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REVIEW ARTICLE
Surface topography of dental implants: A review
Varun Dahiya, Pradeep Shukla, Shivangi Gupta
ABSTRACT
Pure titanium (Ti) and Ti alloys are well-established standard materials in dental implants due to their
favorable combination of mechanical strength, chemical stability and biocompatibility. The concept of
osseointegration was discovered by Brånemark and his co-worker and has had a dramatic influence
on clinical treatment of oral implants. The first generation of successfully used clinical Ti implants,
which were machined with a smooth surface texture, now approach 50 years in the clinical use. Since
then, implant surfaces have long been recognized to play a vital role in molecular interactions, cellular
response and osseointegration and scientists all over the world have developed the second generation
implants with surfaces which can accelerate and improve implant osseointegration.
KEY WORDS: Implants, osseointegration, titanium
INTRODUCTION
Replacing lost teeth with dental implants is today
a reliable treatment method associated with good
long-term clinical results. Different surface modifications
alter the surface topography at micro- and nano-meter
level of resolution as well as chemical properties, which
have shown to be of importance for osseointegration.
Research within the field of implantology is still
intense and aims at further improving the implant
properties to achieve successful treatments for patients
with compromised bone as well as developing a
surface that provides faster integration to shorten the
treatment period.[1] Dental implant quality depends on
the chemical, physical, mechanical and topographic
characteristics of the surface.[2] A major factor that
determines the success of dental implantation is
osseointegration, which is the stable anchorage
of an implant in living bone achieved by direct
Department of Periodontics and Implantology, D.J. College of Dental
Sciences and Research, Modinagar, Uttar Pradesh, India
Address for correspondence: Dr. Shivangi Gupta,
Department of Periodontics and Implantology, D.J. College of Dental Sciences
and Research, Modinagar, Uttar Pradesh, India.
E-mail: shivangigupta69@gmail.com
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bone-to-implant contacts (BIC). [3] Osseointegration
derives from the Greek osteon (bone) and the Latin
verb integrare (to make whole).[4]
The main objective for the development of implant
surface modifications is to promote osseointegration,
with faster and stronger bone formation. This will
likely confer better stability during the healing
process, which, preferentially, will improve the clinical
performance in the area of poor bone quality and
quantity. Recently growing micro and nano-technology
is rapidly advancing surface engineering in implant
dentistry. Surface roughness also has a positive
influence on cell migration and proliferation, which
in turn leads to better BIC results, suggesting that the
microstructure of the implant influences biomaterial–
tissue interaction. [5] Various surface modification
methods to improve the osseointegration of a titanium
(Ti) dental implant, such as surface-roughening (e.g.,
sandblasting and/or acid etching) and coating, for
example, with hydroxyapatite (HA) Ca10(PO4) 6(OH)
2, to improve the implant’s bioactivity.[6]
The main objective, hence, is to develop effective and
practical techniques that create a long-lasting electric
field on the implant’s surface, in order to promote
the implant’s osseointegration without incurring the
drawbacks of existing surface-treatment methods.
IMPLANT SURFACE TOPOGRAPHY
DOI:
10.4103/0974-6781.131009
66
Implant surface topography refers to macroscopic and
microscopic features of the implant surface. Although
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Dahiya, et al.: Surface topography of dental implants
commercially pure Ti is the prime material of dental
implants, the success rates of different commercially
available implant systems vary. Ti implants with
adequate roughness may influence the primary stability
of implants, enhance BIC and may increase removal
torque force.[7] Ti is the most widely used metallic material
for dental subgingival implants, due to its invaluable and
outstanding biomedical and biomechanical properties.
These are its availability, high biocompatibility, high
strength and stiffness and relatively low density. More
importantly, Ti implants are known to osseointegrate
with living bone tissues.[8]
Macro-roughness comprises features in the range of
millimeters to tens of microns. This scale directly relates
to implant geometry, with threaded screw and macro
porous surface treatments. The primary implant fixation
and long-term mechanical stability can be improved by
an appropriate macro-roughness.[12]
Goal of various surface textures and techniques is to
enhance bone growth toward the implant surface.
A number of in vivo studies have demonstrated that
increased surface area on the implant improves BIC after
the implant placement.[9]
Nanotechnology involves materials that have a
nano-sized topography or are composed of nano-sized
materials with a size range between 1 and 100 nm.
