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Enrico Cassai

History of Endodontic Instruments

37212 Views - Apr 2016

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The first endodontic file was crafted in the mid 1800s by Edward Maynard by notching round wires at first from watch springs and then from piano wires, into files that were capable of removing pulp and debris from teeth. K-files, which are, to these days, the most commonly used stainless steel hand files in endodontics, were developed by the Kerr company in 1915. Stainless steel hand file techniques, including the step-back, the anti-curvature, the step-down and the balanced force techniques have all been promoted in order to fulfill the instrumentation objectives proposed by Schilder. In 1960 a novel nickel-titanium alloy was developed by William Bueller in Silver Springs, Maryland at the United States Naval Ordinance Laboratory (that is why we often refer to NITINOL where NOL stands for Naval Ordnance Laboratory).

FIRST GENERATION The first rotary NiTi instrument was designed by Dr. John McSpadden with a 0,02 taper and was placed on the market in 1992, changing how dental practitioners envisioned instrumentation. File breakage issues were substantial at that time. In 1994, Dr. Johnson introduced the PROFILE line, 0.04 and 0.06 tapered instrument series and the “ORIFICE SHAPERS.” Their cross-sectional shape resulted from the machining of three U-shaped grooves around a tapered NiTi wire, with and unground space remaining between the grooves, providing the so-called “radial land” area. Other rotary file lines, such as LightSpeed (Senia and Wildey), Quantec (McSpadden) and Greater Taper files (GT Rotary System by Dr. Buchanan) were developed soon afterwards. All of the first-generation NiTi rotary files featured passive cutting radial lands and constant tapers over their working parts, and, most of all, required a considerable number of files to achieve preparation objectives.

SECOND GENERATION The next generation of NiTi rotary files came to market by the end of the 90s. These instruments differed from the previous generation in their cutting edges (and the absence of radial lands). This generation aimed to reducing the number of instruments needed to achieve the preparation goals. To this generation belong ENDOSEQUENCE (Brasseler USA), BIORACE (FKG Dentaire), PROTAPER (Dentsply Tulsa), K3 (Sybron Endo), M-TWO (Sweden & Martina), FLEXMASTER (Dentsply), HERO 642 (Micro-Mega®, Besançon, France).

THIRD GENERATION The development of new manufacturing technologies made it possible to optimize the microstructure of NiTi alloys, thus giving birth to 3rd generation instruments. Special heat treatment provides files with a more resistant, both to stress and fatigue, alloy; the instruments that underwent this type of processing include HYFLEX CM (HyFlex; Coltene Whaledent, Cuyahoga Falls, OH), K3XF (SybronEndo, Orange, CA), PROFILE GT SERIES X (GTX; Dentsply Tulsa Dental Specialties, Tulsa, OK), PROFILE VORTEX (Vortex) and VORTEX BLUE (Dentsply Tulsa), TYPHOON™ Infinite Flex NiTi (TYP CM; Clinician’s Choice Dental Products, New Milford, CT), and TWISTED FILES (TFs; SybronEndo).

FOURTH GENERATION Better performance reached in reciprocation technology gave birth to this new generation of reciprocating files. The 4th generation comprises instruments used with a motion different from rotary or those crafted for as “single file techniques”, meaning used as the only tool to perform the whole shaping phase. Single-file shaping techniques were launched both by WAVEONE (Dentsply Tulsa Dental Specialties and Dentsply Maillefer) and RECIPROC (VDW) in 2011. The self-adjusting file (SAF; ReDent-Nova, Raanana, Israel) was designed as a thin-walled, hollow cylinder made out of a delicate NiTi grid, featured with an abrasive surface: the SAF system provides a new mode of operation as it uses a simultaneous irrigation, allowed by the void cylinder.

FIFTH GENERATION The fifth generation of shaping files exploits a wave motion along the active part of the files: this is allowed by an off-set design that conveys mechanical rotation into wave motion. Brands that produce variations of this technology are REVO-S,ONE SHAPE® (Micro-Mega®, Besançon, France), and PROTAPER NEXT (PTN; Dentsply Tulsa Dental Specialties/Dentsply Maillefer).

