Different Types of Endodontic Files

Let’s face it — root canal procedures aren’t the most glamorous part of dentistry, but mastering endodontic files can turn you into a root canal superstar! Whether you’re a seasoned endo-expert or navigating the canals for the first time, the right file can make all the difference between a routine success and a time-consuming headache.

This blog dives deep into the hand files that provide reliable precision to the latest rotary files designed for smooth and effortless shaping, that helps to empower your daily dental practice. Explore a comprehensive overview about the different types of endodontic files, from their evolution to their modern-day modifications so that you can perform root canals with confidence and finesse.

Ready to elevate your endodontic game? Let’s get into the nitty-gritty of these essential tools and discover how they can make your root canal procedures faster, safer, and more effective.

What is an endodontic file?

An endodontic file is an instrument used by dentists to clean and shape the root canal during a root canal procedure. These dental files help in the removal of infected, damaged, and dead pulp from the canal. It also helps in shaving the dentin and shaping canal space to be filled by appropriate materials like gutta-percha to increase a tooth’s life span even after carious exposure or damage due to various reasons.

Components of an endodontic file:   

• Taper: Taper denotes the per-millimeter increase in file diameter from the tip toward the file handle. The taper is denoted either in numerical or in percentile. In other words, a size #20 ISO file with 2% taper will have a tip diameter of 0.20mm and would have a 0.22mm diameter 1mm from the tip, 0.24m diameter 2mm from the tip, and 0.26mm diameter 3mm from the tip. Greater tapered instruments have been developed with 4,6,8 and even 10% taper.
• Flute: It is the groove or relief on the working surface of the file which collects the debris as the file cuts through the substrate. 
• Blade (cutting edge): It is the working area of the file and is the surface with the greatest diameter that follows the flute as it rotates. 
• Land: In certain file designs, a surface projects axially from the central core to the cutting edge between the flutes. This feature is incorporated to reduce transportation and supports the cutting edge.
• Pitch: It is the distance from one cutting edge to the next. A file with a short pitch will have more spirals than a file design with a longer pitch.
• Rake angle: On perpendicular sectioning of a file, the angle which the leading edge forms with the radius of the file is known as the rake angle. If it forms an obtuse angle, then the rake angle is considered to be positive. An acute angle is termed a negative rake angle.
• Helix angle: It is the angle the cutting-edge forms with the long axis of the file.

Classification of Endodontic Instruments based on Method of Use:

• Group I: Hand-operated endodontic instruments

A.   Barbed broaches and rasps

B.  K-type reamers and files

C. Hedstrom files

• Group II: Low-speed instruments with latch-type attachments

A. Gates- Glidden drills

B. Peeso Reamers

• Group III: Engine-driven instruments

A. Rotary NiTi Endodontic instruments

B. Reciprocating instruments

C. Self-adjusting file (SAF)

•  Group IV: Ultrasonic and sonic instruments 

In this blog, we will discuss about K- files, H- files, Gates- glidden, Peeso Reamers, NiTi rotary files, Reciprocating files, Endo shaper, and finisher files.

K type Files

• Manufactured in the 1990’s, by Kerr manufacturing company with a square(four-sided) cross-section.
• The number of flutes incorporated in a blank determines whether the instrument is a reamer (less flutes) or a file (more flutes).
• K-type files do not break unless they have an undetected defect in the steel shaft or until the instrument is strained or deformed.
• USAGE: These files should be used in a filing and rasping motion during the biomechanical preparation once the canal patency is achieved.

•  Modifications: 

–  K-flex:- Rhomboidal or diamond-shaped blanks have been twisted to produce a file called as K-flex file. This design increases the flexibility and cutting efficiency of the instruments. The rhomboidal blank produces alternating high and low flutes that are supposed to make the instrument more efficient in the removal of debris.

–  Flex-R file:- The stainless steel file’s metallic memory to return to its original position increases the tendency to transport or ledge the canal. A reduction in the cutting tip angle makes the file stay more centered within the canal and enables a more circumferential cutting action. This modified- tip file has been marketed as a Flex-R file.

Hedstrom files or H- files

• These dental files are manufactured from round stainless steel wire machined to produce spiral flutes resembling cones or a screw.
• Has higher cutting efficiency than K-files, but is fragile and fractures easily.
• The better cutting efficiency is attributed to its more positive rake angle and to its blade which has a cutting rather than a scraping angle.
• USAGE: Dentists should always employ the Hedstrom file in only one direction, retraction, and never in a torquing action.

