Anticurvature filling technique should be known by everyone as it prevents breaking of instruments into the canal and it helps to do instrumentation in the narrow canals

1. ANTICURVATURE FILING
TECHNIQUE
DR Aman Sachdeva
3rd PG
DEPT OF CONS AND ENDO

2. CONTENTS:
 INTRODUCTION
 ANTICURVATURE FILING
TECHNIQUE
 CONCLUSION
 REFERENCES
danger
zone

3. INTRODUCTION
• The preparation of curved and narrow root canals presents a special challenge to the
dentist.
• Many procedural errors, such as ledge formation, loss of root length, perforation and
stripping of the canal walls, instrument fracture, and overfills and underfills, can occur
during the preparation of root canal therapy.
• The purpose of anticurvature filing is to file the bulkier root structure away from the
curvature and thinner danger zone.

4. Apical stop. The apical limit of the root canal preparation located within 1
mm from the radiographic apex to confine the filling material during the displacement
and filling process.
Anticurvature filing. The controlled and directed preparation into the bulky or safety
zones and away from the thinner portions or danger zones of the root structure where
perforation or stripping of the canal walls can occur.
Stripping. Thinning of the dentin to the cementum
border, which can develop into a perforation.
Definition of terms:

5. Danger zone. The thin area in the root canal wall that is vulnerable to stripping by
injudicious filing .
Ledge is an artificially created
deviation of the root canal
wall that prevents the
passage of an instrument to
the apex of an otherwise
patent canal
Zipping is defined as the
apical transportation
of a curved canal caused
due to improper
Shaping technique.
Elbow is the narrowest
portion of the zipped
canal.

6. Circumferential filing involves working
files progressively around all the walls of the
canal. It is used to ensure that the maximum
area of dentine is instrumented.
Over-zealous filing, however, can result in
perforation.
Even with overlapping file strokes it is
unlikely that all the surfaces of the canal will
actually be instrumented.
Anticurvature filing involves filing preferentially
towards the outer curve of the root canal, away from
the furcation, to avoid strip perforation.
For example the buccal, mesial and lingual walls of the
mesial canals of a mandibular molar would be filed more
than the distal wall during coronal flaring, with
more strokes on each of these walls in a ratio of 3:1
Lim and Stock suggested this
method as a substitution for
circumferential filing so that the wall
toward the depression receives
decreased rasping action
Weine

7. • THE NEED FOR ANTICURVATURE FILING:
• The anatomy of the root canal, curvature direction, and canal diameter should be carefully
analyzed before access and canal preparation.
• The original internal morphological design of the canal should be modified to produce the
proper canal design, condensation space, and apical stop to obliterate the canal and
prevent perforations of the canal walls.
• In round and nearly straight roots, in which the canal is centered in the root, wall
thicknesses are approximately equal in the buccolingual and mesiodistal cross sections, and
circumferential filing can be used.
• In curved canals, anticurvature filing is necessary to prevent perforation and weakening of
the root structure by stripping.
• Anticurvature filing is based on radiographic and topographic analysis of the root and root
canal anatomy.

8. Schematic drawing of root canal preparation by
anticurvature filing shows modified
direct access to apex, avoiding thinner danger
zones, and definitive apical stop and displacement
space for care of filling with gutta-percha.

9. Note the concavity
(arrows) in the
furcation area of this
mandibular molar.
The furcal region of
molars at the level of
the curvature (danger
zone) is a common site
for stripping perforation.

10. • The curved canal should be straightened as much as possible to ease the cleaning,
designing, and filling of the apical third.
• In an extreme apical curvature, the canal is straightened as close as possible to the point
of apical curvature.
• The wall thickness of curved canals can be irregular and variable.
• In the buccolingual or mesiodistal directions, circumferential filing could be hazardous .
• The danger of perforation is greater as preparation is performed to larger sizes.

11. The anticurvature filing method to prepare the curved root canal
Marwan Abou-Rass et al
• Canals are often not centered in
mesial roots of maxillary and
mandibular molars; instead,
they are located closer to the
furcation.

12. The anticurvature filing technique.
Instruments are directed away from the furcal “danger
zone” toward the line angles (safety zone) where the
bulk of dentin is greater.
Anticurvature filing is advocated during coronal flaring
procedures to preserve the furcal wall in the treatment
of molars.

