1. SELF ADJUSTING FILE
K.OHM NIJANDHAN

2. SYNOPSIS
INTRODUCTION
NICKEL - TITANIUM ROTARY INSTRUMENTS
SELF ADJUSTING FILE DESIGN AND OPERATION
MECHANICAL ANALYSIS OF SAF
CHALLENGES: CURVED AND NON – ROUND CANALS
BACTERIOLOGIC CONSIDERATIONS
REMOVAL OF SMEAR LAYER IN THE APICAL PART OF THE CANAL
HISTOLOGIC CONSIDERATIONS
ROOT CANAL OBTURATION OF SAF PREPARED ROOT CANALS
CONCLUSION

3. INTRODUCTION
The cleaning and shaping of the root canal system is an important objective of
root canal treatment.
- Baugh et al 2005
- Bartha et al 2006
 Original root canal path should be maintained and the root canal wall dentin
should be cut circumferentially so that prepared root canal wall outline reflects
the original outline.
- Baugh et al 2005
 The goal of instrumentation is to provide a continuously tapered preparation
that maintains original root canal anatomy, keeping the foramen without any
ledge and transportation from the original canal curvature.
- Carvalho et al 1999
- Matwychuk et al 2007

4. Variety of instruments are available for the root canal instrumentation. For
many years, hand files are the most commonly used for endodontic
instruments.
- Walton et al 1996
Traditionally, this group of instruments has been manufactured from
stainless steel and comprises two basic designs, the k-type instruments (k-
files and k-reamers) and the hedstrom file .
- walton et al 1996
- Wein et al 1996
Although almost all these instruments were designed between many years
ago, important changes have introduced in recent years with regard to their
quality, efficacy, and standardization .
- Leif et al 2003
 Nickel-titanium instruments for manuel and rotary use have been
developed during the last decade
- Yoshmine et al 2005

5. However, the cleaning, shaping, and disinfection of canals that are flat and
oval-shaped in cross-section, as well as curved canals, represent a
significant clinical challenge to endodontic treatment.
These canal configurations represent about 25%- 50% of root canal
systems.
- wu M-K et al 2003
Many enhancements have resulted in better cleaning and shaping, but
investigations using digital subtraction micro-CT and microbiologic
assessments have shown our ineffectiveness to adapt to the true cross-
sectional shape of all but the most round root canals, leaving almost half of
the canal walls untouched by endodontic instruments.
- peters et al 2011
Until the recent introduction of “adaptive” cleaning/shaping instrument
technology, the basic tenets of endodontic treatment have been
unattainable.

6. NICKEL – TITANIUM ROTARY
INSTRUMENTS
Since the early 1990s, several endodontic instrument systems
manufactured from nickel titanium have been introduced into
endodontic clinic practice.
The specific design characteristics vary, such as tip sizing, taper,
cross section, helix angle, and pitch.
 To date, several devices and methods have been used to perform
endodontic treatment.
The specific design characteristics vary, such as tip sizing, taper,
helix angle, cross section and pitch.

7. In flat oval root canals ,rotary file system may be difficult to
instrument the entire wall of oval canals and often fail to adequately
clean and shape the canal.
The self adjusting files which a new concept in cleaning and shaping
was developed to overcome the inherent remaining problems of the
nickel titanium instruments.

8. SELF ADJUSTING FILE DESIGN AND
OPERATION
Self adjusting file which is a hollow file designed is a
novel system among the nickel titanium files
operating in a different manner.
It adapts itself to the canal original anatomy and
shape ,longitudinally to a curved canal as will all
rotary nickel titanium files especially adapts itself to
the cross section of the canal providing a 3D
adaptation .
SAF is a hollow file designed as a compressible ,thin
walled pointed cylinder either 1.5 or 2.0 mm in
diameter composed of 120 micro meter thick nickel
titanium lattice composed of a thin derivate of nickel
titanium lattice with high torsional and fatigue
resistance.