Nanometer roughness plays an important role in the
adsorption of proteins, adhesion of osteoblastic cells and
thus the rate of osseointegration.[13]
The primary aim of the surface texturing or treating
the implant surface is to enhance cellular activity and
improve bone apposition. Surface topography of an
implant can be designed by making porous and/or by
coating the implant surface with other suitable materials
to increase bone-implant contact since the anatomic
surface of bone cannot be controlled.[10] A number of
surface treatments are available to create controlled
roughness on the surface of the implants. It is not
clear whether the height of surface irregularities is
more important than the distance between them and
which combination of these factors could improve
osseointegration.
Roughness can be produced on the implant surfaces
through the addition or subtraction procedures.
A plasma arc is a kind of addition process, which
involves the deposition of bioactive HA material on the
surface of the implants. Polishing, machining and acid
etching, on the other hand, are subtraction procedures.
These treatments may also be classified into mechanical,
chemical, electrochemical, electropolishing, vacuum,
thermal and laser methods.[11]
Implant surface roughness is divided, depending on the
dimension of the measured surface features into macro-,
micro- and nano-roughness Figure 1.
a
b
Micro-roughness is defined as being in the range
of 1-10 μm. This range of roughness maximizes the
interlocking between mineralized bone and implant
surface. The use of surfaces provided with nanoscale
topographies are widely used in recent years.
METHODS OF SURFACE MODIFICATIONS OF
IMPLANTS
The methods employed for surface modifications of
implants can be broadly classified into 3 types-mechanical;
chemical; and physical. The main objective of these
techniques is to improve the bio-mechanical properties
of the implant such as stimulation of bone formation
to enhance osseointegration, removal of surface
contaminants and improvement of wear and corrosion
resistance.
Mechanical treatment
Mechanical treatments involve either removal of surface
material by cutting or abrasive action, or the surface of the
implant is deformed (and/or partially removed) by particle
blasting.[14] The most commonly employed mechanical
techniques are machining, polishing and blasting.
Chemical methods
The chemical methods of implant surface modifications
include chemical treatment with acids or alkali, hydrogen
peroxide treatment, sol-gel, chemical vapor deposition
and anodization. Chemical surface modification of Ti
has been widely applied to alter surface roughness and
composition and enhance wettability/surface energy.[15]
c
Figure 1: Scanning electron microscopy images in ×3000 magnification of common surface modifications (a) TiOblast™
(b) Osseotite® (c) TiUnite™
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Dahiya, et al.: Surface topography of dental implants
The process of acid treatment serves to remove the
surface oxide and contamination which leads to a clean
and homogenous surface. The acids commonly used
include hydrochloric acid, sulfuric acid, hydrofluoric
acid and nitric acid.
Physical methods
The physical methods of implant surface modification
include plasma spraying, sputtering and ion deposition.
Methods to alter microtopography
Turning - the original Brånemark (Nobel Biocare) implant
was turned Ti screw with no further surface treatment.[16]
It had a minimally rough surface and was for a long
time the most used implant with good long-term clinical
results. [17,18] Scanning electron microscopy analysis
showed that the surfaces of machined implants have
grooves, ridges and marks of the tools used for their
manufacturing. These surface defects provide mechanical
resistance through bone interlocking.
Grit-blasting - with various hard ceramic particles such
as alumina (AlO3), titanium oxide (TiO2), silica or
calcium phosphate is one way of roughening the implant
surface. The size of the blasting particles determines the
roughness created and the blasting particles should be
chemically stable and biocompatible.
Several in vivo studies have shown significantly
improved BIC for TiO2 blasted implants when compared
to machined ones.[19,20]
Acid-etching - of a surface with strong acids such as
HCl, H2SO4, HNO3 and HF creates an isotropic surface
that may enhance osseointegration in vivo.[21,22] The most
commonly used solutions for acid etching of Ti includes
either a mixture of HNO3 and HF or a mixture of HCl and
H2SO4. Acid treatment provides homogeneous roughness,
increased active surface area and improved bio adhesion.
