In the last years several rotary systems had launched to the market for mechanical preparation. The new era in the mechanical instrumentation aims to preserve the maximum amount of the peri-cervical dentine without affecting the proper cleaning and bacterial elimination. This will improve the long-term survival of the tooth with appropriate removal of microbes and microbial irritants.~ProTaper Next is a rotary system made from M wire. It is characterized by an innovative off-centered rectangular cross section that is suggested to give the files a snake-like swaggering movement as it advances into the root canal. This movement minimizes the engagement between the file and dentin and improves extruding debris out of the canal.~TruNatomy (Dentsply Sirona), is recently introduced as a new generation of rotary file system. TruNatomy files are designed to shape root canal systems to a continuously tapering preparation with maximum preservation of peri-cervical dentine. TruNatomy system offers a more safety, simplicity, improved cutting efficiency and mechanical properties compared to previous generations of rotating instruments, Many researches had been conducted to address the effect of ProTaper Next on post-operative pain considering it the most commonly used system. Thus, this study will be performed to evaluate and compare the influence of using the two systems on the intensity of postoperative pain and bacterial load reduction.
This study aims to assess the effect of rotary instrumentation using ProTaper Next rotary system versus TruNatomy rotary system on postoperative pain and the bacterial load reduction following single visit root canal treatment in necrotic mandibular molars.