9. The 1.5 mm and 2.0 mm files may easily be compressed to the
extent of being inserted into canal previously prepared or negotiated
with a #20 k-file and #30 k file.
The lattice surface is slightly abrasive and it allows removing dentin
with back and forth grinding motion
The file attempts to regain its original form and it continues to apply
aperpetual delicate pressure on the root canals.
Its operated with vertical vibrating handpieces with 3000 – 5000
vibrations/min with 0.4 mm amplitude .

10. The hollow design allows for continuous irrigation
throughout the procedure .
The irrigation I performed continuously during the procedure
using a VATEA irrigation unit where its attached by a silicon
tube to the irrigation hub on the shaft of the file and it
provides low pressure irrigation at a flow rate of 1-10
ml/min.
The SAF is operated in 2 cycles of 2 minutes each for a total
of 4 minutes per canal.
The procedure is reported to remove a uniform dentin layer
60 to 75 mm thick from root canal circumference .

11. Irrigation protocol
•First 2 min – sodium hypochlorite 3% at 5ml/min
•Next 2min – EDTA 17% 5ml/min
•Last 0.5 min – EDTA 17% without vibration i.e
manual agitation
•Final rinse – sodium hypochlorite 3% ,5ml to
remove the excess EDTA
•SAF file is extremely durable.
According to ADA, SAF can be rotated for more
than 150 hours at 900 rpm with a 5-mm
deflection with no mechanical failure.

12. MECHANICAL ANALYSIS OF SAF
Compressibility of the SAF force applied as a
•result of compression,
•surface roughness,
•abrasivity test,
•durability (torque test,
•ADA cyclic fatigue test,
•free buckling fatigue test,
•functional fatigue-to failuretest),

15. RESULTS OF EXPERIMENTAL TESTS
Compressibility of the SAF
•The apical 2 mm of the file could be compressed into a 0.25-mm hole.
•The compressible diameter gradually increased in size, with its compressed dimensions comparable to those of
an ISO #20 file
Force applied as a result of compression
•SAF files inserted into channels of smaller dimensions applied higher forces in response .
• In a channel with a 0.25-mm diameter, a force of 300 g was recorded.
•With increasing diameter of the canal, the force declined; at a canal diameter of 0.5 mm, it was only 150 g.
Surface roughness
•2.8micro meter +/ -10%.
Abrasive test
•Most of the dentin removal occurred within the first 2 minutes of operation (3+/-0.02 ISO sizes), with a slower
removal of dentin thereafter for a total of 3.5 +/- 0.01 ISO sizes by the end of 4 minutes.

16. Durability
•Torque test:
•the SAF could be turned 7 x 360deg before separation.
•The SAF’s torque durability was 29.7 +/- 3.2 g/cm.
•Free buckling fatigue test:
•The SAF files endured 600,500 (+/- 15,800) buckling cycles before
•the first sign of mechanical failure appeared.
•This is equivalent to approx. 120 minutes of operation at 5,000 vibrations per minute.
•Functional fatigue to failure test
•When tested in standardized conditions, the first mechanical fatigue failure was detected after 29.1 (+/-
1.2) minutes .
•A typical failure was detachment of one of the arches at one of its connection points to the longitudinal
beams .
• Rarely did a strut or a longitudinal beam detachment occur.
• In no case was there a full separation of the SAF file.
SAF degradation as a function of W/T
•Prolonged use gives less efficiency
•No extrusion of irrigants seen.

17. The SAF file may be elastically compressed considerably from a diameter of 1.5 mm to dimensions resembling those
of an ISO # 20 K-file because of the special design of the file.
The SAF file creates circumferential force when initially compressed.
The rough surface, combined with the force and the in-and out vibrational mechanism, allows for the removal of
dentin by filing.
The circumferential force and the ability to remove dentin decreases as the diameter of the canal enlarges.
If the file is reused, the ability to remove dentin declines.
The SAF file is mechanically durable for continuous operation for 29 minutes.
SAF application does not push the irrigant beyond the apical foramen.

