Anterior Bridge Preparation and Cementation

Anterior Bridge Preparation and Cementation

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Welcome to the University of Michigan Dentistry
Podcast Series promoting oral health care worldwide. We’re going to prepare a three unit anterior
bridge this afternoon utilizing the maxillary right cuspid and the maxillary right central
incisor. This patient had a large diastema between the two central incisors and through
orthodontics the two central incisors were realigned. This is a procedure we use very
often in aesthetic anterior bridge work we re-align teeth to better draw abutments or
re-align teeth so that we can minimize a display of gold or give us some advantage in pontic
placement. Both this patient and his brother have congenitally
missing lateral incisors and as a result the two central incisors have spread apart and
there is an uneven spacing between these teeth. The procedure in orthodontics was to fully
band these teeth and bring both central incisors together to close that space and rotate the
cuspids, the cuspids were turned quite a bit, they were rotated so that they would line
up better as abutment teeth. In doing this then we have space gained for a lateral incisor
pontic on each side. After a year of orthodontic treatment, the
two central incisors have been brought together so now there is no more diastema there and
the cuspids have been rotated now to give us optimal placement for the facings. This
space isn’t overly large but still we’ll be able to get a much more aesthetic end result
this way than if the orthodontics had not been completed. The radiograph of the cuspid shows the pulpal
architecture. You’ll notice that the pulpal is mainly confined to the central portion
of the tooth giving us plenty of room on either side to drill our pin holes. On the central incisor you’ll note that the
root is very short for some reason it did not develop completely. The root was this
shape before the orthodontic treatment and you’ll also note the usual pulp horns that
we do see in a central incisor are absent and there has been some recession of the pulp
again giving us plenty of room to draw our pin holes. We’ll be utilizing a unilateral pin ledge
for the abutment retainer on both the cuspid and the central incisor. With these plaster
models I would like to show you briefly what we’re going to be doing. We will make an initial
cut with inverted cone diamond going from incisal to cervical and then by turning that
diamond at right angles we’ll make our initial cuts of the enamel at the level of the incisal
ledge and the cingulum ledge. Following this, we will reduce the lingual
surface, sharpen the incisal ledge and the cingulum ledge and then a slice will be placed
on the distal surface. And when that is done the finishing line will be extended around
to the notch that was placed with the inverted cone diamond. With a 170L carbide then the ledges are refined
and then small recesses are placed in the areas where the pins will eventually be drilled.
Following this, the little dimplets are placed in the areas to allow a place for the twist
drill to seat and drill. Also the incisal edge has been protected and beveled. And lastly,
the pinholes are drilled in the three spots on this tooth, the incisal pin to a depth
of three millimeters and the cingulum pin to a depth of two and a half millimeters. We have placed an elastic or rubber band around
the two central incisors. Because of the orthodontic movement the teeth are very mobile and I’m
afraid they’re going to drift apart so during the procedure we’ll leave this elastic on
until we take our impression. In order to mark, or to know where to place the incisal
ledges it’s a good idea to use a Boley gauge to determine the thickness of the tooth with
where these ledges are going to be placed. And the way this is done is the Boley gauge
is set at two and a half millimeters. And in setting it at two and a half millimeters
this then will mean where we place this Boley guage on the tooth that at the point where
it binds, at the point where it binds – turn your head this way a bit perhaps you
can see it a little better – At that point where it binds the tooth is two and a half
millimeters wide. Then if we take a half a millimeter off the lingual surface, the lingual
reduction and make a ledge a half a millimeter that means we have one and a half millimeters
of tooth structure left. And the reason this is important is if you thin this enamel out
too much then the gold will show through as gray and make a very unaesthetic restoration.
We then take a little graphite or pencil lead and place that on the end or tip of this Boley
gauge and just scribe across that incisal edge of the central incisor and the cuspid.
