Differential Scanning Calorimetric (DSC) Study of New and Sterilized Nickel-Titanium Rotary Endodontic Instruments

Introduction: Nickel-Titanium (NiTi) files have become popular in endodontic procedures compared to traditional stainless steel hand files owing to their increased flexibility which is especially advantageous in curved canals. Due to the associated costs, endodontic instruments are frequently re-used, which requires sterilization between uses. With the application of temperature NiTi has the ability to undergo phase transformations, altering the properties of the instruments. The purpose of this study was to investigate phase transformations of four brands of NiTi rotary endodontic instruments in the as-received condition and after multiple sterilization cycles under steam sterilization, using differential scanning calorimetry. Materials and Methods: Four brands of nickel-titanium endodontic rotary files size 35, .04 taper were evaluated in this study: ProFile (Dentsply Tulsa Dental Specialties, Tulsa, OK), ProFile Vortex (Dentsply), Vortex Blue (Dentsply), and HyFlex CM (Coltène/Whaledent, Cuyahoga Falls, OH). The transformation temperatures and phase transformations of these files were determined in the as-received condition and after 1, 3, and 5 cycles of steam sterilization by differential scanning calorimetry. Measurements were analyzed using a two-way ANOVA. Results: There were significant differences between file brands in austenite finish temperature (p \u3c 0.05) but the only statistical significant differences in thermal properties when comparing files before and after 1, 3, and 5 cycles of steam sterilization were found with onset heating (p \u3c 0.05). Conclusion: Repeated cycles of steam sterilization do not appear to influence the phase transformations of NiTi endodontic instruments

Comparison of Different Temperatures on Bending Properties of Six Niti Endodontic File Systems

Introduction: Manufacturers claim that modern NiTi files with proprietary heat treatment transform at higher temperatures, thus staying more martensite and being more resistant to cyclic fatigue and more flexible. There are some studies comparing the effect of body temperature and room temperature on cyclic fatigue of these newer NiTi files. However, there is not yet a study published for evaluating the relationship between bending properties of NiTi instruments and temperature following the ISO 3630-1 guideline. The objective of this study was to evaluate how temperature affects the bending properties of six different brands of NiTi rotary instruments with different transformation temperature ranges. Methods: Six commercially available NiTi files were selected for this experiment. The tested files included K3 40/.04 (Sybron Endo, Orange, CA), ProFile Series 29 Green Size 6 (Dentsply Tulsa Dental Specialties), K3XF 40/.04 (Sybron Endo, Orange, CA), Vortex Blue 40/.04 (Dentsply Tulsa Dental Specialties), ProFile Vortex 40/.04 (Dentsply Tulsa Dental Specialties), and HyFlex CM™ 40/.04 (Coltène/Whaledent Inc., Cuyahoga Falls, OH). The Austenite finish temperatures of the files were 9.6 ± 0.5, 17.6 ± 0.6, 24.9 ± 1.1, 35.4 ± 1.2, 45.7 ± 0.9, and 60.3 ± 3.1, respectively. The bending properties of the files were measured using a torsiometer (Sa bri Dental Enterprises, Inc. Downers Grove IL) following ISO 3630-1 guidelines. Twelve of each file type were grouped into 3 groups based on temperatures. Each temperature group had a total of 72 files. Group 1 measured the bending moment (g.cm) at 9±2°C, group 2 at 23±2°C, and group 3 at 35±2°C. The data was statistically analyzed by ANOVA and post hoc HSD (P\u3c0.05) Results: For all tested files, the bending moment of the files increased as the temperature rose from 9to 23 to 35°C. At all temperatures, HyFlex CM was significantly more flexible than other files. ProFile Vortex, K3XF, and Vortex Blue showed similar flexibility with each other. They were significantly more flexible than ProFile Series 29, which was significantly more flexible than K3. Conclusion: Testing temperature and brand of the files were significant independent variables affecting the flexibility of the files