18. STRESS GENERATION DURING SELF-ADJUSTING FILE MOVEMENT:
MINIMALLY INVASIVE INSTRUMENTATION (JOE 2013)
•The SAF induced the lowest von Mises stress concentration and the lowest tensile
principal stress component in root dentin.
•The calculated stress values from ProTaper Universal F1 and ProFile #20/.06 were
approximately 8 to 10 times bigger than that of the SAF.
CONCLUSION:
•Stress levels during shaping and the susceptibility to apical root cracks after shaping
vary with instrument design.
•The design of the SAF may produce minimal stress concentrations in the apical root
dentin during shaping of the curved canal, which may increase the chance of
preservation of root dentin integrity with a reduced risk of dentinal defects and apical
root cracking.

21. Eight Months of Clinical Experience with the Self-Adjusting
File System -Michael Solomonov (JOE 2011)
• One may then advance to clinical use in 10 incisors and then 10 premolars, and only then
should the newly gained skills be applied to molar endodontics.

22. Flat-oval root canal preparation with self-adjusting file instrument: a
micro-computed tomography study.
Versiani et al (JOE 2011)
• In the coronal third, mean increases of area and volume of the canal as well as the
percentage of prepared walls were significantly higher with SAF than with rotary
instrumentation.
• By using SAF instruments, flat-oval canals were homogenously and circumferentially
prepared.
• The size of the SAF preparation in the apical third of the canal was equivalent to those
prepared with #40 rotary file with a 0.02 taper.

23. BACTERIOLOGIC
CONSIDERATION’S
The ideal microbiological goal of chemomechanical debridement is to completely
eradicate intracanal bacterial populations and their toxins.
Bacteria (e.g., E. faecalis) persisting after chemomechanical procedures at levels
detectable by culture-dependent techniques have been shown to increase failing
endodontic treatment outcomes.
Therefore, the main effort should be to maximize root canal disinfection before
obturation.
Unfortunately, anatomic complexities may impede thorough root canal
disinfection.

24. In a recent investigation by Siqueira et al, 44 single-rooted
teeth with oval root canals were analyzed in vitro after the
main canal spaces were first contaminated with E. faecalis.
•After the use of rotary files with syringe irrigation, 55% of the samples had
positive bacterial cultures whereas those canals cleaned and shaped with SAF
Endo System had only
•20% positive canal cultures remaining, again reinforcing the efficacy of the
SAF Endo System over rotary files.
•If the area of dentine contacted is more with SAF which could result in an
increased volume of infected dentine removed from the root canal walls.
• Solomonov et al. 2012
• De Melo Ribeiro et al. 2013
•This infected dentine is suspended in the irrigant thus increasing the
quantum of planktonic bacteria.

25. BASED ON POSTOPERATIVE PAIN
POST INSTRUMENTATION PAIN AFTER THE USE OF EITHER
MTWO OR THE SAF SYSTEM. A RANDOMIZED CONTROLLED
CLINICAL TRIAL (IEJ 2016)
•Teeth with pulpal necrosis had significant pain at 8 hours compared to teeth
with vital pulps.
•Teeth with vital pulps in the SAF group had significantly less post
instrumentation pain compared to the Mtwo group at 6 hours.
•Patients with teeth with non-vital pulps in the SAF group experienced more
post-instrumentation pain at 8 hours and 24 hours .

26. REMOVAL OF SMEAR LAYER IN
THE APICAL PART OF THE CANAL
Besides causing potential peri radicular infection and inflammation, remaining soft-tissue remnants smeared
together with inorganic debris in the canal will prevent adequate adaptation between the canal wall and root-
canal obturation materials.
The intimate adaptation of the SAF instrument to the canal walls and the continuous flow of irrigant,
especially for oval and irregularly shaped canals, is the primary benefit of the SAF system.
In a study Metzger (2010) to evaluate the removal of canal debris and smear layer with the SAF, single-rooted
human teeth were evaluated using a scanning electron microscope (SEM).
Similar to hand and rotary instrumentation, the SAF System produced a smear layer when using 3% sodium
hypochlorite alone; but when alternated with the application of 17% EDTA, the canals were rendered virtually
free of debris and smear layer, with the most pronounced benefit realized in the apical third of the root canal