And we do that like so. And with this we do, we make a fake line that
I will darken and then I will show you this in a mirror. With the pencil I’ve darkened the lines that
were scribed on the lingual surface and you can see the level of the incisal ledge. I’ve
also then marked the level of the cingulum ledge and the extent of the mesial finishing
line. We’ll be running an inverted cone diamond then up this mesial surface. On the cuspid,
we will also darken that line and made a mark on the distal surface and in the area for
the cingulum ledge. We will start the procedure with an inverted
cone diamond. We will run this up that mesial groove that we have scribed on the central
incisor. Now we have to be careful when we use this diamond that we don’t thin out this
incisal portion of that cut too much or else again the gold will show through a grayish
appearance on this incisal edge. Also this cut will be deeper than the rest of the lingual
reduction in the preparation of this tooth. The purpose being to give us a ridge of thicker
metal to give us some strength for the casting. [Drilling sound] Once that cut has been made, we will turn
the diamond at right angles to that cut and we will scribe just go through the enamel
on the incisal edge and the cingulum ledge. Okay, let’s see that. [Drilling sound] Then we’ll move down to the cingulum ledge. [Drilling sound] This diamond can also be used to roughly reduce
the rest of the lingual surface. However, we’re going to be using a torpedo-shaped diamond
for this purpose also a little bit later. Now just clean this mirror off. Now we’re going to do the same thing to the
cuspid. Turn this way just a little bit. Okay. [Drilling sound] Now turn it at right angles. To establish a proper finishing line on the
mesial bicuspid and distal of the central incisor, we will put the patient’s temporary
partial back in his mouth. First we’ll have to remove our elastic so that this temporary
partial and orthodontic appliance can be placed back in the mouth. This is an appliance the
patient wears to retain the position of the teeth. I don’t think we’re up. Did that get
seated all the way? Now close on it let’s see it. Okay. Open. Now this can be done with a ground-in facing
or frequently patients with a missing tooth, an anterior tooth, will have a temporary partial
or a flipper that we can use as a guide. No we will place a pencil mark on the mesial
of the cuspid and the distal of the central incisor and of course if we made the finishing
line out that far the gold would be too far out to the labial surface and it would give
an unnecessary display of metal. So that then we will make a second mark. Okay. About a millimeter in back of this and you
can see both of the marks in the TV screen and now I will place another mark just behind
that. About a millimeter to the lingual. And if you will turn this way I think we can see
that. And now we’ll do the same thing with the cuspid. Close that finishing line a millimeter
back. And then we’ll try to erase the first line
with a large eraser like this. It’s a little difficult to do. You can see how mobile this
central incisor is. Now we’ll place the temporary partial back
in to see if those lines are going to be hidden when the facing is put in. Just a little bit of the pencil mark showing
at the cervical but we’ll modify our finishing line so that won’t show. Now the purpose here is to get the gold lingual
enough so that it doesn’t give an unnecessary display of metal but yet bring it out far
enough so that the patient can clean this gold margin with his toothbrush. Okay. The next step then is to take our – turn
this way just a bit. 699-9 long diamond and prepare the slice and
blend that slice into the lingual of the tooth and then in that in the groove that we have
placed on the lingual with our inverted cone diamond. Okay open as wide as you can now. [Drilling sound] We’ll just come up to that finishing line
and then we’ll bring that around the cingulum. And stop in that little groove we have prepared
on the lingual surface. Now we’ll do the same thing on the mesial of the cuspid. Turn this
way just a bit? Okay. Open as wide as you can. [Drilling continues] With the diamond, the finishing line on the
lingual surface is carried just into the gingival crevice. Now I’d like to show the lingual
surface of those anterior teeth to give you an idea of what we have done. Now turn this way just a little bit. Okay. We prepared the slice on the mesial bicuspid
