How to prevent fracture of NiTi files

Abstract

More certain therapeutic and significantly facilitated solution of everyday endodontic problems are provided by the introduction of NiTi rotary files in endodontic practice and their proper application. However, their widespread use has caused more and more frequent fractures and has become a significant frustrating factor that diminishes their numerous benefits. Torsional stress and cyclic fatigue are the main reasons for the occurrence of a fracture, and the frequency of NiTi file fractures is exactly proportional to the degree of bending of the canal, knowledge of the features of the file, ie. the skill and expertise of the therapist. The most dominant factor for the occurrence of fractures is the dentist who, in addition to manual dexterity, must have a good knowledge of the anatomy of various canal systems and file design in order to make the best choice for each individual case. Properly formed access cavity and knowledge of the working part of NiTi files enable maximum realization of endodontic skills, increased efficiency of intervention and reduced possibility of error during canal instrumentation. The special treatment of NiTi alloy and new solutions related to the design of the working part have significantly increased file flexibility and resistance to cyclic fatigue. Specific design (reduced number of threads, change of conicity, interruption of blade continuity), reduced engagement of file, ie. change of dynamics of movement in the canal (full rotation, reciprocal, eccentric, transaxial), as well as reduced number of processing files, have also significantly influenced the reduction of fracture risks. The aim of this paper was to analyze the most common reasons for the fracture of NiTi files and emphasize measures and factors that can increase their safe use and reduce complications during canal instrumentation.

Uvođenjem NiTi rotirajućih instrumenata u endodontsku praksu i njihovom pravilnom primenom obezbeđena su izvesnija terapijska rešenja i znatno je olakšano rešavanje svakodnevnih endodontskih problema. Međutim, njihova široka primena uzrokovala je sve učestalije frakture i postala značajan frustrirajući faktor koji umanjuje njihove brojne benefite. Torziono naprezanje i ciklični zamor su glavni razlozi za nastanak frakture, a učestalost loma NiTi turpija je upravo srazmerna stepenu povijenosti kanala, poznavanju karakteristika instrumenta, odnosno veštini i stručnosti terapeuta. Najdominantniji faktor za nastanak fraktura je stomatolog, koji osim manuelne spretnosti mora dobro poznavati anatomiju različitih kanalskih sistema i dizajn turpije kako bi napravio najbolji izbor za svaki pojedinačni slučaj. Pravilno formiran pristupni kavitet i poznavanje radnog dela NiTi instrumenata omogućavaju maksimalnu realizaciju endodontske veštine, povećanu efikasnost intervencije i smanjenu mogućnost greške tokom obrade kanala. Poseban tretman NiTi legure i nova rešenja vezana za dizajn radnog dela značajno su povećali fleksibilnost turpije i otpornost na ciklični zamor. Specifičan dizajn (smanjen broj navoja, promena koničnosti, prekid kontinuiteta sečiva) i smanjena angažovanost instrumenta, odnosno promena dinamike kretanja u kanalu (puna rotacija, recipročna, ekcentrična, transaksijalna) i smanjenje broja turpija za obradu, uticali su i na značajno smanjenje rizika od preloma. Cilj ovog rada je bio da ukaže na najčešće razloge za pojavu fraktura NiTi turpija i apostrofira mere i faktore koji mogu povećati sigurnost instrumentacije i smanjiti moguće komplikacije tokom obrade kanala.