K file series were introduced centuries ago and are still considered as the most commonly used for root canal treatment. These files are used to clean and shape the root canal and perform the chemomechanical debridement for the whole length of the canal starting from apical to the surface.
K Files are available in three different taper sizes of 0.02, 0.04 and 0.06 with the lengths of 21mm, 25mm, and 30mm. The positive rake angle provides a more effective cutting and the core diameter enhances the flexibility throughout the length of the instrument. The series of 3 radical lands with a relief of the two lands reduces the friction on the canal wall. It has a safe cutting tip and the variable pitch helps in preventing the screwing effect.
K Files are made up with a wire of cut from a tapered instrument ending at the tip giving its tip a square cross-section. These can be used in filling action or in reaming action. When the file is locked inside the canal the clockwise rotation it unwinds and gives ductile type fracture whereas in anti-clockwise rotation it leads to sudden brittle fracture.
K Reamers have a triangular cross-section with loose spirals around the flute. Reamers have 2.5 times more cutting efficiency. They have a reaming motion. These are used to ream canals, they cut the canals by inserting into the canal by twisting clockwise one quarter to half turn and then withdrawing i.e penetrating, rotating and retracting.
K files have another efficient flex file with better specifications.
K - Flex Files has a cross-section of rhomboid shape and has more flexibility because of the twisted and series of alternate sharp cutting edges. It has obtuse non-cutting edges which increase the cutting efficiency as compared to other K-Files. These files work the best for the debris removal, the obtuse angles of rhombus create anger that helps in removing the debris to a large extent. It also reduces the danger of dentinal filling in the canal.
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