Dual acid-etched technique - immersion of Ti implants
for several minutes in a mixture of concentrated HCl
and H2SO4 heated above 100°C (dual acid-etching)
is employed to produce a micro rough surface.[23] The
dual acid-etched surfaces enhance the osteoconductive
process through the attachment of fibrin and osteogenic
cells, resulting in bone formation directly on the surface
of the implant. The dual acid-etched surface produces
a microtexture rather than a macrotexture. It has been
found that dual acid-etched surfaces enhance the
osteoconductive process through the attachment of fibrin
and osteogenic cells, resulting in bone formation directly
on the surface of the implant.[24]
Experimental studies have reported higher BIC and
less bone resorption with dual acid-etched surfaces
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compared with machined or titanium plasma-sprayed
surfaces.[25]
Hypothetically the blasting procedure creates a
surface roughness for good mechanical fixation and
the additional etching smoothens out sharp peaks.
Commonly, this combination of techniques creates a
moderately rough surface.
Anodization - produces a micro- and or nano-porous
oxide layer on the Ti surface. The appearance of the
layer from the anodization process depends on current
density, concentration and composition of the acids used
in the electrolyte solution and the temperature. In vivo
studies have demonstrated increased bone response
with higher biomechanical and histological values for
anodized surfaces compared with machined ones.[26]
Plasma spraying - is a method where particles, HA or Ti
are projected on the surface through a plasma torch at
very high temperature. The particles condense and fuse
together on the surface thereby creating a coat. Ti plasma
spraying has displayed better bone integration in vivo
as compared to smoother implants. The advantage of
plasma coating is that these coatings give implants a
porous surface that bone can penetrate more readily.[27]
Osseointegration was shown to be fastest and most
effective for rough surfaces with open structure that
varied between 50-400 μm.
Plasma spraying with HA particles creates a 50-200 μm
thick coat but with poor adhesion to the bulk material
and this is believed to be the reason for the long term
negative clinical results of such implants.
Sandblasted and acid etched surface
Commercially available dental implants are usually both
blasted by particles and then subsequent etched by acids.
This is performed to obtain a dual surface roughness
as well as removal of embedded blasting particles. The
etching reduces the highest peaks while smaller pits will be
created and the average surface roughness will be reduced.
Fluoride treatment
Ti is very reactive to fluoride ions, forming soluble TiF4
by treating Ti dental implants in fluoride solutions. This
chemical treatment of Ti enhances the osseointegration
of dental implants.
Sputter-deposition
Sputtering process has been shown to be a particularly
useful technique for the deposition of bioceramic thin films
(based on Ca/P systems), due to the ability of the technique
to provide greater control of the coating’s properties and
improved adhesion between the substrate and the coating.
The disadvantages with sputter coating is extensive time
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Dahiya, et al.: Surface topography of dental implants
There are several sputter techniques and a common
drawback inherent in all these methods is that the
deposition rate is very low and the process itself is very
slow.[28]
Other experimental studies using PSHA-coated dental
implants immersed in pamidronate or zoledronate
demonstrated a significant increase in bone contact area.
The main problem lies in the grafting and sustained
release of antiresorptive drugs on the Ti implant surface.
Increase in peri-implant bone density is bisphosphonate
concentration-dependent
Radio frequency (RF) sputtering
Simvastatin
consuming, produces amorphous coatings and Ca/P
ration of the coating is higher than of synthetic HA.
RF magnetron sputtering is largely used to deposit thin
films of Ca/P coatings on Ti implants. The advantage of
this technique is that the coating shows strong adhesion
to the Ti and the Ca/P ratio and crystallinity of the
deposited coating can be varied easily.
Magnetron sputtering
Magnetron sputtering is a viable thin-film technique as
it allows the mechanical properties of Ti to be preserved
while maintaining the bioactivity of the coated HA.
Nano-roughness and nanostructures
All surfaces possess nano-roughness, however not all
of them have defined nanostructures. Nanostructured
materials are defined in the literature as materials
containing structural elements with dimensions in the
range of 1-100 nm.
Simvastatin, could induce the expression of bone
morphogenetic protein (BMP) 2 messenger ribonucleic
acid that might promote bone formation. In an in vitro
study Yang et al. (2010) showed that simvastatin-loaded
porous implant surfaces promote accelerated osteogenic
differentiation of preosteoblasts, which have the potential
to improve the nature of osseointegration.