Torsion and Bending Properties of EdgeEndo Files

Introduction: One important step of root canal therapy is the process of cleaning and shaping each canal. This process involves using endodontic rotary files combined with chemical irrigants to remove pulpal remnants and infected dentin from the canal while eliminating pathogenic bacteria. It is essential to maintain proper canal anatomy while cleaning and shaping. The challenge for the practitioner is to select a rotary file system that will be flexible enough to maintain canal anatomy but strong enough to prevent breakage under normal use. File flexibility allows for better maintenance of canal anatomy. A file’s resistance to torsional fatigue reduces the chance of file breakage. The purpose of this study was to compare the torsion and bending properties of a brand new file system (EdgeFiles by EdgeEndo, Albuquerque, NM) marketed as being twice as strong but half the price compared to other marketed files Materials and Methods: Thirty files of each type were used. Ten different files systems were evaluated. Size 30 files of .04 taper EdgeFile X7, EdgeFile X5, EndoSequence (Brasseler), Vortex Blue (Dentsply), GT Series X (Dentsply), K3XF (SybronEndo), HyFlex CM (Coltene/Whaledent, Inc.), and .06 taper EdgeFile X3 (EdgeEndo), ProTaper Universal (Dentsply), ProTaper Gold (Dentsply). Testing was done with a torsiometer following ISO 3630-1. Twelve of each file type were evaluated for bending and 18 of each type were evaluated with torsion. Results were separated into 3 different groups due to differences in file design. Group 1 included X3, Protaper Universal, and Protaper Gold. Group 2 included X5 and GT series X. Group 3 included X7, EndoSequence, Vortex Blue, K3XF, and HyFlex CM. Results: In Group 1, X3 showed the most flexibility followed by ProTaper Gold then ProTaper Universal. For strength, ProTaper Gold had the highest resistance to torsion followed by ProTaper Universal then X3. In Group 2, X5 showed more flexibility while GTX had higher strength. In Group 3, HyFlex CM showed the most flexibility followed by X7, then EndoSequence, Vortex Blue, and finally K3XF. For strength, K3XF was highest. X7 and Vortex Blue had similar values which were higher than HyFlex CM followed by EndoSequence. Conclusion: An overall conclusion could be made that strength and flexibility have a relatively inverse relationship in each group. The stronger files tend to be less flexible and the more flexible files tend to be more susceptible to torsional failure. ProTaper Gold and X7 had the best combinations of strength and flexibility

A software interface for supporting the application of data science to optimisation

Many real world problems can be solved effectively by metaheuristics in combination with neighbourhood search. However, implementing neighbourhood search for a particular problem domain can be time consuming and so it is important to get the most value from it. Hyper-heuristics aim to get such value by using a specific API such as `HyFlex' to cleanly separate the search control structure from the details of the domain. Here, we discuss various longer-term additions to the HyFlex interface that will allow much richer information exchange, and so enhance learning via data science techniques, but without losing domain independence of the search control

Sistema de instrumentação mecanizada Hyflex EDM

A Endodontia é uma área em constante evolução. Consideráveis desenvolvimentos nos materiais e técnicas têm sido essenciais para o melhoramento dos resultados nos tratamentos realizados. É exemplo disso mesmo a constituição dos instrumentos Endodônticos primordiais, construídos em cordas de piano, com evolução para aço de carbono, material este que sofria corrosão provocado pelo cloro presente no hipoclorito de sódio. O aço de carbono evoluiu para aço inoxidável e deste as limas endodônticas passaram a ser feitas em níquel-titânio, conferindo-lhes melhor flexibilidade e efeito de memória de forma. Mesmo com todas estas melhorias significativas, fraturas de instrumentos e erros durante a instrumentação continuam a acontecer e com eles veio a necessidade da pesquisa de possíveis melhorias da constituição das limas em NiTi. Como resultado surgiram ligas como o M-wire, fase-R e CM-wire, criadas a partir de tratamentos térmicos, que trouxeram às limas Endodônticas maior flexibilidade e resistência à fratura que os instrumentos feitos em NiTi convencional. A mais recente evolução das limas Ni-Ti, desenvolvida pela Coltene Whaldent (Allstätten, Suiça), são as limas Hyflex EDM, limas para canais radiculares de 5ª geração. O seu processo de fabrico por eletroerosão cria uma superfície única fazendo com que estas limas sejam mais duras e resistam mais à quebra, aliado à sua alta flexibilidade. É possível assim reduzir o número de limas para a limpeza e modelagem dos canais durante os tratamentos endodônticos sem comprometer a preservação da anatomia dos canais. As limas Hyflex EDM possuem, tal como as limas Hyflex CM, o efeito de controle de memória (CM), o que confere propriedades muito similares entre os dois sistemas.Considerable research has been taken into Endodontics in order to improve materials and techniques which have been crucial to achieve better results in the performed treatments. Example of that is the constitution of ancient Endodontic instruments, made of piano strings, which evolved to carbon steel, but as corrosion occurred due to chloride present in sodium hypochlorite, there was a new evolution from carbon steel to stainless steel and thus Endodontic files began to be made of titanium nickel offering them greater flexibility and shape memory effects. Even with all these significant improvements, Endodontic instruments fracture and mistakes during instrumentation still occur, so there was the need to research for possible constitution improvements in Ni-Ti files. As a result, alloys such as M-Wire, R- Phase and CM-Wire, created from thermal treatments, appeared and brought more flexibility and fracture resistance to Endodontic files than the instruments made in conventional Ni-Ti. Hyflex EDM files, the first Endodontic instruments manufactured with EDM, for root canal 5th generation are the most recent Ni-Ti files evolution developed by Coltene Whaledent (Allstätten, Switzerland). Its manufacturing process by electro erosion creates a single surface enabling these files to be tougher and more resistant to fracture, allied to its greater flexibility. Thus, it´s possible to reduce the number of files for cleaning and shaping of canals during endodontic treatments without compromising the preservation of their autonomy. Hyflex EDM files have, such as Hyflex CM files, memory control (CM) effect, which provides very similar properties between the two systems

