Upper Molar Crown Preparation through the Dental Microscope - Video Tutorial

You're about to see our lovely hygienist, Rosanna, who's gonna be getting a crown prep on the top left. 

 

So it's the first molar, it's an endodontically treated molar, and it has a small crack on the mesial, so we did decide to go for full coverage. 

 

This is a really good episode to learn how to do a crown prep under the microscope. 

 

I think a great place to start a crown prep would be on the top left or top right. 

 

So this can be something you review before you do ever jump into doing that with a microscope yourself. 

 

Let's get into it. 

 

All right, so now we're gonna do some anesthesia. 

 

So let's think about positioning here. 

 

How are we gonna get what we need to see? 

 

Well, number one, when your patient is lying supine, in order to be able to visualize the top vestibule where we wanna anesthetize, you can't really do it with indirect vision. 

 

I mean, you could, but it's pretty awkward with a mirror. 

 

So typically, I like to bring the scope further away and then tilt it back, and then that's gonna give us a better view. 

 

The upper lip isn't gonna get in our way, and we'll be able to see what we need to see. 

 

The downside is that you have to get a little bit closer to the oculars and lean forward more in order to see what you need to do. 

 

But given that it's such a short period of time while we're anesthetizing, it's worth it. 

 

So that's the way we do it. 

 

You'll notice that since the last video, we've added an extender here on... 

 

-an extender on the microscope here, and that just brings the oculars further away from the body of the scope, and it allows me to more easily get my oculars- or sorry- my eyes to the oculars, when we're dealing with these more awkward types of positions. 

 

So really, the only reason we're doing anesthesia here is for the gum tissue, not so much for the tooth. 

 

That tooth doesn't have a nerve anymore, so it's not feeling much, but the gum tissue still will. 

 

We've already placed some topical. 

 

You can see I have a beautiful view of the vestibule there. 

 

We'll just start our infiltration. 

 

Now, Zumax has another microscope called the OMS 2050. 

 

That one's gonna be featured later in the course once it arrives, and it's actually designed for general dentists. 

 

So this type of position is much easier to achieve with that microscope because the oculars come straight out horizontally from the microscope and go out quite a ways. 

 

That just gives you a lot better ergonomics when you're dealing with these harder- harder to reach spots. 

 

... 

 

Sensitive? 

 

We're gonna start with the rubber dam here. 

 

Uh, I really like using the rubber dam when you can, even for procedures where you think it might not be necessary. 

 

It just gives you really good macro retraction of the tongue and the cheek, everything you don't want coming in your way. 

 

And when you're using the microscope and you have to actually use your hands to reposition the microscope, it's nice to have things out of the way for you. 

 

So I would suggest, if you're not already doing so, try to use the rubber dam more. 

 

It'll definitely help you. 

 

In this case, we punched kind of a unique type of hole that's going to allow three teeth to be exposed by one hole, and that gives us really good access to the gum line on both sides of this tooth that we're prepping. 

 

So the clamp's gonna go on the tooth behind, and then the first big hole is gonna extend all the way to the mesial of tooth 2-5. 

 

And then that way, that 2-6 is gonna be really nicely exposed for us to do what we need to do. 

 

Again, for rubber dam access, indirect vision is not practical, so we are gonna go ahead and do direct vision on the upper arch, just like that. 

 

You can see the whole row of teeth here. 

 

Really nice view of what I need to see, and we'll place the rubber dam clamp on tooth 2-7. 

 

Upper left molar, second molar. 

 

These clamps, by the way, are amazing. 

 

They're 138s and 139s.

 

They work really well. 

 

They hold on to second molars amazingly. 

 

You can even use them on wisdom teeth, and I find that they work for ninety-five percent of molars in terms of getting a really good grip on them. 

 

So we got our first big hole. 

 

You can see it's been punched kind of like- almost like a butterfly. 

 

Let's spread that over. 

 

-Or a four-leaf clover is another way of thinking about it (the hole). 

 

Your rubber dam's on film now. 

 

Oh, I know. 

 

That's okay. 

 

That's why scissors exist. 

 

There we go. 

 

Yeah. 

 

Yeah. 

 

You can breathe again! 

 

So now, you can see in this case where we're not really doing any sensitive bonding, we don't need perfect isolation, but we do want good retraction, and that's where this is gonna work very, very nicely here. 

 

With a little bit of retraction, we have access to the lingual gum line, buccal gum line, and that'll be great for our prep. 

 

So in some cases, if you have a really small access and a molar that's unrestored, you can get away with actually not doing a crown. 

