Effect of environment on fatigue failure of controlled memory wire nickel-titanium rotary instruments.

INTRODUCTION: This study examined the fatigue behavior of 2 types of nickel-titanium (NiTi) instruments made from a novel controlled memory NiTi wire (CM wire) under various environment conditions. METHODS: Three conventional superelastic NiTi instruments of ProFile (Dentsply Maillefer, Ballaigues, Switzerland), Typhoon (Clinician's Choice Dental Products, New Milford, CT), and DS-SS0250425NEYY (Clinician's Choice Dental Products) and 2 new CM wire instruments of Typhoon CM and DS-SS0250425NEYY CM were subjected to rotational bending at the curvature of 35° in air, deionized water, 17% EDTA, or deionized water after immersion in 6% sodium hypochlorite for 25 minutes, and the number of revolutions of fracture (N(f)) was recorded. The fracture surface of all fragments was examined by a scanning electron microscope. The crack-initiation sites and the percentage of dimple area to the whole fracture cross-section were noted. RESULTS: Two new CM Wire instruments yielded an improvement of >4 to 9 times in N(f) than conventional NiTi files with the same design under various environments (P < .05). The fatigue life of 3 conventional superelastic NiTi instruments was similar under various environments, whereas the N(f) of 2 new CM Wire instruments was significantly longer in liquid media than in air (P < .05). The vast majority of CM instruments showed multiple crack origins, whereas most instruments made from conventional NiTi wire had one crack origin. The values of the area fraction occupied by the dimple region were significantly smaller on CM NiTi instruments than in conventional NiTi instruments under various environments (P < .05). CONCLUSIONS: Within the limitations of this study, the type of NiTi metal alloy (CM files vs conventional superelastic NiTi files) influences the cyclic fatigue resistance under various environments. The fatigue life of CM instruments is longer in liquid media than in air.

Influence of bending mode on the mechanical properties of nickel-titanium archwires and correlation to differential scanning calorimetry measurements.

INTRODUCTION: Nickel-titanium orthodontic archwires are used with bonded appliances for initial leveling. However, precise bending of these archwires is difficult and can lead to changes within the crystal structure of the alloy, thus changing the mechanical properties unpredictably. The aim of this study was to evaluate different bending methods in relation to the subsequent mechanical characteristics of the alloy. MATERIALS AND METHODS: The mechanical behaviors of 3 archwires (Copper NiTi 35°C [Ormco, Glendora, Calif], Neo Sentalloy F 80 [GAC International, Bohemia, NY], and Titanol Low Force [Forestadent, Pforzheim, Germany]) were investigated after heat-treatment in a dental furnace at 550-650°C, treatment with an electrical current (Memory-Maker, Forestadent), and cold forming. In addition, the change in A(f) temperature was registered by means of differential scanning calorimetry. RESULTS: Heat-treatment in the dental furnace as well as with the Memory-Maker led to widely varying force levels for each product. Cold forming resulted in similar or slightly reduced force levels when compared to the original state of the wires. A(f) temperatures were in general inversely proportional to force levels. CONCLUSIONS: Archwire shape can be modified by using either chair-side technique (Memory-Maker, cold forming) because the superelastic behavior of the archwires is not strongly affected. However it is important to know the specific changes in force levels induced for each individual archwire with heat-treatment. Cold forming resulted in more predictable forces for all products tested. Therefore, cold forming is recommended as a chair-side technique for the shaping of NiTi archwires.

Dental devices: classification of dental amalgam, reclassification of dental mercury, designation of special controls for dental amalgam, mercury, and amalgam alloy; technical amendment. Final rule; technical amendment.

The Food and Drug Administration (FDA) published a final rule in the Federal Register of August 4, 2009 (74 FR 38686) which classified dental amalgam as a class II device, reclassified dental mercury from class I to class II, and designated special controls for dental amalgam, mercury, and amalgam alloy. The effective date of the rule was November 2, 2009. The final rule was published with an inadvertent error in the codified section. This document corrects that error. This action is being taken to ensure the accuracy of the agency's regulations.

Dental devices: classification of dental amalgam, reclassification of dental mercury, designation of special controls for dental amalgam, mercury, and amalgam alloy. Final rule.

The Food and Drug Administration (FDA) is issuing a final rule classifying dental amalgam into class II, reclassifying dental mercury from class I to class II, and designating a special control to support the class II classifications of these two devices, as well as the current class II classification of amalgam alloy. The three devices are now classified in a single regulation. The special control for the devices is a guidance document entitled, "Class II Special Controls Guidance Document: Dental Amalgam, Mercury, and Amalgam Alloy." This action is being taken to establish sufficient regulatory controls to provide reasonable assurance of the safety and effectiveness of these devices. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of the guidance document that will serve as the special control for the devices.

