I need help making class III preps

[GoToHolmes]

I'm in operative right now and I am having a lot of trouble making class III preps. I've watched Dr. Stevenson's technique but when I try to do it the plastic tooth does not shave away as smoothly as it does in his video and we were not given whetstones so I can't sharpen my hatchet. Do I need to raise the RPM of my handpiece?

Instructors have told us to make a rectangle with rounded corners running incisal to gingival. Most of the time my axial wall is curved and not flat. Another issue is that my incisal or gingival wall will not be parallel with the other. I don't know how to fix either of these issues without spending too much time making the prep or making it worse than it already is. When extending the prep I find myself in a tug of war battle with the tooth as I try to gently move the bur, resulting in the tooth suddenly giving way and me making a bigger cut than I wanted.

I am not great at indirect vision yet which definitely doesn't help. I admit that I neglected extra lab sessions until recently but I've been going in to practice when I can. It's just frustrating to go through several teeth without having a single example where almost everything was done well. An instructor expressed concern today and it was very frustrating to hear because I know what to do but dont have the skills to pull it off.

We are using 245 and 330 burs. I mostly use the 245 to make the general shape of the outline and for my initial hole in the middle of the prepform. The 330 is used to thin out the proximal wall like Dr. Stevenson advises so I can break it off without damaging the adjacent tooth. I am currently running my handpiece at 40,000 RPM-60,000 RPM (8 to 12 on the screen) but I sometimes go above so I can actually make headway in the prep. I change my bur every prep I do.

I really enjoy operative but my lack of progress is starting to frustrate me especially when everyone else around me seems to get it. I've accepted that I will probably fail the upcoming practical but I would at like to know what you guys do to make good class III preps so I can practice for the future. I do great in class but I am always subpar in lab. I desperately don't want to be the guy who has booksmarts but no actual physical skill.

Please help me. Thank you.

edit: passed my assessment with flying colors. 150,000RPM, used a 245 for the initial punch cut for optimal depth and then finished the rest of the prep using a 330 pear. Thanks to everyone for their help

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[Alexanderia Bertrand]

Hello! I am a D2 student at Louisville. I was struggling with my class 3 preps as well. One of the faculty suggested starting the prep with a 1/4-1/2 round bur, and it helped tremendously!!!

 

[GoToHolmes]

Hello! I am a D2 student at Louisville. I was struggling with my class 3 preps as well. One of the faculty suggested starting the prep with a 1/4-1/2 round bur, and it helped tremendously!!!

Unfortunately we weren't given those burs to use but I'll see if I can buy some tomorrow. Why did it help?

 

[Alexanderia Bertrand]

Unfortunately we weren't given those burs to use but I'll see if I can buy some tomorrow. Why did it help?

I liked that it kind of roughened the surface up and helped me stay in the parameters. Have you tried putting your 330/245 in your slow speed? I know a few of my friends do it this way and it helped them. Other than that, practicing your indirect skills is a must! Definitely easier said than done with the schedules that we have

 

[GoToHolmes]

I liked that it kind of roughened the surface up and helped me stay in the parameters. Have you tried putting your 330/245 in your slow speed? I know a few of my friends do it this way and it helped them. Other than that, practicing your indirect skills is a must! Definitely easier said than done with the schedules that we have

No I haven't tried putting it in my slowspeed. What RPM did they run it at? When you use your highspeed to make class IIIs what RPM do you use?

Also, what do you think about putting holes holes in the prep form to get a general shape and then finishing at a slow speed to prevent enlarging the prep too much? I am good at getting acceptable depth when making my initial hole but extending is where everything goes wrong

 

[Alexanderia Bertrand]

No I haven't tried putting it in my slowspeed. What RPM did they run it at? When you use your highspeed to make class IIIs what RPM do you use?

Also, what do you think about putting holes holes in the prep form to get a general shape and then finishing at a slow speed to prevent enlarging the prep too much? I am good at getting acceptable depth when making my initial hole but extending is where everything goes wrong

That’s a great question on the RPM 🤔🤔 I guess I have never looked. Once I get back from break I can take a peak and see!

