Root canal preparation techniques

2. *Objectives of Root Canal Preparation.
*The principles of shaping.
*Standardized technique
*Step back technique
*Modified step back technique
*Step down technique
*Crown down technique
*Hybrid technique
*Double flared technique
*Modified double flared technique
*Balanced force technique

3. *
1.Eliminate microorganisms.
2.Remove remaining pulp tissues.
3.Remove debris.
4.Shape the root canal system so that it
may be obturated.

4. *
* Develop a continuously tapering funnel
from the apex to coronal orifice.
* Maintain the original shape of the canal.
* Maintain the apical foramen in its original
position.
* Keep the apical opening as small as possible.

5. Techniques can be
divided to:
Apical to
coronal
Coronal to
apical

6. Techniques
Apical to
coronal
1.Conventional
2.Step back
3.Modified step back
Coronal to apical
1.Step down
2.Crown down
3.Hybrid technique
4.Double flared technique
5.Modified double flared
6.Balanced force technique

8. *Also known as conventional technique. One of
the first technique to be used introduced by
Ingle.
*In this technique standardized reamers of
increasing sizes were used sequentially to
enlarge the apical part of the canal.
*The coronal two third were prepared, again,
mainly by reaming.

9. *Determine working length and
select the initial apical file.
*Do circumferential filing by applying
lateral pressure and then with
drawn.
*Increase the apical constriction 2 to
3 files sizes more than initial apical
file but with the same working
length.

10. *Chances of loss of working length due to accumulation of
dentin debris.
*Does not take in to consideration the elliptical forms and large
diameter of root canals.
*Obturation with this techniques dose not provide adequate
sealing of root canal confines specially in curved canals .
*Passage of irrigants and medicaments
is not adequately obtained through the
root canals.
*Increased incidence of ledging, zipping
and perforation in curved canals.

12. *Weine, Martin, Walton, and Mullaney were early advocated of the step
back in 1969. also called telescopic or serial root canal preparation.
*The essence of this technique is preparation of the a distinct apical
stop and to over come the problem of the curved root canal.
*Its divided in to two phases;
Phase I Is the apical preparation .
 Phase II is the preparation of the remainder of the canal.
The completion of the preparation is the refining phases IIA and IIB to
produce the continuing taper from apex to cervical portion of the
canal.

13. Phase I
*Is the apical preparation starting at the
apical constriction.
*The apical region is first inserted with initial
apical file (IAF) which is a fine instruments
tapered stainless steel file ( Nos 10,15, 20
or 25)
*Then it should be enlarged at least three
sizes more than the IAF for four reason:
1. To remove bacteria and there substrates.
2. To remove dead pulp tissue.
3. To increase the capacity of root canal to
retain the larger amount of sterilizing
agent.
4. To prepare the root receive the canal
filling

14. Phase II
Phase II is the step back preparation,
which is achieved by increasing the
size of files and by decreasing the
length, that is, by using Nos 30, 35,
and 40 files of 1, 2, and 3mm
short of working length to produce a
coronal taper.
In between placing each larger
instruments, the master apical file is
inserted to the working length to
clear out any debris collecting in the
apical part of the canal; this is
referred to as

15. Refining phases IIA and IIB
of midcanal
*Ones the apical preparation is
complete, use of Gate-Glidden
drills for initial enlargement of the
coronal part of root canal.
*Then use small Gates-Glidden drills
to prepare the mid root level

16. *Finally use Hedstroem files to flare
the apical part.
*RECAPITULATION ; Again the
Nom 30 file should be used
between each steps to maintain
the apical preparation.
*This preparation allows an
adequate amount of coronal space
in the root for lateral compaction.

17. *Gates-Glidden Drills are side
cutting instruments with
safety tips. They can be used
with both crowns down as
well as step back fashion to
enlarge the coronal third of
the canal during endodontic
treatment.
*used with handpiece
*Different sizes , 6 sizes (#1 -
#6) coded by rings or colored
bands on shank.

18. *slightly flexible and will follow the canal
shape but can perforate the canal if used
too deeply.
*Should be used only in the straight sections
of the canal.

19. Advantages of step back
*Proper apical stop
*Less chances of apical transportation
*Greater flare coronally
Limitations
*Debris extruded will block the canal
*Loss of working length
*Tendency to straiten the canal
*Time consuming.

20. *Modified step back
• Ones the apical preparation is completed,2-3 mm of the
apical portion of the canal is prepared with the MAF. Step
back procedure begins from the 3mm short of the apical
constriction.
• Gives almost a parallel cylindrical retention form to
primary gutta-percha point.

21. *

22. *introduction
Extrusion of canal contents during instrumentation
has shown to cause postoperative discomfort and
delayed healing. This problem was found with
most of instrumentation techniques.
To withstand this problem a different approach
called the coronal to apical approach was
introduced which advocated shaping the coronal
aspect of a root canal first before apical
instrumentation commented.

