Endodontic Instruments Overview

Study Notes

Endodontic instruments are categorized by the International Organization for Standardization (ISO) and the American National Standards Institute (ANSI).
These organizations set standards for terminology, dimensions, physical properties, measuring systems, and quality control for endodontic instruments and materials.
Instruments are classified as either hand instruments or rotary instruments.

Hand instruments are grouped by usage according to ISO standards.
A standard hand file consists of a working area of 16 mm, a handle, a shank, and a rubber stop.
The handle is numbered and colored according to the file's size.
The shank is 16mm long with blades.
The rubber stop is used for length determination.
Files are used for measuring the length and cleaning, widening, and shaping canals.
Files create space for root filling materials.
Hand instruments are made from stainless steel or nickel-titanium.

K-type file: A ground–twisted instrument with a file that is twisted counter-clockwise.
Hedstroem file: A machined instrument, ground on a lathe.
Reamer: A ground–twisted instrument with a file that is twisted counter-clockwise.

ISO defines the size of a file by its diameter at the tip, measured in one-hundredths of a millimetre.
ISO standard files have a 2% taper over their working length.
Example: A #10 file has a tip diameter of 0.10 mm.
Color Coding:
- Pink = 06
- Grey = 08
- Purple = 10
- White = 15
- Yellow = 20
- Red = 25
- Blue = 30
- Green = 35
- Black = 40

Standardization of endodontic instruments began in the 1950s due to variations in instruments from different manufacturers.
Standardization covered the diameter and taper of each instrument, the graduated increase in size from one instrument to the next, and a numbering system based on the diameter of the instrument.

D0: The diameter of the projection of the working part at the tip end of the instrument.
D16: Represents a point 16 mm from D0, where the cutting part of the instrument ends. D16 is 0.32 mm larger than D0.
The taper for standardized instruments is a constant 0.02 mm per 1mm of cutting flute.
The length of instruments ranges from 21mm to 31mm, with 25mm being the most commonly used.

Carbon Steel: No longer used due to its tendency to corrode.
Stainless Steel: More resistant to corrosion but has limited flexibility.
Nickel Titanium: More flexible, adaptable to canal curves (3 times as flexible as stainless steel), and has a very low modulus of elasticity.

Machined Instruments: Created by grinding the instrument on a lathe (e.g., Hedstrom-type files).
Ground–Twisted Instruments: Made by grinding raw wire and then twisting it counter-clockwise (e.g., K-type files and reamers).

Barbed broaches are made from soft steel wire.
Barbs are created by cutting into the metal and forcing the cut portion away from the shaft.
The tips of the barbs point towards the handle.
The cuts are made eccentrically around the shaft.