The same instrument or explorer movement is identified and disturbing to Patients .Even Manual or ultrasonic scaling is disturbing evident from facial expressions
Since the endodontic instruments are placed inside the root canal and root canal procedure done under anaesthesia, hence it does not effect. If same instruments worked without LA the patient complaints unless the tooth is nonvital
Nonvital teeth do not need injection as long as you do not put pressure on the tooth. With the high speed instruments you can drill the tooth with feather touch without putting any pressure. The pressure on the tooth causes pain. Once the pulp chamber is exposed the pus comes out and the patient gets immediate relief.
An ideal irrigant should reduce instrument friction during preparation, Facilitate dentin removal, Dissolve inorganic and organic tissue, Penetrate to canal periphery, Kill bacteria and yeasts and least irritating to the periapical tissues. However, there is no one unique irrigant that can meet al.,l these requirements, even with the use of methods such as lowering the pH, increasing the temperature, as well as addition of surfactants to increase the wetting efficacy of the irrigant. More importantly, these irrigants must be brought into direct contact with the entire canal wall surfaces for effective action, particularly for the apical portions of small root canals.
endodontic instrument is rotated in pulp space after removal of pulp so tooth is sense less and all instrument movement between all around dentinal wall which is rigid and sense less plus we are using reduction gear handpiece so movement of endodonitc instument is very slow and that is why it does not disturb human but if instrument is touching wall very tightly it will rub dentin wall may create heat due to friction it will disturb human while working