Single File Endodontics

Single File Endodontics

ABSTRACT:

The cleaning and shaping of root canals is a key step in root

canal treatment procedure; which aims at removal of all the

tissue debris from the root canal space while removing the inner

layers of root canal dentin. With Nickel titanium (NiTi) rotary

instruments this goal is easier to achieve, even in curved root

canals. But, with the use of Ni-Ti rotary instruments there is a

possibility of instrument fracture on repeated use and

cross-contamination associated with the inability to adequately clean

and sterilize endodontic instruments.The recently introduced

nickel-titanium files such as, self adjusting file, Twisted File,

Reciproc, WaveOne and F2 ProTaper universal Ni-Ti rotary

instrument systems claim to be able to completely prepare and

clean root canals with only one instrument. Use of single -file

rotary systems, are cost effective, time saving, reduce instrument

fatigue and possible cross-contamination. This review article

gives salient features of the single file systems.

Key words: Single file. M wire, Self Adjusting File, Twisted File, Reciproc, WaveOne, F2 Protaper

doi: ...

1_Professor 2_{P.G. Student}

Department of Conservative Dentistry and Endodontics

P M N M Dental College & Hospital, Bagalkot, Karnataka - 587101

3_Professor

Department of Orthodontics P M N M Dental College & Hospital, Bagalkot, Karnataka - 587101

Article Info:

Received: April 10, 2012;

Review Completed: May, 12, 2012; Accepted: June 7, 2012

Published Online: August, 2012 (www. nacd. in) © NAD, 2012 - All rights reserved

Email for correspondence: [email protected]

Quick Response Code

INTRODUCTION:

The cleaning and shaping of root canals is a key step in root canal treatment procedures. Its aim is to remove all tissue debris from the root canal space while removing the inner layers of root canal dentin.1 _For

many years, it has been a common practice to enlarge the root canal to at least three ISO sizes larger than the first file to bind at the apical part of the canal.2&3 _{It was assumed that such preparation will remove the inner}

layers of the dentin while allowing the irrigant to reach the entire length of the root canal for a thorough cleaning and disinfection of the root canal space.4&5

This goal is easier to achieve today, even in curved root canals, because of the Nickel titanium (NiTi) rotary instruments. The elasticity of these files can preserve the location of the root canal axis, thus largely preventing its transportation and ledging, but with the use of Ni-Ti rotary instruments there is a: (i) possibility of instrument fracture associated with increased instrument fatigue caused by the repeated use and (ii) possibility of cross-contamination associated with the inability to adequately clean and sterilize endodontic instruments.6 _{Tooth structure and organic debris were observed on the surface of Ni-Ti rotary instruments,}

and appeared to adhere in the surface cracks despite meticulous ultrasonic cleaning and decontamination.7,8,9

Therefore, single use of endodontic instruments was recommended to reduce instrument fatigue and possible cross-contamination.

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The recently introduced nickel-titanium (NiTi) files such as, self adjusting file (SAF; ReDent-Nova, Raanana, Israel), Twisted File (TF) (SybronEndo, Orange, CA, USA), Reciproc (VDW, Munich, Germany), WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) and F2 ProTaper universal Ni-Ti rotary instrument (Tulsa Dentsply, Tulsa, OK, USA) systems are claims to be able to completely prepare and clean root canals with only one instrument.

Single file endo concept is said to require a minimum or no glide path and only a single file for complete instrumentation for majority of root canals. The recommendation for single use has added advantage of reducing instrument fatigue. Now it seems that in the quest for an endodontic system that is faster and uses fewer files, the technique is supposed to reduce the working time and lower cross-contamination between patients, a common problem associated with the use of multiple files, use of a single file will be very attractive both in terms of time and cost saving.

SYSTEMS

Introduction to individual Single Ni Ti File Systems

Self Adjusting File (SAF)

The SAF is a hollow file designed as a compressible, thin-walled pointed cylinder either 1.5 or 2.0 mm in diameter composed of 120µm thick nickel-titanium lattice. The 1.5mm file may easily be compressed to the extent of being inserted into any canal previously prepared or negotiated with a # 20 K-file. The 2.0mm file will easily compress into a canal that was prepared with a #30 K-file. The file will then attempt to regain its original dimensions, thus applying a constant delicate pressure on the canal walls.10 _{When inserted into a root canal, it}

adapts itself to the canal’s shape, both longitudinally and along the cross-section. In a round canal, it will attain a round cross-section, whereas in an oval or flat canal it will attain a flat or oval cross-section, providing a three-dimensional adaptation. The surface of the lattice threads is lightly abrasive, which allows it to remove dentin with a back-and-forth grinding motion. The SAF is operated with transline (in and out) vibrating handpieces with 3,000 to 5,000 vibrations per minute at an amplitude of 0.4 mm. Such a handpiece may be the KaVo GENTLE power or equivalent combined with either a 3LDSY head (360_ free rotation; Kavo, Biberach Riss Germany) or MK-Dent head (360_ free rotation;

MK-Dent, Bargteheide, Germany) or RDT3 head (80 rpm when free and stops rotating when engaging the canal walls, recently developed by Re-Dent-Nova, Ra’anana, Israel). The vibrating movement combined with intimate contact along the entire circumference and length of the canal removes a layer of dentin with a grinding motion. The hollow design allows for continuous irrigation throughout the procedure. A special irrigation device (VATEA, ReDent-Nova) is connected by a silicon tube to the irrigation hub on the file and provides continuous flow of the irrigant of choice at a low pressure and at flow rates of 1 to 10 mL/min.