23. *
* the pulp chamber filled with irrigant or lubricant now canal is
penetrated using Hedstroem files of sizes nos. 15, 20 and
25,the working length can be established at this time.
* The coronal thirds of the canal is then flared with Gates
Glidden drills nos. 2 and 3 and no.4 are used sequentially
shorter, thus, flaring the coronal segment of the root canal.
*This followed by apical instrumentation using a descending
file sequence, progressing 1mm per consecutive instrument,
apically. Its important to recapitulate with no.25 file to
prevent blockage.
*Note; The apical portion of the canal prepared by enlarging
the canal at the corrected working length 2-3sizes at least in
order to get clear dentin.

25. *
*Permits straighter access to the apical region.
*Eliminate coronal interference which allows
better determination of apical canal sizes.
*Removes bulk of tissue and microorganisms
before apical shaping.
*Allows deeper penetration of irrigants.
*The working length is less likely to change.
*Less amount of necrotic debris could be
extruded throw the apical foramen.
*Less chance of zipping near the apical
constriction due to increased in the access
opening.

26. *
*More time consuming than the step back
technique.
*Excessively flared preparation in the coronal
and middle thirds may weaken the tooth and
create problems.
*If large, less flexible rotary instruments are
used too rapidly and deeply in the root canal, a
ledge may form.
*In canals that curve severely the rotary
instruments cannot be precurved.

27. *
*Marshall and Pappin advocated a “Crown-Down
Pressureless Preparation” which involves early
coronal flaring with Gates-Glidden burs, followed by
incremental removal of dentin from a coronal to
apical direction, hence the term “crown-down”.
*Straight k – type files are used in a large to small
sequence with a reaming motion and no apical
pressure, thereby “Pressureless”
*This technique resulted in a rounder canal shape
when compared to usual step back technique.

29. *
*In this technique a combination of step-back and
crown-down preparation is used.
*Both rotary and hand instruments are used to
prepare the canal.
*Check the patency of canal using number 10 or 15 k
flex files.
*Prepare the coronal third of canal using hand or
Gates-Glidden drills till the point of curveture
without applying excessive pressure.
*Determine the working length.
*Prepare the apical portion of canal using step back
technique.

30. *Recapitulate and irrigate the canal at every step so as to
maintain patency of the canal.
*Blend step back with step down procedure.
Advantages
*Less chances of ledge formation.
*This technique maintains the integrity of dentin by
avoiding excessive removal of radicular dentin.

31. *It was introduced by Fava.
*In this, canal is explored using a small file. Then
prepared in crown-down manner using k files in
decreasing sizes.
*After this, step back technique is in 1mm increments
with increasing file sizes.
*Frequent irrigation and recapitulation using master
apical file is done during instrumentation.

32. Indications
*Straight root canals.
*Straight portion of curved canals of mature teeth.
Contraindications
*Calcified canals.
*Young permanent teeth.
*Teeth with open apex as they have thin
dentinal walls and great pulp volume.

33. *In this, preparation was commenced in the coronal part
of the root canal.
*A #40 Flex R file was instrumented in the straight part of
the canal , using the balanced force technique.
*Sequentially, larger sizes of files were used to instrument
the straight part of the canal using the balanced force
technique and the coronal 4 to 5 mm of root canal was
instrumented with Gates-Glidden drills.
*A #20 Flex R file was taken to the working length and the
canal prepared using the balanced force technique by
sequential use of files.

34. *Preparation at the working length was continued
until clean dentin was removed, the master
apical varying between #40 and #45.
*A step back technique using balanced forces was
then used to prepare the remaining curved
portion of the canal

36. *This technique was developed by Roane and Sabala in
1985.It’s involves using blunt-tipped files.
*The balanced force technique recognizes the fact that
instruments are guided by the canal walls when rotated.
*Since the files will cut in both a clockwise and
anticlockwise rotation, the balanced force concept of
instrumentation consists of placing the file to length and
then a clockwise rotation (less than 180 degrees) engages
dentin.
* This is followed by a anticlockwise rotation (at least 120
degrees) with apical pressure to cut and enlarge the
canal.
* The degree of apical pressure varies from light pressure
with small instruments to heavy pressure with large
instruments

37. *. The clockwise rotation pulls the instrument into the
canal in an apical direction. The anticlockwise cutting
rotation forces the file in a coronal direction while
cutting circumferentially.
* Following the cutting rotation the file is repositioned
and the process is repeated until the corrected working
length is reached. At this point a final clockwise
rotation is employed to evacuate the debris.

38. *With the help of this technique, there are lesser
chances of canal transportation.
*One can manipulate the files at any point in the canal
without creating a ledge or blockage.
*File cutting occurs only at apical extent of the file.
*Extrusion of material is less than with other
techniques.

39. References
Textbook of Endodontics
Anil Kohli
Endodontics, Volume 1
Ingle, Bakland