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TECHNOLOGICAL ENGINEERING
volume XIII, number 2/2016
ISSN 2451 - 3156
DOI: 10.2478/teen-2016-0018
NON-DESTRUCTIVE ANALYSIS OF BASIC SURFACE
CHARACTERISTICS OF TITANIUM DENTAL IMPLANTS MADE
BY MINIATURE MACHINING
1Ondrej
1Roman
Babík, 1Andrej Czán, 1Jozef Holubják,
Kameník, 1Jozef Pilc
1Department
of Machining and Manufacturing Engineering, Faculty of
Mechanical Engineering, University of Žilina, Slovakia
Abstract
One of the most best-known characteristic and important
requirement of dental implant is made of biomaterials
ability to create correct interaction between implant and
human body. The most implemented material in
manufacturing of dental implants is titanium of different
grades of pureness. Since most of the implant surface is in
direct contact with bone tissue, shape and integrity of said
surface has great influence on the successful osseointegration. Among other characteristics of titanium that
predetermine ideal biomaterial, it shows a high
mechanical strength making precise machining miniature
Increasingly difficult. The article is focused on evaluation of
the resulting quality, integrity and characteristics of dental
implants surface after machining.
Keywords
titanium, surface roughness, dental implant, osseointegration
1 THEORETICAL INTRODUCTION
A dental implant is an artificial tooth root that is
placed into your jaw to hold a replacement tooth or bridge.
Dental implants may be an option for people who have
lost a tooth or teeth due to periodontal disease, an injury,
or some other reason. [1]
An endosteal implant is an alloplastic material
surgically inserted into a residual bony ridge primarily as
a prosthodontic foundation. The prefix endo means
“within,” and osteal means “bone.” Root form implants
are the design most often used in restoration of the partial
or completely edentulous patient. [2]
Maggiolo introduced the more recent history of
implant dentistry in 1809 using gold in the shape of a
tooth root. In 1887 Harris reported the use of teeth made
of porcelain into which lead-coated platinum posts were
fitted. Many materials were tested, and in the early 1900s
Lambotte fabricated implants of aluminum, silver, brass,
red copper magnesium, gold, and soft steel plated with
gold and nickel. He identified the corrosion of several of
these metals in body tissues related to electrolytic action.
The first root form design that differed significantly from
the shape of a tooth root was the Greenfield latticed-cage
design in 1909, made of iridioplatinum. Reports indicate
this implant had a modicum of success. Surgical cobalt
chromium molybdenum alloy was introduced to oral
implatology in 1938 by Strock when he replaced a
maxillary left incisor single tooth, an implant that lasted
more than 15 years. In 1946, the desired implant
interface was described as ankylosis, which may be
28
Article history:
Received 30.11.2016
Accepted 11.12.2016
Available online 29.12.2016
equated to the clinical term rigid fixation. The first
submerged implant placed by Strock was still functioning
40 years later. Bone fusing to titanium was first reported
in 1940 by Bothe et al. Branemark began extensive
experimental studies in 1952 on the microscopic
circulation of bone marrow healing. These studies led to
dental implant application in early 1960; 10-year implant
integration was established in dogs without significant
adverse reactions to hard or soft tissues. Studies in human
beings began in 1965, were followed for 10 years, and
were reported in 1977. Osseointegration, as first defined
by Branemark, denotes at least some direct contact of
living bone with the surface of an implant at the light
microscopic level of magnification. The percentage of
direct bone-implant contact varies. [2]
Response of the tissues to the implant is largely
controlled by the nature and texture of the surface of the
implant. Compared to smooth surfaces, textured implants
surfaces exhibit more surface area for integrating with
bone via osseointegration process. Textured surface also
allows ingrowth of the tissues. The role of surface
topography has been the interesting area of investigation
in implant dentistry for several years. Several types of
implant surface textures are currently available for clinical
use. Some of these have the ability to enhance and direct
the growth of bone and achieve osseointegration when
implanted in osseous sites. Endosseous dental implants
are available commercially with many different surface
configurations. Most implant systems of this category are
based on the fact that bone tissue can adapt to surface
irregularities in the 1 – 100 micron range, and that
altering the surface topography of an implant can greatly
improve its stability. [3]
