Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2018-02-22, 15:28:43 | version 1.38.0
10 Dental Tribune Middle East & Africa Edition | January-February 2016 mCME > Page 11 < Page 9 tion of pushback, a momentary, very slight apical resistance can be exerted, then begin to slowly withdraw the needle until the GP fills the canal to the orifice. Using an SOM, this is easily ob- served and gives the operator confidence. If there are two or more canals in the same root, they must be injected in a special manner, especially if they join or are connected by any variation in the canal system (an isthmus, for example). Obturation is ac- complished by filling both of the canals in rapid succession to the desired level in the orifice. Then immediately proceed to the first canal with a premeasured plug- ger to create more hydraulics (deep pack) and start the com- paction process. The GP will remain soft for enough time so the operator can accomplish the shepherding process in two or more canals if done in a timely manner. To insure complete adaptation to the walls of the canal, the warm GP needs to be compacted as it cools to overcome any shrinkage that will normally occur. Since the softness of the GP is mass- dependent, the GP at the orifice level has the greatest mass and will stay softest for the longest time in the canal, regardless of which technique is utilized. Us- ing the Calamus, a pre-fitted Schilder #9 plugger, well short of binding, is then used to com- pact the GP to the pre-measured depth (Fig. 12). The plugger is firmly pushed into the soft GP and held at the measured depth for just a few seconds to achieve compaction of the GP in the apical third. The plugger is now used to “shep- herd” the GP from the walls of the canal into a “wad” and fur- ther compact the GP. The opera- tor works toward the orifice in approximately 2-mm steps as the plugger creates “new wads” in the process. The shepherd- ing of the GP is continued until the desired depth in the orifice is reached. The mistake often made when working with warm GP is the tendency to “bounce” off the GP while compacting, instead of giving the GP time to compact. Just a few seconds are needed for the newly compacted “wad” to cool. Obturation with carrier-based GP (Thermafil) Carrier-based GP (Thermafil) was first conceived by Dr. Ben Johnson of Tulsa, Okla., in 1975; published in 1978; and made commercially available to the dental profession in 1988 (Tulsa Dental).5 It has become one of the most popular and respected tech- niques in the world. Today there are many forms of the Thermafil concept on the market that con- form to the design of various ro- tary burs (Dentsply Tulsa) (Fig. 13). The technique saves the operator a significant amount of time during the obturation pro- cess, and excellent results have been supported by numerous studies over the years. After shaping, cleaning and dis- infection is complete and the ca- nal is still filled with fluid (NaO- Cl, CHOH, etc.), a NiTi verifier the same size as the maximum apical file (MAF) is selected. Us- ing just the fingers, it is spun into the canal to working length. The verifier has to be passive when doing this step. Depending on the canal anatomy (straight vs. curved), if there is significant re- sistance with the selected veri- fier, such as traversing a curve of sufficiently sharp radius, then the carrier of the same size will meet the same resistance when it is placed. Therefore, you would then drop down one size, test-spin that verifier to length, and it should encounter less resistance. This then would be the correct size carrier to choose, regardless of what the final apical size was that you machined. Note: The verifier is not verifying the api- cal size of the preparation, but it is a dress rehearsal for how the carrier is going to behave when it is inserted into the space. It is verifying the ease of insertion of the eventual carrier core. For example, if you instrument- ed to a MAF size 30/0.06 in a significantly curved canal (less than 25 degrees), a #30 size veri- fier may not spin easily to length; you would try a #25 size verifier instead. In all likelihood, the #25 will go to length without significant re- sistance. The resistance it encounters is a function of the file/carrier being distorted by the curvature of the canal space; the greater the cur- vature, the greater the distortion and resistance (and the greater the chance of contacting the car- rier on two opposing sides dur- ing insertion, possibly stripping the GP from the core). Dropping down one size eases that im- pingement without compromis- ing the carrier’s ability to trans- port the softened gutta-percha to length. The use of the size veri- fier is critical to the successful placement of the eventual carri- er, but is often done improperly, or not at all. Once the appropriate carriers are chosen, the canal spaces are dried completely with paper points, the “FIRE technique,” etc. A small amount of sealer is applied to the canal walls with a paper point (pinhead drop) into the shaped canal. If the canal is not dry, the excess moisture will prematurely cool the advancing wave of GP, resulting in a “pig- tail” of GP extruded into the PA area. The same will occur with excess sealer, and it will extrude along with the GP. The carriers are placed singly into the oven, the correct time chosen, and the cores allowed to heat to the proper tempera- ture. The small plastic, and all Gutta-Core carriers, are heated on the first setting (20 to 22 sec- onds); size 30 to 60 Thermafil Plus heated with the second set- ting (40 to 42 seconds); and size 70 or larger, the third setting (44 to 46 seconds). The carriers can be reheated, if necessary, and the time setting for the larger carriers is not critical, as long as they are heated for at least 40 seconds. Insertion of the heated carrier is slow and deliberate; you need to allow the excess material to be vented coronally. Insertion rates are 2 to 3 mm per second, which would translate to an average time of seven to 10 seconds for most canals from orifice to working length. With the larger carriers, you may experience a “rebound” effect after the carrier is inserted a few millimeters into the canal. Release the carrier and it will “rise” slightly from the canal space. This is the GP venting and push- ing the carrier back out of the canal slightly as it vents. Once the rebound is stopped, you can continue the insertion, stopping every few millimeters to check for rebound until the carrier is inserted to length. Pushing through the rebound and not al- lowing the GP to vent coronally will precipitate significant extru- sions. Depending on which type of car- rier is used, the handle is cut at the orifice level using either a Prepi bur, or a thermal tip (Figs. 14a,b). Removal of the handle is essential when placing more than one carrier in the access, as multiple handles in the ac- cess will obscure the view for the succeeding placements. A radiograph is taken to confirm placement, and any adjustments are easily made by engaging the core with a file and removing from the canal. Using a high- speed round bur, the remaining carrier “stubs” are trimmed to the desired level. If a post space is desired, it can be prepared im- mediately with an end-cutting ProPost drill (Dentsply) that will not displace the carrier. Compaction of warm GP using Thermafil for carrier-based ob- turation is slightly different. A simple technique is to segment a GP cone into approximately 5 mm sections prior to the obtura- tion process. Immediately after the Thermafil carrier is separated with a Prepi bur (Dentsply), the GP at the ori- fice is still soft and can be read- ily compacted. To facilitate thor- ough adaptation, a small and lubricated plugger (about a size 8 to 8.5 Schilder) can be used to apically compact the warm GP alongside the carrier. Push apically to a predeter- mined distance, hold briefly and remove the plugger. Then, using one of the pre-cut segments of GP, place it into the void created by the plugger, and compact it into place. More segments of GP may be necessary depending on the size of the canal. In cases when the canal may be ribbon-shaped and large in the M-D or B-L direction, the apical third of the canal is obtu- rated in the con- ventional manner. Then an accessory carrier can be in- serted alongside the initial carrier (Fig. 15). The second core of the second car- rier functions as a gentle spreader to assist in the lateral compaction and spread of the softened GP. The warm GP from the first and second carriers fuse together so any voids are elimi- nated. Excess filling material Historically, any time a case was obturated, there was much concern when anything was ex- truded beyond the apical termi- nus. Many endodontic failures were blamed on vertical over- extension, but in reality the cul- prit was an “under-filled” canal system. As Schilder stated, “You can only fill a canal 100 percent.” If the canal is filled 100 percent, any excess material extruded would be of no consequence. In fact, if the author obturated a canal system and there was no excess filling material, the GP would be routinely removed and re-obturated until there was. The point was, “How else could you be sure the canal system was obturated 100 percent un- less there was some excess filling material present at the apex?” Cases that have a significant amount of excess filling material but are properly shaped, cleaned and packed do heal. Over time, the excess material will slowly be resorbed (Figs. 16a, b). The biggest fear of the new user of injection or carrier-based GP is, “There will be a great amount of excess filling material at the terminus.” The opposite is gen- erally true. At first, the most common problem for the new user was the inability to get to the terminus and completely fill/ obturate the canal system. The usual reason for this was either an improper shape, the absence of patency or fear of the operator to use enough pressure during the injection and com- paction process. A good way to imagine what is happening, while using ther- mo-plasticized GP in a properly shaped and patent canal, is to envision everyone in a theater rushing to get out the same door in a big hurry. The GP molecules are relatively large and warm, so the continually tapering shape is, in itself, a limiting factor for the amount of sealer, or filling material, that will be extruded beyond the apex. If the apical terminus of the Fig. 14a. A Prepi bur (Dentsply) is used to sever the handle of the carrier at level of the orifice. (Photo/Courtesy of Stephen P. Niemczyk, Drexel Hill. Pa.). Fig. 16a. A PAX of the immediate post- op (left) and two-year post-op (right). Fig. 18. These four cases all have excellent root ca- nal treatment, but only the third from left had the entire canal system filled at the final endodontic visit. Which one would you bet on for predictability? Fig. 17a. Teeth #14 & 15 obturated with Therma- fil Plus. (Photo/Courtesy of Stephen P. Niemczyk, Drexel Hill, Pa.). Fig. 17b. Tooth #3 after being obturated using the Calamus. Table 1. A comparison of thermo-plasticized GP obturation with Calamus vs. Obtura. Fig. 16b. A PAX of the immediate post- op (left) and four-year post-op (right). Fig. 15. A second carrier is inserted alongside the first carrier to enhance compaction. (Photo/Courtesy of Ste- phen P. Niemczyk, Drexel Hill. Pa.). Fig. 14b. Carrier shaft and GP are severed at the orifice of the ca- nal. (Photo/Courtesy of Stephen P. Niemczyk, Drexel Hill. Pa.). CALAMUS 1) Flow is consistent and can be preset 2) GP & needles in single packaging 3) Single needle use the norm 4) Barrier protection easy to place 5) Less patient discomfort upon injection 6) Easier to relate/teach proper use 7) Can easily be rotated for ergonomics 8) No hand fatigue during use 9) No patient response during obturation 10) Generally, very clean to use OBTURA 1) Flow dependent on operatorʼs “squeeze” 2) GP pellets delivered several in a box 3) Multiple needle use the norm 4) Barrier protection more involved 5) Patient often felt a “flash of warmth” 6) Proper “squeeze” a longer learning curve 7) Unit difficult to turn to different angle 8) Hand fatigue can occur 9) Patients often felt apical pressure 10) More time consuming to clean