and brought that finishing line around to the little groove that we had prepared on
this distal lingual and the central incisor, a slice is prepared on the distal surface
the finishing line brought around that lingual and then it ends at this little notch at the
very cervical that serves as an indication to the lab technician now that that is where
the preparation ends. Now I would like to reduce the lingual surface
and protect the incisal edge with this diamond. It is a small torpedo-shaped diamond that
is used for reducing the lingual surface. And by carefully rolling this along the lingual
surface… about a half millimeter of this lingual enamel can be removed. [Drilling sound] You have to take care that you don’t reduce
this too much. As you will recall, we want the mesial ridge to be deeper than the rest
of the preparation. With this same instrument we’ll slightly bevel the distal edge line
angle here. And then we will protect the incisal edge by slightly hollow grinding that very
edge of the tooth. Then we’ll move over to the cuspid and also reduce that lingual surface,
grazing about a half a millimeter of that lingual surface away. Then again making an
incisal protection followed by the incisors so we have a bulk of metal [drilling sound]
on the lingual surface. We’ve reduced the lingual surface then of
the central incisor and the cuspid. About a half a millimeter of enamel has been taken
off. We have also protected that incisal edge. You can see. Can you close just a bit? All
the way down. It’s a good idea to check the clearance. We should have two thicknesses
of 28 gauge green wax as clearance on the lingual surface. Open just a bit now. Also
on these incisal edges, you can see the type of bevel that we’ve placed on this that the
gold would be on the lingual surface and we have not bought out the finishing line out
to a labial but we’ve hollow ground this incisal edge so that there would be a bulk of gold
to protect the thin, delicate incisal enamel and yet you won’t have a display of a lot
of metal when you look at it directly from the patient from front on. Now we’re going
to take a 170-L carbide and refine our ledges slightly and place some recesses where we’re
going to drill our pinholes. Open just a – that’s it. I’m just going to put some
air in there. [Drilling sound] These recesses… might be very deep. They
remind us also that the placement of the recesses on things are quite far apart to gain stability
in these pins by having them fall apart like the legs of a tripod. This mesial recess and
pin should be tucked way into the mesial surface of the, of the tooth. If it’s brought too
far to the center of the tooth then we’ll probably get a pulp exposure. Now we’re going to change carbide tips and
we’re going to place a half-round dia—a half-round carbide on this tooth, make little
dimples where we’re going to draw the pinholes. Now we’re going to place the dimples in the
recesses that we have placed on the lingual of these anterior teeth. This happens to be
a number one lomb bur. You can use either a half or number one carbide and the purpose
of this is just to make a seat for the twist drill and we do… drill with the twist drill. [Drilling sound] The twist drills do not drill well through
enamel so it’s very important that these little dimples are drilled through the enamel. Now
I’d like to set up a parelleling device and show you how that will be used to drill our
parallel pinholes. There are many ways of paralleling these pinholes
for this anterior bridge. One is to use guide pins and then by eye line up each succeeding
pin. There are also many paralleling devices on the market. This Dent-O-Guide is one device
we’re going to use on this patient. I’d like to very briefly show you how this device is
set up to fit the patient’s mouth. A study model of the patient’s maxillary arch
is placed on this surveyor and then the actual arm of the paralleling device is placed on
this mounting surveyor and the contra-angle handpiece is placed in the paralleling device
to line the bur head up with the little pin that you see right here. This thing parallels
the bur with the mounting table. When this is done, then the model is lined up so you
have the optimal line of draw with your handpiece and the model can be changed back and forth
until the line of draw is exactly the way you want it for your preparations. Then the
model is locked on the surveyor. And then this entire thing then is turned around so
that we can then mount the model to the, and relate the model to the paralleling device.
