Dental Hypotheses

: 2019  |  Volume : 10  |  Issue : 4  |  Page : 108--111

Can the Separated Instrument be Removed From the Root Canal System out by Magnetism? A Hypothesis

Mohammad Daryaeian1, Sanjay Miglani2, Abdol Mahmood Davarpanah3, Hyeon-Cheol Kim4, Mohsen Ramazani5,  
1 Private Endodontist, Zahedan, Iran
2 Department of Conservative Dentistry and Endodontics, Faculty of Dentistry, Jamia Millia Islamia, Jamia Nagar, New Delhi, India
3 Department of Physics, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran
4 Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea
5 Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Correspondence Address:
Mohsen Ramazani
Iranian Center for Endodontic Research, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran,


Introduction: Procedural errors might occur during the treatment of the root canal system as a consequence of uncontrollable factors by the clinician. The fracture of endodontic instruments is unpleasant occurrences that happen rather frequently in the endodontic clinic. The hypothesis: As metals are magnetized to some extents, the clinicians might be able to move separated stainless steel and NiTi rotary instruments by magnets from the canals out. Evaluation of the hypothesis: The instruments (Hand Stainless Steel and Rotary NiTi) are tried to move away through using magnets at the first stage of experiment. For the next steps, the blocks and extracted natural teeth can be utilized as a situation more clinically relevant.

How to cite this article:
Daryaeian M, Miglani S, Davarpanah AM, Kim HC, Ramazani M. Can the Separated Instrument be Removed From the Root Canal System out by Magnetism? A Hypothesis.Dent Hypotheses 2019;10:108-111

How to cite this URL:
Daryaeian M, Miglani S, Davarpanah AM, Kim HC, Ramazani M. Can the Separated Instrument be Removed From the Root Canal System out by Magnetism? A Hypothesis. Dent Hypotheses [serial online] 2019 [cited 2020 May 31 ];10:108-111
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Full Text


Different accidents might happen during the root canal treatment, among which, the instrument separation is one of the most unpleasant occurrences.[1] A fractured instrument hinders the endodontic therapy, making it even more complex from the chemomechanical preparation to the moment of the obturation of the canals, negatively affecting the long-term prognosis.[2] Clinical studies have reported an incidence of fractures ranking 0.39 to 5% among the cases of endodontic retreatment.[3]

The existence of a fragment inside the canals requires detailed evaluation of the treatment options. The complicating factors when a fragment is removed from the root canals include the anatomy of the root canal system (RCS), the devices available to remove, the professional expertise and ability, and the localization, size, position, and diameter of the fractured instrument.[3],[4]

Initial possibilities when dealing with a fractured instrument inside the root canals are leaving the fragment into the canal, sealing it inside the canal, or removing it from the RCS.[1] It is also essential to analyze the contamination risk moment when the fracture happened, so the removal of the instrument will be dependent on the condition of the foraminal area.[5],[6]

If the fractured instrument is removed out from the RCS, the success chances of the therapy increase, although it requires complex procedures and specific materials that not always are available in the clinic for a great number of professionals.[7] When the fragments are left into the canals, the prognosis is unclear, and this choice is still being discussed in the literature.

Respecting that the removal of fractured instruments is one of the most difficult procedures in endodontics, and that it is essential to achieve success of the endodontic treatment, it is important to develop or adapt some techniques to facilitate.[8] Although several devices have been developed, but none of them can completely be effective to retrieve fractured instruments for all the cases. Moreover, there is no standardized protocol in the literature to be followed when it is necessary to remove a fractured instrument from the root canals.[9]

Iatrogenic accidents such as perforation and canal destruction have been reported during the removal of separated instruments.[10] The file removal process becomes even more difficult when breakage occurs in a curved canal or in the apical third of the canal. Overall, it is the result of cinematic movements applied on instruments incorrectly, or the use of instruments already damaged, which increases the chances of fracture by torsion or cyclic fatigue.[11]

Several factors have to be considered before choosing to remove fractured instruments. The success chances have to overweigh the possible complications. Studies affirm that the success of fragment removal is dependent on the type of instrument fractured, the anatomy of the canal, the type of tooth involved, and the technique applied to take the broken instrument out of the RCS.[8],[11] Regarding the impact of the size and of the irregularities of the canals on the success of the removal of the fractured instruments, there is higher success rate for anterior teeth with wide and straight canals than for posterior teeth canals, which are narrow and curved.[12] Suter et al.[13] also demonstrated a lower success rate for the cases when the fragment has to be removed from the apical third than when it has to be taken out of the medium or coronal third. Among the several techniques available in order for removing the fractured instruments from the canals is the bypass followed by traction, which can or not be followed by the use of ultrasonic instruments, the traction using the Masserann Kit and the Canal Finder System, etc. Depending on the type and size of the fractured instrument, the first technique might not be effective. However, the rest of the methods, in addition to requiring specific devices that make them the most expensive procedure, still show necessity of huge wear, compromising the tooth prognosis due to the excessive enlargement, and besides they are rarely used in areas of difficult access to canals.[14] Comparing with the other techniques above listed, the removal of a fractured instrument using a hypodermic needle associated with cyanoacrylate adhesive is a simple alternative technique and with low cost, since it does not need special devices, and uses routine materials in the dental clinic, and besides it is fast to be executed and does not require direct view of the light to the canal. Moreover, it is possible to verify one of its main advantages that it performs a small dental wear leading to minimum weakening of the tooth structure in comparison to techniques described in the literature. However, this technique presents the difficulty of attaching the needle to the coronary portion of the fragment, although is not a problem when the clinician has appropriated training and hand ability. The clinicians need a conservative, secure, simple, and low cost option that can be performed in the day-to-day of the endodontic clinic.[15] Ultrasound, as a newer method for removal of fractured instruments may lead to formation of microcracks in root canal dentin which might not disappear or propagate after canal preparation. Considering the incidence, cause, and consequence of such complication it is needed to implement ultrasonic intervention conservatively.[16]

