Our final projects at Temple (most likely they vary from year to year) were a porcelain crown and some root canal projects. This article will highlight the cast post and core, duralay, and other root canal projects that were due the last week of lab. The other project we had in lab was the gold onlay.
This project was confusing at first because there are three different teeth and different criteria for each tooth. I’ll talk about each one independently. There was no order or sequential path we had to follow, there was just a due date and every project had to be done by this date.
The upperclassmen had an endodontic project during the 2nd semester of the 2nd year (we will do this next semester) where they had some extracted teeth which they placed into buff stone and then accessed the canal and then filled them with gutta percha. They then took x-rays and turned them in. (It was probably much more detailed but this is the basics) We were handed this project and told to burn out the gutta percha.
We were also given the xray which we used to measure the depth of the canal. We took out our burning instrument and measured the depth of the canal and then measured how muh we would have to burn out to leave 4mm of gutta percha at the apex. In other words we would be burning out all the gutta percha except for 4mm at the apex of the tooth. We heated the instrument to a nice glowing red and then started burning out.
For this project we were supposed to use a prefabricated post. When the proper depth and width was reached we glued in our prefabricated post with Zinc Phosphate cement (don’t call it glue). When the post was set we restored the tooth with composite. Some people had molars, some people had incisors. Check mine out:
The second project we had was to cast a post and core into a tooth we had collected. I used a lower anterior tooth. It was pretty small but still manageable. The first thing we did with our extracted tooth was sterilize it. After that we cut off the top 2/3 of the crown and then crown prepped the tooth table top. An indication of a cast post and core would be if there is very little root structure remaining and extra support would be needed - hence the removal of the incisal 2/3 of the crown. After the crown preparation was done we accessed the canal. I opened it up with a round bur until I felt like there was enough access for my hand files. Always start with the smallest hand file and work your way up to the biggest. When working with hand files patience is the key. Starting with a ten file pick a canal to tart on (if more than one) and twist the ten file in. Right when you feel it bind start to file like crazy. Back and forth until there is no binding. Then twist further. Right when you feel it bind - file like mad. This is the technique explained to me by a current Temple endodontic resident. When the proper depth has been reached, move to the next file. Work your way up to 50 - 60 or so depending on the size of the tooth.
When the proper depth is achieved it is time to duralay. Duralay is an acrylic that can be burned out in the oven (it leaves no residue or ash when burned out) so it can be used for investment patterns. To remind you an investment is when you take a pattern - like a Duralay pattern of a root canal - and wax a sprue to it (a sprue is a post of wax) and then pour stone around the pattern. When the stone dries the wax/Duralay is burned out and then you can ’spin’ molten metal into the stone and get an exact replica of your wax pattern. I have a video of it here. We wee also required to make a provisional crown using a paper clip as a temporary core. Funny but true!
Here are some pictures of this project:
The final project was similar to the previous one except we used a molar for this one. We did not have to cast this one though. Here are pictures:
Here are all the projects that we had to do not in any particular order but were due at the same time. The RD III class tested your organizational skills. We had daily work, projects (gold inlay/onlay, porcelain crown, and our endo projects), practicals, plus the other tests and quizzes we had in other classes. It is very possible to juggle, it just takes some organizational skills. For another great resource on Endodontics please visit Dr. Jason Hales website about some interesting cases he treats in his office. Also if Dr. Hales decides to visit this maybe he has some advice for us budding dentists who are new to the world of ENDO!
5 responses so far ↓
1 Jason Hales // Dec 23, 2007 at 12:33 am
I remember doing those cast posts & cores! Great pictures. Keep up the good work.
2 shilpa // Jul 18, 2009 at 12:04 pm
hi i am a student of sibar dental college in A.P.(INDIA).These valuable detials with pics made my confusions and doubts abt post and core away.its very great and useful for all undergraduates and postgraduats.thanks a lot.
3 Carrette Stobbs // Jan 19, 2010 at 11:47 pm
I would like a step by step procedure of a cast post/core build-up done on a patient with little tooth structure within the dental office.
4 sil // Feb 5, 2010 at 7:34 pm
I second Carrette stobbs..
5 Ben // Feb 5, 2010 at 9:37 pm
OK, here are the steps:
Assuming the tooth is already endo treated, the first thing you are going to want to do is remove gutt percha. This is best done by burning out the GP or by removing it with a gates glidden. You want to leave enough GP so there is still 4mm left at the apex.
The next step is to use some duralay (the red stuff) and place it in the canal so it extends to the bottom of the canal where you removed GP. The tooth may need to be lubricated with some vaseline to keep the duralay from sticking. While the durlay ‘post’ is hardening make sure to remove it slowly a few times so it does not set up inside the canal. Build up the core with a paintbrush making sure to provide 3D anatomy so it only has one way to fit inside the tooth.
Remove the whole thing and check for undercuts. Place the duralay back in the tooth and prep it like you would a crown. Make sure that there is 2mm of natural tooth left below the duralay where the crown will be cemented to (ferrule effect), otherwise the crown will fail.
See the pictures, it should help. When you are done remove the duralay post and core and using the lost wax technique, cast the duralay in gold. This final gold post and core will be cemented in.
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