Measurement of torque generated during intra‐canal instrumentation in vivo

Abstract

Aim

To compare two different clinical techniques when using endodontic rotary instruments by monitoring the torque in vivo.

Methodology

Ten single rooted maxillary anterior teeth were prepared by an endodontist using size 25, .06 taper TF rotary instruments (KerrEndo, Orange, CA, USA). All instruments were rotated at 500 rpm with maximum torque set at 2.5Ncm using an endodontic motor (Kavo, Biberach, Germany), which automatically recorded the torque values every 1/10 of a second. Instruments were used with two modi operandi: (a) Inward action: short length intermittent progression with slight apical pressure aiming to reach the working length (also known as pecking motion), followed by (b) Outward action: lateral brushing action selectively directed to address the canal circumference while removing instruments in the coronal direction. The mean, maximum and accumulated torque values were recorded and analyzed statistically (t test and Wilcoxon test with a significance level set at 5%. None of the recorded values exceeded the selected torque limit.

Results

A significant difference between inward and outward actions was found regarding the evaluated parameters (p<0.05). The outward action (brushing) was significantly safer (requiring less torque) compared to the inward action (pecking).

Conclusions

Torque measurements during in vivo instrumentation provided useful information regarding the techniques evaluated. Although the torque limit was not reached by any of the two actions, the technique impacted significantly on the torque applied to the instrument.

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