Dr. Rich Mounce discuss strategies using “stiff” hand files
One of the most common challenges in clinical endodontics is obtaining patency. Blocked, calcified, curved, and transported canals challenge clinicians on a daily basis. This clinical article was written to discuss strategies using “stiff” hand files designed exclusively for these issues such as the Mani® D Finders (DF) (Figures 1-2).
Negotiating the canal to the apex (gaining patency) requires patience, diligence, and an awareness of the three-dimensional nature of the canal before and during canal exploration. Mentally, to optimize apical hand file advancement, the clinician must focus on tactile feedback during file insertion and correlate this feedback with preoperative radiographic images. Blindly forcing hand files arbitrarily to length is the harbinger of all manner of iatrogenic events and should be avoided at all costs.
A critical first step in the achievement of patency occurs during examination of the 2D and/or 3D radiographic images. Open and easily negotiable canals visualized radiographically often are quite forgiving in that they are large enough to remain patent, even if mismanaged. Unfortunately, the reverse is true as complex canals often have one best attempt to achieve patency; hence, the steps recommended below.
Having available the required files is far preferable to imposing onto the canal solely what files the clinician has available. In other words, a variety of hand files should be available for every case, as indicated by the anatomy encountered. To this end, it is noteworthy that hand files exist for every indication (aside from DF), which can provide the clinician what is needed for the given anatomy. These include hand files for rapid shaping (Mani RT files), reciprocation (safe-ended Mani SEC O K files), flexibility (Mani Flexile files), canal obstruction removal (Hedstrom files), gross canal shaping (Mani Reamers), and preparation of canal taper (Mani stainless and nickel-titanium Flare files). Many of the file types are available in “medium” sizes: 12, 17, 22, 27, etc.
Optimal utilization of any hand file has several requirements beginning with profound anesthesia, straight-line access, orifice management (adequate opening and shaping of the orifice), and removal of all pulp chamber contents prior to hand file canal negotiation.
Once the orifice is enlarged, and the other preceding steps are taken, regardless of the anatomy encountered, I virtually always insert the No. 6 Mani K file. Using a No. 6 Mani K file first allows me to determine the complexity of the canal without risk of blockage, especially in complex anatomy. Using larger files first can, in some canals, push tissue apically into the narrowing cross-sectional diameters of the canal and cause blockage. If the No. 6 advances easily to the apex, the clinician can move quickly to the next larger size (No. 8). Alternatively, if the No. 6 meets resistance (of any type), the canal is complex, and a DF is indicated for further negotiation.
Of the many marketplace options for “stiff” hand file options, I use the Mani D Finders for their rigidity, cutting ability, quality of manufacture, and economy. The DF’s cross section resembles the shape of the letter D, hence its name. While primarily used for canal negotiation, the DF can also be used to prepare a glide path with or without a reciprocating handpiece such as the NSK ER-10 (MounceEndo.com) (Figure 3).
The .02 tapered DFs are available in 21 mm and 25 mm, and in Nos. 8, 10, 12, and 15 tip sizes. DFs are designed to cut with ¼ to ⅓ turns with a reaming motion, accompanied by frequent irrigation. The DF has 16 mm of cutting flutes and a unique safety tip. The DF’s tip has a unique blend of non-cutting and cutting features. It is designed to avoid transportation and yet enhance achievement of patency in narrow and highly curved canals.
Empirically, in my hands, a No. 8 DF is approximately 3-4 times stiffer than a standard No. 6 K file and, as a result, allows a significantly greater vertical pressure to be placed on them. DFs are an excellent option to allow apical negotiation in canals where a K file kinks and/or resists apical advancement. The DF’s cross-sectional design prevents the screwing-in effect that is possible with more heavily fluted files. Less screwing in allows the forces placed on the file to be directed to the file tip, improving tactile sensation and apical movement.
Regardless of whether the clinician is using a K file or a DF, it may be necessary for him/her to insert the file in many orientations in order to initially locate the canal path and subsequently gain length, especially in an acute apical curvature. Hand files should never be forced, as doing so can create a false canal path and/or blockage. That said, experience can guide the clinician to put firm but flexible pressure while watch winding the DF to push through debris blockages or advance around curves.
It is axiomatic that all hand files be pre-curved and that the canal be filled with irrigant during all phases of negotiation and shaping. Personally, I use a new hand file for each individual insertion and subsequently use a new file. While hand files can certainly be sterilized and used in multiple cases, the sharpest and greatest degree of tactile acuity results from use of a new hand file with every insertion.
Once the clinician reaches the apex with the first DF, a glide path is subsequently prepared using the Mani hand files of choice (K, Flexile, RT, SEC O K, D Finders, etc.) followed by bulk canal shaping with, for example, Mani’s new and novel Mani Silk nickel-titanium system. Mani Silk is anatomy-based, shaping canals with three-file “Simple,” “Standard,” and “Complex” anatomy pack configurations (Figure 4).
This article has described the negotiation of curved and calcified canals using the Mani D Finders. Emphasis has been placed on straight-line access, optimal orifice management, and the intentional but firm pressure using pre-curved D Finders in an irrigant-filled canal to reach the apex, followed by subsequent glide path creation and shaping with Mani Silk nickel-titanium files. I welcome your feedback.