Aim: To evaluate the effects of lubrication on torque generated during rotary preparation of simulated root canals in dentine using ProFile and ProTaper Nickel-Titanium instruments.
Methodology: Thirty-two 3 mm thick dentine discs were used for this study. Four pilot holes were drilled perpendicularly through each disc. These simulated root canals were filled with water, aqueous 15% ethylenediamine tetraacetic acid (EDTA) or a paste-type lubricant (Glyde). Empty canals served as controls. Peak torque values and apically directed forces of rotary instruments were measured using a specially designed testing platform. Full torsional loads over time were calculated by integration of continuous torque records. Data were compared using analyses of variance with the alpha-type error set at 0.05.
Results: Maximum torque values using ProFile instruments were significantly (P < 0.005) reduced by the EDTA solution, whilst no reduction was observed using Glyde. With ProTaper instruments, no lubricant effects on maximum torque values were observed (P = 0.372). Full torsional loads over time were significantly reduced for both ProFile and ProTaper preparation (P < 0.005) by the use of lubrication. The two fluids performed significantly better than paste-based Glyde. All lubricants reduced force when applied to ProTaper by mean reductions ranging from 12 to 54%, whilst Glyde lead to increased force when applied to ProFile.
Conclusions: Under the conditions of this laboratory study, lubrication appeared to be advantageous. Aqueous solutions generally performed better than the paste-type product under investigation, which showed untoward effects when used in conjunction with a rotary instrument with a U-shaped cross-section (ProFile).