 

In Rosanna's case here, I wouldn't feel comfortable with doing that because if you look closely, you'll see a little crack line already starting in the mesial marginal ridge. 

 

With the access the size it is and those cracks, we're definitely gonna wanna cover these cusps. 

 

We're gonna do a full coverage crown here. 

 

Again, you might consider an onlay instead. 

 

I'm gonna go to a more neutral scope position now. 

 

Again, I don't really need to be leaning so far forward anymore. 

 

If I can be more comfortable while I'm working, I'll take that opportunity. 

 

So moving the scope closer to me, and either straight up and down or slightly pointed towards Rosanna, is a good scope position for the upper arch when you're doing indirect vision. 

 

And then open wide there, Rosanna. 

 

Perfect. 

 

When you're working on the top arch, you don't have to move the microscope all that much because your mirror can move. 

 

So you can change your perspective with your mirror or just little nudges to the microscope with your nose. 

 

That's enough to usually get you the position that you need for most of the top arch. 

 

I just nudged the scope to the right, and then I changed my-

 

So I'm gonna just show you that again. 

 

So I'm here, and I wanna... 

 

You can see my hand piece is blocking my view. 

 

I wanna just look at this area while I'm actually prepping it. 

 

So to do that, I'm just gonna nudge the scope to the right and then reposition my mirror.... 

 

so I can see exactly what I need to see, just like that. 

 

Again, that mirror gives you so many options. 

 

And right now I'm out of focus. 

 

Normally, I would just be totally fine working this way, but for you guys, to just get things back in focus, you can just adjust the focus knob there if you need to. 

 

Yeah, good. 

 

I'm gonna go back to my original position. 

 

So again, if I wanna be able to get back there, I'm gonna move the scope back this way with my nose and then just straighten my mirror, and adjust my focus. 

 

This becomes pretty much second nature once you get used to it, and all of that happens simultaneously without you even being aware of it. 

 

I'm slowing down here to be able to show you how I'm actually moving the scope and taking the steps to make sure you understand how to get into these different positions while you're learning. 

 

So there, our occlusal reduction is done. 

 

You can see that crack now a little bit more clearly, and it is extending into the dentin. 

 

So I got the explorer. 

 

So you can see this is not just in the enamel, right? 

 

This crack is now into the dentin about a millimeter. 

 

I wouldn't be surprised if there's a little bit of decay right under the surface right here. 

 

I just see this little white hint here. 

 

It looks a tiny bit dark to me there, so I'm not gonna be surprised if we see a bit of decay under the surface. 

 

And these are the type of cues that you'll pick up on more and more as you use the microscope more and more. 

 

Uh, could I trouble you for a KS0 bur, please? 

 

Sorry. 

 

Fine. 

 

Oh, she's ready! 

 

Look at this. 

 

That is service. 

 

Oh, man. 

 

Oh, you bet. 

 

Oh, life is good. 

 

Life is good. 

 

I really like the KS1 and KS0 burs. 

 

I think they were originally developed by Kois and Spears, which is hence the name KS, Kois / Spears. 

 

But they are great, and they're really nice for margination as well. 

 

All right, so let's see if we're correct about our decay here. 

 

it's just a little bit darker there. 

 

We're gonna see if there's any soft tissue structure in that area. 

 

Yeah. 

 

Do our interproximal reduction on the other side, again, maintaining the same scope position, just doing fine-tuning if I need to. 

 

So especially with me filming at higher magnifications, I might be tweaking a bit more than you would. 

 

If you're working at a low magnification to begin with, it's so much easier because you can see so much more. 

 

You don't have to move the scope as much. 

 

I'm gonna just film it at about medium magnification here, and then you can kinda see what I'm doing. 

 

All right, so now with where we're at here, we've got our interproximal reduction done. 

 

We're gonna pack our cord. 

 

Working on the maxillary arch, I will say, is probably the most enjoyable and easiest to work on in terms of indirect vision. 

 

So maxillary posterior teeth, it's a great place to start if you're just learning the microscope, and that is because there's minimum scope movement. 

 

You're already used to using a mirror on the top arch anyways. 

 

So by starting here with a microscope, you'll have a lot more early successes, and you won't get so discouraged. 

 

Because if you try to do a lower second molar crown prep your first day with a microscope, you'll probably never wanna touch the thing again. 

 

So don't do that. 

 

Start with the top arch, and I'd say simple, direct restorations first, even the prepping, and then you can just switch to your loupes for the restorative phase. 

 

But just work your way up and get more and more comfortable with the microscope. 

 

Those early successes make a big difference. 

 

Okay, so we got our retraction cord here. 

 

you wanna retract this- ... 

