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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