Endodontic treatment has a very high success rate. There are very few restorative procedures that can claim they will last lifetime of the patient without the need for retreatment. But there is a weak link in this chain of success - the canal orifice. Sealing of the canal orifice is necessary for overall endodontic success.
There are two occasions where we have the opportunity to affect that seal:
1. Immediately after the endodontic treatment (temporization) and
2. When the final restoration is being placed.
This month's endo fax will examine the literature with respect to interim (temporary) seal.
In last month's EndoFax, we examined research that supported the need for cuspal protection of all posterior teeth that have been previously treated with endodontics. Many clinicians reacted to that EndoFax by saying that patients often cannot afford to have the tooth crowned immediately after endodontic treatment because their insurance benefit maximums have been reached. In some cases, sufficient benefits remain for placement of a post and core restoration. In others, patients and their dentists "let the case go" until the next calendar year when a fresh set of benefits are available for proper restoration. The question remains: What materials and techniques are we using to temporize these unfinished cases? What affect can this have on the long term prognosis of the case or the canal seal when we finally DO manage to convince the patient to have the tooth properly restored?
Dr. Martin Trope ( a leading Endodontic researcher) recently wrote: " In the usual endodontic practice I think I am correct in saying the patient can be reasonably seen within a month for a second visit or back to the referring dentist. In this case IRM or Cavit will be sufficient. If however there is any doubt that it will be over 6 weeks (no idea about the specific time) the restoration should be of a better quality."
An interesting quiz was recently posted on the ROOTS internet discussion forum. It asked some important questions about endo temps.
Take the quiz and see how you do:
1. How thick in terms of millimeters does IRM or Cavit have to be in order for it to create an effective seal?
2. Which of the two …….Cavit or IRM……….holds up best under function?
3. Which of the two …….Cavit or IRM……..has the best seal?
4. How long does IRM create or keep a seal before it starts to leak?........ie : allows coronal leakage to occur?
5. How long does Cavit create or keep a seal before it starts to leak?...........ie: allows coronal leakage to occur?
6. In a situation of heavy function and or poor occlusal clearance where a possible adequate thickness of IRM or Cavit cannot be achieved or in the same case where there is some reservation that the patient's occlusal function will destroy or break down the temp material in an inappropriate time period, name at least two materials that can be used as temporaries other than IRM or Cavit.
7. Of those two materials ….which is the most convenient and probably the most applicable in everyday practice?..........why?
1. 4mm thickness of material is required, minimum.
2. IRM holds up better under function than Cavit.
3. Cavit has a much better seal than IRM.
4. At 30 days an IRM "seal" is gone, it leaks like a sieve.
5. The literature shows that a 4mm thickness of Cavit will hold a seal that is bacteria free for 3 weeks under normal or "no" function. This is the only confirmed "time limit". COMBINATION (sandwich-type) temps were found to give the best and most predictable long term seals Use Cavit as a base for the best seal and then cover that with IRM to give the best function. Cavit/Ketac combination is also good.
6. Bonded composites can be used for longer term temporization. Glass Ionomers such as Ketac or Fuji GI are also convenient and a clinically applicable material.
7. Although poor as a permanent material, Glass Ionomer's properties exceed that of most if not all temp materials. It naturally has a bond to dentin without any treatment of the dentin, thereby giving a really good seal in a situation where you don't have the 4mm. Dentin treatment just increases the bond strength. In an endo situation where it will serve as a temp it can be just "squirted" into the access opening and the patient sent on with the knowledge that you will come back at a later date a place a permanent restoration with a permanent material. Bonded composites require etching, curing and may be applicable in certain situations but time of application and material costs are much greater. (Special Thanks to Dr. Craig Barrington who posted this quiz and the answers.)
Bonding of Orifices - Has the time come for us to "Finish" our cases better?
One of the most interesting recent developments in endodontics has been the shift toward examination of the orifice seal. Gutta Percha is actually a very poor material for permanently sealing the canal orifice. If there is a "weak link" in the treatment chain, it is in the coronal seal during temporization and final seal of the case…the time that occurs between completion of the endodontics and the seal of the canal orifices by the final restoration. Some endodontists have begun to treat the orifices as part of the endodontic seal.
Here is an example of how Dr. Ken Serota (Toronto) does it:
(1) Finish the case with a slight countersink (very slight) below the orifice (where the colour changes).
(2) Clean and Rinse the chamber thoroughly with Ethyl alcohol (many of use still use ZOE based sealers and any remaining Eugenol can affect the bond strength)
(3) Etch the chamber with Ultra-Etch ( Ultradent)(4) Place Optibond or PQ1 - both filled dentinal adhesives (you can see the gutta-percha get softer at the junction of the dentin and the gutta percha) - cure for 20 seconds and then place Permaflow to a level of about .5 mm over that. Call it for want of a better term a subfloor prior to the core.
"The bottom line is: whether or not coronal leakage is an issue, it's a ton and a half better interim seal than cotton and Cavit."(Serota)
As with many new procedures, Canada's UCL&S (List of insurance codes) does not yet have an entry for "bonding of Endodontic orifices". Until it does, dentists will have to either have to:
1. Absorb the cost of performing this procedure themselves
2. Raise endodontic fees to compensate
3. Use some other restorative code (Single surface composite?) to obtain reimbursement for the time and material costs. Endodontists hope to have this matter placed before the CDA's UCL&S Committee so that it can be included in the next revision of the UCL&S.