Antibiotic coating
Gentamycin along with the layer of HA can be coated
onto the implant surface, which may act as a local
prophylactic agent along with the systemic antibiotics
in dental implant surgery.
During the sol-gel process, a liquid with a specific
composition (i.e., the Sol) is converted into a solid gel
phase. Thin coatings can be deposited onto a surface by
dip- or spin coating techniques. The procedure makes it
possible to produce coatings of Ti, HA or combination
of both.
Tetracycline-HCl functions as an antimicrobial agent
capable of killing microorganisms that may be present
on the contaminated implant surface. It also effectively
removes the smear layer as well as endotoxins from
the implant surface. Further, it inhibits collagenase
activity, increases cell proliferation as well as
attachment and bone healing (Herr et al., 2008).
Tetracycline also enhances blood clot attachment and
retention on the implant surface during the initial
phase of the healing process and thus promotes
osseointegration.
Nanocrystalline HA coatings
Future directions in implant surface modifications
Some methods to alter nanotopography
Sol-gel coatings
Nanoparticles of HA is prepared by mixing H3PO3 and
Ca (NO3) to a Ca/P ratio of 1.67 in the presence of a liquid
crystalline phase. The crystalline phase limits particle
growth to ~5 nm. When HA particles have formed, the
liquid crystalline phase is dissolved and the particles can
be deposited onto a surface using dicyandiamide.
Biologically active drugs incorporated dental
implants
The adhesion of plasma proteins on the surface of Ti
implants has been reported to play an essential role in the
process of osseointegration.[30] Polypeptide growth and
differentiation factors and cytokines have been suggested
as potential candidates in this regard to stimulate a
deposition of cells with the capacity of regenerating the
desired tissue.
Bisphosphonates
Growth factors released during the inflammatory
phase have the potential of attracting undifferentiated
mesenchymal stem cells to the injured site. These growth
factors include platelet-derived growth factor (PDGF),
epidermal growth factor, vascular endothelial growth
factor, transforming growth factor (TGF-β) and BMP-2
and BMP-4.
Bisphosphonate incorporated on to Ti implants increased
bone density locally in the peri-implant region.[29] with
the effect of the antiresorptive drug limited to the vicinity
of the implant.
The surface of Ti dental implants may be coated with
bone-stimulating agents such as growth factors in order
to enhance the bone healing process locally.
Some osteogenic drugs have been applied to implant
surfaces. Incorporation of bone antiresorptive drugs,
such as bisphosphonate, might be very relevant in clinical
cases lacking bone support.
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Dahiya, et al.: Surface topography of dental implants
Members of the TGF-β superfamily and in particular bone
BMPs, TGF-β1, PDGF and insulin-like growth factors are
some of the most promising candidates for this purpose.
The effects of recombinant human protein BMP-2 on the
osseointegration of Ti implants have also been investigated.
PRGF can accelerate bone regeneration in artificial defects
and improve the osseointegration of Ti dental implants.
A study by Nikolidakis et al. (2006) investigated the effect
of local application of autologous platelet-rich plasma on
bone healing in combination with the use of Ti implants
with 2 different surface configurations – Ca/P coated
and non-coated implants. The role of the osteoinductive
TGF-β1 application to Ca/P implant surfaces have been
studied in animals using a goat model. Although the
possibility of incorporation of a plasmid containing
the gene coding for a BMP exists, it is associated with
disadvantages related to poor efficacy and a possible
undesirable overproduction of BMPs.
CONCLUSION
The new generation dental implants exhibit a large
variation in surface properties, both in terms of structural
and chemical compositions. Ti and its alloys are the
materials of choice clinically, because of their excellent
biocompatibility and superior mechanical properties. The
selection criteria for the first generation dental implants
were mainly based on their mechanical properties and
corrosion resistance under physiological conditions. The
current surfaces have mainly underwent topographical
modification and to a lesser extent, alteration in chemical
composition. These topographical modifications
have boosted the success rate of the implant therapy,
especially in patients with poor bone quality sites and
have significantly reduced the healing period. The
cellular mechanisms involved in this faster and improved
osseointegration are yet to be fully determined.
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How to cite this article: Dahiya V, Shukla P, Gupta S. Surface
topography of dental implants: A review. J Dent Implant 2014;4:66-71
Source of Support: Nil, Conflict of Interest: None.
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