SAF is an elastically compressible file that effectively removes dentin and can mechanically endure use under its recommended mode of operation with a minimal loss of efficacy. The SAF file is extremely flexible and pliable. It does not impose its shape on the canal but rather complies with its original shape. This is true both circumferentially and longitudinally.

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. Root canal obturation of SAF-prepared root canals may be done by any of the common methods

Twisted File (TF)

The Twisted File (TF) (SybronEndo, Orange, CA, USA) system represents a quantum leap forward in endodontic capability over previous rotary nickel titanium (RNT) cleaning and shaping methods. TF is manufactured from a proprietary process of heating, cooling and twisting of nickel titanium in the rhombohedral crystalline phase configuration (an intermediate phase between austenite-the phase at rest and martensite-the phase present during function).

TF stands in distinction to other rotary nickel titanium (RNT) alternatives that are manufactured by grinding or produced using M-wire (Dentsply Tulsa Dental, Tulsa, OK, USA).

TF is available in 5 tapers and various tip sizes. These include: .12/25, .10/25, .08/25, .06/25/30/35, .04/ 25/40/50 in 23, and 27 mm lengths.

TF is inserted passively and gently. TF will unwind in proportion to the excessive force used. TF is far more ductile than files manufactured by grinding. TF is always in motion either being inserted or withdrawn, but never held stationary in the canal. TF is inserted to resistance and withdrawn. This motion cuts approximately 5µm of dentin per insertion. The flutes of TF are wiped after every insertion. Irrigation and recapitulation should follow every insertion. Insertion is continuous, controlled, and takes approximately 2-3 seconds. TF is not pumped into the canal like a toilet plunger. Such use can lock the tip and cause instrument fracture. Manufacturer recommends 500 rpm for TF. Any electric motor can power TF. TF can be used with or without torque control and auto reverse.

TF is the most flexible instruments, with a significant improvement in flexibility (P< 0.05). ranging from 100% to 250% over the other tested instruments. Cutting flutes are created by twisting the file, not grinding, eliminating micro fractures for greater strength. TF system was found to cut dentin efficiently with more uniform cutting than machined nickel-titanium endodontic files.11

TF can prepare a .08 taper around a 90-degree curvature in approximately 3-4 insertions in a tooth that has been accessed correctly with a glide path. TF 3-4 times greater resistance to torsion and cyclic fatigue relative to ground files. The TF system eliminates the need for orifice openers.12

TF system produced significantly less transportation and preserved the original canal to a greater degree.13 _{The new manufacturing processes}

appeared to offer greater resistance to cyclic fatigue in a simulated canal model.14

WaveOne

The new WaveOne NiTi file system from DENTSPLY Maillefer is a use, SINGLE-file system to shape the root canal completely from start to finish. Shaping the root canal to a continuously tapering funnel shape not only fulfils the biological requirements for adequate irrigation to rid the rootcanal system of all bacteria, bacterial by-products and pulp tissue, but also provides the perfect shape for 3-D obturation with gutta-percha. The files are manufactured using M-Wire technology, improving strength and resistance to cyclic fatigue by up to nearly four times in comparison with other brands of rotary NiTi files.

The WaveOne file 25.08 has a continuously decreasing taper from its tip to its shaft (0.8, 0.65,

0.6, 0.55) and is characterized by different cross sectional designs over the entire length of the working part. In the tip region, the cross-section presents radial lands, while the middle part of the working length and near the shaft, the cross-sectional design changes from a modified triangular convex cross-section with radial lands to a neutral rake angle with a triangular convex cross-section analogue to the ProTaper F2 file near the shaft. On the contrary, A glide path of at least size 10 is recommended in the manufacturer’s instructions for the use of WaveOne instruments. Reverse “balanced force” action15 _{using a pre-programmed motor to}

move the files in a back and forth “reciprocal motion”.

The files are manufactured with M-Wire (Dentsply Tulsa Dental, Tulsa, UK) NiTi alloy16

improving strength and resistance to cyclic fatigue by up to nearly four times in comparison with other brands of rotary NiTi files, greater flexibility, less debris extrusion and maintaining canal shape, amongst other advantages.17-19 _{There are three files}

in the WaveOne single-file reciprocating system available in lengths of 21, 25 and 31mm:

1. The WaveOne Small file is used in fine canals has tip size is 21 with a continuous taper of 6%.

2. The WaveOne Primary file is used in the majority of canals has tip size is 25 with an apical taper of 8% that reduces towards the coronal end.

3. The WaveOne Large file is used in large canals has tip size is 40 with an apical taper of 8% that reduces towards the coronal end.

