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HyFlex EDM Files: Where Flexibility Meets Fracture Resistance A unique manufacturing process makes HyFlex EDM files both more flexible and more fracture resistant than typical rotary instruments. That may sound contradictory, but as Dr. Ric Gray explains, it works very well and allows him to achieve beautiful results.
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hen shaping a canal during root canal therapy, how do you make sure the file is soft enough to follow the natural anatomy of the tooth canal, but not so soft that it unwinds or even breaks? For Dr. Ric Gray, it’s all about the metallurgy. “Back in the ‘90’s, rotary files were revolutionary for the endodontics profession. But those first Austenite (nickel-titanium) files were really stiff and tended to auger out the canal rather than respect the natural anatomy,” Dr. Gray said. Five generations later, Coltene’s HyFlex EDM files represent the latest and greatest in the evolution of rotary files, in his opinion. EDM files have a cuboidal cross-section from the tip to about D5, ensuring maximum strength at the tip. Then, they transition to a triangular cross-section from there to the top at D16, providing maximum flexibility to follow the canal anatomy. The result: EDM files are more flexible and yet more fracture resistant than NiTi Ric Gray, DDS files from previous generations. How do they do it? Spark machining. In the EDM manufacturing process, files are fabricated by generating an electrical arc between the electrode and the NiTi wire. The sparks generated in this process cause the surface to melt and evaporate. So, Coltene can manufacture files that contain more than one specific shape to the file— a unique advantage that cannot be accomplished with conventional grinding techniques. “Now, you can use these files quite a bit more without being fearful of them separating on you,” Dr. Gray said. He noted several other advantages:
“ I think it’s extremely important that we offer a file that is strong, flexible, efficient, and simple to use. I think the HyFlex EDM system is uniquely designed for general dentists, personally.”
• Much more resistant to cyclic fatigue. Spark machining creates a uniquely hardened surface that is up to 700% more fracture resistant that traditional NiTi files. “Most dentists think they can spin a file until they’re done with it, but that’s not always the case.” • More tolerant of binding caused by curved or calcified canals. “Because of the way that controlled memory works, you can stress a file a little more. The file can open slightly to relieve stressing as you proceed down the canal. No other files can really do that the way CM files do.” • Regenerate after autoclaving. With proper autoclaving, the file will return to its original shape and can be reused. “Now, I will never tell you how many cases you can use a file on,” he joked. “It depends on the case—for example, how gnarly is the root system? You as the clinician have to make that determination.” • Appropriate for general dentists performing RCT. “I think this is a great file for GPs. Most general dentists are what I call cookbook endodontists. They follow a recipe. A general dentist may not do as many cases, or as difficult cases, as we endodontists may do. So, I think it’s extremely important that we offer a file that is strong, flexible, efficient, and simple to use. I think the EDM system is uniquely designed for general dentists, personally.”
VIDEO Click here to see a typical root canal shaping procedure using HyFlex EDM NiTi files.
The HyFlex EDM system includes an orifice opener, glide path file, single variabletaper shaping file, and 3 finishing files, plus matching gutta-percha obturators and a cordless handpiece. Dr. Gray’s typical approach is: Open the orifice and establish the glide path, then use the 20/05 prep file, then the 25 variable-taper shaping file, and finally, a 40/04, 50/03, or (rarely) 60/02 finishing file. “You know, we’re tackling cases now that I wouldn’t have dared to try 20 years ago,” he said. “We as endodontists are so passionate about trying to save teeth, and some of the cases we’re treating nowadays are just astounding.” While Dr. Gray continuously researches new endodontic products, he admits that in his hands, EDM files are the best choice 95% of the time. “I’ve been at this game for 30 years, and since I’ve changed over to Coltene, I have been thrilled with it. I don’t see myself ever going back,” he concluded.