I started this post as a reply to a comment on Episode 217 - custom dowel post. But...it turned out to be longer than I initially thought it would be, so - as in the words of Latte Ice - "here we go"
Anonymous said...
What do you mean by adhesive technology? You use fiber posts/cores (ie. with luxacore?) Could you elaborate a little? Thanks!
You raise a great point. After reading your question, I actually started second guessing what I meant as well. I am referring to using fiber reinforced composite posts and a dual cure adhesive. I reviewed the literature this morning and afternoon on the current status of post systems. This article summarizes almost everything, except Cast Post and Cores.
Ok, so - here is where I was about 1.5 years ago. I was trained to use 1 of 3 techniques to retain a core.
1. Good ol' metal serrated post. I believe that the idea is to passively fit the post into the canal system, lute it with some cement and build up the coronal portion with amalgam....and maybe composite? I think the composite was old school (I just saw an article from 1987) - but - that was newer school than I was before the residency. The worse part of using these is drilling the post space. I can't stand it. Even today, after 10 years of practice.
2. The golden beast. I've fabricated a number of these and although the idea before starting the procedure is entertaining - fitting one always seems to be a challenge. Also, once the tooth is broken from one of these - it's really broken.
3. Amalgam Radicular Core - something like this radiograph below. I still use these on occasion. We have access to 3 CAD/CAM machines, therefore, the use of amalgam is fairly low at the moment.
Fiber Reinforced Composite Post and/or Ribbond
I'm not an expert by any stretch of the imagination, and, I've asked a number of really smart folks here and they don't know the answers either when it comes to using adhesives and posts.
Metal Posts
Fairly straightforward - Fence post in ground to a decent depth so the wind won't blow fence over, concrete the base -let set, finish fence. Got it.
Adhesive Posts
Here is a great place for some material reviews
D.T. Light-Post Review by the Airforce
What are we really trying to achieve with a fibre reinforced post? Is it:
- Monoblock structure of composite in the canal?
- Post adhered to the dentin walls with shrinkage gaps between the post and cement?
- Long parallel sided post for "mechanical" retention?
- How long does the post now need to be if I"m adhering it?
- Do we need a post at all? What about Fibers - ie - Ribbond?
As far as I can see, there are a number of factors affecting adhesive posts. I've now come to question what we're trying to achieve with a post anyways. I mean, if we're trying to adhere to the inner canal system - why use a post? Why not just place some luxacore down the canal system and build up the core on that? I"m sure that's not a great idea secondary due to composite shrinkage, C-factor and many other little details.
What about the fact that the adhesives don't bond to the posts very well - and - what about the obturation junk left on the canal walls, including AH+, Roths, NaOCl, EDTA? Yikes. A poor dentin bonding MPa of RelyX Unicem of 7 mPa to fresh dentin isn't surely going to bond well to canals with mud on them - even after you clean them mechanically...But then, do you really need 3.5 mPa of shear strength to retain a post? The data is in the document below.
So, maybe the idea is to create a monoblock structure, try to reduce adhesive shrinkage, reduce C-factor (or manage it) - what about something like Ribbond? What I like about this idea is:
- No need for a drill like a parallel sided post (I haven't perforated during post placement - I've perfed other times during endodontic access, however....)
- Perhaps the best attempt at creating a monoblock structure in the canal system.
- The fibers are used to decrease the amount of cement shrinkage
- No post to shrink away from.
- The ends of the fiber are placed in the pulp chamber to bond to as well as to decrease C-factor on the pulpal floor.
More to follow...the never ending post discussion.
Let me know what you think.
Ashley
 |
| Adhesive shrinkage away from the fibre reinforced post |
 |
| It was there, now it's not! |