The effect of a brushing motion inside a sequence: an in vivo study

The aim of the present study was twofold: To propose a new methodology to analyze instrumentation stress in vivo by measuring the torque provided by an endodontic motor during the clinical use of the nickel-titanium rotary (NTR) instruments; and to compare the advantage of brushing techniques in reducing operative torque. 40 canals were divided in two groups (n=20) and prepared by a skilled endodontist using TF 35. 04. rotary instruments (KerrEndo, Orange, Ca). In one group, a 30 s brushing was previously performed with a (TF 25.06) to increase flaring. All instruments were rotated at 500 rpm with maximum torque set at 2,5 N using an endodontic motor (Kavo, Biberach, Germany), which automatically records and saves torque and speed values every 1/10 seconds. Data were recorded and statistically analyzed with the significance level set at p. Previous coronal flaring (brushing) with the first instrument (size 25, taper 06) significantly reduced instrumentation torque (both mean and maximum torque values), time and number of steps needed by the second instruments (size 35, taper 04) to reach working length. The development of new and more sophisticated means of analysing torque during intracanal shaping provides useful information for a better understanding of the instruments performance in vivo, aiming at improving efficacy and safety.