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type they were. And what was wrong?
There was a missing piece. Even if the
implants were 3 mm apart, we still had
a problem. The problem was that we
were missing the supracrestal attachment
that a natural tooth has. That’s
why a single-tooth implant looks so
good on the lecture circuit. Everybody
can’t wait to show you a single-tooth
implant because if there’s a healthy
tooth on either side, the biologic
width on a healthy tooth, the connective
tissue fibers and epithelium are
supracrestal. So they actually wind up
helping to support the papilla. That’s
2 mm of biologic width supracrestal,
not subcrestal. But if I have an implant
there instead of a tooth, the biologic
width is subcrestal down to the first
thread. So the biologic width is below
the crest of bone, not above the crest.
That’s why we’re 2 mm short. And
that’s what we need.
So, where are we today? The real challenge
today that we’re all working on
is getting attachments onto an abutment
and keeping them there, and
not continuing to break the seal. And
keeping the biologic width, which we
can get to form on an abutment — we
have enough data to show that certainly
happens. The issue is when we
take an abutment on and off multiple
times as opposed to “one abutment,
one time” — I think Dr. Henry Salama
quoted that. If we keep breaking that
seal, the biologic width goes down. If
we get it right with the initial seating
of the abutment, we want to keep it
there if we can. So, based on Abrahamsson’s
work, maybe one change is
OK, but more than that, and it starts to
drop down. So we’re at a point where
what we must do in order to put two
implants next to each other in the esthetic
zone, with a high smile line and
to keep the papilla, is get supracrestal
biologic width. This is a very big challenge,
and that’s what everybody is
trying to work on now. Between two
centrals we get away with it because
if the papilla is a little short, it’s right
down the middle. So you don’t see any
comparison, you just close it down
with a little fatter contact point and it’s
OK. As long as you have a little scallop
and no black spot, you’re OK, even if
it’s a little short. But central lateral, in
a high smile, with a lateral cuspid? It’s
a nightmare waiting to happen. A high
smile with the natural teeth on the
other side, with good papilla, always
looks lopsided to the eye. So that’s
what we have to be careful about.
People used to
say, ‘Look at my
implant. There’s
no biologic width
on my implant.’
That’s ridiculous.
There’s always a
biologic width on
an implant.
DC: Does implant design play into any
of this?
DT: It sure does. That original article in
2000 that you asked about was without
a platform switch. So now, what we’re
looking at — myself with Dr. Xavier
Vela Nebot and others at the Barcelona
Osseointegration Research Group — is
platform switching. We looked at this
and saw that when you put a platform
switch on an implant, the horizontal
component is no longer 1.4 mm or 1.5
mm like the old Brånemark implant
was. What we realize now is that the
horizontal component is only about
0.3 mm to 0.5 mm. This is because the
platform switch is there, and there’s
an abutment in the middle, and there’s
a shoulder to the implant instead of
being straight up, and the abutment
connection between the bevel, or
shoulder, allows room so the bone
doesn’t have to move as far down to
protect itself from the irritant. The
bone can stay up there higher because
the extra coverage of soft tissue acts
as a buffer between the possible
irritation of the abutment connection
to the bone. Long story short, we lose
less bone down the side when we
have a platform switch; we only see
about 0.3 mm to 0.6 mm, depending
on the system, but under 0.5 mm or in
that range, whereas we used to see 1.5
mm to 2 mm. Now we’re seeing about
0.5 mm down from the shoulder.
That’s because there’s still a biologic
width there.
People used to say, “Look at my implant.
There’s no biologic width on my
implant.” That’s ridiculous. There’s always
a biologic width on an implant.
Once an implant is exposed to the oral
cavity, there’s always a biologic width
— there has to be one. The bone covers
itself with connective tissue in the
periosteum. The periosteum covers itself
with epithelium. So there’s always
a biologic width. We will never change
that. The question is, “Where is it?” Not
whether it exists. On an X-ray it might
look great. The bone may be covering
the shoulder of an implant, if you
place it deep enough. There’s always a
biologic width, but is it on the shoulder,
or even on the abutment? If you
never took off the abutment, it could
be on the abutment. So the bone could
look great, but once you take the abutment
off a few times, the bone will go
down a little — but not as far with a
platform switch. So I think you’re going
to see that platform switching is
here to stay, and I think it will keep
growing, and that almost every company
will eventually have one to offer.
DC: Let’s talk about guided surgery. Is
that something you embrace? How do
you decide when to do a case using a
surgical guide?
DT: That’s an important question. I
think that it is going to get better, but
that it got pushed too far, too quickly.
One of the companies pushed way
– Implant Q&A: An Interview with Dr. Dennis Tarnow – 17