In order to increase the success rate of dental
implants, research has focused on the control of surface
properties such as morphology, topography, roughness,
chemical composition, surface energy, residual stress, the
existence of impurities, thickness of Ti oxide film, and the
presence of metallic and nonmetallic compounds on the
surface. These properties profoundly influence the
osseous and tissue response to the implant by either
increasing or decreasing healing times and
osseointegration. [4]
To increase the surface roughness, the following
methods have been listed: machining - The surface is
manufactured and then, implants are subject to cleaning,
decontamination, passivation and sterilization; but there
is not subsequent finishing, meaning that the surface is
untreated; plasma spraying - common method in which
powders of different substances (e.g., Ti or calcium
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phosphates) are heated to high temperatures and then
are projected onto roughened implant surfaces to form
coatings between 30 µm to 50 µm thick; machine gritblasting - one of the most frequently methods of surface
alterations, in which the implant surface is roughened by
projecting hard particles (alumina or TiO2) at high
velocities at implants to alter the surface roughness; acidetching - This technique consists on increasing the
thickness of the oxide layer and the roughness by
immersing the metallic implant into an acidic solution
which erodes the surface producing micro pits with sizes
ranging from 0.5-2 µm; coating - Dental implants can be
coated with a variety of materials and/or molecules
depending on the specific application and requirements;
anodization – (subject of this experiment) It is an
electrochemical process where the implant is immersed
in an electrolyte while a current is applied, resulting in
micro pores of variable diameter (70 - 110 nm) and an
increase of the oxide layer. Main advantages of
anodization technique include improved biocompatibility,
increased cell attachment and proliferation. [4,5,6]
Titanium and its alloys belong to the group of metallic
biomaterials. Biomaterials designed for implants are
defined as materials capable of interacting with biological
systems when applied in medical products. Unalloyed
Commercially Pure (CP) Titanium is available in four
different grades, 1, 2, 3 and 4, which are used based on
the corrosion resistance, ductility and strength
requirements of the specific application. Grade 1 has the
highest formability, while Grade 4 has the highest strength
and moderate formability. TiGr2 is stronger than Grade 1
and equally corrosion-resistant against most applications.
Biocompatibility of Grade 2 Titanium is excellent, especially when direct contact with tissue or bone is required.
Mechanical Properties of TiGr2 are Rp0,2 = 275
– 450 MPa, Rm = min. 345 MPa, A5 = 20% and
HV10 = 146. TiGr5 is an alloyed titanium product
containing 6% Aluminum and 4% Vanadium is a medium
strength product. This titanium grade is predominantly
used in airframe, turbine engine parts and for use in
surgical implants. Mechanical properties of TiGr5 are
Rp0,2 = min. 828 MPa, Rm = min 895 MPa, A5 = 10% and
HV10 = 314. Nanostructured titanium (nTi) belongs to the
so-called bulk nanostructured metallic materials. For
these are considered materials with gran size between 1
– 100 nm. Production of Nanostructured titanium consists
of forming commercially pure titanium (cpTi) by SPD
technology – high plastic deformation at which chemical
properties remain unchanged, but the mechanical properties are improved significantly in relation to the strength.
Mechanical properties of nTi are Rp0,2 = 1200 MPa,
Rm = 1240 MPa, A5 = 12% and HV10 = 336. [7,8,9]
2 EXPERIMENT PROCESS
The aim of the experiment was to determine the
characteristic of surface roughness of dental implants
made of different types of titanium (TiGr2, TiGr4, TiGr5
and nTi) when given the same manufacturing conditions,
since our research will be addressing the anodic oxidation
of dental implants made of titanium and its alloys in
future. Surface roughness and its parameters Ra, Rz a Rp
make direct impact on the quality created micro-pores,
whereas their average dimensions are in tens of
nanometers. The surface roughness measurements were
carried out on the so-called “crestal module” of the dental
implant (Fig. 1), located at the transition from endosseal
area into oral cavity area. Its task is to transfer of load to
the compact bone tissue shortly after implantation, and
also serves as a wound seal in the bone.
For the experimental measurement was designed 3D
model which contains all the basic elements of root dental
implant design as thread, crestal module, anti-rotational
surfaces and the base for the abutment (Fig.1).
