Cyclic Fatigue of Different Nickel-Titanium Rotary Instruments: A Comparative Study

Since the introduction of nickel-titanium alloy to endodontics, there have been many changes in instrument design, but no significant improvements in the raw material properties, or enhancements in the manufacturing process. Recently, a new method to produce nickel-titanium rotary (NTR) instruments has been developed, in an attempt to obtain instruments that are more flexible and resistant to fatigue. NTR instruments produced using the process of twisting (TF, SybronEndo, Orange, CA) were compared to NTR instruments from different manufacturers produced by a traditional grinding process. The aim of the study was to investigate whether cyclic fatigue resistance is increased for TF NTR files. Tests were performed with a cyclic fatigue device that evaluated cycles to failure of rotary instruments inside curved artificial canals. Results indicated that size 06-25 TF instruments showed a significant increase (P< .05). In the mean number of cycles to failurewhen compared to the other tested 06-25 NTR. Hence, it can be concluded that size 06-25 TF NTR instruments were found to be significantly more resistant to fatigue than those produced with the traditional grinding process

L&#8217;otturazione di apici canalari ampi o alterati con MTA Giornale Italiano di Endodonzia

RiassuntoObiettiviIl trattamento canalare può incontrare complicanze in presenza di apici molto ampi. È opinione diffusa che sopra i 0,6mm sia difficile ottenere un adattamento adeguato della guttaperca in apice, con conseguente mancanza di sigillo apicale. Se poi la scelta è quella di una tecnica di otturazione “a caldo” della guttaperca, ottenere una buona conicità della preparazione apicale dove compattare il cono di guttaperca può diventare rischioso per l’eccessivo assottigliamento delle pareti canalari.Materiali e metodiSe fino a pochi anni or sono, per ottenere una barriera apicale (apicificazione), l’impiego dell’idrossido di calcio rappresentava il metodo di elezione, da qualche anno l’introduzione nei protocolli clinici di cementi di derivazione Portland (MTA) ha permesso di semplificarli, permettendo la formazione di barriere apicali stabili e biocompatibili. Questa tecnica di apicificazione permette la successiva otturazione canalare con le tecniche della guttaperca termoplasticizzata.Risultati e conclusioniIn questo lavoro saranno presentate le indicazioni cliniche, le caratteristiche generali del materiale e infine saranno descritte le fasi operative con gli strumenti necessari per ottenere una corretta chiusura apicale per via ortograda.SummaryObjectivesThe treatment of wide open apices may lead to complications during root canal therapy. It is assumed that guttapercha, in case of an apical diameter more than 0.60mm, may not adequately adapt to root canal walls with a subsequent defective apical seal. Furthermore, if a “warm guttapercha” obturation technique is selected, the need to create an optimal tapered shaping for the condensation of the guttapercha point may increase the risk of an excessive dentin removal from the canal walls.Materials and methodsApexification with calcium hydroxide has been considered the gold standard treatment to gain a calcified apical barrier for many years. However, the introduction of Portland cements (MTA) in clinical practice have shown their efficacy in the formation of a stable and biocompatible apical barrier in case of open apices, with a semplification of the clinical procedure. The MTA apical plug technique is usually followed by root canal back-packing with thermoplasticised guttapercha.Results and conclusionsClinical indications and general characteristics of the material will be presented in this article, as well as the clinical procedures and the related instruments to obtain a correct orthograde apical closure

Textural and mineralogical constitution of mineral trioxide aggregate: A comparison among different products

Objectives: To determine the mineralogical, chemical, and microtextural differences between commercially available MTA products, clarifying common differences with Portland and between each other. Materials and methods: The study was done on four commercially available MTA cements, that is Ogna Aureoseal®, Proroot white MTA®, Angelus white and gray MTA® and on a commercial Portland cement. After preliminary X-ray diffraction characterization of the powder, the samples were consolidated following the same procedure used in clinical practice. The consolidated material was embedded in epoxy and polished, and subsequently investigated, by means of SEM-EDS analysis of back-scattered electron images on all samples and of quantitative compositional mapping on MTA. Results: The MTA and Portland cements differ for the grain size, the hydration rate, and homogeneity of the set products, and for lower Fe and S content in MTA. Previously reported presence of opacizing agents (Bi2O3 and CaWO4) was confirmed in all samples, whereas low Al content was not observed in all MTA. Although the MTA products are all mainly composed by di-calcium and tri-calcium silicates, the post-setting texture and the chemical and mineralogical constitution differ. Finer texture was observed in Ogna Aureoseal® and Proroot white MTA®; in Ogna Aureoseal® the presence of apatite and Ca-tungstate was reported; Mg and Al content changed in samples, following the clinker composition. Conclusions: Significant differences exist between Portland cement and MTA, but also among different MTA formulations. MTA products can be classified as a form of Portland cement, specifically modified for dentistry purposes. © 2011 Società Italiana di Endodonzia. Published by Elsevier Srl. All rights reserved