Chairside - Glidewell Dental Labs

Give me an example of a case that might be one of those highrisk
cases.
LB: Well, the first one I think of, which is super common
in your scenario of a fractured cusp, is you’re going to do
an upper or lower second molar. For most folks, if we look
at, percentage-wise, which tooth in the arch is the one that
trains our lateral pterygoid and has our brain know how to
find intercuspal position, it’s going to be on a second molar.
Now you look at that tooth and you don’t know, when you
prep the rest of the occlusal table away, if they are going
to lose that muscle memory, and therefore, the instant you
do your prep, you go in to check and there’s no occlusal
clearance. I don’t know if you’ve done this, but I’m geeky
enough that I’ve actually looked at the research, and five
minutes is nowhere on the bell curve for normal supereruption.
Teeth don’t do that. If you lose your occlusal
clearance literally while you’re prepping, it’s because the
lateral pterygoid muscle is relaxing and releasing and the
condyle is receding.
So what do I look for in that situation? Sometimes it’s hard
if the cusp is broken because they may have just eliminated
their own first point of contact. But I look for wear because
patients who have wear on their second molars — no place
else on their arch but on their second molars — what runs
through my head is they get their condyles back in centric
relation. They either peri-function back there or this is a
place they go to. I need to be thinking about this. I also
always look for the difference between intercuspal position
and that seated condylar position from a standpoint of the
relationship of their front teeth. How much do their front
teeth come apart vertically? Is there an A-P piece of that?
What’s the distance? Because if their front teeth open 3 or
4 millimeters when you get their condyle seated, and that
gets deprogrammed, that is going to translate to 1 or 1.5
millimeters off the top of your prep, and there goes your
clearance. If the discrepancy is little, which fortunately for
us it is in 85 percent of the population — it’s less than
1 to 1.5 millimeters — we’re never even going to notice on
that second molar.
MD: OK, let’s say the patient comes in and it’s not a broken
cusp. Somebody’s got a large amalgam in a lower second molar
and it’s got a little recurrent decay and you’re getting ready to
prepare it. How do you handle that and how do you go into that
to minimize the risk of those kinds of sequelae happening when
you prep that second molar?
LB: For me, it’s super simple. I reach for a leaf gauge. I keep
a leaf gauge on my exam tray. It takes me probably less
than a minute with a leaf gauge to find out, number one, if
they have a positive load test, which tells me their lateral
pterygoid is kind of tight. If I can get it released, can I find
first point of contact? Is it marking on the tooth I’m about
to prep? If it’s marking on a different tooth, my risk is really
For the majority of my patients, we do
dentistry in very small units. Honestly,
even when I do patients where we’ve
talked about a comprehensive treatment
plan and the patient is ready to
do that, because of their time restraints
or their economic restraints, we have
to figure out how we do dentistry in
little pieces over 10 years.
Interview with Dr. Lee Ann Brady47