The new Genius Proflex are engine-driven endodontic files with unique features that make these instruments the most practical option for root canal mechanical shaping. With a exclusive heat treatment innovation, Genius Proflex files are made with different customized heat treatments for each group of instruments, making flexibility and resistance to be consistently balanced depending on the metal mass of each instrument in the series. In addition, two different cross-sections are used, triangular rhomboidal and double S, ensuring once again that each instrument suits perfectly to the instrumentation phase, whether it be the glidepath preparation, enlargement or even final apical shaping. The files’ series has options for preflaring, mechanical glidepath, and shaping with three distinct heat treatment recipes, discernible by the colors of the blade: purple for a more austenitic performance, blue for a perfect balanced austenic-martensitic performance; and gold for a super flexible martensitic predominant phase file. With exquisite grinding process using the state-of-the-art CNC machines, all finishing details were strictly observed, such as double-angled penetration guide, progressive pitch, variable helicoidal angles, slightly positive rake in the flaring and enlargement files, among others.
Genius Proflex files have been designed so that the operator has option of three instruments in sequence for standard cases, up to a complete set for more challenging canal anatomies. With more than three times more cyclic fatigue resistance than its predecessors, the second generation of Genius endodontic files can be used in any endodontic motor in rotation, or even with the Genius motor in right cutting reciprocation. In addition, the most advanced cordless endodontic motor on the market, the new Medidenta ACE, has specific programs for Genius Proflex files in rotation and reciprocation, in addition to the unprecedented Genius Autosense special program, which automatically changes the movement from rotary to reciprocation, and back from reciprocation to rotary, determined by the dentin walls resistance.
Customized Heat Treatment
The importance of the heat-treatment
by: Carlos A. Spironelli Ramos
Root canal instrumentation is accomplished by the use of endodontic instruments and irrigating solutions under aseptic working conditions. Root canal instrumentation may be carried out using hand-held or engine-driven instruments. Up until the last decade of the past century, endodontic instruments were manufactured out of stainless-steel. Stainless-steel ﬁles have an inherent stiffness that increases as the instrument size increases. As a result, when preparing a curved root canal, restoring forces attempt to return the instrument to its original shape, especially when the operator uses a ﬁling motion. Therefore, in curved canals, steel instruments must be pre-curved for use, which effectively prevents them from being used in a rotary motion. An instrument that is too stiff will cut more on the convex (outer) side than on the concave (inner) side, thereby straightening the curve.
Engine-driven files manufactured out of a nickel–titanium (NiTi) alloy have proven to be a valuable adjunct for root canal therapy. NiTi instruments are highly ﬂexible and elastic. Advantageously, NiTi rotary shaping ﬁles have nearly eliminated the iatrogenic instrumentation complications that are often connected to endodontic steel instruments. NiTi instruments were introduced over two decades ago. Since their ﬁrst appearance, instrument design has changed considerably; progress has been made in manufacturing as well as alloy heat-treatment. Traditionally ﬁles had been produced according to empiric designs, and even today many instruments are still devised by individual clinicians rather than developed through an evidence-based approach. Clinical procedures and ideal working parameters are still being reﬁned as new instruments continue to be introduced to the market. With new versions rapidly becoming available, the clinician may ﬁnd it difﬁcult to choose the ﬁle and technique most suitable for an individual case or even during one case instrumentation protocol. NiTi instruments have undergone a revolution regarding different designs to produce an instrument that cuts effectively while exhibiting resistance to fracture even in the most challenging anatomical conﬁnes. One should always bear in mind that all ﬁle systems have beneﬁts and weaknesses. Instrument properties are derived from the type of alloy, degree of taper, cross-sectional design and heat-treatment protocol.
