Date: 22nd Dec. 2017
In the past few years, root canal treatment or the branch of dentistry called endodontics has gained a great prominence in the lives of both dentists and patients. Since the last couple of years, a lot of dentists have moved on from exodontia to endodontics, reasons being the availability of knowledge, technology, greater patient awareness, acceptance about endodontics, and the growing desire amongst all people to save their teeth.
There is also the psychological factor amongst patients about extraction of teeth. A root canal is a relatively safer way to treat patients as compared to exodontia. However, even endodontics is not totally complication free.
The 3 main complications in endodontics:
1. Broken instrument in the canal or in the periapical area
2. Ledge in the canal
This article focuses on the first complication, which is broken instrument in the canal.
A separated instrument, particularly a file, leads to metallic obstruction in the canal, thus preventing proper biomechanical preparation of the canal leading to post op pain to the patient, if this instrument is not retrieved or bypassed.
Let us discuss the various factors that could contribute to this particular complication.
The anatomy of the root canal that is the canal width, length, morphology, thickness of dentin, depth of concavities, experience of the dentist, cooperation of the patient, the frequency of use of the instruments, the number of times an instrument is used, the canal status (weather dry or wet) while instrumenting, the torque and speed control are some of the factors that play a very crucial role in this subject.
The thinner a canal, the tougher it is to instrument. The more acutely curved a canal is, the tougher it gets. The longer a canal, the tougher the negotiation becomes, as the chances of mistaking the working length and ledge formation are higher. After which, a forcible attempt to bypass the ledge can cause a fracture of the instrument.
In most circumstances, this complication arises from incorrect or overuse of instruments. Till today, no one knows for sure the maximum number of times a nickel titanium file can be used safely before discarding. Most manufacturers believe these files are single use only. Also, since no two root canal cases are the same, it is difficult to come up with a standard answer to this query.
A separated instrument in the canal dramatically increases the level of complexity for the clinician to complete the case. It completely changes the final outcome and the prognosis totally.e reason for this is that once an instrument is separated in the canal, the possibility of further cleaning, shaping, and eliminating debris, plus irrigating the canal becomes highly questionable.
If the instrument separates early on in the treatment, much of the pulp extirpation has not been completed, these tissue tags can harbour bacteria and get infected very easily, very fast.
This is true in case of highly vascular pulps seen in young individuals and there is a slightly diminished possibility in older individuals because their pulps undergo regressive changes.
The best way to avoid this complication is to first study thoroughly a pre-op radiography, following which only a new 10k-file must be introduced in a wet canal to instrument and that too very discreetly.
Never is a no.15 k-file first introduced in the canal.
Studying the radiograph will help determine all challenges with respect to the case and keep the dentist alert at all times.
Some Facts About Separated Instruments
– Separated instruments can be removed more easily from front teeth as compared to back teeth. And it’s easier to remove them from the upper teeth as compared to the lower teeth.
– With respect to the location, they can be removed more easily when they are coronal to the curvature as compared to apical curvature. This is because the higher the instrument is in the canal the greater is the visibility and access to it.
– Unfortunately, because of the high flexibility, NiTi files fracture more apically or they fracture beyond the apex. This makes their removal extremely challenging.
– The basic challenge in this case is to remove the separated instrument from the canal without removing too much dentin to safeguard the long-term prognosis of the tooth. This prevents perforation at any point in the curvature of the canal and root fracture.
NiTi files appeared first in dentistry in 1993 and since inception became widely used by dentists worldwide since they provided predictable and efficient outcome. NiTi has shape memory and super elasticity that really helps for easy access to all types of canals. The elasticity leads to reduced forces between the file and the canal wall. These factors have given NiTi a prominent place in endodontics.
Cyclic fatigue and torsional stress are two main causes of breakage of NiTi endo files. Cyclic fatigue is when a material has repeated stress placed on it over a period of time and ultimately this repetition breaks the material. It is similar to taking a piece of wire and bending it back and forth until it separates.
Torsional stress is when an object is twisted with applied force, a portion of material is locked into place and the rest continues to rotate. Eventually, a breaking point is reached and then the snapping occurs intracanal. The clinical application of this is rotational movements in curved canals that bends these files – ultimately leading to hardening and brittle fracture known as cyclic fatigue. If a portion of the file binds in the canal and the shank continues to rotate, a fracture will occur.
The type of endo instrument that has separated is also important. It is easier to retrieve a thinner instrument than a thicker instrument like a Gates Glidden Drill. It is easier to retrieve a stainless-steel instrument as compared to a nickel titanium instrument.
The reason for this is that there is a possibility that there is a slight space between the canal wall and the instrument into which another file can be placed, and the thinner instrument can be retrieved.
While trying to retrieve NiTi file, they may further break due to heat build-up of the ultrasonic device the chances of breakage of a stainless-steel file during retrieval are relatively less.
This a is basic preview into the subject. The techniques for instrument retrieval will be discussed in depth in the subsequent articles.
Dr. Shawn D'souza
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