27. Supplementary Steps for Removing Hard Tissue
Debris from Isthmus-containing Canal Systems
(Ali Keles JOE 2016)
•In the experimental groups, the mean percentage reduction of AHTD ranged from 29.15%-39.90% after the irrigation protocols, with no statistical
difference between groups

28. HISTOLOGIC CONSIDERATIONS
Infected dentin, soft tissue, and bacterial biofilm can cover an enormous portion of the inner surface of the
root canal system and their removal can challenge even the most assiduous cleaning and disinfection protocol.
It has been well documented that the assessment of canal morphology and the true extent of tissue removal
and quality of obturation cannot be accomplished by evaluation of two dimensional bucco-lingual radiographic
projections.
Oval and flat-shaped canals occur in approximately 25% of teeth.

29. In a recent investigation, De-Deus, et al (personal communication, 2011) histologically evaluated 12
pair-matched vital mandibular canines slated for extraction whereby the canal spaces were prepared
with either the SAF System or rotary-file instrumentation.
Only teeth with vital pulps and oval-shaped root canals were included.
The SAF System was found to reduce the amount of remaining pulp tissue by 57% compared to
conventional rotary files.
In addition,21% of the rotary file prepared canals still contained pulp tissue remnants.
The investigators concluded that sodium hypochlorite irrigant, applied with syringe and needle, failed
to compensate for the inadequate cleaning by the file itself

30. ROOT CANAL OBTURATION OF SAF
PREPARED ROOT CANALS
In a study METZGER 2010 comparing the obturation efficacy between canals cleaned and
shaped with rotary files and the SAF system, lateral compaction of gutta percha cemented with
AH26 was evaluated.
The results revealed the SAF system allowed as much as 83% of the canal wall to have intimate
contact with the obturation material compared to only 55% for rotary files.
The efficacy of the Self-Adjusting File versus WaveOne in removal of root filling residue that
remains in oval canals after the use of ProTaper retreatment files: A cone-beam computed
tomography study. Pawar AM (JCD 2016)
•When SAF was used after ProTaper retreatment files, significantly less root filling residue was left in the canals compared to
when WaveOne was used.

33. BASED ON PATENCY MAINTENANCE
Patency process is reported to displace apical debris into the
irrigating solution thus decreasing the chance of extruding debris
apically.
•Lambrianidis et at. 2001
•Vera et al. 2012.
Arias et al. (2009) reported that apical patency has no influence
on post-operative pain.

34. BASED ON SAF FILE RETRIEVAL
SELF-ADJUSTING FILE (SAF) SEPARATION IN CLINICAL USE: A
PRELIMINARY SURVEY AMONG EXPERIENCED SAF USERS
REGARDING PREVALENCE AND RETRIEVAL METHODS (JCD 2015)
•A total of 2517 SAFs had been used by these operators, and 15 cases of file
separation were reported (0.6%).
•Twelve of these 15 separated files could be retrieved within a few minutes using
Hedstrom files, with no additional dentine removal required.
•In the three cases in which the separated files could not be retrieved, the
separated file segment was successfully bypassed.

35. BASED ON ENDOTOXIN REDUCTION
IN RETREATMENT CASES
Influence of apical enlargement and complementary canal preparation with the
Self-Adjusting File on endotoxin reduction in retreatment cases (IEJ 2016)
•After root filling removal, endotoxin was detected in 100% of the root canals (S1, 4.84 EU mL 1).
•CMP with the R25 file was able to significantly reduce endotoxin levels (P < 0.05).
•Apical enlargement protocols were
•effective in significantly reducing endotoxin levels.
•Complementary preparation with the SAF system failed to eliminate residual endotoxin contents
beyond those obtained with the R40 instrument. Increased levels of endotoxin removal were
achieved by apical preparation with the R40 file (P < 0.05).
•Complementary CMP with SAF did not significantly reduce endotoxin levels (P > 0.05) following
the use of the R40 instrument