Nickel–titanium (NiTi) alloy has been used in endodontics for almost 30 years and has brought a major breakthrough to root canal therapy. NiTi endodontic instruments with super-elasticity have gained extensive popularity amongst clinicians due to their higher ﬂexibility and greater torsional resistance than the traditional stainless-steel ones. Therefore, an increasing number of super-elastic NiTi endodontic ﬁles with various geometry designs (cross-sectional shape with or without “radial lands” or sharp cutting edges, constant or variable pitch, and progressive or constant taper) have been developed. However, the undesirable and unexpected separation of NiTi endodontic rotary ﬁles during root canal instrumentation caused by flexural (cyclic) fatigue and/or torsional overload still remains a serious concern and drawback in clinical use. Torsion overload is one of the primary mechanisms responsible for the intracanal separation of NiTi endodontic instruments, which accounts for 55.7% of the failures of NiTi rotary files. It can be generated within the rotary ﬁle when the tip or some part of the instrument is locked against the canal wall while the shank of the ﬁle (driven by the handpiece) continues to rotate or is subjected to excessive pressure by the operator. The tip fractures when the handpiece torque exceeds the ultimate strength of the metal. High torsional stiffness is desirable for the clinical performance of small sizes of rotary ﬁles owing to the enhanced cutting efﬁciency and reduced torsional failure risk. Cyclic fatigue occurs when a metal is subjected to repeated cycles of tension and compression that cause its structure to break down, ultimately leading to fracture. It is the main reason for the majority of broken instruments. The fracture caused by cyclic fatigue of NiTi endodontic instruments is difﬁcult to detect during clinical practice due to the invisible signs of permanent deformation during cyclic fatigue. That is why many attempts have been made to improve the resistance to cyclic fatigue for NiTi files, predominantly novel heat-treatment protocols.
In recent years, novel kinds of NiTi endodontic ﬁles fabricated by proprietary heat-treatment processes are being propose to mitigate file breakage during its clinical use. In this case, normally the heat-treatment gives more flexibility to the file, increasing cyclic fatigue resistance. This particular feature is adequate for larger sizes of the files since they have more metal mass. If the same method is accomplished in small files sizes, a side effect can occur leading the file to unwinding when some pressure is undergoing.
NiTi endodontic files used in clinical practice are subjected to both ﬂexural fatigue and torsional load simultaneously during root canal preparation procedures, probably leading to instrument separation due to hybrid forces. Bending is imposed by the root canal anatomy, in the case of blockage, it is also associated with torsion. Clinically, both cyclic fatigue and torsional failure probably occur simultaneously. The mechanical properties of NiTi endodontic instruments including ﬂexibility, torsional resistance, and ﬂexural fatigue are fundamental requirements of endodontic instruments for successful use. The ﬂexibility is beneﬁcial for maintaining the original shape of root canals, especially for the ones with severe curvatures. Adequate torsional resistance and ﬂexural fatigue resistance favor reducing the occurrence of file breakage. Thus, ﬂexibility and resistance to fracture constitute properties expected for an ideal root canal ﬁle.
From a material point of view, the properties of NiTi alloys depend on their chemical composition, phase constitution, and fabrication procedures, among which the metallurgical properties including the chemical composition and phase constitution are the internal factors and the fabrication procedures such as cold working, heat-treatment before and/or after grinding the blank are the factors that can determine mechanical properties for NiTi endodontic ﬁles. Controlling mechanical properties and their association with the metallurgical properties of NiTi rotary instruments is helpful for clinicians to make decisions regarding which instruments are appropriate for each phase of the instrumentation procedures of root canal therapy. The inﬂuence of metallurgical properties on endodontic files mechanical properties is possible to be adjusted to each file size by controlling the heat-treatment for each specific file on the instrumentation sequence. In this sense, tailoring the heat-treatment for each file size can keep flexibility to larges files while maintain torsional resistance to small sizes files.
NiTi alloy can exist in two different temperature-dependent crystal structures called martensite (lower temperature or daughter phase) and austenite (higher temperature or parent phase). The crystal lattice structure can be altered by either temperature or stress. This is important because several properties of the two forms are notably different. Near equiatomic NiTi alloys contain three microstructural phases (i.e., austenite, martensite, and R-phase), the character and relative proportions of which determine the mechanical properties of the metal. When the material is in its martensite form, it is soft and ductile and can easily be deformed, while austenitic NiTi is quite strong and hard. The conventional super-elastic NiTi ﬁle has an austenite structure at room and body temperatures. It is well known that the nature of the alloy and the manufacturing process greatly affect the mechanical behavior of the instrument. To improve the fracture resistance of NiTi ﬁles, new alloys were introduced to manufacture NiTi ﬁles or developed new manufacturing processes. A series of proprietary thermomechanical processing procedures has been developed with the objective of producing super-elastic NiTi wire blanks that contain the substantially stable martensite phase under clinical conditions. Enhancements in these areas of material management have led to the development of the new generation of endodontic NiTi instruments. NiTi ﬁles with heat-treated process contain a mixture of austenite and martensite conditions at body temperature. The martensitic phase of NiTi has some unique properties that have made it an ideal material for many applications. The martensitic phase transformation has excellent damping characteristics because of the energy absorption characteristics of its twinned phase structure. In addition, the martensitic form of NiTi has an excellent fatigue resistance.
