K file is called round file, there are three kinds of root canal file, KRH file, K-shaped structure is similar to the expansion needle, twist-shaped drill bit, diamond-shaped cross-section, four blades, the blade is arranged in a spiral shape, the groove is narrow, but shallow, K The root canal wall filed is very smooth. The other two files, the H file is called a rough file, the working end blade is circled around the needle shaft, and the groove of each knife edge changes from shallow to deep from the top to the tip. The shape is like a pyramid, this structure has a strong cutting effect. The R-shaped file, called rat tail file, is characterized in that the blade is not continuous, but has inverted tooth-like protrusions. This kind of inverted tooth is also hovering around the long axis. The R file has a very sharp blade and high cutting efficiency. But the filed wall is not smooth. The root canal file is often used in conjunction with the expansion needle to achieve the purpose of expanding the lumen and filing the wall of the tube. Clinically, the root canal file has 6 numbers, and it should be used from small to large.
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