 

for me? 

 

This is why we have the one big hole for the rubber dam instead of having individual holes, because then we get good access to the gum line here when we're doing our cord packing. 

 

Again, so now I wanna see the lingual here, right? 

 

But I can't with my current scope position. 

 

Normally, you'd just move and look at your mirror, but what we're gonna do is do this in sequence. 

 

First of all, I need to see more of the lingual, so I'm gonna move the scope with my nose, and I'm gonna reposition my mirror. 

 

And now this is pretty good here, but we can tweak this even better. 

 

If you were at low magnification, this would not be a consideration. 

 

If you're working at high magnification, then what I would do is just bring the scope towards me a bit, and then that recenters the tooth in our field of view. 

 

But again, when you're first starting, use lower magnifications. 

 

It's just so much easier. 

 

You're gonna be moving the microscope less, and you'll find it way, way easier to get used to it, and then once you're really comfortable, then start using the higher magnifications. 

 

And just for reference, I barely ever use the highest magnifications unless I'm taking a photo of a crack or something like that, and even then, you don't really need the highest. 

 

I'm hoping that the microscope manufacturers figure out that generalists want lower magnification, and wider field of views, because that's what we really benefit from. 

 

I'll just show you what I did there. 

 

I wanna see more of the buccal, so I'm gonna move the scope to the left and then reposition my mirror, so I can see and get a better view. 

 

This is super subtle movement with your nose and your mirror, and that's all you need. 

 

Okay, now I'm heading towards the pericervical dentin. 

 

We're gonna do 0.6 millimeters, half of my bur.... 

 

So now I just wanna drop my margin a little bit more, so I see the coronal aspect of the cord all the way across, and then that'll be my finish line (i.e margin) position for the buccal. 

 

And I can even give you a better view, at higher magnification. 

 

Don't do this if you're learning. 

 

Stick to the lower magnifications- [what I'm doing is] just so you can see what the microscope's capable of here. 

 

Yeah, that's looking good. 

 

So we're just beyond half a millimeter there on the margin. 

 

Can you pull the buccal away from me, Amy? 

 

Yeah, and just beyond a half millimeter there. 

 

So I'm really happy with that margin. 

 

That's looking good. 

 

It's a little bit wet right now. 

 

You can see how that's looking good. 

 

We're happy with that margin. 

 

Now we're just gonna keep moving along. 

 

Okay, so again, a lot of this is just side-to-side movement and then changing the position of the mirror that gives you the full view of that upper molar. 

 

So let's do the lingual now. 

 

Middle third. 

 

And now I'll get you to retract if you can. 

 

Yeah. 

 

So you're always looking for your angle, right? 

 

Right now, I can see exactly what I need to, but sometimes if your angle's a little bit off, say, I'm over here, and I'm tilted this way... 

 

I'm just gonna show them. 

 

Sometimes  you kind of get in your own way, so you gotta think about, okay, how can I see more of what I need to see? 

 

Well, right now, I need to see over this part of the handpiece, so I'm actually gonna move the scope this way, horizontally away from me, and then that should correct for that problem. 

 

Now I can have my view over the handpiece, and I can see exactly what I'm doing. 

 

Let's move this scope to the left and then correct my mirror just to check my crown prep's draw, see how that's looking. 

 

I see no undercuts yet. 

 

We're not quite done our margins yet, but we're moving in the right direction here, so that's great. 

 

Now I'm running into a problem where I can't see the interproximal. 

 

So what do I do? 

 

I'm gonna go to a top-down view of the tooth. 

 

Interproximals are always easier if you've got a top-down view. 

 

So there's my top-down view. 

 

I position the scope to the left and then change my mirror angle, and now I got a great view of the interproximal here. 

 

So I'm just gonna get rid of this ledge here and connect my lingual margin with the mesial. 

 

You'll constantly see me moving back and forth to get the angle I need. 

 

Now again, just to emphasize something, if I'm looking at this at really low magnification, I can move my mirror without having to move my scope, and I can still see what I need to see. 

 

The reason I'm moving so much is because I like to work at high magnification, especially for this video, and that's why I have to move my scope. 

 

But luckily, it's very easy to do so. 

 

Just taking a look at our margination here. 

 

I'm very pleased. 

 

The only thing I would say is that we have a little bit of an overhang over the mesiolingual. 

 

Also, notice where there's still a little bit of enamel left relative to the dentin, so there's still enamel in this area. 

 

That is a cue that you might not have enough reduction in those areas. 

 

So when you notice enamel hanging around, not always, but sometimes it can be a little clue that you might need to take a little bit more off to get your two-millimeter occlusal reduction. 

