The restorability and longevity of anterior restorations on teeth with endodontic treatment and post & cores depends on ferrule. So what is ferrule? Ferrule is the amount of tooth structure on the buccal and lingual walls of the prep. Tooth structure on the mesial and distal do not count, as anterior teeth are not loaded toward the interproximals. Ferrule is both the height of the natural tooth from the margin, but also the thickness of the tooth structure from the external wall of the prep to the internal wall opposing the post space.
There have been many studies on the amount of ferrule to create a predictable survival of the restoration. If you bond the post and core and bond the crown, the minimum amount of ferrule is 1.5-2mm. If either part of the system, the post & core or the crown are cemented it increases the amount of ferrule we need to 2-3mm. These are minimal numbers and do not guarantee any specific number of years of survival. Longevity will be a factor of functional risk and repetitive load.
It is important to make sure patients understand when we are being heroic and the predictability of the dental procedure is low and the risks are high. As tough as it is to sit with a patient and tell them they will lose a front tooth, it is ten times harder to sit with them when the restorative fails prematurely based on their expectations. Many patients will chose to save a tooth with a poor or fair prognosis and restore it again or chose an alternate treatment in a short time frame. Others will want to proceed with treatment that has a higher chance of longevity. The amount of ferrule is a key component in determining the future of an anterior tooth treated with endo, post & core and crown.
When would you choose a direct post and core build up over an indirect post and core?
Regards
Hany
For me, when I am adding wall height to the prep of more then 1-2mm to gain retention and resistance form and have minimal ferrule I will use a lab processed post & core, wither cast metal or zirconia. I want to eliminate the interface between the post and core material that is one additional thing that can fail under load. If I am using the post for reinforcement only and only adding very minimal core material I will use a prefabricated post with composite as a core material.
I used to do a lot of post/cores with crowns after endos. Several years ago I saw a study by someone I respected well at the time, who said there was no clinical advantage to posts in molars as the forces are more vertical and compressive. He also said in the anteriors it lead to more structural failure due to the loss of tooth structure for the post itself, which resulted then in fractures of the root right at the end of the post. His contention was posts only have value in the functioning cusp of the bicuspids, where there was net value added to the retention and enough structure of tooth to support the post with reduced compromise. It was also important that it be placed in the lingual canal of upper premolars and facial of lower premolars when facial/lingual canals are options. I am curious what your perspective on this would all be? Thank you.
Rohn,
Using posts and not using posts has been a debate for quite some time, I have not recently looked at the research and thoughts about posterior teeth, but in general I try not to use a post unless I have to to meet the requirements to restore the tooth, and then I make sure the patient understands the unknowns and the risks.
Lee