The plastic colour coding in the handle becomes deformed once sterilised, preventing the file from being placed back into the handpiece.

First hand file into the canal will aid in the selection of the WaveOne file. The manufacturers claims to use WaveOne files with a progressive up and down movement no more than three to four times, only little force is required; as preparation time is short, activate the irrigating solutions to enhance their effect; the EndoActivator (DENTSPLY Maillefer) is ideal for this system.20

Reciproc File

Reciproc (VDW, Munich, Germany) are also made of a special NiTi-alloy called M-Wire that is created by an innovative thermal-treatment process to increase flexibility and resistance to cyclic fatigue. These files are also used in a reciprocal motion that requires special automated devices.

Reciproc files are available in different sizes 25, taper 08; 40, taper 06; 50, taper 05. The reciprocating movement relieves stress on the instrument and, therefore, reduces the risk of cyclic fatigue caused by tension and compression.21,22 _{The reciprocation}

working motion consists of a counterclockwise (cutting direction) and a clockwise motion (release of the instrument), the angle of the counterclockwise cutting direction is greater than the angle of the reverse direction. Due to the fact that the counterclockwise angle is greater than the clockwise one, it is claimed that the instrument continuously progresses towards the apex of the root canal. The angles of reciprocation are specific to the design of the particular instruments and are programmed in an electronic motor. In general, reciprocating root canal preparation is an evolution of the balanced force technique that allows shaping of even severely curved canals with hand instruments to larger apical diameters.15

The manufacturer of Reciproc instruments does not strictly recommend creating a glide path when using the reciprocating instrumentation. Reciproc instruments possess sharp cutting edges. Reciproc files have a continuous taper over the first 3 mm of their working part followed by a decreasing taper until the shaft. An S-shaped cross-section is used for the entire working part of the instruments.

Reciproc And Waveone systems are the direct

full-sequence counterparts of the single-file reciprocating systems, these are the new single-file instruments were well within the range of current rotary full-sequence NiTi systems. Curved root canals can be instrumented with only minor canal straightening by only one instrument used in a

reciprocating motion.23,24 _{Comparing with rotary NiTi}

systems investigated under a similar experimental setup, the Reciproc and WaveOne single-file systems maintained the original canal curvature well. Both single-file systems showed relatively good cleaning ability and can be regarded as suitable for cleaning of even severely curved with only one instrument. 25

Reciproc was significantly faster than WaveOne (P < 0.05). The use of Reciproc decreased the preparation time by up to 60%. The use of Reciproc and WaveOne files resulted in significantly shorter preparation times. Root canal preparation with Reciproc resulted in significantly less debris in the apical part of the canals compared to canal preparation with WaveOne(36).

The reciprocating files can only be used for one patient, as it cannot be sterilized, and a theoretically possible transmission of bacteria or proteinaceous infectious particles is definitively avoided.

F2 Protaper Universal

F2 ProTaper Ni-Ti rotary instrument (Tulsa Dentsply, Tulsa, OK, USA) is used for the canal preparation in a clockwise (CW) and counterclockwise (CCW) movement. The F2 is used in conjunction with a 16 : 1 reduction ratio contra-angle connected to an ATR Vision (ATR, Pistoia, Italy) motor which allows the reciprocating movement. The CW and the CCW rotations are set on the motor at four-tenth and two-tenth of a circle. The rotational speed is set at 400 rpm.

The F2 instrument is used in the canal with a slow pecking motion and an extremely light apical pressure until resistance is encountered (i.e. until more pressure is needed to make the F2 advance further in the canal). The instrument is then pulled out of the canal, cleaned with a gauze to remove the debris filling the flutes, and reinserted and employed in the same manner. This step is repeated until the F2 reaches the working length. No further enlargement would be required for narrow and/or curved canals.24

Limitation for the application of the F2 PROTAPER is the presence of a sharp (non-gradual) canal curvature. In such a case, the instrumentation with the F2 would be carried to a level coronal to the curvature; the preparation of the apical part would then be completed with hand files.

For larger canals, hand files can be used after the F2 reaches the working length to complete the apical enlargement.

For all the above systems canal preparation is accomplished with continuous canal irrigation using a 2.5% solution of sodium hypochlorite during root canal treatment is widely recommended. The vibration of the file’s metal lattice within the irrigant facilitates its cleaning and debridement effects and a final rinse with EDTA 17% followed by NaOCl.

When 2.5% sodium hypochlorite and 17% EDTA were used as alternating irrigants for all the file systems, the root canal surface (including its apical third) was rendered clean of debris and the smear layer.26

Conclusions

All the systems discussed in the present review would offer the single use of endodontic instruments to be more costeffective and reduce instrument fatigue. Now it seems that in the quest for an endodontic system that is faster and uses fewer files, the techniques are supposed to reduces the working time and lower cross-contamination between patients, a common problem associated with the use of multiple files.

Further research and clinical results are required for better application of these file systems.

DISCLAIMER

This study is nothing to do with the above mentioned commercial file systems.

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