Reamer: Design & Structure, sizes, colors, uses, safety tips
Design & Structure
A reamer is manufactured from a triangular or square steel wire that is twisted to give the typical shape of a reamer. The angle between the long-axis and the cutting blade is small, which is why preparation by reamer is effective only in rotating motion.
The tip of the instrument is cutting which makes a reamer suitable for the preparation of straight canals only without the risk of ledging.
Sizes & Codes
Reamers come in sizes 06 – 140, all with a taper of 0.02. Reamer design is identified by the triangle symbol on the handle.
A reamer is the most effective hand instrument in straight canals. It is used by continuous rotation (upper picture) when the resistance is small or moderate and by balanced force (lower picture) when the resistance is greater.
In curved canals ledging easily occurs with even small reamer sizes if instruments are not pre-curved. Reamers are excellent instruments in straight canals but poorly adaptable to curved canals.
Reamers can be rotated only using moderate pressure. Use of force, particularly with smaller sized instruments, may result in distortion of the helical structure and ultimately in fracture. Each instrument should be checked for symmetry by rotating it against an even background before introducing it into the canal.
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