Describing three-dimensional obturation of the root canal system is a bit like asking what is the sound of one hand clapping or if a tree falls in the forest, does it make a sound? In essence, it can be challenging. Three-dimensional obturation of the root canal system might be defined as placing a homogenous (without voids) and dense filling material from the canal orifice to the minor constriction of the apical foramen as well as into all anatomical ramifications (fins, bifidities, trifidities, anastomoses, cul de sacs, etc).
To me what makes the obturation three-dimensional is that when viewed from any angle either radiographically or in cut sections, there is obturation material packed as densely as possible into all of the canal space present. Caution is advised. Radiographs can be misleading. A radiograph showing a fully obturated canal does not assure that every anatomical complexity is obturated fully. This last statement taken alone would imply that knowing an obturation was three dimensional as per the previous definition would be elusive as unless the tooth was extracted and sectioned. In addition, even if a radiograph appears to be ideal, the clinician must evaluate the coronal seal to determine if any microleakage has occurred which is reaching the obturation material.
While a book could be written about what factors create three-dimensional obturation, the following (amongst others) factors are certainly paramount:
1) adequate irrigation,
2) obtaining and maintaining apical patency
3) creation of a tapered funnel with narrowing cross sectional diameters to the minor constriction of the apical foramen
4) prevention of iatrogenic events of all types
5) warm gutta percha techniques.
While the list could be much longer this list compromises a set of core objectives, which if met, enhance the achievement of three- dimensional obturation.
While a comprehensive discussion of obturation techniques and materials is well beyond the scope of this column, bonded obturation, which relies upon removal of the smear layer for adhesion into the tubules, holds great promise. Resilon (Resilon Research, Madison, CT, USA) and RealSeal (SybronEndo, Orange, CA, USA) have been recently introduced, which provide a significant level of bonding to canal walls and diminished microleakage in a coronal to apical direction. In my opinion, bonded obturation provides a filling, which is more three-dimensional than gutta percha in the sense that now obturation materials can penetrate the tubules and be bonded to the core resin material in the canal. Conversely, gutta percha has no inherent ability to diminish microleakage or to bond to canal walls.
Dr. Mounce is in private endodontic practice in Portland, OR.
REFERENCES
1.J Am Dent Assoc. 2004 May;135(5):646-52. Fracture resistance of roots endodontically treated with a new resin filling material. Teixeira FB, Teixeira EC, Thompson JY, Trope M.
2.J Endod. 2004 May;30(5):342-7. An evaluation of microbial leakage in roots filled with a thermoplastic synthetic polymer-based root canal filling material (Resilon). Shipper G, Orstavik D, Teixeira FB, Trope M.
