Endodontic files- whats their purpose?

When do we need endodontic files?

When root canal treatment or endodontic treatment is necessary your dentist should inform you about the procedure. You will be informed about the entire protocol and the duration and number of visits expected until therapy is completed.

There are many reasons for root canal treatment. In most cases, the main reason is pulp or periradicular tissue infection, but sometimes, due to prosthodontic rehabilitation, some teeth need to be edodontically treated. Whatever the cause is, the essence of the procedure is pretty much the same. The main idea is to remove the pulp tissue and the infection from the pulp chamber and root canal system, which is followed by obliteration of this empty space with adequate filling materials. Since endodontic dental procedures weren’t always the treatment of a first choice for a toothache the alternative option was usually tooth extraction. With the development of new materials, instrument and devices the survival rate of endodontically treated teeth have significantly raised in the last 20 years.

Diagnostic procedures didn’t change much except in the area of radiographic diagnostic and with the introduction of CBCT technology in everyday dental practice. This kind of radiographs allows the dentist to explore the suspect tooth and the surrounding tissues much more precisely. The presence of the periradicular lesion can be seen in all three dimensions so as the presence of missed or accessory canals. In many cases, this diagnostic method helped mainly in failed endodontic treatment and their successful retreatment.

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One of the most important steps in endodontic procedures is mechanical cleaning and irrigation of the root canal system. The main goal is to mechanically clean the debris from the canal walls and to wash it out of the canals. For mechanical cleaning different types of files can be used, rotary or hand files, made out of stainless steel or Nickel-Titanium. Intensive development of endodontic starts in the mid of 18th century, with intensive progress through the 19th century. During this period dentists and scientists from all over the world explored different opportunities for saving the inflamed tooth by preserving the pulp tissue or removing it from the tooth in order the save the one. First, the stainless-steel hand files were used for removing the pulp and debris from the canal system. Several techniques were introduced by well-known doctor Schilder: crown-down, step-back and balance-forced technique. These techniques are still learned in dental schools around the Globe, as fundamentals of endodontics, and many dentists still use only these techniques with great success.

What types of endodontic files are available?

There are many classifications of endodontic files:

  1. Exploring files
  2. Extirpating files
  3. Enlarging files (for cleaning and shaping)
  4. Filling files

Exploring files are usually intended for locating and shaping the orifices or removing the calcifications from the pulp chamber. Besides these files, some drills so as specifically designed endo-openers can be used for this purpose. It is important to mention that contemporary endodontics often uses ultrasonic devices with specially designed endo-tips. Different tips are used for detection of orifices, removing the calculus from the pulp chamber, removing metal posts from the canals, irrigation, or even cleaning sclerosed canals. Some tips are intended for endodontic surgeries in the sense of periradicular surgeries, mainly for retrograde closure of obturated canals that cannot be treated by conventional endodontic treatment.

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Extirpating files are used for pulp extirpation. These are specially designed instruments called barbed broach files with numerous short and sharp needles that are intended to retain and remove the pulp tissue from the root canals.

Enlarging files present a wide group of different instruments. These files are intended for cleaning and shaping the root canals and are intended for manual cleaning and shaping (hand files) or mechanical treatment (rotary files). They can be made out of stainless steel or nickel-titanium alloys that are basically specially twisted wires made out of one of the named alloys. There is also a difference in the cross-sectional shape of files which makes an elementary distinction among them.

Hand files are classified into three categories: K-files, K-reamers, and H-files. The main differences among these files are in the design of cross-sectional shape and number of threads. K-files have a square cross-sectional shape, while K-reamers has a triangular shape. This means that contact and cutting surface is greater with K-files than K-reamers. All K-files are mainly intended for rotary motions inside the canals. On the other hand, H-files are specially designed for shaping canals after they are previously cleaned and enlarged with K-files. They are made out of the ground wire and have a tear-drop cross-sectional shape. These files are intended only for retraction movement inside the canal and should never be torqued during manipulation since their usage needs to scratch all irregularities of canal walls in order to achieve smooth surfaces.

All hand files are color coded, which means that each color presents the appropriate size of the instrument’s tip. This is important in order to know how large the apex of the root canal should be prepared during the instrumentation, whether we talk about K or H files.

However, in choosing hand or rotary files, the great advantage is given to nickel-titanium (NiTi instruments) mainly because of their great flexibility. This alloy has many advantages over conventional stainless-steel alloy. Their greater flexural strength provides better and safer manipulation in curved and narrow canals and this way reduces the chance of instrument’s fracture inside the canal during manipulation. That is why the NiTi instruments are the first choice for cleaning and shaping canals nowadays.

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With the introduction of rotary files, endodontic treatments became less time consuming, more efficient and that way, more comfortable for the patients so as for dentists. These files use an electric motor to mechanically rotate the files during cleaning and shaping. Endo-motor can be adjusted for certain speed and torque during manipulation. Speed and torque are suggested by company declaration so the dentist can be sure how to program the device for each treatment. Today they are exclusively made out of NiTi alloy which makes them safe to use with minimal chance for fracture or instrument separation during manipulation. Another great thing with rotary files is the fact that the number of instruments is reduced to 3-5 instruments for the entire procedure, which leads to less in-chair time.

Filling files are intended for intake of obturation material and their compaction so the three-dimensional obturation of root canals can be obtained. Depending on the filling technique, different instruments and appliances can be used. Ford lateral compaction technique, obturation paste can be placed into the canal with Lentulo spiral drill. This drill spreads the paste during its rotation in the canal from the apex to the orifice using centrifugal force to place the pace to all canal walls. This technique requires following compaction of gutta-percha points which can only be achieved with help of finger spreaders, instruments in much like hand files, only with smooth surfaces. Another technique, called heated compaction, have similar protocol except it needs the use of heat-carrier and pluggers that will heat up gutta-percha and compact it with an appropriate plugger. Great technological development in dentistry brought contemporary devices that can achieve better, more precise and faster obturation and many dental companies started with the production of different types of electrical heaters that can place warm gutta-percha directly into the canal without the possibility of periradicular extrusion of material.

Entire endodontic dentistry has faced numerous improvements in the last 20 years, considering therapeutical materials so as instruments and electrical devices. Besides choosing a well-trained and experienced dentist who can make right diagnose and good treatment plan, it also important that they are up to date with these improvements on the market in order to provide the fastest, safest and high-quality treatment for their patients.