Now this is where the handpiece was and this part of the paralleling device then is placed
on the model with a small tray. And then with a Formatray plastic it’s placed in the tray,
the teeth are lubricated and then this is placed down on the model and an index of the
occlusal surfaces then will be recorded on this little tray. Then this can be taken to
the mouth and this will relate to the maxillary arch to the contra-angle and anything that
will be cut will be parallel and it will be in the same line of draw as we have on the
model here. Now I’d like to take this paralleling device to the mouth and show you how the contra-angle
relates to the anterior teeth. A portion of the paralleling device that we
have made the acrylic index for goes on the maxillary arch and we’ll place this in position
and have the patient close on the bottom portion. Now the bottom portion of this can be lined
with compound if you need the extra room. Close on that. In this particular situation
I think we’ll have enough room and then our contra angle will be related to the paralleling
device and any cut that we make then all along here, all the way to the posterior, would
be parallel. Would be parallel. Now we have to be sure that we’re turning
this twister in the proper direction and once we start drilling with the twist drill we
don’t stop too in the teeth, go to the depth and pull it out but we never stop a rotating
twist drill in the tooth. We’ll start with this distal incisal pin once we’ll start rotating
the twist drill, we should never stop it in the tooth but always bring it back out again.
And we’ll move to the mesial. In the pin, we’ll drill in and out and then
the cingulum pin. And then we’ll quickly move over to the cuspid. The mesial of the cuspid.
Distal. And we’ll then go cingulum pin. And then we’ll take the paralleling device
out and check the depth of the pinholes. The incisal pin should be three millimeters
deep. And the cingulum pin two and a half millimeters.
And we just have a little bit… to go on the cingulum pin and we will have that the
central incisor and what would be the proper depth and the mesial pin on the cuspid has
to be deepened a little bit. So then we’ll place the paralleling device
back in the mouth. And then we’ll be ready to take our impression. Okay, rinse. We have the impression pins in place. Now
the patient has been tissue packed. We’ll now take a rubber base impression. We have…
Now we’ll base our next, we’ll inject this next around the tooth – and open wide now
please – into the crevice, around these pins. These steal impression pins tend to
float up in the rubber base impression so that we have to make sure that we have them
seated all the way. So before we take our rubber base impression it’s a good idea to
tap each one of those to make sure they’re seated all the way. That one I can’t find. Oh, there it is okay.
And also in the fabrication of the impression tray, you have to relieve it enough in these
areas where the pins are because if you don’t there’s a good chance of bending these pins
or perhaps cracking the pin enamel around the, around the pin holes. Now we’ll remove the cotton roles. And seat our, our tray. Okay. And we’ll wait until the rubber base has set. The rubber base is set now and we’ll remove
this impression. Some of the pins may remain in the tooth, on deep pins this very often
happens, so we have to check very carefully and a couple of them did. This is no problem.
Before the patient swallows the pins – open please – the pins are placed back into
the rubber base impression. These are perfect cylinders and they are all of the same length
so that they are interchangeable. And so if the pin does stay in the tooth, you simply
remove it and place it back in to the impression. Now let me show you then the impression I’ll
try to turn it side-ways after I place this pin back in. Ah, if we can get a close-up of that. You can see we have the three pins that are
parallel to each other and the three pins in the other preparation that are parallel
to each other and we do have a good impression of the cervical finishing line all the way
around. Now this impression will be silver-plated and all we have to do now is temporize his
teeth. The bite is such that there is no occlusion on these anterior teeth and we will be able
to hand articulate the models. All we’ll have to do now is take a shade and temporize the
anterior teeth. We’ll place some cotton rolls back in the
mouth and then we have Williams plastic pins that we’ve placed in a little bit of utility
wax and these will be placed in the pin holes. So they seat all the way. Utility wax around
the Williams plastic pins acts as a seal. Where did that go? There it is. And we’ll seal this pin like a cork in a wine
bottle. When you’re handling pin it’s a good idea to use a hollow beak pliers. These pliers
