|Year : 2016 | Volume
| Issue : 1 | Page : 89-92
Peregrination of endodontic tools-past to present
Ashwini Tumkur Shivakumar, Sowmya Halasabalu Kalgeri
Department of Conservative Dentistry and Endodontics, JSS Dental College and Hospital, Mysore, Karnataka, India
|Date of Web Publication||12-Feb-2016|
Dr. Ashwini Tumkur Shivakumar
Department of Conservative Dentistry and Endodontics, JSS Dental College and Hospital, Mysore, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The clinical practice of yesterday's endodontics becomes the heresy of today, and today's endodontic practice becomes the heresy of tomorrow. The history of endodontics begins in the 17 th century. Since then, there have been numerous advances and developments, and research has proceeded continuously without pause. The manufacture of the first instruments for endodontic use dates back to 1875. These early instruments were made by hand from thin steel wires, and they performed the function of modern barbed broaches. In 1955, Ingle was the first to express the need for standardization of canal instruments. In 1965, the American Association of Endodontists adopted the terminology and nomenclature of the proposed standardized system. For many years, the standard cutting instruments have been the reamer, the K-type file, and the Hedstroem file. Recent changes in both metallurgy and endodontic concepts have led to the introduction of a wide range of new instruments. An effort has been made here to present the journey of endodontic instruments from the past to the present.
Keywords: Files, reamer, recent endodontic instruments, rotary endodontics
|How to cite this article:|
Shivakumar AT, Kalgeri SH. Peregrination of endodontic tools-past to present. J Int Clin Dent Res Organ 2016;8:89-92
This article is the result of an effort to delineate in brief the journey of endodontic instruments from the past to the present. Endodontic therapy or root canal therapy is a sequence of treatments for the infected pulp of a tooth that results in the elimination of infection and the protection of the decontaminated tooth from future microbial invasion. 
Root canals and their associated pulp chambers are the physical hollows within a tooth that are naturally inhabited by nerve tissue, blood vessels, and other cellular entities, which together constitute the dental pulp.  Endodontic therapy involves the removal of these structures; the subsequent shaping, cleaning, and decontamination of the hollows with small files and irrigating solutions; and the obturation (filling) of the decontaminated canals with an inert filling such as gutta-percha.
Endodontic files and reamers are the instruments used by dentists when performing root canal treatment. These tools are particularly used to clean and shape the root canal, with the concept being to perform complete chemomechanical debridement of the root canal to the length of the apical foramen. 
Files are commonly made from metal. They are usually of carbon, SS, or nickel titanium (NiTi) alloy. Files may be made from metal blanks that are twisted or machined to produce various sizes and tapers. Typical file lengths are 21 mm, 25 mm, and 31 mm. An International Organization for Standardization (ISO) sizing system is used to describe the tip size of endodontic files. Files are usually color-coded in an ISO color system to aid the dentist. Typically, steel files have 2% tapers, but in recent years, NiTi files with up to 12% tapers have been popularized. Endodontic instruments are usually available as both hand and rotary instruments  [Figure 1].
Even though the stainless steel (SS) instruments are corrosion-resistant and stiff in nature, they are considerably prone to facture and distortion. Hence the breakthrough in clinical endodontics involved the progression from utilizing a long series of SS hand files and several rotary Gates Glidden drills to the integration of NiTi files for shaping canals. Regardless of the methods, the mechanical objectives were brilliantly outlined by Dr. Herbert Schilder almost 40 years ago. 
In 1988, Walia proposed nitinol, which is an exotic metal: It does not conform to the normal rules of metallurgy and is also known as controlled memory wire, or shape-memory alloy. The NiTi alloys used in root canal treatment contain approximately 56% (wt.) nickel and 44% (wt.) titanium. NiTi instruments are two to three times more flexible than SS.  A game-changing feature of files manufactured using NiTi was that curved canals could be mechanically prepared through continuous rotary motion. By the mid-1990s, the first commercially available NiTi rotary files were launched on the market. 
This write-up is a discussion of the history of endodontic instruments, a mechanical classification of each generation of file systems. Rather than identify the cross sections, files will be characterized on the basis of having either a passive or an active cutting action.
| First-Generation Systems|| |
In order to appreciate the evolution of mechanical NiTi instruments, it is useful to know that first-generation NiTi files, and this generation of instruments in general, have passive cutting radial lands, which helped a file to stay centered in the canal curvatures during work and fixed tapers of 4% and 6% over the length of their active blades.  In addition, this generation of files have negative rake angles, which makes the file passive; these instruments perform a scraping or burnishing rather than a real cutting action, remove dentin slower, and have less of a tendency for canal straightening.
