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Dental Tribune Middle East & Africa Edition | January-February 2016 11 mCME < Page 10 canal is kept as small as practi- cal, about the size of a 20KF, it is hard to obtain more than a small “puff” at the apex, no matter how hard the operator compacts the thermo-plasticized GP (Figs. 17a,b). However, it makes sense that the larger the apical open- ing, the larger the amount of ex- cess material might be extruded. In a short period the operator develops the necessary “feel” to be very predictable with the ob- turation and compaction. This is the essence of the learn- ing curve when beginning to use a thermo-plasticized technique. Also, since the softness of ther- mo-plasticized GP is maintained for a longer time in a larger mass size (volume), the apical extent is the first to become solid since it has the smallest volume of mass. These techniques are easy, fast and predictable for achieving excellent obturation, if all is done as described. Now for the rest of the seal The final step of the System “S” protocol is to fill the entire canal system. It is self-defeating to do a beautiful job in the apical half of the canal system and turn the case over to another person to complete the coronal half of the obturation. As endodontists, we are generally concerned with “the fill” and forget the impor- tance of sealing “the rest of the system.”6 To illustrate this concept, look at the four cases depicted in Figure 18, and then decide which one would have the most predictable chance of success. They all have well-done endodontic treat- ment, but only one case has had the entire canal system sealed. A survey taken not too long ago showed that 95 percent of gen- eral/restorative dentists did not use a rubber dam while placing a foundation restoration in an endodontically treated tooth. To maximize the predictability of success and avoid possible post- op complications, the “endo-do- er” must be responsible for the seal of the entire canal system. Here are just a few reasons to do the foundation restoration at the same visit: 1) Patient is “in the chair.” 2) Patient is anesthetized. 3) Rubber dam is in place. 4) Access is sterile for placement of the foundation restoration. 5) All previous restorative mate- rials are easily removed. 6) The “endo-doer” has micro- scopically enhanced vision. 7) The “endo-doer” knows cor- rect angle, size anddepth of the canal system. 8) There is no chance of con- tamination of the canal system. 9) Inadvertent perforations are eliminated. 10) The tooth can be “roughed prepped” with dam in place. 11) The patient has more time to plan for the final restoration. 12) After RCT, doctor knows, within two minutes, the time to schedule for crown prep. 13) On anterior teeth, appoint- ments can be coordinated for placement of a provisional. It has been shown that coronal leakage is the major cause of root canal treatment failure.7 Therefore, it behooves us to do all that is possible to prevent it. If multiple visits are required, the doctor should not rely on “cot- ton and Cavit” to maintain ste- rility. With the current bonding and composite technology, the temporary placed between visits should be a bonded composite. A good example of an easy-to- use temporary is auto-cure Ten- ure Uni-Bond and Core Paste (Denmat). CaOH (Ultracal by Ultradent) is injected into the canal system and covered with a sterile cotton pellet (Fig. 19a). Then Tenure Uni-Bond is used to condition the access opening (Fig. 19b). After just a few min- utes, the auto cure Core Paste is set completely, the occlusion is ready for any adjustments, to make sure there are no interfer- ences left to irritate the tooth be- tween visits. On occasion, a patient is unable to keep the appointed return visit and may have to delay his or her return visit for weeks or months (Fig. 19c). There may be an important change of events in his or her life, or the doctor may also have to change the scheduled visit. If a temporary is placed, such as Cavit, IRM or Tempit, all control of the bacte- rial environment in the canal system is lost in a relatively short period if the patient does not re- turn in a timely fashion. Who would be better to control the coronal aspect of the tooth following endodontic obturation than the “endo-doer,” while the case isolated with a rubber dam in place? As Dr. Denny South- ard of Tulsa, Okla., commented almost 15 years ago, “When we slap in Cavit and turn our heads, the case is destined for contami- nation or worse [perforation, for example].” However, if a more definitive seal is maintained, that part of the equation becomes a non- issue.6 An easy foundation restoration technique After the obturation of all canals, the guttapercha is removed to the proper depth in the orifice as required for retention. This is quickly and easily done using a Munce Bur at approximately 5,000 rpm. If a post space is required using carrier-based GP, a ProPost drill can be used to remove a little GP at a time, until the desired depth is reached. Using the co-observ- er tube of the SOM and a precise flow of air from the Stropko Ir- rigator, the chairside assistant can aid in the removal of all bits of sealer and GP to maintain vi- sion while final cleaning of the access/post space is done. After the mechanical cleansing of the access is accomplished, it is flooded with 95 percent ethanol to remove any remain- ing sealer and scrubbed with a micro-applicator (SybronEndo). Another application may be necessary to achieve a clean surface. If there is a post space, it can be cleaned the same way, but after flooding the space with 95 percent ethanol, use a Versa- brush (Vista) turning at approxi- mately 500 rpm to be assured of getting the post space walls free of sealer. After this step, the post used can be tried in to be sure it fits passively. The FibreKor post kit (Pentron) has a very good selection