The ProTaper Technique-Shaping the Future of Endodontics

There have been significant advancements in the development of NiTi rotary instruments in recent years. This evolution is driven by market demand and the continuous improvement in the manufacturing process. Dentists have increasingly identified the features they deem essential on the endless journey towards a more perfect file. These features include flexibility, efficiency, safety, and simplicity. The ProTaper system has been designed to provide these features; consequently, its entrance into the marketplace has had a profound effect.
The ProTaper NiTi files (Dentsply Maillefer; Ballaigues, Switzerland) represent a revolutionary generation of instruments for shaping root canals. This post will review the ProTaper geometries, then describe the ProTaper concepts, techniques and finishing criteria that may be utilized to fulfill the mechanical and biological objectives for shaping canals. Learning the ProTaper concept will lead to discovery then appreciation for this six instrument set, comprised of just three Shaping and three Finishing files.

The canals of this mandibular molar were shaped with ProTaper files and three-dimensionally filled. Note the flowing shapes, apical one-third curvatures and multiple portals of exit.

Protaper geometries
The following will describe the ProTaper geometries and specific features that make these Shaping and Finishing files remarkably unique.

The Shaping Files
Shaping File # 1 and Shaping File # 2, termed S1 and S2, have purple and white identification rings on their handles, respectively. The S1 and S2 files have D0 diameters of 0.17 mm and 0.20 mm, respectively, and their D14 maximal flute diameters approach 1.20 mm (Fig. 19.3). The Auxiliary Shaping File, termed SX, has no identification ring on its gold-colored handle and, with a shorter overall length of 19 mm, provides excellent access when space is restrictive. Because SX has a much quicker rate of taper between D1 and D9 as compared to the other ProTaper Shaping files, it is primarily used, after S1 and S2, to optimally shape canals in coronally broken down or anatomically shorter teeth. The SX file has a D0 diameter of 0.19 mm and a D14 diameter approaching 1.20 mm.

Progressively Tapered Design
A unique feature of the ProTaper Shaping files is each instrument has multiple “increasing” percentage tapers over the length of its cutting blades. This progressively tapered design serves to significantly improve flexibility, cutting efficiency, and safety.Fortuitously, a progressively tapered design typically reduces the number of recapitulations needed to achieve length, especially in small diameter or more curved canals. As an example, the SX file exhibits nine increasingly larger tapers ranging from .035 to .19 between D1 and D9, and a fixed .02 taper between D10 and D14. The S1 file exhibits twelve increasingly larger tapers ranging from .02 to .11 between D1 and D14.
The S2 file exhibits nine increasingly larger tapers ranging from .04 to .115 between D1 and D14. This design feature allows each shaping file to perform its own “crown down” work. One of the benefits of a progressively tapered shaping file is that each instrument engages a smaller zone of dentin which reduces torsional loads, file fatigue and the potential for breakage.

The Finishing Files
Three Finishing files named F1, F2 and F3 have yellow, red and blue identification rings on their handles corresponding to D0 diameters of 0.20 mm, 0.25 mm, and 0.30 mm, respectively. Additionally, F1, F2, and F3 have fixed tapers between D1 and D3 of .07, 08, and .09, respectively.

The ProTaper technique

Canal preparation is improved when instruments pass through the access opening, effortlessly slide down smooth axial walls and are easily inserted into the orifice. The potential to consistently shape canals and clean root canal systems is significantly enhanced when the coronal two-thirds of the canal is first pre-enlarged followed by preparing its apical one-third.

Scout the coronal two-thirds
When straight-line access is completed, the pulp chamber should be filled with a viscous chelator and/ or irrigant. Based on pre-operative radiographs, ISO 0.02 tapered sizes #10 and #15 K-files are measured and precurved to match the anticipated full length and curvature of the root canal. However, in this method of canal preparation, these instruments are initially limited to the coronal two-thirds of a root canal. The #10 and #15 K-files are utilized within any portion of the canal until they are loose and a smooth reproducible ‘glide path’ is confirmed. The loose depth of the #15 K-file is measured and this length transferred to the ProTaper S1 and S2 instruments.

