Providing root canal treatment can be challenging in teeth with incomplete root formation. The apex is large and open, the canals walls are thin and fragile, and this makes disinfection and obturation hard to do. Before the advent of MTA, calcium hydroxide was used in teeth with open apices over a long period of time, anywhere from 6 months to 24 months, to induce a calcified barrier over the open root apex. It was and still is a very effective treatment modality, especially with a good coronal seal. Calcium hydroxide is also still very important for treating resorptions, and aiding in disinfection of root canals! However, we now know that keeping calcium hydroxide for many months in a weak root can possibly further weaken dentin, and using MTA can shorten the treatment time to one or two visits. The placement of a “plug”, usually a 3-5 mm plug of MTA at the end of an open apex root canal, provides an “instant” apical barrier against which we can place gutta percha and sealer into the remainder of the root canal.
In this particular case, the patient was going to have new crowns placed very soon. I removed the old gutta percha quite easily with a #35 Hedstroem file, and you can see all sorts of things growing on it in the photo! Because the tooth was purulent and “weepy”, the root was allowed to drain for a few minutes, and then irrigated with 5.25% sodium hypohlorite using a closed-end side-vented irrigation needle after the working length was determined. I packed calcium hydroxide into the root for about 2 weeks in this tooth before doing the one-visit MTA apexification procedure due to the continued exudate and to aid in disinfection.
On the day of MTA apexification, this is what I did:
1. Rubber dam of course, irrigate calcium hydroxide out with full strength sodium hypochlorite, circumferential filing, and final irrigation procedures
2. Dry the canal. At this point, if the canal continued to well up with exudate, I would consider remedicating with calcium hydroxide.
3. Place an apical matrix of collagen (for example, Collacote) if you feel you might need an apical matrix to “contain” your MTA plug; this serves as a support against which you can gently condense the MTA.
4. Using a small carrier, such as a Dovgan carrier or MAP system (like a mini amalgam carrier), place MTA as far apically as possible, and then carry/tamp down gently using a pre-measured plugger or a moist paper point (a big one, like extra coarse!).
5. I usually take a radiograph here after the first 1 mm increment, to make sure that I have placed it flush with the root apex. Once this is confirmed, you can place a 3-5 mm plug.
6. The rest of the canal can be obturated with sealer and thermoplasticised GP, and the tooth definitely restored. Many also advocate placing a damp cotton pellet and temporary filling before definitively restoring the access to ensure the MTA has set. In the x-ray, I have placed 5 mm of MTA, sealer and GP on top, a 2 mm layer of glass inonomer, and then a bonded restoration (double seal). The dentist has completed the case with beautiful crowns.