This generation's systems require numerous files for completing preparation of the root canal, which was the major disadvantage  [Table 1] and [Figure 2].
| Second Generation|| |
The second generation of NiTi rotary files appeared on dental markets in 2001.  The feature that distinguished this generation of instruments from the first generation is that they have active cutting edges and thus require fewer instruments to prepare a root canal. In general, active instruments cut more effectively and more aggressively, and have a tendency to straighten the canal curvature , [Table 2] and [Figure 3].
| Third Generation|| |
Improvements in NiTi metallurgy became the hallmark of what may be considered the third generation of mechanical shaping files. In 2007, some manufacturers began to focus on using heating and cooling methods for the purpose of reducing cyclic fatigue, and improving safety with rotary NiTi instruments in canals that are more curved. The intended phase transition point between martensite and austenite was identified as producing a more clinically optimal metal than NiTi, i.e., M-wire and R-phase technology. This third generation of NiTi instruments significantly reduced cyclic fatigue and consequently, less breakage of files occurred  [Table 3] and [Figure 4].
| Fourth Generation|| |
This technology was first introduced in the late 1950s by a French dentist Dr. Blanc. An advancement in canal preparation procedures was achieved with reciprocation, a process that may be defined as any repetitive up-and-down or back-and-forth motion. Innovation in reciprocation technology led to a fourth generation of instruments for shaping canals. This generation of instruments and its related technology have again fuelled the hope for a single-file technique. The reciprocating movement allows a file to progress more readily, cut efficiently, and remove debris from the canal effectively  [Table 4] and [Figure 5].
| Fifth Generation|| |
The latest generation of shaping files have been designed in such a way that the center of mass or the center of rotation, or both are offset. When in rotation, files that have an offset design produce a mechanical wave of motion that travels along the active length of the file. In addition, it enhances the removal of debris from a canal and improves flexibility along the active portion of the file. This generation's files have been recently introduced, adapting the advantages from both the second and the third generations  [Table 5] and [Figure 6].
| Conclusion|| |
Each generation of system offered further development toward a better system, with its own advantages and disadvantages. It is up to a clinician to decide which system to use based on the type of the case.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Hargreaves KM, Cohen S. Cohen's Pathways of the Pulp. 10 th
ed. USA: Mosby; 2010. p. 21.
Nancy A. Ten Cate's Oral Histology: Development, Structure, and Function. 8 th
ed. USA: Mosby; 2012. p. 168.
Shanon P, Justin JB. The Principles of Endodontics. 2 nd
ed. ???: OUP Oxford; 2013. p. 58.
Nisha G, Amit G. Textbook of Endodontics. 2 nd
ed. India: Japeey Publishers; 2013. p. 140-1.
Ruddle CJ, Machtou P, West JD. The shaping movement: Fifth-generation technology. Dent Today 2013;32:94, 96-9.
Walia H, Brantley WA, Gerstein H. An initial investigation of the bending and torsional properties of nitinol root canal ﬁles. J Endod 1988;14:346-51.
Thompson SA. An overview of nickel-titanium alloys used in dentistry. Int Endod J 2000;33:297-310.
Bryant ST, Dummer PM, Pitoni C, Bourba M, Moghal S. Shaping ability of .04 and .06 taper ProFile rotary nickel-titanium instruments in simulated root canals. Int Endod J 1999;32: 155-64.
Walsch H. The hybrid concept of nickel-titanium rotary instrumentation. Dent Clin North Am 2004;48:183-202.
Shen Y, Zhou HM, Zheng YF, Peng B, Haapasalo M. Current challenges and concepts of the thermomechanical treatment of nickel-titanium instruments. J Endod 2013;39:163-72.
Yared G. Canal preparation using only one NiTi rotary instrument: Preliminary observations. Int Endod J 2008;41:339-44.
Hashem AA, Ghoneim AG, Lutfy RA, Foda MY, Omar GA. Geometric analysis of root canals prepared by four rotary NiTi shaping systems. J Endod 2012;38:996-1000.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]