Tuesday, May 28, 2013
My previous Dentalcompare article discussed the clinical uses of Gates Glidden Drills (GGDs) in orifice management and shaping the coronal third. This column will discuss alternatives to GGDs to achieve the same clinical objectives.
The critical importance of proper orifice management cannot be overstated. The canal orifice is the gateway to the apical third. If the orifice and coronal third is not enlarged correctly, compromises will occur in subsequent apical treatment. Alternatively, if the orifice is managed well, optimal apical cleaning and shaping can occur.
Management in this context means the orifice is enlarged to the appropriate circumferential dimension (width) and the canal is left negotiable after orifice shaping. Such a dimension allows unrestricted access to the more apical portions of the canal, allows a tapering funnel to be prepared without risk of perforation or other iatrogenic events, allows optimal activated irrigation, and facilitates a heat softened three dimensional obturation in addition to other attributes.
Optimal orifice and coronal third shaping is only possible when straight-line access (SLA) is prepared first. SLA provides the clinician with the ability to place a hand file into the canal without deflection to the point of first canal curvature.
Canal anatomy should be carefully considered before making access. Searching fruitlessly for canals during access can lead to both perforation and excess dentin removal putting the tooth a risk of fracture. Having a clear idea how many canals are likely present, where they are located, how calcified they are and how far apically one must go to access them can go far toward avoiding iatrogenic potential. CBCT technology is invaluable in this regard.
Clinically, the doctor must decide what instruments and techniques will be used to shape the orifice and coronal third. In addition to GGDs, stainless steel orifice openers (OOs) and rotary nickel titanium (RNT) OOs are available for this purpose (Fig. 1: An example of a rotary nickel titanium orifice opener, the MounceFile Controlled Memory .08/25 Orifice Opener is pictured above at left.). Each of these options have pros and cons.
Stainless steel OOs, while inexpensive, have limitations. They are stiff and create a greater potential for blockage, transportation and perforation when inserted to the point of first canal curvature relative to the available RNT options. While these iatrogenic events are uncommon in simple canal anatomy, in complex anatomy they pose a greater risk.
If the stainless steel hand file touches the axial walls of the access preparation and deflects, optimal tactile and visual control over all subsequent canal-shaping instruments is impeded. Such a deflection makes iatrogenic events much more likely and diminishes apical cleaning and shaping effectiveness.
When using a RNT OOs, there is little if any benefit to a taper larger than .08. If the orifice is especially large, and the clinician desires to prepare a larger orifice diameter, the .08/25 RNT OO can be used with vertical amplitude to brush along the orifice walls to increase its size or increase coronal third taper.
Aside from optimal lighting and magnification, it is essential that all debris from access be removed as it is formed before entering the orifice. Such debris removal minimizes the chance of apical canal blockage through apical compaction. Once access is made, the clinician should assure that all canals are visible in one mirror view and that a smooth axial wall is present that optimally extends from the occlusal surface to the point of first canal curvature.
Fig. 2: An example of a completed case using the techniques described in this article.
Fig. 3: Another example of a completed case using the techniques described in this article.
When using a RNT OO, regardless of the type, similar actions are needed to maintain tactile control as well as to prevent the instrument from “screwing in” and leading to possible fracture. The clinician should assure an excellent tactile grip on the OO and only insert the file as far as desired based on the anatomy. It is unproductive to force a RNT OO to any predetermined depth. Rather, the file should be inserted passively to the point of resistance. Such a tactile motion usually takes about 3 seconds. The RNT OO can be inserted again as needed to move further apically. After every insertion of the RNT OO, the canal should be irrigated and a stainless steel hand file, for example a #6 or #8 Mani hand K file inserted into the canal to assure patency beyond the level of the RNT OO insertion.
Many simpler canals, especially in the anterior teeth of younger patients, will allow a RNT OO to progress down the canal often to or near the minor constriction. In these canals, depending on the anatomy, the RNT OO may be the only file needed to shape the body of the canal.
In summary, proper orifice management is essential to allow the clinician to reach the apical third with complete tactile and visual control. Emphasis has been placed on choosing the appropriate sized RNT OO or GGD and leaving the canal patent once the orifice is shaped. I welcome your feedback.