January 1, 2005
by Rich Mounce, DDS
It must first be remembered that all endodontic instruments have given tolerances within which they must fall to be ISO (International Standards Organization) certified. For example, some #15K files can in actuality be slightly larger or smaller, i.e. a 15.5 or a 14.5 at the tip or anything in between. Such variance and tolerance occurs with paper points, gutta percha points, RealSeal (SybronEndo, Orange, CA) and Resilon (Resilon Research, Madison, CT) bonded obturation points as well as hand files, etc.
In practical terms, while the clinician may use a .06 tapered rotary file of a given tip size, for example, a 35 as the master apical rotary file and expect a gutta percha point to match it, it is by no means assured that a tip size 35 gutta percha cone will fit with tugback at the desired length. In fact, it is very uncommon that there is an ideal match between the master apical rotary and an ISO standard gutta percha cone or soft-core resin point such as Resilon or RealSeal.
As an aside, even though some tolerances are fairly close between corresponding gutta percha and resin points and their corresponding hand and rotary files, most often these points must be trimmed to achieve tugback. I recommend using non-standardized obturation points (medium, fine medium, etc.) which can be custom fitted via trimming, to achieve tugback instead of ISO sized points.
These are available as Autofit gutta percha (SybronEndo, Orange, CA). It is noteworthy that RealSeal points are marketed as Autofit cones. Paper points are also available as Autofit points which closely match the tapers of the Autofit gutta percha and RealSeal cones.
In addition, if a given obturation point doesn’t fit; the clinician has several avenues to solve the problem. First off, the canal can be prepared to a slightly larger apical diameter and/or taper or a larger or smaller obturation point can be selected which gives the appropriate tug- back at true working length assuming the canal has been prepared to an ideal size and taper. It is axiomatic that it is simple to obturate a well-prepared canal; it is very difficult to obturate a canal that is under prepared.
With experience, using the Autofit paper points for drying canals has proven for me over time to very closely match the Autofit gutta percha points saving time and effort and creating efficiency.
In other words, if a Autofit paper point will fit to the true working length with tugback, it is very likely that a close match will occur with the corresponding Autofit gutta percha point or Autofit RealSeal point requiring minimal trimming and correction to obtain ideal tug back. I welcome your questions and feedback.
Dr. Mounce is in private endodontic practice in Portland, OR.