Análisis de la distribución de tensiones en elementos dentarios restaurados con diferentes sistemas de endopostes / Analysis of stress distribution in teeth restored with different endodontic post systems

El pronóstico del diente tratado endodónticamente depende no sólo del éxito del tratamiento del conducto, sino además del tipo de restauración seleccionada. El objetivo de este estudio fue determinar mediante el método de análisis de elementos finitos, si existen diferencias en la distribución de tensiones en la reconstrucción dentaria con sistemas de endopostes y diferente cantidad de remanente dental, ante la aplicación de una carga oclusal simulada. Se reconstruyeron con dos sistemas de pernos: a) preformado de fibra de carbono con matriz de resina epoxi; b) colado de cromo-níquel y restaurados con coronas coladas de cromo-níquel. Un modelo fue reconstruido con resina sin restauración a perno (control). Se aplicó una carga estática de 200 N, en 45 grados sobre la vertiente interna de la cúspide palatina. Se evaluó concentración, localización y distribución de las tensiones (compresión, tracción, Von Mises). Los resultados mostraron que los postes de fibra de carbono absorbieron menores tensiones en comparación con los colados. Se observó presencia de tensiones de compresión en el extremo inferior del perno en correspondencia con la zona de máxima tensión presente en el poste. En la raíz palatina se presentaron esfuerzos de compresión y en la vestibular de tracción.

Load-deflection characteristics of superelastic nickel-titanium wires.

OBJECTIVE: To determine the mechanical properties of commercially available thermodynamic wires and to classify these wires mathematically into different groups. MATERIALS AND METHODS: The samples examined were 48 nickel-titanium (NiTi) alloy orthodontic wires commercially available from five manufacturers. These samples included 0.016-inch, 0.016- x 0.022-inch, 0.017- x 0.025-inch, and 0.018- x 0.025-inch wires. The superelastic properties of the NiTi wires were evaluated by conducting the three-point bending test under uniform testing conditions. The group classification was made under mathematically restricted parameters, and the final classification was according to their clinical plateau length. RESULTS: The orthodontic wires tested are classified as follows: (1) true superelastic wires, which presented a clinical plateau length of >/=0.5 mm; (2) borderline superelastic with a clinical plateau length of <0.5 mm and >0.05 mm; and (3) nonsuperelastic, with a clinical plateau length of

A proposal for the classification of dental alloys according to their resistance to corrosion.

OBJECTIVES: The purpose of this study was to establish a method to compare and classify dental alloys in relation to their resistance to corrosion. METHODS: Alloy samples and pure metal samples were prepared and tested in chemical and electrochemical corrosion according to ISO 10271. For electrochemical test, the rest potential versus time and a potentiodynamic scan were recorded. After chemical corrosion test, the ions released were analyzed by ICP (induced coupled plasma) spectroscopy. RESULTS: High gold alloys had a similar polarization curve than gold. The same effect was observed for Pd-base alloys, their curves were similar to the one of palladium. The ions released during chemical corrosion were non-precious metallic ions. Thereby Ni-Cr alloys were found to release the most ions. Au-Pt alloys showed the highest release of ions compared with other precious alloys but low compared with Ni-Cr. Electrochemical corrosion was more aggressive than chemical corrosion and every type of elements was etched, the higher the precious metal content, the higher the resistance to corrosion of the alloy. DISCUSSION: Using the recorded data, a classification system for electrochemical corrosion was developed and discussed to judge the results. Hereby were gold and zinc used as reference materials. The applied classification system defines five classes and it is proposed that alloys of class V are not acceptable. For chemical corrosion resistance, three classes were distinguished according to the quantity of metallic ions released and it is proposed that class III (100-1000 microg/cm(2)week) is not acceptable. Palladium and Pd-base alloys showed a higher electrochemical and chemical corrosion resistance than gold.

The effect of surface treatment and clinical use on friction in NiTi orthodontic wires.