generally hold the pins a bit better than just a regular plain cotton forceps. We’ll do the same thing to the cuspid. Is
that saliva ejector jammed up? Assistant: Yes. I need a saliva ejector. Can you clean that
up? Once these pins are placed in the proper position
then a Duralay will be painted around these to lock them together and to temporize this
until we have the patient back to seat the bridge. We’ll make a very, very thin… paint-on mix
of Duralay, a little bit of liquid and a little bit of powder and join the three pins together. And when this has been hardened and set up,
we’ll just… polish with a little rubber wheel. The occlusion is checked. We make sure the incisal edge is protected
and we’ll bring this bur right to the very edge of the tooth to protect this delicate
incisal edge while we’re fabricating the bridge. And then we’ll dismiss the patient until the
bridge is completed. You can see the Williams plastic pins through
the Duralay temporaries and they have held up quite nicely. We have Duralay built up
over the incisal edge to protect that delicate incisal edge. Now these temporary crowns will
be removed using a 26 spoon and you place the 26 spoon at the very cervical and tug
and… they usually come out in one piece. And if the pin does break off as one of them
did, you can very easily take it out with a spiral end tool. The cuspid’s coming out a little easier. When we last saw this patient, we had taken
a rubber base impression. Here we have the fabricated anterior bridge and we have already
cemented the facing, the shade has been checked and the contour. We will try the bridge in
before cementation now to make sure that the margins are correct. You can see we have burnished over the platinum
pins and this has been polished and the margins all seem to be adequate. So we will remove
the bridge and then a mix of aluminous EBA cement will be made. You can start mixing
Judy. As you can see these pins are very retentive. It’s important that the pin holes are completely
dry so we’ll take some pippa points and make sure that we have these pin holes dried sufficiently.
When you’re using an EBA cement, aluminous cement. We uh, do not use a varnish. Okay
you can set that right down here. Because we want the zinc oxide eugenol to be in contact
with the tooth tissue here. We will spin the cement up in the pin hole. Go ahead. Keep
it down low. That’s it. Right near that side. And by using a spiral end tool – open real
wide – spinning the cement down the spiral, you’ll get cement up in the pin holes. Be
careful that you turn the spiral in the proper direction or else that cement will be coming
out of the pin instead of right down into the pin hole. One more pin hole to go. Okay. Now we simply seat the bridge with a
little bit of pressure and use an orange wood stick. Okay. And close please. Now this zinc oxide eugenol cement … rather
quickly in the mouth. Faster than the zinc phosphate cements it. Give you a little bit
of working time. Because zinc oxide eugenols will not sit up quickly on a slab but once
they have moisture and warmth they will – cotton roll please. Thank you. They will
set up very rapidly. Okay close again. I’m just… Oh, you’re getting saliva. Okay.
Okay. Okay, close. Open. Close again. Okay close. Uh-huh. That’s it close real tight.
Open. That’s it just keep your teeth together. Now we’ll use a tunnel number one plastic
instrument and this can be used as a burnisher and open just a little. The surfaces of the
gold that are exposed can be burnished with this tunnel instrument or a 5S burnisher.
Now once the surfaces that are visible are readily accessible are burnished. Then this
bridge, under pressure… and close please…. is allowed to set for a period of 10 minutes. When the cement has sufficiently hardened,
it’s important to remove the cement from around the bridge especially under this soft tissue
and under the pontic. It’s a good idea to take a dental floss with a bridge threader
and thread underneath the pontic area and also instruct the patient on how to thread
dental floss under this pontic area to make sure that they can maintain the cleanliness
under that area. You’ll notice that when we look at this bridge
from straight on – tip your head down a little bit – that the way we have prepared
our incisal protection that the display of gold is minimal on that incisal edge. And
when we’re talking to this patient in the conversational position that this gold doesn’t
show at all and yet when we look at the incisal edge you’ll see there’s sufficient gold protecting
the incisal edge. It’s a good idea to recall this patient then in about a week to check
the oral hygiene and to recheck the occlusion and see how they’re getting along with the
bridge. You have been listening to a presentation
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