Shape the coronal two-thirds
Once a reproducible glide path is verified this portion of the canal should be pre-enlarged by first utilizing S1 then S2. Prior to initiating shaping procedures, the pulp chamber is filled with a 5.25% solution of NaOCl. Without pressure, and in one or more passes, the ProTaper Shaping instruments are allowed to passively ‘float’ into the canal and ‘follow’ the glide path. To optimize safety and efficiency, the Shaping instruments are used, like a ‘brush’, to laterally and selectively cut dentine on the outstroke. A brush-cutting action creates lateral space, which will facilitate the larger, stronger and more active cutting blades on the Shaping instruments to safely and progressively move deeper into the canal. If any ProTaper instrument ceases to advance within the verified portion of a canal, withdraw it, and recognize that intrablade debris has deactivated and pushed the instrument off the wall of the canal.

Upon removing each Shaping instrument, visualize where the debris is located along its cutting blades to better appreciate the region within the canal that is being prepared. Following the use of each Shaping instrument, irrigate, recapitulate with a #10 file to break up debris and move it into solution, then reirrigate.
Without pressure, and in one or more passes, S1, then S2, is used in this manner until the depth of the #15 K-file is reached.

Scout the apical one-third
When the coronal two-thirds of the canal is shaped, then attention can focus on apical one-third procedures. With the pulp chamber filled with a viscous chelator or irrigant, the apical one-third of the canal is fully negotiated and enlarged to at least a size #15 Kfile, working length confirmed and patency established. At this time, a decision must be made between whether to finish the apical one-third with rotary or hand instruments. If a new and straight #15 file can gently ‘slide’ and passively ‘glide’ to length, then rotary instruments will generally follow this confirmed and reproducible glide path. However, certain canals exhibit anatomical challenges that necessitate a reciprocating handle motion in order to move pre-curved #10 and #15 files to length. When there is an irregular glide path then the apical one-third of a canal may be finished with pre-curved 
ProTaper hand instruments.

Shape the apical one-third
When the apical one-third of the canal has been scouted and a glide path created, then the pulp chamber is filled with NaOCl. The ProTaper sequence is to carry the S1, then the S2, to the full working length. Float, follow and brush as previously described until the terminus of the canal is reached. S1, then S2, will typically move to length in one or more passes depending on the length, diameter and curvature of the canal. Following each ProTaper instrument, irrigate, recapitulate with a #10 file, then re-irrigate. After using the Shaping instruments, particularly in more curved canals, working length should be reconfirmed, as a more direct path to the terminus has been established. At this stage of treatment, the preparation can be finished using one or more of the ProTaper Finishing instruments in a ‘nonbrushing’ manner. The F1 is selected and passively allowed to move deeper into the canal, in one or more passes, until the terminus is reached. When the F1 achieves length, the instrument is removed, its apical flutes are inspected and if they are loaded with dentine, then visual evidence supports the shape is cut. Following the use of F1, flood the canal with irrigant, recapitulate and confirm patency, then re-irrigate to liberate debris from the canal.

ProTaper finishing criteria
Following the use of the 20/07 F1, the ‘ProTaper Finishing Criteria’ is to gauge the size of the foramen with a 20/02 tapered K-file to determine if this instrument is snug or loose at length. If the #20 Kfile is snug at length then the canal is fully shaped and, if irrigation protocols have been followed, ready to fill.

Following the use of F1, if the #20 K-file is loose at length, then gauge the size of the foramen with a 25/ 02 tapered K-file. If the #25 file is snug at length, then the canal is fully shaped and ready to fill. If the #25 file is short of length, proceed to the 25/08 F2 and, when necessary, the 30/09 F3, gauging after each Finisher with appropriately sized hand files. If the #30 file is loose at length, then use an alternative NiTi rotary line or manual files to finish the apical extent of these larger, easier and more straightforward canals. ProTaper shapes are easy to fill utilizing a ProTaper matching gutta percha master cone in conjunction with a warm vertical condensation technique.

Video of Protaper Demonstration on a Block

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