[The Traditional Crown Preparation A Free Biomimetic Dental Course for Patients Matt Nejad]
In this video, we're going to cover the traditional preparation technique versus
the biomimetic technique which conserves a lot of tooth structure and takes away
less of your tooth. So let me get my loops on and let's go for it.
Okay, so here we have a very typical scenario
which is a silver filling and the silver filling has cracks, which are these red
dots over here because a silver filling is a metal filling, but it doesn't
adhesively bond or join the tooth together so every time you chew on this,
like every time you're eating, grinding, clenching, any of that, little by little
stresses build up and create cracks in the tooth, okay.
The traditional way to address that now is to say okay this tooth is
structurally compromised, it's not strong so I need to shave away the whole enamel
outer layer and cover it with a crown. So I'm going to show you what that means,
it's a lot of shaving, it's a lot of reduction. On average, we're talking about
70 or 75 percent of the tooth being shaved away. So let's go ahead and do
that so you can see what we're talking about for a crown. So first step in a
crown, there's different techniques, but most of the time you start with either
reducing the outside or the top, let's do the top first.
When you're doing a crown, first you know you need to reduce a large amount
of tooth and you know exactly how much you need to reduce, different materials
have different reductions, but what you do is you make these grooves that are
about a millimeter and a half or two millimeters deep so that you know that
you have enough space for your crown to be thick enough. So I'm going around
making several sets of these grooves and I'm checking because I know how big this,
see this burr, I know how big it is okay. So it's about 1.6 and when I do this, I
can just check that I'm deep enough everywhere. Okay, now I can go and join
these areas together.
As you can imagine, we have a lot, a lot, a lot of tooth reduction here that could
have been avoided and we're not even done yet.
So this is called the occlusal reduction, almost done here, that's how much we need
to take off the top so that there's room for the crown.
Okay and we see from the
side here how much reduction we have. I still need to finesse some things, but
this is just the reduction portion so before I do the finessing, now I'm going
to reduce the sides because a crown covers the top and all around. Okay, so
just to take care and strengthen this tooth, we have to take away not only a
lot of the top, but also the sides so I'm going to turn this sideways here and now
you can see what we call the axial reduction, which is the reduction on the
sides of the teeth.
Same idea, go ahead and place my grooves again depending on the material, we have
different reductions, but a rather common reduction amount is one, one and a half
millimeters depending.
So once I have a few of these grooves,
I can start joining them again.
Okay, so we have some of the side completed here and this is still pretty
conservative for a crown, okay. We've taken away a lot of the side, this is just shy
of one millimeter on the margins, but we've taken away this whole side of the
tooth and we're right near the gum and we really want to avoid taking margins
near the gum because it's always best to have your own tooth structure up against
the gum, but with a crown procedure you have to go there in order to just have
the space for the crown. If you don't go near the gum, you won't have enough
retention which is what holds the crown in place and then you have problems. So
the traditional technique requires a lot of tooth reduction just so that the
crown will stay on, but if we were to use adhesion, we wouldn't need to take away
the area near the gum because our retention comes from our glue. We don't
have to take away more tooth just so the crown can stay on, we can actually use
adhesion to make sure that the restoration stays on. Now I'm gonna come
right here through the middle, I'm using a smaller burr so I don't get the
neighboring tooth.
Now we have the side and the top, but not the inside near the tongue, so I'm going
to come back there and we'll work on that again.
Okay, let's go this view right
over here. So now we have to do the same thing we did on the outside over here, so
I'm gonna make a few grooves here.
Now I can start connecting again.
Okay, so now we have what's called the gross reduction of the crown done, which
means we've reduced a majority of what we need to, but now we need to finesse
and make sure that we create a shape so that something can come over this and
what does that mean? If I want to put a crown on top of this tooth right here, I
need to be able to get the crown to come straight from the top, come all the way
over, so it's important that the crown tapers or kind of leans a little bit on
each side, like this side needs to lean inwards, this side also needs to lean inwards,
so we're gonna now spend a little bit of time to create that shape that
will allow something to sit over the top without getting stuck.
So I kind of give it a little bit of shape up here.
Okay, now we'll go to the other side, do the same thing so I'm going to take away
the sharp edge and make sure there's a little bit of lean.
Okay and lastly, smoothing the top surface which we worked on originally.
So now I'm gonna take a look everywhere, make sure I have what's called
convergence, which means I have the ability for a crown to seat over without
having any area that would hold it up, okay so I look on all the sides here,
make sure I have the, basically an angle that kind of approaches the middle of
the tooth, so you see here if I were to continue, I'm kind of tapering towards
the center, same thing on this side, then we look from the sides over here and
confirm same thing and we're essentially done. There's still a little bit of
refining that I would normally do here for a crown, but very important is that I
would never normally prep this tooth for a crown okay, you can see how much tooth
we took away. Let me clean this up a little bit.
So we took away this much tooth in order to supposedly strengthen a tooth that
had problems from the previous silver filling and cracks, okay. Now in the next
prep, I want to show you what I would do for the same situation with the
biomimetic approach, which saves at least thirty to forty percent of what we just
removed because when we look here, we removed about seventy percent of the
volume of the tooth that's above the gum, so this is about a seventy percent
reduction from here to there and that is also associated with higher chance of
root canals, higher chance of sensitivity, and other problems such as irritation
around the gum lines and inflammation, harder to keep clean and so on. Okay guys,
so I cleaned up this so you can see it better. So here's our completed crown
preparation and really important to notice or to note is that this is still
considered a conservative crown preparation. The margin I have right over
here where the crown will end is not that big of a margin compared to what we
typically see in the traditional approach so even more would be taken
away, but when you look at this, this is still about a seventy percent reduction
in the tooth structure that is above the gums and all so that the crown could be
fitted on there, because our goal was to strengthen this tooth, but in the
traditional approach, we have to take away more of the tooth in order to
strengthen it and that's counterintuitive and with adhesion and
biomimetic dentistry, we're able to strengthen that tooth while keeping more
of the parts that are not damaged.
[Matt Nejad]