Please can anyone tell me about FGC, PFM, FC, 3/4th and 7/8th crown preparation, inlays, onlays? i want to know about measurement for all.
Please anyone.
Here is a link to the blog which might be of help. It has several other links which can help you most of the things you need.
http://youth-towards-divinity.blogspot.com/2010/03/bench-test-preparation-tips.html
Thank you so much drsrn. i really appreciate your help. 85 people have seen this and only you replied. Thanks.
No problem Morphology. Its my pleasure. Anyways did you find the website useful?
No problem Morphology. Its my pleasure. Anyways did you find the website useful?
Hey can you tell me for PFM preparation? when we give champher and shoulder, junction looks different and looks like there is more reduction on facial . so when we give the bevel on shoulder, it should be continuous with champher. without bevel also shulder should be continuous with champher. i am so confused. and do we put any grooves on molars or premolar for full gold crown preparation or full ceramic preparation? we palce grooves on 3/4th or 7/8th crown, right?
the link you gave me, there i saw for anteriors and it is different from the book, Rosenstiel.
Please help.
Thnaks
Since the bevel on the shoulder is a separate entity it has nothing to do with the chamfer. So, it does not matter if it is continuous or not continuous with the chamfer.
Generally, you do not place grooves for full metal/ceramic preparations on a bench test. Grooves are only in partial veneer preps. The only case where you may want to put a groove on a full crown is in clinical situations when the clinical crown height is less than optimal for retention. Some books may show you grooves with adequate crown heights, but that is not needed and definitely not expected in bench tests unless indicated in the instructions. I hope this answers your questions.
yes i got it and thank you so much for help. and one more thing, how do you connect shoulder and champher? sorry to trouble you friend.
thank you so much.
Actually, I was wrong about the bevel and the chamfer. I read through Rosenstiel and the book mentions that the bevel on the shoulder should be continuous with the chamfer. So, after you finish the entire prep and place the bevel, just touch your finishing diamond point at the shoulder-chamfer interface to achieve a continuum with the bevel on the shoulder.
It is difficult to explain in words, you will understand it much better once you start practicing.
Hey can you tell me for PFM preparation? when we give champher and shoulder, junction looks different and looks like there is more reduction on facial . so when we give the bevel on shoulder, it should be continuous with champher. without bevel also shulder should be continuous with champher. i am so confused. and do we put any grooves on molars or premolar for full gold crown preparation or full ceramic preparation? we palce grooves on 3/4th or 7/8th crown, right?
the link you gave me, there i saw for anteriors and it is different from the book, Rosenstiel. Please help. Thnaks
drsrn said:Since the bevel on the shoulder is a separate entity it has nothing to do with the chamfer. So, it does not matter if it is continuous or not continuous with the chamfer. Generally, you do not place grooves for full metal/ceramic preparations on a bench test. Grooves are only in partial veneer preps. The only case where you may want to put a groove on a full crown is in clinical situations when the clinical crown height is less than optimal for retention. Some books may show you grooves with adequate crown heights, but that is not needed and definitely not expected in bench tests unless indicated in the instructions. I hope this answers your questions
Thank you so much for bringing a very good point for discussion here. In my opinion, Junction as a line of demarcation comes into place because shoulder on facial aspect is 1.5 mm in width where as chamfer on palatal aspect is approx. 0.6-0.7 mm in width. There's more reduction on facial aspect since you remove more enamel to prepare a shoulder. Yes, shoulder and chamfer should be continuous with each other at both junctional line and bevel, that could be achieved after placing the bevel and while doing finishing work on your tooth prep, you may use your finishing burs at slow speed on shoulder/chamfer interface and move the bur same as of spreading butter on the bread(or kissing the proximal surface by finishing bur!); continue in a same manner till shoulder-chamfer interface is EVEN. btw, use the same high-speed handpiece apparatus and you may still reduce the rotation speed by paddle controlller!! work cautiously since there's a high risk of making undercuts or damaging the finish line.
In most cases, you won't need to place grooves for PFM/Full Gold crown preps on a bench test. Grooves are for secondary retention purpose and FULL GOLD/PFM crown has adequete surface area both occlusally and axially to provide primary retention. Since you work on typodont normal teeth during bench exams, no such features are required on FULL Gold/PFM tooth preps. (Yes, partial veneer preps such as three-quarter & seven-eighth do require grooves!).
Lastly, Where should the junction of shoulder and chamfer be placed? You may put the junction LINGUAL to the contact area so that you'll be in a position to achieve some more bulk of porcelain towards the facio-proximal aspect for both esthetic reasons and gingival health. On the anteriors, certainly the junction has to be lingual but in posteriors, it does not actually matter much whether you keep it lingual or facial. I would suggest to keep equal amount of chamfer and shoulder for posterior teeth OR even placing a shoulder/chamfer interface slightly LINGUAL to the contact area is fine. (reason: If placed buccally, then the junction allows little space at facio-proximal aspect for the metal, opaquer and porcelain. This may result into an "opaque" and unnatural looking restoration in the proximal area, since the porcelain will be relatively thin in that region and metal backing will get exposed on the facio-proximal region. Besides, when junction placed buccally, the lab technician may have to overcontour this region in order to compensate for the thinness of the porcelain which, inturn, may compromise the periodontium.) hope that makes it more clear now! Best!!
Thanks Youth. ok so if there is a more reduction on facial surface then the proximal surface reduction is not even, right? so if you see from the buccal surface, you can see the lingual wall. like how the premolar looks like in the book, Rosenstiel, right?
Yes, there you go. you're right. It's pretty much self-explanatory, isn't it? As I said earlier, you may round off the sharp interface between shoulder and a chamfer to make it even!
Yes, there you go. you're right. It's pretty much self-explanatory, isn't it? As I said earlier, you may round off the sharp interface between shoulder and a chamfer to make it even!
