Endodontics: Rotary or reciprocating instrumentation. clinical uses and advantages

OBJECTIVES The purpose of this Module is to critically describe the evolution of endodontic instrumentation techniques and of rotary and reciprocating instruments to identify their clinical advantages and limitations in the clinical practice. Morphological aspects, importance of bacteria contamination and other clinical aspects are described and discussed. MATERIALS AND METHODS All concepts and techniques described in this didactic Module are supported by an extensive analysis of the literature ranging from in vitro studies on the mechanics of movements to the microscopic analysis of alloys, passing through long-term clinical and microbiological studies on various endodontic instrumentation techniques. The most recent technological innovations in the endodontic field were subsequently analyzed. In particular, the application of heat treatment to rotary instruments has led to a significant reduction in the risk of fracture, even in the presence of canals with severe curvatures with mineralized or sclerotic dentin. The development and introduction of the reciprocating movement applied to NiTi instruments allowed a reduction in the operating sequences and it is proposed as a single-instrument technique. Different instrumentation techniques will be described, analyzed step by step and correlated according to the present clinical situation. In association with the instruments, some of the main endodontic motors that introduce torque and reverse function will be analyzed in order to control the speed and mechanical stress of the instrument, to prevent instrument fracture and to facilitate the operator in clinical practice. The authors will describe several clinical tech niques and the use of different instruments. RESULTS The first NiTi instruments, marketed around 25-30 years ago, presented only austenitic phase at room temperature. These instruments were rigid and presented a high risk of fracture. More recently, rotary NiTi instruments characterized of thermal or chemical treatment have been introduced, with presence of austenitic, martensitic and R phase at room temperature. These instruments have greater resistance, deformability, flexibility and shape memory, allowing their use in preparation of curved and complex endodontic canals reducing significantly the risk for fracture. The reciprocating movement is introduced in clinical practice with specific motors. The technique offer the possibility to prepare root canals with simple and moderately curved morphology. CONCLUSIONS The described techniques, per formed with heat treated rotating and reciprocating NiTi instruments, allow to approach to both simple and complex root canals with a lower risk of instrument fractures. The use of such complex endodontic techniques in complex anatomy canals is only possible after an adequate training of the operators to prevent any clinical error and fracture of the instrument. CLINICAL SIGNIFICANCE The use of the most suitable preparation technique allows to perform root canal treatment with greater safety and minor risks for intra-operative complications.