by Richard Mounce, DDS
Preventing postoperative pain and swelling (POPS) is far preferable to managing its occurrence. While there are statistical predictors of POPS (nonvital teeth, patients already in pain, asymptomatic teeth with lesions, etc.), POPS is not inevitable, and to a large extent, can be avoided. Moderate to severe POPS should be relatively uncommon. In large measure, its prevention is a function of providing excellent treatment (a well-cleaned and shaped canal minimizing extrusion of canal contents during the process). The converse is true.
In many endodontic courses, the instructor may show the creation of the “endodontic worm,” a tubular mass of canal debris produced primarily by debris propelled through the apical foramen by forceful instrumentation, improper irrigation, and a lack of recapitulation.
This worm of debris, or some facsimile, is the primary source of POPS. The worm includes bacteria, dentin chips, irrigants, intra-canal medicaments, and inflamed or dead pulp. These are the contents of the canal. This debris is toxic when placed in the apical tissues, and POPS can be the result.
Here are some strategies for avoiding POPS.
1) Make an accurate determination of the TWL, the position of the minor constriction of the apical foramen. Leaving the MC in its original position and size is correlated with less POPS. Conversely, transporting the MC in any way will give rise to a far greater probability of POPS. I use the Elements Diagnostic Unit (SybronEndo, Orange, Calif.) numerous times during treatment to determine the TWL, along with a bleeding point determination on a paper point. Transporting or enlarging the MC can easily lead to extruded irrigants or leaving the debris just described, which can be harbored in the apical third. The MC is the point above which all instrumentation, irrigation, and obturation should be focused and contained. Said differently, other than patency files (6 to 10 hand K files), the MC should not be violated. Irrigation should cease at the MC, and the master cone should have a precise fit to the MC (and not beyond) before down packing. These steps are done with the intention of minimizing extrusion and production of the toxic worm.
2) In irrigation, using a side-venting and close-ended needle can prevent unnecessary extrusion. Irrigation should be slow, passive, and done with control and intention. The presence of an open or resorbed apex should always be considered, even in a tooth that appears radiographically normal so as to appreciate the possibilities of extrusion when it is otherwise unexpected. Factors that can predict POPS are cumulative. An open apex with a lesion in an asymptomatic patient is a high-level predictor of POPS. This scenario is a strong candidate for two-visit treatment with an inter-appointment dressing of calcium hydroxide. In general, such complex cases are best referred.
3)In my opinion, rotary nickel titanium files are best when inserted crown down with the coronal third instrumented first, the middle third second, and the apical third last. This strategy minimizes extrusion because the coronal two-thirds of the canal have been cleaned and cleared before the apical third contents are addressed. To employ this technique, a clinician should determine an EWL and estimate where he or she is at any time during the cleansing and shaping process. A clinician should stay out of the apical third of the root until the more coronal two-thirds are ideally prepared. Crown down instrumentation is consistent with fewer iatrogenic events, cleaner canals, and more efficient treatment. RNT insertion is slow, gentle, and passive. RNT used with force directed apically makes an effective piston to propel debris from a patents apical foramen.
4)Cone fit and sealer selection may have an influence on POPS. I use RealSeal (SybronEndo) for obturation. Aside from the benefit of bonding the obturation, the sealer is prepared in a mixing tip. Thus, there is no chance for the proportions of powder to liquid to be mistaken. Excess eugenol extruded into the periapical tissues are highly irritating. Empirically, while using RealSeal and its resin-based sealer, I have had less POPS than when using ZOE-based sealers. Ideal cone fit implies that the master cone only contacts the canal wall in the apical 3 to 4 mm. During down pack, this reduces the chances for extrusion of the filling material and - by extension - any canal contents that otherwise might be forced apically.
I welcome your comments and questions.
Dr. Richard Mounce lectures globally and is widely published. He is in private practice in endodontics in Vancouver, Wash. Among other appointments, he is the endodontic consultant for the Belau National Hospital Dental Clinic in the Republic of Palau, Korror, Palau (Micronesia). He can be reached at Lineker@aol.com.