What I usually do when I am first learning is drawing my prep on the tooth with a pencil with the slightly smaller than the exact parameters so that I have a little wiggle room. This way I can visually see what I am doing. Eventually I stop drawing (since we can’t draw in real life).

 

[somefuturedoc]

40-60k is way too low. Jack that up to 100k minimum. I generally use 150k for 90% of the prep then make the final adjustments/refinements on 50k. Take however long necessary to make them good right now and then you will build speed as you do more. There is no secret to getting good at them besides practicing.

Also, changing burs after every plastic tooth is unnecessary.

 

[TanMan]

For ivorine teeth, dull burs are better. They can see the gouges too easily with sharp new burs. If you're burning the plastic, go with a higher rpm. If you have poor angulation control, stick with a 330. A 245 is longer and any slight deflection leads to more errors. If your instructors love rounded line angles, use a pear shape, if they love sharp line angles, you may need to use a 56/556 with some sharp hatchets. If you don't have a whetstone, go get one online, but for the time being, you can probably use a kitchen whetstone.

If you want to avoid indirect vision and aren't being graded on posture, just bring the typodont to your head level and work on it like a mechanic. You'll get all the direct vision you need. Also, practice drawing a straight line with your handpiece at the angle you want to execute your prep.

RGS is pretty good at ideal preps, but his own named instruments are a testament to the man's ego and everything else that went on with him back in the day.

Don't feel bad about not being able to execute in preclinic. Preclinic has nothing to do with real world skills.

 

[GoToHolmes]

For ivorine teeth, dull burs are better. They can see the gouges too easily with sharp new burs. If you're burning the plastic, go with a higher rpm. If you have poor angulation control, stick with a 330. A 245 is longer and any slight deflection leads to more errors. If your instructors love rounded line angles, use a pear shape, if they love sharp line angles, you may need to use a 56/556 with some sharp hatchets. If you don't have a whetstone, go get one online, but for the time being, you can probably use a kitchen whetstone.

If you want to avoid indirect vision and aren't being graded on posture, just bring the typodont to your head level and work on it like a mechanic. You'll get all the direct vision you need. Also, practice drawing a straight line with your handpiece at the angle you want to execute your prep.

RGS is pretty good at ideal preps, but his own named instruments are a testament to the man's ego and everything else that went on with him back in the day.

Don't feel bad about not being able to execute in preclinic. Preclinic has nothing to do with real world skills.

Thank you. I will try using the 330 because I def have poor angulation control. The 330s we got are pear shaped so no problem there.

Bringing the typodont up is a good idea but I want to avoid doing this because it might be against exam rules.

What happened to RGS back in the day? You can't bring that up and not share!

 

[Alpha Centauri]

Operative in general is much easier on real patients that have defined decay to remove rather than trying to replicate an ideal prep on plastic

 

[Rfrosty]

When people make the dreaded saucer, I've notice that its usually because they're trying to correct it by drilling axially from the center of the prep and then moving the bur incisally and gingivally.

When you see the saucer, put your 330 bur in the incisoaxial wall and move it axially until it is at equal depth with the center wall axially. Then do the same with the gingivoaxial wall (don't go in as deep axially as you did on the incisal wall because your axial wall should be deeper on the incisal by about 1/4-1/2mm.) Use a 55 or 56 (straight fissure) bur if necessary just remember to gently go over it again with a 330 to get your undercuts.

Start your prep right below the contact. Not at the contact. Try not to extend beyond the marginal ridge axially on any aspect of the prep. Its super easy to overextend gingivally so be careful there. If your walls aren't parallel maybe the curvature of the tooth is throwing you off or you're extending your gingival wall too far gingivally.

If you can make a slot prep on molars/premolars you're basically doing that but on an anterior tooth.

If its any consolation, your preps on real teeth will rarely look anything like ideal for composite and making saucer preps is sometimes done purposely to lower the C factor or something along those lines. Good luck, you'll get the hang of it with practice.

 

[schmoob]

Try a 33 1/2 carbide.

Also a 245=330, just longer cutting length. Stick with the 330 for this.

 

[samnoladental]

Try using the 835 and 35 burs with a biangle chisel to smoothen out the facial and internal walls!