition to a good adhesion of osteoblasts, presented                        adhesion processes and the growth of the trabecular
an orientation of adherent cells depending on the                            bone directly on the surface of the titanium implant,
direction of mechanical processing of samples.                               shortening the post-implantation healing period.
It has been observed that any further processing                             c. the anodic oxidation method creates surfaces
plays a decisive role in how the cells are oriented                          covered with a uniform, continuous, adherent oxide
and adhered to these surfaces and annihilate the                             film with a special morphological configuration with
influence of previous processing.                                            a decisive role in stimulating the processes at the
                                                                             interface.
5. CONCLUSIONS                                                               d. mechanically processed surfaces contribute
                                                                             to obtaining biosurfaces with a profile of micro-
The research highlights the possibilities of processing                      roughness and values of roughness parameters
the biosurface of the implant with a role in improving                       depending on the degree of processing and



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                    Vasilescu VG, et al.
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                    influence the orientation of the adhered cells                       AUTHOR CONTRIBUTIONS
Original Articles
                    according to the direction of processing.
                    e. however, it was not noticed for corroded or                       VGV: participated in the elaboration, writing and translation of
                    anodized Ti10Zr, suggesting that additional                          the paper and contributed to the introductory part (synthesis
                    processes have changed the properties of these                       of specialized information on the topic), to establishing
                    surfaces, and thus have decisively influenced cell                   the experimental conditions, interpreting the results and
                    orientation and adherence;                                           formulating the research conclusions. EV: contributed as follows:
                    f. these differences detected in surfaces with                       characterization of the materials researched and the interpretation
                    different processing could have a major influence on                 of the results obtained in the investigation by advanced methods
                    how osteoblasts managed to adapt and be the best                     (SEM Microscopy, EDS Analysis). VS: participated in the writing
                    option for dental implant.                                           and translation of the paper and contributed to structuring the
                                                                                         bibliographical references. LTC: participated in the research of
                    CONFLICT OF INTEREST                                                 the documentary sources (bibliographical references), in the
                                                                                         structuring of the research conditions and methodology and in
                    The authors declare no conflict of interest.                         the elaboration of the abstract.


                    ACKNOWLEDGMENTS


                    None.




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Improving the osseointegration of the oral implant
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                                                                                                                                    Original Articles
                                                                          Vlad Gabriel VASILESCU
                                                                            DDS, PhD, Assistant Professor
                                             Department of Prosthesis Technology and Dental Materials
                                                                               Faculty of Dental Medicine
                                           “Carol Davila” University of Medicine and Pharmacy Bucharest
                                                                                      Bucharest, Romania



CV
Dr. Vlad Gabriel Vasilescu is Assistant Professor at the Department of Prosthesis Technology and Dental Materials, Faculty of
Dental Medicine of “Carol Davila” University of Medicine and Pharmacy Bucharest. In 2016, he obtained the PhD in Dentistry with
the thesis entitled “Contributions to the study of biocompatible metal materials for oral implantology”. Areas of interest in the
research activity: obtaining and characterizing dental materials and highly biocompatible materials, characterizing implantable
systems in relation to the biocompatibility of materials and surface microtopography. Disseminating research results involves
communications at prestigious scientific events and publications in specialized journals, awards and distinctions: Gold Medal for
“High biocompatibility alloy for dental implants”, Diploma of Excellence for the works “Electron Microscopy Studies of Depositing
Metallic Silver with Antibacterial Role on the TiZr Dental Implant Surface”.




Questions
1. Improving the osseointegration of the implant is possible by:
qa. The modification of the microtopography that determines the increase of the biosurface area;
qb. Use of implants with smooth (unprocessed) surfaces;
qc. Early implant loading;
qd. The use of materials with high fatigue resistance.

2. Changes in biosurface morphology by anodic oxidation have the following effect:
qa. Increase of the oxide layer on the implant surface;
qb. Improve osteoinductive properties;
qc. Decrease biological processes at the tissue-implant interface;
qd. Decreased cell adhesion.

3. Maintaining tissue integration is improved:
qa. By an implant biosurface design that increases the effect of shear forces;
qb. By factors that diminish the primary bone-implant stability;
qc. By a design of the implant biosurface that reduces the effect of shear forces;
qd. In structures with low bone density.

4. The role of the microroughness of the implant surface is:
qa. To inhibit the growth of bone tissue to the surface of the implant;
qb. To improve protein adsorption in the cellular interaction at the interface between tissue and biomaterial;
qc. To reduce the bone-implant contact surface;
qd. To prevent the interfacial reaction in the post-implantation period.




Stoma Edu J. 2021;8(1): 18-25                                                      pISSN 2360-2406; eISSN 2502-0285                   25