Therefore, endodontic files with high expression of austenitic phase will have more torsional fatigue resistance, while files with high expression of martensitic phase will have a better cyclic (flexure) fatigue resistance. If the same heat-treatment is performed for all sizes, some of them will benefit of the accomplished metallurgical changes while others will be harmed. One method doesn’t equally benefit all sizes needs and it is imperative that customize heat-treatment protocols be applied so that all files’ sizes are adequately improved in its mechanical behavior.
- Genius Proflex is the only engine-driven files in the market that have different heat treatment customizations for each group of instruments in the sequence. Genius Proflex files have progressive flexibility due to a proprietary sequence of different heat treatments recipes.
- 30 .08 19 millimeters orifice shaper. The double-S cross section increases debris removal. Blue heat treatment and 12 millimeters working lamina gives the exact scope of action to preflare the cervical third, provoking a straight-line access for your next files.
- One of the most important instruments in the line is the Curvature Sweetener. This 25.06 file is 19mm long with a 14mm blade. The double S cross section guarantees efficiency, while the gold heat treatment ensures flexibility to work within the curvature. With a 1mm wire diameter, this instrument causes a subtle enlargement at the curvature level.
The minimally invasive preparation provided by the .08 or 1.0mmm wire diameter of the Genius Proflex will preserve sound dentin structure located on the cervical third, preventing eventual post-treatment root fracture. Comparing the design of the 25 06 Curvature Sweetener with a regular 25 06, note the difference on the cervical diameter of both files. Genius Proflex Curvature Sweetener is almost 20% thinner than the regular 25 06.
- Pathfinders instruments are essential in calcifiedand constrict cana The first Genius Proflex glidepath instrument is the delicate pathfinder 13 .03 taper file. This triangular rhomboidal instrument has a purple thermal treatment, which guarantees the right hardness to open the way for the other larger files in the sequence. With a 0.8 wire diameter and an elongated pitch, this instrument easily slides through the anatomical canal, generating a smooth enlargement.
- Pathfinder 17 finalize the glide path preparation. It is a17 tipdiameter with 05 taper. The pathfinder 17 has a triangular rhomboidal cross section with purple heat treatment, and it is made using a .8 mm wire.
Graph showing the enlargement created using the Pathfinder 13 03 in white-gray, followed by the Pathfinder 17 in yellow.
- The geniusProflex 25 04 file has a S cross section with a slight positive rake, which guarantee the right cutting action on both rotary or asymmetric reciprocation motion. The purple heat treatment ensures that this file open the final apical third space without compromising centering, with efficiency and security.
- GeniusProflex 30 and 35 04 files have a triangular rhomboidal cross-section, giving for these apical finishing enlargement files a smooth cutting action, avoiding typical screw-in effect of larger files. The blue heat treatment gives an intermediate austenic-martensitic performance, with the desired flexibility even in accentuated curvatures.
- The larger files’ group are 40, 50 and 60 04 files. The triangular rhomboidal cross-section avoids the screw-in effect, while the gold heat treatment assures the highest martensitic phase level of flexibility.
- One of the biggest challenges of rotary instruments production engineering is the tip finish. GeniusProflex tip has an entry angle of approximately 65 degrees, and a transition angle of approximately 20 degrees, allowing the instrument to smoothly follow the canal anatomy with no ledge formation.
- Using the state-of-the-art CAD-CAM technology, the GeniusProflex files are grinded by the Rollomatic CNC cutting tool, ensuring that features like progressive pitch and different helicoidal angles are meticulously reproduced on the instruments.
- GeniusProflex files are offered in different configurations packages and are available in 21, 25 and 31mm lengths.