• Modifications:

–  Safety Hedstrom: It is a Hedstrom file with a noncutting side in order to prevent ledging in curved canals

–  HyFlex file- It has a cross-section that presents an “S” shape instead of the traditional single-helix teardrop cross-section of the Hedstrom file.

–  S- file- It has a double–helix cross-section.

Gates – Glidden drills

• The gates-glidden drill has a long, thin shaft ending in a flame-shaped head, with a safe tip to guard against perforations.
• It is made from stainless steel and used with an electric slow-speed handpiece in a rotational speed range of 800- 1200 rpm.
• Its flame head cuts laterally and is used with gentle, apically directed pressure.
• An advantage of using these drills is that, if they bind during use, they will fracture at the neck of the shaft and will extrude from the tooth.
• The fractured segment can be easily removed by grasping the broken shaft with pliers and pulling it out of the tooth.
• USAGE: Helps to remove the lingual shoulder during access preparation of the anterior teeth and to enlarge root canal orifices.

Peeso reamers

• Peeso reamer has long, sharp flutes connected to a thick shaft and cuts laterally.
• Made from stainless steel and used at slow speed in electric handpieces in a rotational speed range of 800-1200 rpm.
• Both gates-glidden drills and peeso reamers are aggressive cutting instruments that are inflexible and should be used with extreme caution to prevent over-instrumentation and perforations.
• USAGE: A reamer is primarily used for the preparation of post space when gutta-percha has to be removed from the obturated root canal.

Nickel- Titanium Rotary files

• The alloy of these dental files consists of 55% nickel and 45% titanium by weight.
• The superelastic alloy does not exhibit proportional strain under stress until a specific level is attained that ultimately causes fracture.
• This unique property is due to the austenitic crystalline structure of the alloy which gets transformed into a martensitic crystalline structure under stress.
• Thus, these files exhibit shape memory i.e., the ability to return to its original shape once the stress is removed.

Reciprocating endodontic files

• These reciprocating instruments function at unequal bidirectional angles. The counterclockwise engaging angle is five times the clockwise disengaging angle and is designed to be less than the elastic limit of the file.
• Strategically, after three counterclockwise and clockwise cutting cycles, the file will have rotated 360° or one complete circle. 
• This novel reciprocating movement allows a file to progress more readily, cut efficiently, and effectively auger debris out of the canal.
• USAGE:  Helps with single-file shaping systems that aim to simplify the shaping procedure and reduce the operative time of the procedure.

XP- Endo Shaper and Finisher files (Self Adjusting Files):

• XP- Endo Shaper instrument is a rotary snake–shaped instrument made of a proprietary alloy.
• This alloy helps the file to change its shape according to the temperature.
• When cooled, in its martensitic phase, the file stands straight with a size #30 and an initial taper of 0.01.
• However, when introduced to body temperature, it changes to its austenitic phase assuming a snake shape that can achieve a final minimum canal preparation of 30/0.04 when using this instrument alone.
• Best file system that can be used in complex canals due to its high flexibility.

•  XP- Endo Finisher is an anatomical finishing file that consists of a small-core-size (tip size 25 and non-tapered) rotary NiTi instrument made of a proprietary alloy.
• When submitted to body temperatures, it changes to its austenitic phase assuming a spoon shape of 1.5mm depth in the final 10mm of its length.
• The austenitic phase shape allows the dental files to access and clean areas that other instruments might not have reached. These files do not cut the dentin but rather scrap the walls thus, not altering the original canal shape.

Conclusion: Explore the Power of Precision with Dental Files

Mastering the use of various endodontic files is key to achieving exceptional results in your root canal treatments. From reliable K-files and sharp Hedstrom files to advanced rotary NiTi and reciprocating systems, each tool plays a unique role in ensuring precise canal shaping and efficient cleaning. These files are designed to make your procedures smoother, faster, and more effective, giving you the confidence to tackle even the most complex cases.

As dental professionals, staying updated with modern advancements is crucial for the success of your practice. The right tools can transform the way you work, improving patient outcomes and enhancing your efficiency. So, why not explore the wide range of endodontic files available today? Visit DentalKart and find the perfect instruments to elevate your endodontic game.

Reference- Grossman’s Endodontic Practice, 14^TH Edition

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