WAVEONE

[Drsumitra]

 WHAT IT IS

In most instances, the WaveOne concept provides a single-file shaping technique, regardless of the length, diameter, or curvature of any given canal. In fact, it has been shown that a single-file reciprocating shaping technique utilizing unequal CW/CCW angles is more than 4 times safer and almost 3 times faster than using multiple rotary files to achieve the same final shape.^8,9 Pundits should not concern themselves with whether one file or multiple files are utilized to prepare canals, whether the movement is continuous rotation versus reciprocation, or if the files are manufactured from stainless steel or Ni-Ti, as long as the final shape fulfills the mechanical and biological objectives for shaping canals. The WaveOne concept represents a solution for any dentist who has concerns with any of the following:

• Using stainless steel files for shaping canals.
• Breaking mechanically driven files.
• Ledging curved canals.
• Transporting the prepared foramen.
• Using too many shaping files.
• Mastering hybrid techniques.
• Spending too much time preparing canals.

Conveniently, the WaveOne concept is system-based. Each WaveOne file has matching paper points, gutta- percha master cones, carrier-based obturators and carrier-free GuttaCore obturators. Importantly, the WaveOne single-file technique is the convergence of a unique file design, advancements in Ni-Ti alloy, and a novel reciprocating movement.

DESIGN
Strategically, only one file is generally utilized to fully shape virtually any given canal. However, there are 3 WaveOne files available to effectively address a wide range of endodontic anatomy commonly encountered in everyday practice (Figure 2). The 3 WaveOne instruments are termed small (yellow 21/06), primary (red 25/08), and large (black 40/08). The small 21/06 file has a fixed taper of 6% over its active portion. The primary 25/08 and the large 40/08 WaveOne files have fixed tapers of 8% from D1 to D3, whereas from D4 to D16, they have a unique progressively decreasing percentage tapered design. This design serves to improve flexibility and conserve remaining dentin in the coronal two thirds of the finished preparation. 
Another unique design feature of the WaveOne files is they have a reverse helix and 2 distinct cross-sections along the length of their active portions (Figure 3). From D1 to D8, the WaveOne files have a modified convex triangular cross section, whereas from D9 to D16, these files have a convex triangular cross section. The design of the 2 WaveOne cross sections is further enhanced by a changing pitch and helical angle along their active portions. The WaveOne files have noncutting modified guiding tips, which enable these files to safely progress through virtually any secured canal. Together, these design features enhance safety and efficiency when shaping canals that have a confirmed, smooth, and reproducible glide path.

ADVANCED NICKEL-TITANIUM ALLOY
Technological improvements in Ni-Ti metallurgy have generated a new supermetal, commercially termed M-wire. Engineers can identify the desired phase-transition point between martensite and austenite and produce a more clinically optimal metal than traditional Ni-Ti itself. Studies have shown that M-wire technology significantly improves the resistance to cyclic fatigue by almost 400% compared to commercially available 25/04 Ni-Ti files.¹⁰ The good news is that reducing cyclic fatigue serves to clinically decrease the potential for broken instruments.

RECIPROCATION MOVEMENT
The e3 motor (DENTSPLY Tulsa Dental Specialties) is specially engineered and programmed to drive the new WaveOne reciprocating files (Figure 4a). This motor produces a feature-specific, unequal bidirectional file movement. Because of the reverse helix design, the CCW engaging angle is 5 times the CW disengaging angle (Figure 4b). Additionally, it should be noted, this motor can drive any market version file system in full CW rotation at the desired speed and torque.
There are 3 critical distinctions with this novel, unequal bidirectional movement. One, compared to continuous rotation, there is a significant improvement in safety, as the CCW engaging angle has been designed to be smaller than the elastic metallurgical limit of the file. Two, opposed to all other reciprocating systems that utilize equal bidirectional angles, the WaveOne system utilizes an engaging angle that is 5 times the disengaging angle. Fortuitously, after 3 engaging/disengaging cutting cycles, the WaveOne file will have rotated 360°, or turned one CCW circle. This unique reciprocating movement enables the file to more readily advance toward the desired working length.⁷ Three, compared to an equal bidirectional movement, an unequal bidirectional movement strategically enhances augering debris out of the canal.11 Auguring debris in a coronal direction promotes the biological objectives for preparing canals, 3-D disinfection, and filling root canal systems.

SINGLE-FILE/SINGLE-USE CONCEPT
The WaveOne technique is both a single-file and single-use concept. As stated, it is a single-file concept given that one single file is able to transition a secured canal to a well-shaped canal, in most instances. Further, appreciate that a single WaveOne file is frequently used to prepare multiple canals in a single furcated tooth, performing a significant amount of work. The WaveOne concept must be considered a single-use concept due to the obvious stress and wear on the active portion of the file. This is in line with the growing concern in the dental community, especially in institutional settings, that all endodontic files be considered single-use. The rationale behind this legitimate concern is the documentable potential for cross-contamination between and among patients, regardless of the sterilization protocol utilized.¹²

FILE SELECTION
Although there are 3 WaveOne files, the primary 25/08 file is invariably used first in any canal that has a confirmed, smooth, and reproducible glide path equivalent to at least a loose No. 10 file. The WaveOne development team has prepared several thousand canals during the past 4 years. From our collective experiences, our group can report that the primary 25/08 file will produce an optimal final shape in almost 90% of all canals, regardless of their length, diameter, and curvature. However, in longer, narrower, and more curved canals, even when the 10 file is loose at length, the primary 25/08 WaveOne file will more predictably advance to the terminus of the canal when the glide path is expanded.
The small 21/06 WaveOne file is used when the primary 25/08 WaveOne file will not progress apically through a smooth reproducible glide path. The 21/06 is designed to work in smaller diameter, longer length, or more apically curved canals. In certain canals, when this file reaches the working length, the clinician may deem the preparation completed or, alternatively, may desire more deep shape. In these instances, the small 21/06 is considered a "bridge file" because it promotes safety when transitioning back to the 25/08 WaveOne file. Even in these instances, the WaveOne technique is still a safe and efficient 2-file sequence compared to virtually all other mechanical shaping systems.
The large 40/08 WaveOne file is used to complete the shape in larger diameter canals that are typically straighter. Examples include certain maxillary incisors, single-canal bicuspids, and larger diameter canals within maxillary and mandibular molar teeth. Recall, the usual WaveOne protocol is to initiate shaping procedures using the primary 25/08 file. However, after carrying the primary 25/08 file to the working length, gauging procedures may confirm that the foramen is bigger than 0.25 mm. In these instances, the clinician will require the 40/08 WaveOne file to fully shape and finish these larger canal systems. With experience, the clinician will learn to recognize these larger and more straightforward canals and is encouraged to initiate canal preparation procedures utilizing only the 40/08 WaveOne file.
In summary, there are 3 WaveOne files. Following access and GPM procedures, the primary 25/08 WaveOne file will generally progress to the desired working length in 3 or more passes. As previously mentioned, infrequently but on occasion, the clinician may require a second WaveOne file to complete a predictably successful final shape.