Figure 1. Designed 3D model of experimental dental
implant
Production of dental implants was performed on
Swiss-type CNC machining centre DIAMOND CSB 20
(Fig.3). design and technological parameters are
specialized for manufacturing of miniature components
such as dental implants with max. ф = 3,95 mm and max.
l = 16mm.
When machining the measured part of the dental
implant, cutting condition were set: f = 0,06 mm.rev-1,
n = 2200. As a cutting tool was used insert DCMT 11 T3
04-PM 4315 with 0,4 mm tip radius (Fig. 2).
Figure 2. Cutting tool DCMT 11 T3 04-PM 4315
Figure 3. DIAMOND CSB 20 – swiss-type CNC machining
centre
One finished sample of experimental dental implant is
illustrated in Fig. 4. It is planned to optimize the cutting
conditions for the machining of thread, given the quality of
its surface.
Figure 4. One of manufactured samples of experimental
dental implant
Subsequent measurement of the crestal module
surface roughness was performed on roughness tester SJ400.
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29
3 Conclusion
Figure 5. SJ-400 surface roughness tester
Figure 6. Implant fixation and measurement preparation
A mentioned above, the measured roughness
parameters were Ra - Arithmetic Mean deviation of the
roughness profile, Rz - Maximum Height of roughness
profile, Rp – maximum peak height of the roughness
profile. Bulk of measured samples included 3 implants
made of one of each materials (TiGr2, TiGr4, TiGr5 and
nTi). The results are shown in Tables 1,2,3,4.
Table 1
Surface roughness parameters of TiGr2 samples
1.
2.
3.
∑
Ra 0,6 μm 0,33 μm 0,71 μm 0,55 μm
Rz 4,4 μm
4 μm
4,4 μm
4,26 μm
Rp 1,8 μm
3,1 μm
2,7 μm
2,53 μm
Table 2
Surface roughness parameters of TiGr4 samples
1.
2.
3.
∑
Ra 0,57 μm 0,53 μm 0,56 μm 0,55 μm
Rz
3,6 μm
3,8 μm
3,7 μm
3,7 μm
Rp 1,4 μm
1,7 μm
1,5 μm
1,53 μm
Table 3
Surface roughness parameters of TiGr5 samples
1.
2.
3.
∑
Ra 0,44 μm 0,5 μm 0,53 μm 0,49 μm
Rz
3,5 μm
3,4 μm 3,4 μm
3,43 μm
Rp 1,3 μm
1,4 μm 1,6 μm
1,43 μm
Table 4
Surface roughness parameters of nTi samples
1.
2.
3.
∑
Ra 0,26 μm 0,37 μm 0,43 μm 0,35 μm
Rz
2 μm
3 μm
3 μm
2,6 μm
Rp 0,9 μm
1,8 μm
1,7 μm
1,46 μm
Parameter value
[µm]
Average value graphs of measured roughness
parameter depending on given materials are illustrated in
Figure 7.
5
0
TiGr2
TiGr4
TiGr5
nTi
Material
Ra
Rz
Surface characteristic have significant impact on the
successful application of dental implants. To improve
the success rate, different surface treatment methods
are used such as etching, plasma spraying, anodic
oxidation etc.
Since our research will be addressing in particular
anodic oxidation in future, it is necessary to know the
parameters of the surface roughness Ra, Rz and Rp,
which make direct impact on the quality of surface after
treatment.
The goal of this research was to determine, which
type of titanium material carries the best surface
roughness, given the cutting conditions. From Graph 1
it is clear, that the best results (i.e., the lowest average
of the parameter values) were obtained using
nanotitanium, except for Rp value (TiGr5), which has the
highest mechanical strength and the finest grain
structure. The second lowest average values were
obtained using TiGr5 (contains 6% Aluminum and 4%
Vanadium).
Given the achieved results, our research will continue
to study roughness of machined titanium surfaces of
dental implants with efforts to achieve ideal conditions
for the anodic oxidation of the surface, which aims to
create the ideal structure of micro-pores.
Acknowledgements
This article was funded by the University of Zilina project
APVV-15-0405 – “Complex Application of X-Ray Diffractometry
for Identification and Quantification of Functional Properties of
Constructional Elements Dynamically Loaded Produced from
Important Technical Materials.”
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Rp
Figure 7. Average surface roughness parameters values
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