November 1, 2001
by Houman Abtin, BDS
Just like fiber optics in telecommunication, nickel titanium files in endodontics have made this branch of dentistry simpler, safer and less time consuming. An advance in systems and technologies like microscopes, digital x-rays, thermoplastic gutta percha and apex locators have changed this frustrating, back paining field of dentistry, making it more enjoyable, like never before.
Selected cases can now be completed in a single visit, when a few years; ago it would have taken two or more visits. Multi-visit treatments often resulting in a few patients not returning midway through their treatment, after pulpectomy, once they were free of pain.
A 54-year-old female patient complains of dull, intermittent pain in tooth #47, for a few months. On clinical examination the patient did not respond to thermal changes. Since she had experienced pain for two months RCT was initiated, during pulpal exposure no signs of vascularity were evident, hence the non vital tooth was concluded (Fig. 1).
Due to previous bad experiences by many of her family members with root canal treatment, she was more inclined to having her tooth extracted. However, after educating her on the importance of this tooth and the important role it played for her tooth supported denture, she agreed to get a RCT done.
Methods and Instrumentation
A successful RCT cannot be completed without a good anesthesia. The patient was medicated with Halcion 0.5mg, one hour prior to the procedure. Local anaesthetic injection was administered to block the Inferior Alveolar nerve, buccal nerve and later using the intra-ligamentary and intraosseous analgesia. Intraosseous analgesia is the method I resort to when all other methods have failed, but in cases where patients are hesitant to have the RCT done in the first place, I do not take chances and proceed with intraosseous technique using a Stabident tip, resulting in an immediate profound anesthesia. In the intra-ligamentary technique, I inject into the periodontal ligament membrane under pressure, it is important that no local anaesthetic solution oozes out of the tissue during this procedure.
A good access to the canal is as important as cleaning and shaping of the canal. A conservative approach in preparation may result in missing a canal orifice, or an excess strain on a file resulting in instrument breakage which is every dentist’s nightmare. I began by using a round diamond high-speed no. 4 bur and after opening the pulp chamber, I changed to a round end, tapered shaped diamond bur. The shape of this bur helps to flare the walls, making them diverge occlusally, hence preventing excessive loss of tooth structure from the chamber, yet maintaining a good field of vision. Then I smoothly ran a no. 2 slow speed round bur over the pulpal floor to expose the canal orifices and remove the loose dentin.
Using a K1 stainless steel pathfinder file coated with RC-PREP, the canals were located and pulpectomy initiated. These files are flexible and will follow the canal anatomy hence no pre curving is required. The lubricant enhances instrumentation and prevents soft tissue blockage. Using the Crown Down Technique, first I widened the coronal 1/3 of the canal and in the end the apical 1/3. The Coronal segment was enlarged using the Gates-Gliden drills no.2 and 3, applying pressure outwards to avoid furcal perforation, with in and out movements. Later I shaped the coronal segment using ProFile rotatory nickel titanium files no. 50/.07 and 40/.06 (Fig. 2) operating at 280 rpm using a slow speed hand piece (Fig. 3).
By first enlarging the coronal segment, there is better canal irrigation where loose debris will float on the solution minimizing the chance of blockage. It also enhances dissolution properties of NaOHCL in the apical region. The middle 1/3 was shaped using ProFile nickel titanium files no. 25/.04, 30/.04 and 35/.04 (Fig. 4) with in and out movements. The instrument was not left in the canal for more than 10 seconds. These instruments find their way through the canal, joining the coronal and middle segments and avoiding ledge formation. They are designed such that debris is pushed upwards. After each use I would irrigate and recapitulate using file #8 or #10, as a larger file may push the debris apically. To enhance instrumentation I use RC-PREP as it has a few advantages: 1. Lubricates the instrument 2. Its EDTA content softens the dentin and helps in removing the smear layer 3. Once in contact with NaOHCL it has an effervescent property pushing the loose debris upward. Working length was determined using x rays in conjunction with Root ZX apex locator (Figs. 5 & 6). I like Root ZX for its simplicity and combination of audio and a visible digital display to guide the operator. Apex locators do not indicate how far you are from canal terminus but will indicate the canal terminus point. I Flattened the cusps to make a reliable guide for the rubber stopper and transferred the working length to the master cone.
The apical segment was shaped using pre curved stainless steel file #10, #15, #20 and #25 (Fig. 7). By looking at the X-ray I was able to get a better understanding of the root anatomy and how to curve the file. The instrumentation was done with an anti-curvature action. This action causes more dentin removal from the thicker regions of the tooth, minimizing furcation involvement. By using the Crown Down Technique there was a limited file restriction in the coronal area.
After establishing the patency, the canal was irrigated with EDTA to remove the smear layer.
For obturation I used a combination of vertical and lateral condensation techniques resulting in a 3 dimensional canal seal, The Master cone was selected according to the apical size, and coated with thermoseal sealant. While pushing the master cone apically there should be a snugness at the apical segment, if not one may have to trim the excess. I placed a spreader along the master cone and applied pressure on it laterally, then holding the master cone in place, the spreader was removed to make place for an accessory cone. I removed the excess coronal gutta percha with system B at 200C temperature (Fig. 8). Then made the gutta percha compact with a pre-fitted condenser, No. 10 Shilder (Fig. 9), again heated the gutta percha and made compact with a smaller condenser, No. 8 Schilder. This process of heated gutta percha removal and condensation was continued till the middle 1/3 of the canal was filled. Never over heat as this burns the gutta percha and makes it too soft to compact and can cause thermal shrinkage in the future. The coronal segment was back filled with the injectable technique using an Obtura 11 (Fig. 10). The gutta percha was heated to 190C for a few minutes. To ensure proper depth I placed the needle tip into the canal and paused for 10 seconds before injecting. As the gutta percha was injected the needle tip gradually pushed itself out of canal and then before the gutta percha hardened it was made compact with the pre fitted condenser (Fig. 11).
Considering the patient could not afford the cost for a crown we decided to restore the tooth with amalgam. Restoration should have closely resembled the old filling so it will not interfere with the occlusal rest as this was a tooth supporting a denture.
Slow setting amalgam was selected. After air condensing the amalgam, the denture was inserted before the amalgam sets, to help contour the amalgam according to the denture and then the excess amalgam was removed. After the amaigum had set, the denture was removed and amalgam burnished (Fig. 12).
Endodontics is a combination of patience, art and science. A good tactile sensation and knowledge of canal anatomy with today’s advancement in bio-materials can result in a three-dimensional root filling. Nevertheless, none of these are possible without good pain control. An extra minute spent during anesthesia using intraligamentry and intraosseous technique will make the journey more pleasant both for the dentist and his patient.
Dr. Houman Abtin graduated from Manipal Academy of Higher Education, India and is in private practice in Thompson, MB with an interest in endodontics. Oral Health welcomes this original article.