implantaten und Aufbau - BEGO

Originalia – Materials Science
7
In-vitro corrosion current measurement between
titanium implants and superstructures made
of titanium, gold and cobalt chrome alloys
M. Gente, J. Dati, P. Günter, S. Pruss, S. Rickmeyer, S. Vittur
Marburg
When a tooth is lost, the resulting gap can be
closed with a bridge. Although the adjoining
teeth may have no hard tissue defects, or only
minor defects, they will inevitably be damaged
during construction of the bridge. Placement of
an implant is therefore the more favourable solution.
Furthermore, implants can be used in
isolation for tooth replacement, which is why
they are becoming increasingly popular in spite
of their high cost. Nevertheless, account must
be taken of the effect that the implant material
will have on other metals in the mouth as regards
corrosion. In this context, corrosion means
the gradual degradation of a material due
to the influence of other materials in its surroundings.
The implant and the respective metal
superstructures form a galvanic cell. The
aim of this paper is to investigate the corrosion
currents between a titanium implant and various
metallic superstructure materials.
Materials and method
The aim was to investigate the corrosion currents
between an implant (Semados S 3.75 L13
LOT 902621, Bego Implant Systems, Bremen)
and the superstructures made of a cast, highgold
alloy (Degunorm, Degussa Hanau), prefabricated
superstructures made of commercially
pure titanium (Sub-Tec titanium abutment S
5.5, LOT 901728, Bego Implant Systems, Bremen)
and prefabricated CoCrMo superstructures
(Sub-Tec Wirobond ® MI abutment 5.5, LOT
902286, Bego Implant Systems, Bremen). The
compositions of the alloys, as stated by the manufacturers,
are given in Table 1.
As it was not possible to prepare the surface of
the cylindrical superstructures evenly using
abrasive paper, a uniform finish was ensured by
sandblasting all the superstructures with an
abrasive of grit size 110 µm (Korox, BEGO, Bremen),
at a pressure of 2 bar, until a matt surface
was produced. The superstructures were then
Corrosion currents were investigated between titanium implants and superstructures
made of various dental metals (CoCrMo alloy Wirobond, grade 4
purity titanium and high-gold alloy Degunorm) when in electrical contact.
The electrolytes used were unbuffered normal saline solution with a pH of 6
and also with a pH of 2.3, created by the addition of lactic acid. The pairing
of titanium implant and cobalt-chrome superstructure displayed the lowest
corrosion current density, at approx. 3 nA/cm 2 in both solutions. The corrosion
current density measured with superstructures made of titanium or
high-gold alloy was significantly higher, at up to 100 nA/cm 2 and 180 nA/cm 2
respectively. The results of this investigation indicate that CoCrMo superstructures
can be used on implants at least as safely as titanium or high-gold
precious-metal alloys.
stored in dry air for 7 days so that passivation
layers could form again.
The wires required for voltage measurement
were attached to the implant and the superstructure.
To prevent the copper of the wires
from going into solution, the connection points
were carefully covered with light-curing composite
(Grandio Flow A1, VOCO, Cuxhaven). Fig.
1 shows an implant and Fig. 2 shows a CoCr superstructure
with the sealed connection point.
For the investigation, two test-tubes were set
up as shown in Fig. 3. The test-tubes were
sealed airtight using Parafilm to prevent evaporation.
A salt bridge connects the two vessels; a
Table 1
Composition of the alloys
Key Words
Dental Corrosion – Implants
– Dental Alloys
Gold Titanium CoCr
Degunorm % by Pure titanium
% by Wirobond
weight
grade 4
weight
% by
weight
Gold 73,8 Titanium 99,8 Cobalt 61,5
Platinium 9,0 Others 0,2 Chromium 26,0
Silver 9,2 (oxygen, Molybdenum 6,0
Copper 4,4 carbon, Tungsten 5,0
Zinc 2,0 hydrogen) Others 1,5
Others (iridium,
indium)
1,6 (iron, silicon)
ZWR ̶ Das Deutsche Zahnärzteblatt 2008; 117 (10)