of sizes (Fig. 20). The 1.125 mm (laven- der colored lid on tube) fits most of the post spaces passively. If the fit of the post is not passive but is the desired size, a very fine, tapered diamond is used to taper the apical end until it does fit passively into the space. Note: A post space should never be enlarged to fit the post. The post should always be adjusted to fit the post space. A post should only be used for retention of the core buildup and does not strengthen the tooth. Rinse and air dry the access, and then flood it with 37 percent phosphoric acid gel (Ultradent), letting it remain for approxi- mately 20 seconds to accomplish the proper etch of the walls. Rinse very thoroughly and air dry, being careful not to desic- cate the dentinal surface. Apply two coats of Tenure A&B (Den Mat) for conditioning of the den- tin, air drying between each and inject Core Paste (Den Mat) to fill the access completely. If needed, the FibreKor post can be cemented with the initial ap- plication of Core Paste. It is a good idea to also coat the fiber post with the Tenure A&B before insertion into the newly injected, soft Core Paste. Note: Do not use the Tenure UniBond for this step, as it is thicker in consistency and may affect the passive fit of the post. Core Paste is one of the most forgiving and easy-to-use ma- terials. It is auto-cure, has ad- equate working time and can be “stacked” or added onto, so enough bulk is easy to achieve for the desired buildup, and it always sets up in two to three minutes. The tooth can then be rough prepped and returned to the referring doctor (Figs. 21a– c). At any rate, the endodontical- ly treated tooth is ready for the final crown prep and impression if the doctor wishes to do it at the same appointment. Respect for the endo-pros rela- tionship Current technology has allowed endodontic treatment to achieve a very high degree of success when the coronal seal has been accomplished. Weine has stated that more endodontically treated teeth are lost due to improper restoration than to endodontic failure.8 More recently, it was shown that in 1.5 million people over an eight-year period, there was a 97 percent success rate for endo- dontically treated teeth. Of the 3 percent that failed, 85 percent of those had no coronal coverage.9 It is necessary to appreciate some basic restorative/prostho- dontic principles to establish a degree of predictability we want to achieve with the System “S” protocol of treatment. It has been shown that teeth do flexduringnormalfunction.The less radicular structure present, the weaker the tooth will be. And the weaker the tooth, the more it flexes. The more it flexes, the more micro leakage occurs, and it becomes only a matter of time before the tooth fails. The canal system can be contaminated due to micro leakage, by fracture due to lack of radicular strength, or the crown/post/core can break or come out. If a restora- tion is placed, entirely based on the retention of the foundation restoration, it is not an issue of whether the restoration will fail; it is a matter of when it will fail.10 It is critical that a minimal cir- cumferential ferrule of 1 to 2 mm be established for reten- tion of the restoration. A bio- logical width of approximately 2 to 3 mm is required between the osseous crest and the cervi- cal margin of the restoration.11 Therefore, a minimum total of 3.5 mm is necessary between the intended cervical margin of the restoration and the osseous crest. mCME SELF INSTRUCTION PROGRAM CAPPmea together with Dental Tribune provides the opportunity with its mCME - Self Instruction Program a quick and simple way to meet your continuing education needs. mCME offers you the flexibility to work at your own pace through the material from any location at any time. 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The answers and critiques published herein have been checked carefully and represent authoritative opinions about the questions concerned. Articles are available on www.cappmea.com after the publication. For more information please contact events@cappmea.com or +971 4 3616174 FOR INTERACTION WITH THE AUTHORS FIND THE CONTACT DETAILS AT THE END OF EACH ARTICLE. Fig.19a.CaOHinjectedtofillcanalsystemandcoveredwithasterilecottonpellet. Fig. 19b. Core paste is placed to seal the access opening. Fig. 19c. A bonded temporary that has been in place for three months without leakage. Figs. 21a–c. The canal systems have been filled 100 percent and are ready for res- torations without any concern for micro-leakage until they are more permanently restored. Fig. 20. The FibreKor posts have a wide selection of posts with good re- tention and are easy to use. > Page 12 Another important considera- tion for conserving root struc- ture is the necessity of a post for retention. It is worth repeating, “A post is only indicated if retention of the core is inadequate without it. Posts are only indicated when needed for retention. The post space must never be shaped to fit the post. Instead, the post must be shaped to fit the existing post space.” The more radicular substance removed, the weaker the tooth. Posts nev- er strengthen a tooth. Conservation of the radicular structure also needs to be con- sidered when accessing and shaping the canal system. Only enough tooth substance should be removed to achieve vision and desired shape needed to completely disinfect, clean and obturate the entire canal system. If the access is compromised, the correct shape may be diffi- cult if not impossible to achieve. Likewise, if we compromise the shape, the cleaning and obtura- tion will also not be as complete as desired for predictability. The author is amused by anyone willing to compromise access and shaping in the name of tooth conservation. What good does all that tooth structure do if the Dental Tribune Middle East & Africa Edition | January-February 201611 +97143616174