Endodontic is a major field of dentistry in which practitioners keep on updating their knowledge to cope up with the fast evolving dental practice. Unique materials, advance methods and modern instruments are being introduced that have revolutionized the clinical practice of endodontics. The underlying approaches of root canal treatment includes debridement, shaping and sound filling of the root canal. Variety of instruments are available to achieve these goals. Endo files and endo reamers are instruments that are used for root canal preparation. Below is the review of different groups of instruments used in endodontics.
Endodontic Hand Files
There are different types of root canal files. Most of times they are made from stainless steel that gives them high degree of elasticity and tensile strength. Endo files are mainly used with filing or rasping actions during which there is almost no rotation of instrument in the root canal. Purpose of their usage is complete cleaning and debridement of root canal up to the length of apical foremen. Correct usage of endo files facilitate disinfection of root canal and produces shape that is suitable for obturation. Following are common types of files used during endodontic treatment:
- K- file
K file, introduced by Kerr Company, is most commonly used for cleaning and shaping. It is made by twisting a rectangular or a square blank into a closely packed series of spirals. This twisting results in 0.9 to 1.9 cutting edge per millimeter length.
These files are classified in group 1 by International Organization for Standardization (ISO). There are different colors on the plastic handles along with the sizes that can easily be distinguished while using. Recommended procedure is to start with the smallest size and increasing gradually until desirable shape is obtained.
2,Motion of file
They work either in reaming or push or pull filing motion. They can only be rotated clockwise and if the specific flute design is contorted then the file should no more be used. It is inserted till working length and ¼ to ½ turn after which it is removed while keeping it supported to the wall.
These files can be re used after sterilization by dry heat, glutaraldehyde and steam autoclave. It is observed that sterilization using this method do not cause corrosion, weakness or increased rotational failure.
Their different types are available in markets. These are mentioned below.
- It has rhomboidal shaped cross section.
- It has alternate acute cutting flutes and obtuse non cutting flutes.
- It has greater flexibility.
- Its disadvantage is that it quickly loses its cutting efficiency.
- It is more flexible and resistant to fracture.
- It has sharper cutting flutes and more room for debris removal.
- It has active cutting tip.
- Available in different size.
- Has quadrangular stem.
Flex R file
It is relatively sharper.
It does not produce steps in preparation.
It is more twisted.
It is formed by milling of steel sheet which is round in cross-section. This results in raised cutting margins. The tapering produces series of overlapping cones. This pattern produce a sharp and flexible instrument but file is weak because of decrease in diameter of shaft. Hence, resulting in fracture. Therefore, they should not be rotated more than 30 degrees. It is an effective instrument for capture and eliminate broken instruments, gutta-percha and silver points. As they majorly used for gripping, so there major function is increasing the diameter of canal after the use of k-file. NiTi or steel are used for their composition.
- ISO Classification
Similar to k-files, they are manufactured according to ISO classifications, with color coding and number on the handle. Thus it is easy to use for the practitioners.
As, its main purpose is traction, so it is highly efficient when used in pull motion. Moreover, as already mentioned, being prone to fracture they should not be rotated more than 30 degree.
They are also re-usable and can be sterilized by using various methods, including dry heat, autoclave and glutaraldehyde solution without damaging affecting their efficiency.
4.Difference from k-files
H-files are more efficient and quicker than k-files. Steps produced by k-file are more visible than that of h-file. Moreover, h-files have secure tip while k-files have sharp tip.
Protaper files have triangular cross-section. They have a convex design with altering percentage of taper across the length which decreases friction between file and dentine during rotation .Its increasingly tapered pattern enormously increase pliability and cutting efficacy. Protaper files have save ended flat tip which increases its ability to move through dental debris. The altering helical angle reduces the danger of file accidently moving into the canal.
The Protaper System
It has 3 shaping and 5 finishing filesa,
a,The shaping file
It is comprised of two shaping files: S1 and S2. S1 has purple rings while S2 has white rings on their handles meant for recognition. Diameter of S1 is 0.17mm while that 0.02 mm. There is another shaping file called SX (auxiliary shaping file), it has handle of gold color that has no rings. It is comparatively shorter having length of 19mm. It is best used in narrow canals. Tapering of the shaping file increase along their length due to which they grip, cut and clean canal and carry out crown down configuration. SX is used after S1 and S2 files to completely shape canals in fractured crowns or shorter teeth.
b,The finishing files
There are 5 finishing files with identification rings of different colors on their handles. Each color is for specific file. For instance, F1 file is identified by yellow color: F2, red; F3, blue; F4, double black and F5, double yellow. Each file has decrease in taper which increase flexibility and decrease the danger of taper lock. It also lessen the risk of enlarging coronal tooth head of the canal.
They are made by folding a pointed stainless steel blank to form a spiral instrument having acute cutting edged. They are either made up of triangular or square blank. Following is one of its major types:
K-reamer has an open twisted pattern. It has 3 cutting corners with 60 degree tip and an angle of 120 degree. They are also produced from nickel titanium and are known as NiTi k-reamers.
They are used to clean the canal walls. It is a great instrument for widening root canal and removal of debris.
It is used by a pull action after twisting it half way.
It is available under ISO classification with sizes ranging from 06 to 140.
They are found in multiple sizes, including 21mm, 25mm, 28mm, 31mm and 35mm.
They can be sterilized; thus can be used.
With the advent of nickel titanium in clinical dental practices, use of rotary instruments for endodontic treatments has increased. Rotary files have increased cutting efficacy as compared to hand instruments. Rotary instruments are used with the help of electric endodontic motor in which rotation and speed are conveniently controllable. Following are some of the characteristics of rotary files:
- Reciprocating System
It includes anticlockwise as well as clockwise rotation of file. Due to this character, it efficiently grips dentine and results in shaving of dentinal chips. It comes with increased advantages like
- Decreased danger of cyclic failure
- Decreased danger of torsional failure
- Simple procedure
- Cost effective
2. Adjustable files
These files are made to reduce complexities that occur because of complicated design of canal. It has following characters
- 3D adaption
- Uniform removal of dentine
- Disinfection and irrigation
- Results in good obturation
3. D- files
These are the rotary files used in the cases where endodontic treatment has failed for the effective removal of gutta percha. They are available in 3 sequences: D1, D2 and D3 for coronal, mid and apical removal respectively.
4. Time Efficacy
With novel designs and convenient handling, rotary files are of great value for their use in canals having unpredictable morphology. It is of enormous use in primary molar endodontics where young patient are uncooperative.
Hence, these basic endodontic instruments are of great value because it determine the accuracy of final root canal filling. More the practitioner is aware of technique and usage, more he will be able to secure time and increase the probability of perfect obturation. In modern times, it is inevitable for dentists to keep themselves updated with evolving techniques and instruments to earn the confidence of their patients. Furthermore, when purchasing endodontic instruments that the manufacturers matters. Always prefer established names, a quick survey before purchasing might help, it will reduce the risk of instrument breakage, rusting and ineffective treatment of patients. Likewise, dental staff should be expert enough to consider the correct usage and the sequence of endodontic files according to the clinical case.