Img. 1 NEW CLASSIFICATION - CLINICAL USAGE If we evaluate the endodontic instruments on the basis of their clinical, everyday usage, we should consider a classification, as shown in the diagram above, depending on the distinct phases of the endodontic treatment, namely: - Elimination of the middle third coronal interference - Scouting of the apical third - Glide path - Final shaping PREFLARING FILES After opening the pulp chamber and identifying root canal entrances the first step is to remove the interference of the middle third of the root canal. Included in this category are all Ni-Ti and Stainless Steel rotary instruments or Ni-Ti reciprocating files that are used to remove the interference of the medium-coronal third to allow manual instruments to better scout the apical third. Ultrasonic smallest tips may also fall into this category, when used under magnification and focus on their high cutting capacity.

Img. 2 SCOUTING FILES This group includes all the hand instruments that allow to reach the correct working length of a root canal. The choice of scouting instruments is closely related to the anatomy of the canal: wide / normal / narrow, straight / curved.

Img. 3 GLIDE PATH FILES All files, both manual and rotary, that allow the clinician to create a smooth tunnel from the canal orifice to the correct working length are included in this group. Glide path creation is essential for prevention of rotary file separation and most effective rotary use.

Img. 4 SHAPING FILES Enter this category all rotary NiTi instruments or manuals that make the complete shaping of the root canal system. Rotary instruments of this group can be distinguished depending on the movement in rotating and reciprocating motion, and depending on the number in single or multiple instruments.

Img. 5 - CLINICAL CASE 1 (GT rotary System) Tooth 2.6 is necrotic, pulp chamber already accessed by a colleague PREFLARING: Gates Glidden 1-3 SCOUTING: k-file 10 GLIDE PATH: Manual (10, 15, 20 at WL) SHAPING: GT 30.08 on MB, MB2 and DB,GT 40.10 on P Obturation: Continuos wave

Img. 6 - CLINICAL CASE 2 (PROTAPER) Tooth 2.6, acute pulpits PREFLARING: Gates Glidden 1-3 SCOUTING: k-file 10 GLIDE PATH: Manual (08, 10, 15, 20 at WL) SHAPING: Protaper F2 on MB, MB2, Protaper F3 on DB, Protaper F3 on P Obturation: Thermafil 30 on MB, MB2, DB; Continuous wave on P

Img. 7 - CLINICAL CASE 3 (PROTAPER NEXT) Tooth 2.6, acute pulpits PREFLARING: Gates Glidden 1-3 SCOUTING: k-file 10 GLIDE PATH: Rotary (Proglider) SHAPING: X2 on MB, MB2 and DB, X3 on P Obturation: Thermafil 30 on MB, MB2, DB; Continuous wave on P

Img. 8


Various generations of endo instruments have come out on the market to these days: most of them provide effective improvements in design and material, but they can't do all the work for us. We need to follow the concepts of Pre-flaring, Scouting, Glide Path and Shaping, understanding when each of these steps must be performed and when some can be skipped, and use the instruments according to our clinical experience. Some skepticism about producer claims is useful, though: our experience and skills help us in finding the best menu, made up of one or two entrees, not always needed, and two main courses, glide path and shaping that can never be missed in an endodontic dinner.


New endodontic files for root canal instrumentation are put on the market non-stop, just like older systems are updated. The evolution of designs and the implementation of new endodontic instruments has given emphasis on different aspects of the endodontic workflow. First generation NiTi rotary files focused on the superelasticity of the metal, while its design emphasized maximum safety (e.g. radial lands) rather than cutting effectiveness. Subsequently, the focus was put on new manufacturing processes and features, such as a variable cross-section along the length of the active portion of the file. Many physical properties affect the clinical performance of NiTi rotaries. Nevertheless, clinical experience, associated with handling properties and safety constitutes one of the most important factors in case outcome, thus determining the fate of a new designs.
So, what should we expect from the future? New instruments are most likely to try and fulfill the three sacred tenets for shaping canals: safety, effectiveness, and simplicity and both research and clinic should validate the characteristics of every renewed system.



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