13. 1) Descriptions by Weine et al.
illustrate the tendency of the instrument to move to the outer wall.
They describe the movements by identifying the "elbow" (narrowed portion of the
canal near the middle Portion of the curve) and the "zip" (ever-widening tear dropped
shape of the apical foramen).
Schilder (2) also describes the instrument movement when he
discusses "foramen transportation taking two forms, namely the
development of an elliptical or teardrop foramen, and outright root
perforation.“
Mullaney (3) describes the step-back procedure and
maintains the curvature by keeping the apical preparation
small and gradually enlarging the canal coronally.
Phase I is the
apical preparation
starting at the apical
constriction.
Phase II is the preparation of the
remainder of the canal, gradually
stepping back while increasing the
instrument size.

14. Goerig et al. (5) describe the step-down technique where a gradual
enlargement is accomplished from coronal to apical, thereby minimizing the
coronal interferences and allowing reduced pressure for apical preparation.
Roane et al. (6) use a rotation force to center the
instrument in the canal minimizing the outer wall forces.
(Balanced force technique)
Abou-Ross et al. (4) describe the anticurvature filing preparation which
keeps the preparation away from the inner curvature near the furcation
and reduces the degree of total canal curvature by anticurvature
enlargement coronally.
Instrumentation of Curved Canals Using a Modified
Tipped Instrument: A Comparison Study

15. ACCESS PREPARATION:
• A well executed access preparation makes it easier to locate all canal orifices and to
facilitate the preparation stage.
• To prepare the apical stop with the anticurvature filing method, the access outline and
extension may have to be modified.
• Clinically, the access outline may have to differ from the traditional geometric forms; an
accurate access outline should blend smoothly into the pulp chamber.
• It should include the total removal of the pulp chamber roof and all pulp horns and
provide, as much as possible, a direct and unobstructed approach to each canal.
• The access preparation is never static and should be altered as necessary to provide
convenience for root canal preparation.

16. The lip of dentine is removed with Gates-Glidden
burs during coronal flaring or with special ultrasonic
tips, giving better straight-line access.
The completed access cavity
Crown-down preparation

17. Straight-line access can result in stripping perforations in the furcal areas of molars
The use of large Gates-Glidden drills and over preparation
has resulted in the stripping perforation.
the perforation is in the
concavity of the furcation.
Endodontics principles and practice

18. RADIOGRAPHIC AND FUNCTIONAL CONSIDERATIONS.
• The root anatomy and morphology is all-important in the planning and execution of root
canal preparation.
• The practitioner should maintain digital and directional control over the endodontic
instrument when performing the following steps:
—The danger zone where the walls are thin is located.
—To minimize torquing of the endodontic instrument, a functional access opening that
allows for as much direct and unobstructed access to the apical stop level as possible is
made.
—A radiograph of the region with a size no. 15 file in place should be examined to determine
the torque of the instrument generated by the canal.

19. Direction of initial
instrument in place
Allison et al. indicate that
preparation size/design has an influence
upon the final seal.
They found that the best seal was
achieved when a stepback preparation
was used.
Roane described the technique
termed "the balanced force concept"
The "Balanced Force" Concept for
Instrumentation of Curved Canals
Roane

20. This will disclose the degree of canal curvature and indicate where the filing should be
directed.
—The endodontic instruments are curved to ease insertion and negotiation of the canal.
—The curved canal is progressively and directionally filed away from the thin areas and done
towards the region where bulky tooth structure is present.
If the curve of a root is to the distal, the canal is filed mesially, buccally, and lingually.
—Overzealous circumferential filing and restricted access openings should be avoided, as
they lead to perforation or stripping.
—Evaluation of radiographs and frequent irrigation during the procedure, and the use of
sharp instruments will ease the preparation.

21. • Stripping perforations occur primarily during
use of the Gates-Glidden drills .

22. Anti curvature filing directs preparation into bulky portions away from thinner
zones of root to avoid perforation or stripping of canal wall.
The anticurvature filing method to prepare the curved root canal
Marwan Abou-Rass et al

23. • The canal orifice may be enlarged using a suitable rotary instrument such as a no. 1
or a no. 2 Peeso reamer.
• To prevent this procedural
error, the Gates- Glidden
drills should be confined to
the canal space coronal to
the root curvature and used
in a step-back manner.
It also incorporates coronal flaring with rotary instruments
after the use of hand instruments, but it is stated that such
instruments should not be introduced more than 3 mm
into root canals.
The final use of a manual instrument to blend
the apical and coronal segments was
advocated.
‘‘coke bottle’’ configurations
that occur when inflexible engine-
driven instruments
such as GG or Peeso drills are
advanced past the middle
root canal third
Ingle’s endodontics

24. coke bottle’’ configurations
The excessive wear of coronal
dentin also increases the risk of
vertical root fractures in safety
zones.

