SELF ADJUSTING FILEK.OHM NIJANDHAN

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

INTRODUCTIONThe 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

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 1996Traditionally, 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

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 2003Many 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 2011Until the recent introduction of “adaptive” cleaning/shaping instrument technology, the basic tenets of endodontic treatment have been unattainable.

NICKEL – TITANIUM ROTARY INSTRUMENTSSince 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.

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.

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.

- Metzger et al 2010

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 .

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 .

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.

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),

RESULTS OF EXPERIMENTAL TESTSCompressibility 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.

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.

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.

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.

Eight Months of Clinical Experience with the Self-AdjustingFile 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.

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.

BACTERIOLOGIC CONSIDERATION’SThe 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.

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.

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 .

REMOVAL OF SMEAR LAYER IN THE APICAL PART OF THE CANALBesides 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

Supplementary Steps for Removing Hard TissueDebris 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

HISTOLOGIC CONSIDERATIONSInfected 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.

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

ROOT CANAL OBTURATION OF SAF PREPARED ROOT CANALSIn 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.

• When SAF was used after ProTaper retreatment files, significantly less root filling residue was left in the canals compared to when WaveOne was used.

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)

BASED ON PATENCY MAINTENANCEPatency 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.

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.

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

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

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 

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.

STIMULATION MODEL EXPERIMENTSDEFORMATION 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.

A COMPARATIVE STUDY OF BIOFILM REMOVAL WITH HAND, ROTARYNICKEL-TITANIUM, AND SELF-ADJUSTING FILE INSTRUMENTATIONUSING 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

CONCLUSIONThe 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.