The temperature at which martensite is completely transformed is called the martensite transformation finish temperature (Mf). The temperature at which this phenomenon begins is called the martensite transformation start temperature (Ms). If the alloy is cooled, from a certain temperature the crystals of the alloy change to the martensitic phase up to a certain temperature at which all the crystals of the alloy have become martensitic. Shape Memory: Phase Change by TemperatureĪt a relatively high temperature (100 ☌) the NiTi alloy is in the austenitic phase. However, some of these accidents could be avoided.įor all these reasons, this study aims to review the concepts and knowledge that all professionals preparing to perform endodontic treatment should bear in mind: the characteristics of rotary instruments, nickel (Ni)-titanium (Ti) alloy, advances in NiTi alloys, instrument design, continuous and reciprocate rotation, and instrument fracture.ģ.2.1. Therefore, this review aims to be a quick guide that summarizes what we must know and take into account to choose the best endodontic instrument in each case.ĭespite the advantages of rotary NiTi systems, there is a consensus among researchers stating that the main disadvantage of rotary NiTi systems is the unexpected fracture of the instruments, directly influencing the prognosis of root canal treatment. Despite all the information that exists in the literature, it is difficult to find a review in which all the main information on rotary instruments is grouped. The main problem in deciding which file to use in each case is often not knowing what to look for and why. These designs seek to provide advantages in the instrumentation of root canals however, the wide variety of systems on the market could be considered a disadvantage. The manufacture of manual endodontic instruments in stainless-steel is standardised under ISO regulations however, Ni-Ti rotary instruments do not have a single standard to comply with, so manufacturers design the geometry of the active part of the instrument in a non-standardised way. This paper provides the key points to keep in mind when making this type of treatment. In conclusion, when performing root canal treatment, the characteristics of the instrument and the tooth must be taken into account, and the operator’s own limitations should be known. The movement performed by the file is another of the fundamental keys to understand rotary instruments. Moreover, the geometry of the instrument will determine its behaviour, being the mass, the one that marks its resistance to a greater extent. It will be essential to know characteristics, of alloy from which the instrument is made. Therefore, this review is intended to summarize the characteristics that should be taken into account when choosing one instrument over another. The wide variety of nickel–titanium (Ni-Ti) rotary systems on the market and the lack of standardisation of this type of instrument makes the choice in each specific case difficult. Clinicians should be aware of all the characteristics and capacities of the instruments that are possible to use when conducting a root canal treatment.
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