25. Abou Rass,
Glick, and
Frank
anticurvature filing
to prevent excessive
removal of dentin
from thinner root
sections in curved
canals.
The underlying observation was that the
furcation side (danger zone) of cross sections
of mesial roots of mandibular molars has less
dentin thickness than the mesial side (safety
zone). the use of precurved hand files that
were purposefully manipulated to file
the canal away from the danger zone.
Ingle’s endodontics
Summary

26. Kessler et al. as well as Lim and
Stock demonstrated that
‘‘anticurvature’’ filing in fact
helped to reduce the risk of
perforation.
These files had cutting edges that were
flattened and thus dulled at one side and
were therefore believed to remove less
material in one direction.
However, subsequent research showed
that Safety Hedstrom files when used as
engine-driven versions are in fact not safe
but tend to create preparation errors.
Later, Safety Hedstrom files (Kerr/Sybron,
Romulus, MI) followed a similar concept,
namely filing away from the danger zone.
Ingle’s endodontics

27. Determination of canal path and
anatomical points (IC, CPP, PL, and MP);
Grid overlapping the mesial root
Morphometric evaluation and planning of
anticurvature filing in roots of maxillary
and mandibular molars -Maria et al
IC - initial path of the root canal;
CPP -critical penetration point of the file in the
canal;
MP - maximum canal projection; and
PL - periodontal root limit
pre-determined anatomical points on
teeth to establish directions for
proper implementation of the technique.
will prevent excessive filing of the root
structure.
(CPP) represents the initial curvature of the
root canal path, in which endodontic
instruments find the first obstacle.
(MP) represents the maximum vertical
limit for the orientation of filing on the
outer walls of the root canal

28. Simulated straight access filing (SF); Simulated conservative filing (CF). Remaining dentin in
the safety (RSZ) and danger (RDZ) zones (*yellow arrows),
and areas of dentin removal in the root (*blue triangle)
and in the crown
Morphometric evaluation and planning of
anticurvature filing in roots of maxillary and
mandibular molars -Maria et al
Filing extension until the maximum
projection of the canal (MP) is suggested
the greater the distance
between CPP and MP points,
the higher the root dentin area
removed

29. Crown-down
preparation
technique
A hand-filing technique with
precurved files:
Goerig et al (1982).
Stepdown Modified Double
Flare
• Precurving Files
• Initial Coronal Flare
• Apical Preparation
• Apical Flare
(Stepback)
A technique that uses the balanced force
instrumentation action
Roane -1985
Saunders and saunders -1992
• Coronal preparation
• Preparation of apical section
• Apical flaring(Stepping
Back)

30. Canal transportation is less likely
when a Crown-down preparation technique
is used
If the canal is to be prepared with hand
instruments, better results are achieved
with a reciprocal technique, such as the
Balanced-force technique, rather than
with a filing action
stainless steel files -triangular
cross-section-Flexofile
NiTi files are most effective.
non-cutting tip
Recapitulation
Harty’s endodontics in clinical practice
(Roane et al 1985)
This instrumentation technique uses clockwise/
anticlockwise rotational motion to remove dentine
with flexible stainless steel files or nickel-titanium
files .
It is useful for rapidly removing dentine in curved
canals whilst maintaining curvature (files are
not precurved).

31. Listen for a 'click' as a bite of dentine is removed
(the control phase).
Greater Taper files are manufactured from nickel-titanium
and have to be used with a reverse balanced force action
Merging
The apical and coronal preparation should merge into one
another in a gradual smooth taper.
Endodontics problem solving in clinical practice

32. This technique has been used since the
1980s, first with hand instruments and
Gates-Glidden drills and later with
rotary instruments.
However, recent studies have shown that
there is no reduction in the perforation risk
in danger zones (furcal region) when
anticurvature filing is performed, even with
Nickel-Titanium (NiTi) rotary systems.
Instruments with a symmetrical
triangular cross section and pilot tips
(e.g., Flex-R files

33. CONCLUSION:
• The anticurvature filing method maintains the integrity of canal walls at their thin
portion and reduces the possibility of root perforation or stripping.
• With this method, the dental practitioner maintains digital control over the endodontic
instrument, and the preparation of the curved canal is eased.

34. The anticurvature filing method to prepare the curved root canal
Marwan Abou-Rass et al
Instrumentation of Curved Canals Using a Modified Tipped Instrument: A Comparison Study
Clyde L. Sabala et al
Ingle’s endodontics
Endodontics principles and practice
Morphometric evaluation and planning of anticurvature filing in roots of maxillary
and mandibular molars -Maria et al
REFERENCES:

35. The "Balanced Force" Concept for Instrumentation of Curved Canals
James B. Roane
Harty’s endodontics in clinical practice
Endodontics problem solving in clinical practice
Weine endodontic therapy