EDI - European Association of Dental Implantologists

38
EDI
EDI News
Implementation and design
Some of these limitations were disadvantageous,
most importantly those concerning the planned randomized
study. However, it was still our goal to
secure public sponsoring, as the university budget
did not cover our need for human and technical
resources. A number of German institutions took
part in developing the “Tübingen implant”: the Institute
for Medical Biometrics in Tübingen; the Institute
of Pathology (and animal farm) at the University of
Heidelberg; the Fraunhofer Institute for Mechanics of
Materials in Freiburg, the Max Planck Institute for
Metal Research in Stuttgart; and the development
department of Friedrichsfeld GmbH in Mannheim.
In the 1960s, extensive investigations of periodontal
histology had been performed in Tübingen. Other studies
had focused on oral wound healing and specific
hematological reactions for bone regeneration. The
results of these studies went into the implant body
design. For a comprehensive overview of the research
program, the reader is referred to ZM 74 (19/20), 1981 and
Quint Int 15: 2267, 1984. Numerous references are offered
in these sources. Following basic anatomical studies,
plans for implant placement were originally confined to
specific jaw segments (sites 15 to 25, 34 to 44).
The transmucosal implant element was polished
to a high gloss. In addition to reducing plaque accumulation,
this surface treatment was intended to
ensure the organismic principle of ectodermal
integrity in the transmucosal area. In natural teeth,
this integrity is ensured by hemidesmosomal attachment
of the inner junctional epithelium to the
cementoenamel junction. However, lack of such
attachment can remain without consequences for
decades in the presence of recessions because the
epithelium will also become attached to the very
smooth mesodermal cementum.
Based on previous haematological findings about
blood-clot attachment, the enossal surface was blasted
with aluminium oxide particles. The resultant
microtexture was characterized by peaks and valleys
of 1 to 5 μm, causing the coagulation and attachment
of blood to aluminium oxide surfaces in a matter of
seconds. Connection was established down to the
molecular level, meeting the quintessential requirement
for speedy organization of endosteal tissue!
Both principles were implemented for the first
time and have since been adopted by almost all
implant manufacturers, most notably in recent systems.
Incidentally, the effect of surface roughness on
final strength really continues to be an open question.
This conclusion was drawn after we measured
the osseointegration of different implant systems in
vivo using the Periotest system.
The implant body was designed
as a conical step cylinder. This
shape was based on the consideration
that implants cannot – as
natural teeth can – introduce
loads into the cranial skeleton by
a push-pull transformation within
the periodontium. Most of
today’s implants are designed
with threads. However, the ethical
requirements defined by the state
ministry precluded the use of
threads, since they would have
involved bone loss in the event of
treatment failure. Rather than
threads, the implant body was
designed to feature lacunae, initially filling with
blood and later with bone. The gross surface (not
including the microstructure) was generally around
55 to 65 percent larger than the surface of a natural
root.
The results obtained in animal experiments were
so excellent that, as soon as 1978, the Tübingen/Heidelberg
group won the DGZMK award for
best performance of the year. Optimal results were
even obtained in clinical studies, despite entering
uncharted territory. A number of rules (frequently
disregarded or highly controversial ever since) were
considered essential. Care was taken to preserve the
marginal gingiva with its fibrous structure and inner
junctional epithelium, requiring careful handling of a
periotome to separate the periodontal ligament. Any
reduction of the facial alveolar wall and bony interdental
septa was strictly avoided. Instead, the
implant bed was palatally relocated (in relation to
the alveolar axis) and cranially deepened. Finally, an
undisturbed healing period of three months was
observed prior to loading the implants.
Excellent statistical results were also obtained. As a
result, another eleven universities agreed to take part
in the clinical studies. These collaborations started in
1977 and were followed up by annual symposia in
Tübingen.
After the phase of sponsoring by the Baden-Württemberg
State Ministry of Economic Affairs had
ended and Frialit-1 had been introduced in the
market, the German Research Society (Deutsche For -
schungs gesellschaft, DFG) created an opportunity
for the study groups to continue their work. The
research objectives were considerably broadened.
Led by the author, a dedicated research institute was
launched and maintained from 1984 to 1996. Being
the largest effort of its kind worldwide, this initiative
The Tübingen
implant.