Offline Learning for Selection Hyper-heuristics with Elman Networks

This is the author accepted manuscript. The final version is available from the publisher via the link in this record.Offline selection hyper-heuristics are machine learning methods that are trained on heuristic selections to create an algorithm that is tuned for a particular problem domain. In this work, a simple selection hyper-heuristic is executed on a number of computationally hard benchmark optimisation problems, and the resulting sequences of low level heuristic selections and objective function values are used to construct an offline learning database. An Elman network is trained on sequences of heuristic selections chosen from the offline database and the network’s ability to learn and generalise from these sequences is evaluated. The networks are trained using a leave-one-out cross validation methodology and the sequences of heuristic selections they produce are tested on benchmark problems drawn from the HyFlex set. The results demonstrate that the Elman network is capable of intra-domain learning and generalisation with 99% confidence and produces better results than the training sequences in many cases. When the network was trained using an interdomain training set, the Elman network did not exhibit generalisation indicating that inter-domain generalisation is a harder problem and that strategies learned on one domain cannot necessarily be transferred to another

A systematic literature review on synchronous hybrid learning : gaps identified

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Les modalités de cours qu'on peut exploiter au collégial : les définir pour mieux les choisir

Comprend des références bibliographiques.Ce texte consiste d'abord en une synthèse des différentes modalités de cours qu'on peut exploiter au collégial. Il énonce les caractéristiques, les propriétés et l'intérêt de chacune d'elles. Il propose ensuite un modèle de réflexion, ou modèle décisionnel, qui s'avèrera fort utile quand viendra le temps de décider, parmi l'ensemble des possibilités, quelle modalité serait la plus appropriée pour enseigner dans un contexte précis, embrassant diverses situations. Recherche très appuyée, très détaillée, qui renvoie à de multiples sources et saura, par là, contenter tout lecteur interpelé par le sujet, cet article est particulièrement susceptible d'intéresser les personnes qui se questionnent à propos des cours hybrides, de leur fonctionnement et de leurs avantages. Les auteures décrivent et décortiquent d'ailleurs ici un modèle de conception de cours spécialement adapté à ce mode d'enseignement et d'apprentissage

A modified choice function hyper-heuristic controlling unary and binary operators

Hyper-heuristics are a class of high-level search methodologies which operate on a search space of low-level heuristics or components, rather than on solutions directly. Traditional iterative selection hyper-heuristics rely on two key components, a heuristic selection method and a move acceptance criterion. Choice Function heuristic selection scores heuristics based on a combination of three measures, selecting the heuristic with the highest score. Modified Choice Function heuristic selection is a variant of the Choice Function which emphasises intensification over diversification within the heuristic search process. Previous work has shown that improved results are possible in some problem domains when using Modified Choice Function heuristic selection over the classic Choice Function, however in most of these cases crossover low-level heuristics (operators) are omitted. In this paper, we introduce crossover low-level heuristics into a Modified Choice Function selection hyper-heuristic and present results over six problem domains. It is observed that although on average there is an increase in performance when using crossover low-level heuristics, the benefit of using crossover can vary on a per-domain or per-instance basis