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.
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