Category Archives: Handpiece

I had an interesting conversation with a good friend of mine the other day. He works for a large lab and gets to see all sorts of lab work that is sent into the lab from dentists and the work that is done by the lab and sent back out to the dentists. He talked mainly about two dentists who send in work to the lab.

One dentist, we will call him Dr. Malpractice sends in crown preps that look absolutely horrible. Crooked margins, too much tooth structure removed in some places and not enough in other places. There is no rhyme or reason as to what the dentist is trying to do (as far as the lab can tell). This may be slightly exaggerated, but you get the point. On the other hand there is another dentist, we’ll call him Dr. Millionaire, that sends in his work and every single prep is a masterpiece. Crowns are easy to read and the exact amount of tooth structure has been removed which makes the labs job easy.

I wondered what would make the difference between these two dentists. Education? Age? Patient demographics? I know most of the readers of this blog won’t care, so I have decided to talk about my crown practical and relate it to these two dentists. The first crown prep you make will look like Dr. Malpractice’s prep. After a few (maybe 20) tries in the fake mouth you will create a decent looking tooth. Then you get to move onto the maxillary (upper) arch and relearn everything backwards looking in your mirror. Top that off by the fact that you have no suction so your mirror get water on it as soon as you start to drill and you can’t see anything anyway…

I am not trying to scare you, school will strike the fear into your heart all by itself, I am just preparing you mentally. I was reading the blog by Ping about how they had to set dentures in less than 3 hours for one of their practicals. I am sure that must have been quite the experiance.

Last Monday we had to do a crown prep for our practical and I felt like I did alright. It was one of those practicals where you grade your own work and then the instructor grades your work. You aren’t penalized for the grade you give yourself, so I always give myself one check. What I wanted to talk about is the intricacy required to do a proper crown prep. Have you ever sat down and looked at ruler with a mm measurement on it? One mm. Go and look. It is small. A tooth has functional cusps (cusps that fit into the central groove of the opposing arch) and non functional cusps (these do not fit into the opposing arch cusps) and each of these have to be reduced a certain amount. 1.5mm for functional cusps and 1mm for non functional cusps. The best way I have found out to gauge this depth is to make depth cuts into the tooth at intervals so I know how deep I am going (this is also the method taught at Temple).

Next would be axial reduction. Axial reduction is the sides of the teeth. This is reduced by .75 mm and can be difficult when using a large bur. It has been recommended to us as students to get the 850 diamond bur to do crown preps. i don’t exactly know why we just didn’t get this bur in our kit to begin with, but it costs 5.50 cents in our dental school store. (If you want a box, let me know, I get discounts on everything!)

So after all of these technical measurements and drilling (measure twice, cut once!) you should end up with a beautiful crown prep that you would be proud to put into your own mouth and make Dr. Millionaire jealous. While I am not close to making Dr. Millionaire envious of my work (I DO still work on plastic teeth) I would like to think I am better than Dr. Malpractice which, from my friends description, isn’t very hard.

When comparing this class to Restorative Dentistry II class I would say the only difference is that in this class you have to hit the ground running. It helps if you are a fast runner. The first day of class we were given a packet of papers that describes the projects we will be doing over the course of the semester. We also were shown how to access the syllabus and all the required reading. Last year in restorative we did a lot of wax-ups, some acrylic temporaries, some composite restorations and some amalgam restorations. Last year when we were told to do a Class II prep in the ivorine tooth, we just kind of carved away and filled the tooth. This year we are learning the mechanics involved in doing all the types of preperations. We need to know the depth to go, the width, the different burs to use, the various instruments involved, etc. When they are talking about motor skills in dental school, it really means that you need to develop motor skills. (You don’t have to have them before dental school, in fact no one does), but this is why there is a pre-clinic in dental school. It is one thing to play the piano, or be able to build a model airplane (Some of the many ‘hand skills’ people put on their dental school application), it is another to drill exactly 1.5 mm into a tooth in the maxillary arch and then ‘drop a box’ that is supposed to meet perfect dimension. D2-D4 and current dentists may think this is childs play now, but just remember your learning curve. Also from what our Restorative teacher tells us, there are still some 3rd and 4th year students who struggle with this. It is difficult but possible. To get good we get to practice, practice, practice! We started practicing with an ivorine block. This is a plastic rectangular block of plastic. It has been stamped with the outline of teeth on all four sides. Our first goal was to drill exactly 1.5-2 mm into the tooth and follow the tooth anatomy. We practiced this on all four sides. Here is how some of mine turned out. I will also mention that all initial cuts were made using a #330 bur and followed or finished using a #245. All these projects had to be checked by our row instructor before we could move on. If you messed up horribly or your row instructor thought you needed more practice you have to go buy another block/tooth/etc. and redo the project before moving on.

The idea is to get good at producing the ‘ideal outline form’. This means that when drilling into a tooth you want to produce an ideal outline that follows the anatomy. After this ideal outline is formed, you look for caries and remove it accordingly. It is a several step process that I will not discuss here as I do not yet fully understand it. The idea is simple though. When making a cut into a person in any health profession it is very wise to measure twice and cut once. Make the small ideal outline form, at the correct depth, using the proper instruments, and if more cutting needs to be done then you do it. I think a lot of people don’t understand what goes into dentistry. It’s not as simple as drilling out a crater into someones tooth and filling it with some material that is supposed to last a lifetime. It involves a great deal of skill and technicality. This is one reason why we students get to practice on so many teeth before we get to see a patient.

After the ivorine block looked somewhat decent our next task was to practice on some real teeth. Not real teeth in real patients, but real teeth that USED to be in real patients. We were asked to collect teeth from our local Oral Surgeons over Christmas break and bring them to school on the first day. We sorted through the teeth, picked the best ones, sterilized them, and set them into dental stone. Then we proceeded to drill. Here are my results:

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