Efficacy of Two Retreatment NiTi Systems In Removal of Root Canal Obturating Materials and Apical Extrusion of Debris /

Abstract

Endodontic therapy aims to eliminate infection and decontaminate the affected tooth, so that the root canal system is rendered free from pathogenic bacteria and is filled to avoid recurrent microbial invasion. However, inadequate removal of bacteria can result in pain and periapical inflammation, and might require re-treatment if healing does not occur. Non-surgical retreatment involves removal of the obturating materials from root canal system to regain access to the apical foramen and to stop the infectious process. To remove the obturating material for retreatment, different techniques are available, such as manual instrumentation, rotary instrumentation, ultrasonics, heat and solvents. Despite the multiple options, it is still difficult to completely remove filling materials from the root canal system. Many rotary instruments have been introduced with different designs including the cross section, rake angle, radial lands and various tapers to aid in nonsurgical retreatment. Conventionally, the removal of Gutta-percha using rotary instruments can be a time saving process, safe and easy technique. Many rotary systems are used nowadays in retreatment. Some systems are used specifically in retreatment such as D-Race retreatment system due to its safety, speed and cutting efficiency(2). While other nickel titanium (NiTi) rotary systems are designed to be used in conventional root canal treatment but have shown high efficiency in removal of remaining filling materials. Profile system was the first rotary file used in retreatment in 1995. Recently, Hyflex EDM was introduced into the market. It is considered as one file shaping system that can be used alone due to its high flexibility, cutting efficiency and fracture resistance.

The success of endodontic retreatment depends on multiple factors, one of which is the amount of apically extruded debris. Several factors affect the amount of apically extruded debris, including root curvatures, cross section of endodontic files, technique of instrumentation and type of file. The more debris extruded apically, the higher the chance of post-operative inflammation and flare-ups. In addition to the filling material, the root canal sealer used in the initial root canal treatment also affects the efficiency of Gutta-percha removal. Resin based sealer is the gold standard in sealing the root canal. it has been widely introduced due to its good adhesion, sealing ability and low solubility. Another sealing material that was recently introduced is called calcium silicatebased sealer. It was introduced as being bioactive, inducing biomineralization and hard tissue formation. Thus, retrieval of calcium silicate-based sealers is considered difficult due to the hydroxyapatite crystals that they form at the interface between sealer and dentin. Complete removal of the filling materials from root canals without extrusion of debris remains challenging. Few studies showed the ability of DRace retreatment system to remove filling materials from the root canal while up to our knowledge only one study evaluated the effectiveness of Hyflex EDM system in retreatment.