Recent advances in metallurgy and design of rotary endodontic instruments: a review

Abstract

A variety of instruments are available for the extirpation of the pulp and the instrumentation and preparation of the root canal. Recently, nickel-titanium (NiTi) alloy is utilised for the manufacturing of endodontic instruments. Compared to other metals, these alloys are highly flexible, which significantly enhances ease of canal shaping. This review article gives an account in the advances of NiTi endodontic instruments with an emphasis on metallurgical, mechanical properties, the design features of each generation with a special focus on the latest generations of NiTi instruments.

Evaluation of surface characteristics of new rotary nickel-titanium instruments - SEM-EDS analysis

“…This finding is in accordance with the results of a research on a significant reduction of surface irregularities of electropolished instruments [3]. Electropolishing creates a homogeneous oxide layer during the production process, which reduces the appearance of surface defects and increases resistance to corrosion and fracture [27]. Electropolished surface of instruments is visibly brighter than the untreated surface [26].…”

“…Subsequent heat treatment of finished Ni-Ti instruments (HyFlex) potentially offers the most promising method of manufacturing rotating instruments [27]. These instruments do not have the shape memory that traditional Ni-Ti instruments have, and a special thermomechanical procedure significantly increases their flexibility [28].…”

“…Naknadna termička obrada gotovih Ni-Ti instrumenata (HyFlex) potencijalno nudi najperspektivniju metodu proizvodnje rotirajućih instrumenata [27]. Ovi instrumenti nemaju memoriju oblika koju imaju tradicionalni Ni-Ti instrumenti, a poseban termomehanički postupak značajno povećava njihovu fleksibilnost [28].…”

“…Ovaj nalaz je u saglasnosti sa rezultatima istraživanja o značajnom smanjenjenju površinskih nepravilnosti elektropoliranih instrumenata [3]. Elektropoliranjem se tokom procesa proizvodnje stvara homogeni oksidni sloj koji smanjuje pojavu površinskih defekata i povećava otpornost na koroziju i lom [27]. Elekropolirana površina instrumenata je vidljivo sjajnija u odnosu na netretiranu površinu [26].…”

Effects of sodium hypochlorite on corrosion of the rotary nickel-titanium endodontic instruments - SEM analysis

“…The current results of studies on the impact of sterilization on the occurrence of corrosion are contradictory and there is no clear position on this issue. Multiple sterilization cycles can cause corrosive changes on the surface of Ni-Ti files due to changes in the surface layer of titanium oxide [16,17]. However, it has also been observed that after sterilization, resistance to cyclic fatigue and torsional stress increases in certain types of Ni-Ti instruments because the sterilization process acts as a form of heat treatment [18].…”