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How many obturation systems and techniques should a general dentist have at his or her immediate disposal? Are there teeth that might be amenable to an obturation technique in one canal and yet another technique in a different canal? Are either of these questions affected by whether treatment is rendered in one or two visits? This two-part column will discuss these questions and related ones in a clinically relevant manner.
FIRST, the quality and efficiency of obturation is directly related to the canal shaping. Canal shaping, if performed correctly, optimizes irrigation and obturation hydraulics. Ideal irrigation, as a result of canal shaping, is made possible in part by attainment of canal patency, the desired continuously tapered final prepared canal shape, prevention of iatrogenic events, "deep body" shape, as well as use of the correct irrigant solution concentration, application, volume, and activation. "Deep body" shape in this context refers to attaining a continuous taper between the middle and apical canal thirds. Simply put, attainment of the correct shape makes obturation far simpler, irrespective of the particular technique used. The converse is true.
SECOND, visualizing the canal and having tactile control over enlargement is vital in order to prevent iatrogenic obturation issues (short or long obturations), and yet to provide a three dimensional obturation that fulfills the goals of treatment. The optimal instrument for obtaining visual and tactile control over the endodontic access is the surgical operating microscope (Global Surgical, St. Louis). Another excellent option, in the absence of or in addition to the SOM is the use of the loupes such as the Class IV 4.8X HiRes Plus loupes by Orascoptic (Middleton, Wis.).
THIRD, obturation quality depends on attainment of the correct working length. Determination of an accurate working length is an absolutely vital requirement for the highest quality treatment. While opinions among clinicians differ slightly, the minor constriction of the apical foramen (MC) is the natural termination point for endodontic cleaning, shaping, and obturation procedures. I obturate vital and nonvital cases to the MC. While a comprehensive discussion of the means to determine the position of the MC is beyond the scope of this column, it bears mentioning that the greater the number of means used to locate the MC, the better. Each of the various means should confirm one another, be these electronic apex location, radiographic techniques, tactile feel, and/or bleeding point determination.
FOURTH, the significance of optimizing the size of the apical preparation cannot be overemphasized. The endodontic literature states that the larger the master apical diameter, the cleaner the canal preparation that results. In essence, apically, a No. 50 master apical diameter is cleaner than a No. 30 master apical diameter, etc. One additional benefit of larger apical diameters is that cone and obturator fit for warm obturation techniques are made simple relative to smaller canals.
FIFTH, the master apical taper should be optimized. The ability to create a taper above a size .06 is related to the capabilities of the instrumentation system used, the risk of strip perforation, root length, root width, root curvature, and the degree of calcification. Simply stated, the more complex the root, the greater the chances of iatrogenic outcomes using rotary nickel titanium files. In addition, some instrumentation systems do not possess the flexibility to prepare larger tapers to the apex. Because it is manufactured by twisting nickel titanium in the rhombohedral crystalline phase configuration, the Twisted File* possesses the flexibility to prepare a .08 taper along the length of virtually any mesial lower molar root if used correctly. This larger taper will allow for easier cone fit relative to cone fit into canals of smaller taper.
Sixth, the type of obturation matters. While gutta percha has its champions, there are alternatives, for example, the use of a bonded material such as RealSeal*, available in either a master cone or obturator form. RealSeal creates a bond between the core obturation material, the sealer, and dentin wall. In vitro and in vivo, there is significant literature-based evidence that RealSeal diminishes the migration of bacteria in a statistically significant manner relative to gutta percha. I have used RealSeal since January 2004 for all of my obturation and would never go back to gutta percha; the body of scientific evidence supporting the material is far too strong. RealSeal does not require the clinician’s obturation technique to change, only to remove the smear layer before obturation with a one to two minute rinse of liquid EDTA (SmearClear*).
Part 2 of this two-part column will address this subject in further detail. I welcome your feedback.
*SybronEndo (Orange, Calif.)
Dr. Mounce is the author of the nonfiction book Dead Stuck, "one man’s stories of adventure, parenting, and marriage told without heaping platitudes of political correctness," available at Pacific Sky Publishing or DeadStuck.com. Dr. Mounce lectures globally and is widely published. He is in private practice in endodontics in Vancouver, Wash.
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