A new idea is first condemed as ridiculous and then dismissed as trivial, until finally, it becomes what everybody knows
The powerful quote by philosopher William James aims to remove skepticism related to a new concept that is presented for the greater good. With that quote in mind let’s have a look at the differences between the conventional rotary instrumentation techniques and the newer and less time consuming reciprocatory endodontic instrumentation.
Endodontic files have undergone various changes since the time that they were introduced. (If you haven’t read our blog on “Evolution of Endo Rotary Files” yet, now would be a good time) Through the various evolutionary processes, the field of motor driven endodontics saw the emergence of a newer and advanced file designs. In addition to the changes made in instrument design, metallurgy and other features, the manner in which the instruments were driven was also modified (Rotation & Reciprocation).
Roane’s Balanced Force Technique:
In 1981, Dr. James B Roane, who was an associate professor in endodontics at the University of Oklahoma, developed the balanced force technique. The balanced force technique, if followed properly, can help the dentist reduce instrument breakage, minimize straightening of the canal and eliminate other undesirable outcomes such as apical zipping or transportation. When Dr. Roane presented his technique in 1985, in an article published in the “Journal of Endodontics”, most people found it difficult to study and understand. Dr. Eugene Pantera, an associate professor of endodontics at the New York State University at Buffalo, says that he balanced forced technique is an excellent shaping technique and is widely misunderstood by a lot of practitioners.
Preloading the file through the clockwise rotation and shaping the canal through counterclockwise rotation was the description of the technique. Studies have shown that by using the balanced force technique, apical transportation and ledging have been greatly reduced.
Dr. Roane used the Flex-R or Flexofile, which was a new K-type hand file having a flexible triangular design and a non-cutting tip. By using the balanced force technique in severely curved canals, clinicians were able to reach the complete electronically measured working length and achieve great results.
Reciprocation motion is similar to the balanced force technique but, applied to motor driven instrumentation. In short, reciprocation may be considered as a “mechanically driven balanced force”.
What is Reciprocation?
Reciprocation is defined as any repetitive back-and-forth motion. This has been utilized in clinical dentistry since 1958, using endodontic stainless steel hand files. The reciprocating movement has shown similarities to manual instrumentation to a certain extent while eliminating the risks involved with files used in continuous rotation. Reciprocating motion, when applied to nickel titanium file systems, has many differences from the ones used with stainless steel files.
Rotation vs Reciprocation:
The two methods of endodontic instrumentation have been compared under the following parameters and their clinical relevance.
There are two types of reciprocation motions – Symmetric & Asymmetric Oscillations.
In asymmetric oscillation, the overall speed used is much lower than in the case of symmetric oscillation. The rotational effect guarantees that the net difference between the clockwise and counter-clockwise movements help maintain adequate cutting efficiency while reducing the torsional stress on the endodontic file. This effect greatly reduces the cyclic fatigue of the file and ultimately increases its life span.
While employing continuous rotation, the file is subjected to persistent engagement and stress which makes it less resistant to fatigue. Reciprocation offers non-continuous rotation which causes alternating engaging and disengaging movements, reducing the number of cycles of the instrument, which explains the reduction in cyclic fatigue.
Removal of Debris
Studies were conducted to test the efficacy of files used in continuous rotation and reciprocation to effectively remove debris from the root canal system. The results of the study concluded that the files used in reciprocatory motion resulted in lesser residual debris when compared to the files used in continuous rotation.
A study conducted by Dr. Nicola Maria Grande et al aimed to evaluate the differences between rotary and reciprocatory motions in the biomechanical preparation of the root canal. With regard to dentin microcracks, they concluded that the microcracks that occurred were independent of the types of files used or the kinematics involved. The results of the study showed that the use of reciprocating files led to fewer or an equivalent amount of dentinal microcracks when compared to a complete sequence of rotary files.
A study was conducted to compare the time taken for biomechanical preparation using reciprocation and continuous rotation. Wave One was used in reciprocating motion while One Shape was used in continuous rotation. The results showed that biomechanical preparation with Wave One used in reciprocation motion took 1.49 minutes to complete the procedure, while One Shape used in continuous rotation took 3.12 minutes. From these results, it is inevitable that files used in reciprocatory motion allow effective shaping of the root canal in less than half of the time taken by files used in continuous rotation.
Extrusion of Debris
With respect to extrusion of debris beyond the root apex, files used in continuous rotation have shown better results than with those used in reciprocation. Reciprocating files have shown to produce significantly more debris than the other rotary file systems. The reason for this might be the absence of the back pressure offered by the tissues of the periapical region.
Watch this video that shows the differences between rotary and reciprocal endodontics with regard to extrusion of debris
Elimination of Bacterial Load
The shorter working time required to shape the root canal when using files in reciprocal motion has lead to concerns about the ability to eliminate the presence of bacteria in the canal. In vitro studies conducted to test this revealed that the single file reciprocation technique resulted in canal cleanliness that was comparable to the ones shaped using continuous rotation. However, clinical studies have to be conducted gain insights into the efficacy of reciprocating files in the removal of the bacterial load.
Maintenance of the Anatomy of the Root Canal
Canals shaped using reciprocatory motion have shown to have preserved the original root canal anatomy to a larger extent when compared to rotary endodontics. The original contour of curved canals was maintained when using reciprocatory motions while rotary files had a tendency to straighten the canal.
Let’s go back to the initial question that led to this blog post
Reciprocating files or Rotary files?
From the various factors that we have considered in this article, it may seem like the arguments are in favor of reciprocation. However, at this point, it would be quite presumptuous to assume that reciprocation can replace rotary endodontics.
Reciprocation, like any other new technique, has a learning curve that every dentist has to go through in order to master it and obtain results with maximum efficiency. If the clinician feels that she is able to obtain adequate results using conventional rotary endodontic techniques, there might not be a necessity to change their shaping techniques. That being said, if the dentist is willing to give this new technique a test drive to find out whether it can augment the quality of the endodontic treatment and crunch the time taken for every procedure, it is definitely encouraged to do so. The dentist can also try using the reciprocating technique for certain cases such as the ones with steep curvatures, along with the conventional rotary instrumentation techniques for other cases.
Will reciprocation become the future of endodontic instrumentation, similar to how rotary endodontics established authority over hand instrumentation? Only time will tell.
If you never try, You’ll never know.