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What is A giromatic handpiece for endodontic instrumentation operates by a: and explain in detail?
Classification of endodontic instruments according to method of use:
Group I: Hand-operated endodontic instruments 
Example: Broaches, files, reamers. 
Group II: Nonrotary endodontic instruments 

Engine driven instruments: 

– Reciprocating or quarter-turn motion.
– Vertical stroke along with quarter-turn motion.

Ultrasonic and sonic instruments 

Group III: Rotary endodontic instruments used with a handpiece

Slow speed rotary stainless steel instruments.
NiTi rotary instruments.

Key concepts 
Commonly used reciprocating handpiece is Giromatic handpiece. It rotates with quarter-turn motion at 3000 rpm.
Since this motion (quarter turn to and fro oscillation) resembles motion of steering of a ship, it is called Giromatic.