 

Now, there's still a tiny bit of enamel left, but I'm comfortable with that, given that we did some nice two-millimeter depth cuts at the beginning and know where we are. 

 

So sometimes if you find yourself flexing [your back] to get your eyes to the oculars, It's just a matter of bringing the oculars down a little bit, and then that sometimes will correct that lower back issue that you might be having if you constantly find yourself flexing. 

 

So bring the oculars a little bit lower, and then you won't be doing that so much. 

 

And let's go ahead and pack our green retraction cord. 

 

Again, Amy's reading my mind. 

 

She can see what I'm dealing with on the iPad, so she just knows I need retraction, which is amazing. 

 

Another option other than the iPad Mini... sometimes the iPad Mini's great, and it's a nice screen for the assistant, but it does get in the way sometimes. 

 

Sometimes. 

 

Sometimes. 

 

Especially when we're doing surgery, for whatever reason, it seems to always get in the way...

 

-So you could consider using an iPhone instead. 

 

This is a smaller screen, easier for the assistant to see over it if they don't wanna be referencing just the screen. 

 

So that's another option.... 

 

Now, we always wanna check our reduction. 

 

We did our two-millimeter guide plane, so we should be good, but there's "should be good enough" and there's "we know we're good enough", and there's a difference. 

 

So let's go ahead and bring your teeth together, and bite down. 

 

Yeah, and, and just kinda just hold it there for me. 

 

That's perfect. 

 

So we definitely have at least two millimeters of clearance. 

 

The only area where I'm thinking, Hey, maybe we could just polish it, is this little rough area on the lingual cusp, or I guess, the palatal cusp. 

 

And, it's coming only a little bit closer to the lingual cusp of tooth 3-6. 

 

So let's go ahead and just smooth that off with our brownie point polisher, and then we'll be ready to take our impression. 

 

So I'm gonna position myself, again, a little bit uncomfortably here for fifteen seconds to make sure I get the best angle for the impression. 

 

And I mean, what you're looking for here for the impression part is you kinda wanna see the buccal and the lingual at the same time, so I'm looking straight down this row of teeth. 

 

That's why I have the scope position off angle a little bit here in order to be able to see exactly what I need to here. 

 

So we're pretty much ready to go, and the idea is, once I take this cord out, I'll be able to see exactly what I'm doing. 

 

I like to stabilize the tip with my other finger, so if I had a mirror, I couldn't do that. 

 

Then I can just go through very nicely and capture everything I need to capture. 

 

Take that out. 

 

As a generalist, you'll have to sacrifice ergonomics once in a while to get what you want done. 

 

But again, it's only short-term here. 

 

I'm gonna try to shake the tip a little bit as I move it, just to vibrate the impression material into place. 

 

Good. 

 

Uh, I'm ready to go whenever you are. 

 

Go ahead and bite down. 

 

Now, we've still got another two minutes until the impression is set. 

 

Let's talk about this upper molar, just a quick summary of microscope positioning for the upper arch. 

 

Again, typically neutral position with the microscope, so you don't need to tilt it this way. 

 

I mean, you can a little bit if you just feel like you need to be further away from the scope, that's totally fine. 

 

Typically, you don't want it this way. 

 

This is better for the lower arch if the microscope's tilted back at you. 

 

your mirror can go further away from the tooth you're working on when you have it tilted this way on the upper arch. 

 

It's just gonna improve the angle, less water splatter on the mirror, so that's what you want. 

 

Neutral is totally fine as well. 

 

Wherever you're comfortable. 

 

Again, minimal movement for most of what you're doing, and then "nose and mirror" positioning primarily is what you're doing to get the angle that you need. 

 

And that's usually enough. 

 

the lingual of the upper left molars is probably the hardest to do. 

 

So sometimes what you can do if you're having a hard time finding the angle that you need, you can actually just point the microscope towards the tooth or towards the surface of the tooth that you wanna prep- so the lingual

 

of the upper first molar- and you can just prep it with direct vision. 

 

You know, obviously, we can't see Rosanna's tooth right now, but if you position it like that, it's not as ergonomic, but when you're first learning, it can get you by. 

 

So that's an option as well. 

 

Take this out. 

 

Take a look under the microscope here, make sure that this is looking beautiful. 

 

It sure is. 

 

Yes, really nice margination all the way around. 

 

But very happy with the impression. 

 

At this point, we'll conclude this session. 

 

Rosanna, thank you again for letting us film your tooth. 

 

It turned out super nice. 

 

I'm really happy with the prep, really happy with the impression. 

 

and then we'll see you next time for the insert.