The Hypothesis

It is hypothesized that using some special magnets (intensity, shape, and direction of use), the clinician could be able to move the instrument fragments trapped in the canal coronally for more easily grasping.

Answering the following questions may be beneficial to go forward for assessment of the situations more practically:Can stainless steel instruments be magnetized?How much is the magnetizability extent of stainless steel instruments?Can rotary instruments be magnetized?How much is the magnetizability extent of rotary instruments?Which kind of magnets is the best to magnetize stainless steel instruments?Which kind of magnets is the best to magnetize rotary instruments?Is it applicable to render a magnet plier to implement in blocks or teeth ex vivo or in vivo?

Evaluation of the Hypothesis:

In general, materials have different properties such as mechanical, electrical, optical, thermal, chemical, and magnetic properties. The last property is one of the most important that less considered by researchers.[17] Magnetic properties can be divided into four categories: ferromagnetism (FM), paramagnetism (PM), super-paramagnetism (SPM), and diamagnetism (DM). Ferromagnetic material can be attracted by magnets.[18]

It was found out in our advanced magnetism Lab. (University of Sistan and Baluchestan, South east of Iran) that Nickel-Titanium (NiTi) rotary instruments cannot be attracted by a magnet [Figure 1]. In order to remove broken NiTi instrument, it is suggested to change the NiTi rotary modality with a magnetic material from the group of a permanent magnet such as NdFeB (neodymium iron boron-based rare earth permanent magnet material) which is one of the strongest type of permanent magnet.{Figure 1}

From the other side, the hand stainless steel (SS) files as a ferromagnetic material can be easily attracted by the same magnet [Figure 2].{Figure 2}

Therefore the authors suggest making a plier from a rare earth permanent magnet such as the NdFeB, or Samarium–Cobalt (SmCo)-based magnet alloys. The NdFeB magnets are cheaper to manufacture, lighter, and stronger than SmCo-based magnets and they have superior magnetic properties at room temperature. The NdFeB magnets can be found from a computer hard disk drive (HDD). Furthermore permanent-magnet of Fe14Nd2Bl has the large uniaxial magnetic anisotropy, the large magnetization, and the stability in the 14-2-1 phase.

Here is a short review about the elements that are used in the mentioned permanent magnets.

Boron (B) is a component of neodymium magnets (Fe14Nd2B), which are among the strongest type of permanent magnet. It is a deoxidation agent which increases the hardness of nickel-based alloys, reduces the surface tension of the molten alloy, improves its castability, and reduces the ductility of the alloys to which it is added.[19]

Iron (Fe) is added to the gold alloys in metal-ceramic systems for hardening, strengthening, and also for bonding the oxygen to oxides. Also, the iron is the base of several types of metallic alloys. It has good complements with nickel and together enhance the ability of processing of the alloy in cold state. Titanium (Ti) is a non-precious metal. Numerous studies prove its good biocompatibility and resistance to corrosion. It reduces the melting range and improves the castability. Also, it increases the hardness of the alloy and forms the oxides at high temperatures.

Nickel (Ni) has a coefficient of thermal expansion close to that of gold, and therefore it forms the basis of many alloys. In addition, it provides the corrosion resistance and allows the elasticity and toughness to alloys. However, nickel is not completely safe for the patient’s health, especially for the female population, because it can cause allergies and dermatitis.[20]

Neodymium magnets (actually an alloy, named Fe14Nd2B) have strong magnetic fields.[21]

Review on applications of nanotechnology in endodontic has mentioned that nanotechnology can be used in fillers, irrigants, and photodynamic therapy. Also, antibacterial nanoparticles can be used for disinfection.[22]

Moreover, nanotechnology can be utilized for the authors’ purpose. There are methods for preparing micro- and nano-structured powder for bonded magnets having high coercivity and also magnet powder like R—Fe—B type anisotropic sintered permanent magnets having high coercivity.[23] Granados-Miralles C, et al. studied the magnetic and microstructural properties of nanocrystalline exchange coupled PrFeB permanent magnets. They were produced to exchange coupled Fe14Pr2B single-phase and Fe14Pr2B+α-Fe two-phase magnets with grain sizes of about 20 nm using the melt-spinning procedure.[24]


Some instruments used in dentistry such as orthodontic appliances have been treated scientifically by the magnetic effect to improve the treatment quality.[25] In endodontics, strong magnetic fields are estimated being required for removal of stainless steel files located in canals. So for this purpose, NdFeB magnet can be a useful option. Of course it is needed to test this hypothesis in vitro preliminarily and then ex-vivo, animal models and finally in clinical practice.

Financial Support and Sponsorship


Conflict of Interest

There is no conflict of interests


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