36. APICAL EXTRUSION OF DEBRIS BY SUPPLEMENTARY FILES USED FOR
RETREATMENT: AN EX VIVO COMPARATIVE STUDY.
PAWAR AM (JCD 2016)
SAF results in less extrusion of debris when used as
supplementary file to remove root-filling residues, compared to WO
and PTN

37. MICROCRACKS
Dentinal microcrack formation during root canal preparations by
different NiTi rotary instruments and the self-adjusting file. (JOE
2012)
• The control, HF, and SAF groups did not show any microcracks.
• In roots prepared with the HS, RS, TF, and PT, dentinal microcracks were observed in
60%, 25%, 44%, and 30% of teeth, respectively.
• There was a significant difference between the control/HF/SAF group and the 4 NiTi
rotary instrument groups (P < .0001).
• However, no significant difference was found among the 4 NiTi rotary instruments

38. Evaluation of radicular dentin erosion and smear layer removal capacity of Self-
Adjusting File using different concentrations of sodium hypochlorite as an initial
irrigant. (OOOE 2011)
•The results showed no significant difference in smear layer removal among different
concentrations of NaOCl and among the regions.
•Clean dentin surfaces were observed in 80%, 70%, and 70% with a score of 1 or 2 of the apical
thirds using 1.3%, 2.6%, and 5.25% NaOCl, respectively.
•The 1.3% and 2.6% NaOCl solutions showed similar erosion patterns on the root canal walls (P >
.05); however, 5.25% NaOCl caused severe erosion.
•When using the SAF with continuous irrigation and vibration, lower concentrations of NaOCl and
EDTA can be recommended for efficient clinical removal of the smear layer even in the apical
thirds and to avoid excessive erosion of root dentin.

39. STIMULATION MODEL
EXPERIMENTS
DEFORMATION OF THE SELF-ADJUSTING FILE ON SIMULATED
CURVED ROOT CANALS: A TIME-DEPENDENT STUDY (OOOE
2011)
•The lattice detachment began at the second period for both groups and
continued to increase along with the ongoing testing time.
•The detachment that occurred in 60° canal curvature was higher at the third and
fourth periods when compared with the 45° group .
•For both groups, during the third period, detachment of the arch of the lattice
was only one sided; however, this deformation was severe between the fourth
and sixth periods with a 2-sided detachment, which was easier to separate.
•The rough surface became smooth after usage.
• No full separation of the file was evident for both groups.
CONCLUSION:
•In multirooted teeth with severely curved root canals, using more than one self-
adjusting file might be recommended to prevent lattice detachment.

40. A COMPARATIVE STUDY OF BIOFILM REMOVAL WITH HAND, ROTARY
NICKEL-TITANIUM, AND SELF-ADJUSTING FILE INSTRUMENTATION
USING A NOVEL IN VITRO BIOFILM MODEL ( JOE 2013)
•The scanning electron microscope showed a consistently thick layer of biofilm grown in the canals of the control group
after 4 weeks.
•Within the groove, a smaller area remained occupied by bacteria after the use of the SAF compared with the ProFile and
the K-file (3.25%, 19.25%, and 26.98%, respectively).
• For all groups, significantly more bacteria were removed outside the groove than inside.
•No statistical differences were found outside the groove .
CONCLUSION:
•Although all techniques equally removed bacteria outside the groove, the SAF reduced significantly more bacteria
within the apical groove.
•No technique was able to remove all bacteria.
• This biofilm model represents a potentially useful tool for the future study of root canal disinfection

42. CONCLUSION
The SAF represents a new approach in endodontic file design and operation. Its
main features are as follows:
•1. A three-dimensional adaptation to the shape of the root canal, including adaptation to its
cross-section.
•2. One file is used throughout the procedure, during which it changes from an initially
compressed form to larger dimensions.
•3. Canal straightening and canal transportation of curved canals are largely avoided because of
the lack of a rigid metal core. The file does not have ‘‘a will of its own.’’
•4. High mechanical durability, thus overcoming the issue of separated nickel-titanium
instruments.
•5. Hollow design that allows continuous irrigation with constant refreshment of the irrigant
throughout the procedure.