OBJECTIVES: Since the low friction of NiTi wires allows a rapid and efficient orthodontic tooth movement, the aim of this research was to investigate the friction and surface roughness of different commercially available superelastic NiTi wires before and after clinical use. The surface of all of the wires had been pre-treated by the manufacturer. MATERIALS: Forty superelastic wires (Titanol Low Force, Titanol Low Force River Finish Gold, Neo Sentalloy, Neo Sentalloy Ionguard) of diameter 0.016 x 0.022 in. were tested. The friction for each type of NiTi archwire ligated into a commercial stainless steel bracket was determined with a universal testing machine. Having ligated the wire into the bracket, it could then be moved forward and backwards along a fixed archwire whilst a torquing moment was applied. The surface roughness was investigated using a profilometric measuring device on defined areas of the wire. Statistical data analysis was conducted by means of the Wilcoxon test. RESULTS: The results showed that initially, the surface treated wires demonstrated significantly (p < 0.01) less friction than the non-treated wires. The surface roughness showed no significant difference between the treated and the non-treated surfaces of the wires. All 40 wires however showed a significant increase in friction and surface roughness during clinical use. SIGNIFICANCE: Whilst the Titanol Low Force River Finish Gold (Forestadent, Pforzheim, Germany) wires showed the least friction of all the samples and consequently should be more conservative on anchorage, the increase in friction of all the surface treated wires during orthodontic treatment almost cancels out this initial effect on friction. It is therefore recommended that surface treated NiTi orthodontic archwires should only be used once.

Effect of a metal primer on the bond strength of the resin-metal interface

Para avaliar o efeito de diferentes tratamentos superficiais sobre a resistência ao cisalhamento da união entre uma liga metálica (Co-Cr-Mo - Remanium CD) e um cimento resinoso (Rely XTM) e analisar o tipo de fratura durante a separação dos espécimes, quarenta pares de discos metálicos foram fundidos, regularizados e polidos, submetidos a quatro ciclos térmicos (vácuo, 960ºC, 8 minutos) e divididos aleatoriamente em quatro grupos. Cada grupo recebeu um tipo de tratamento: Grupo PSP: Polimento com lixa d'água Nº 600; Grupo PCP: Polimento com lixa 600 e aplicação do condicionador metálico Alloy Primer (Kuraray); Grupo JSP: Jato de óxido de alumínio de 100µm, e Grupo JCP: Jato de óxido de alumínio de 100mm, e aplicação do Alloy Primer. Os grupos foram cimentados e armazenados em água destilada a 37ºC por 36 horas e submetidos ao ensaio de resistência ao cisalhamento. A média e o desvio padrão (em kgf/cm2) obtidos para cada grupo foram: PSP 4,0/0,4; PCP 88,9/33,6; JSP 163,2/27,6; JCP 144,5/54,0. Após a análise estatística os autores concluíram que: os maiores valores foram produzidos pelos grupos jateados (JSP, JCP), independentemente da aplicação do primer; o Alloy Primer aumentou a retentividade entre o cimento Rely X e a superfície polida da liga de Co-Cr-Mo, entretanto sua força de união não superou a alcançada através do jateamento; todos os espécimes apresentaram falha adesiva na interface testada.

Direct and indirect restorative materials.

BACKGROUND: In recent years, dentistry has benefited from a marked increase in the development of esthetic materials, including ceramic and plastic compounds. But the advent of these new materials has not eliminated the usefulness of more traditional restorative materials such as gold, base metal alloys and dental amalgam. OVERVIEW: This report outlines important features of direct and indirect restoratives, with an emphasis on the safety and efficacy of each material. CONCLUSIONS AND PRACTICE IMPLICATIONS: This article was developed to help dentists explain to their patients the relative pros and cons of various materials used in dental restorations, which include fillings, crowns, bridges and inlays. The weight of the scientific evidence indicates that all of these materials are safe and effective for their intended use. Patients, in consultation with their dentists, are free to choose the most appropriate among them for their particular needs.

Estudo comparativo da resistência de união entre seis cerâmicas e quatro ligas metálicas utilizando testes de cisalhamento / Comparative study of porcelain-to-metal bonding of six ceramic and four metal alloys using shear planar interface tests

O objetivo deste trabalho foi realizar uma comparação entre diversas combinações de ligas metálicas e cerâmicas utilizando testes de cisalhamento com interface plana, a fim de se determinar a resistência de união entre os materiais. Confeccionaram-se ao todo, 176 corpos de prova cilíndricos com 6,0mm de diâmetro, 6,0mm de altura de metal e 1,5mm de porcelana. Utilizaram-se ligas de ouro, paládio-prata, níquel-cromo e titânio, além de seis diferentes cerâmicas. Do total, 160 corpos de prova foram submetidos a testes de cisalhamento. Os restantes 16 corpos de prova, quatro para cada liga, foram seccionados em seu longo eixo e submetidos à microscopia eletrônica de varredura e análises EDS (difração de raios-x) para medição da camada de interface e caracterização dos elementos presentes na referida camada e definição do tipo de fratura. Os resultados mostraram que a liga de ouro apresentou os melhores resultados de resistência de união (41,66MPa), seguida pela liga de níquel-cromo (37,41MPa), paládio-prata (36,51MPa) e titânio (29,62MPa) respectivamente. Os exames de microscopia eletrônica e EDS mostraram que, para as combinações metal/porcelana que apresentaram os melhores resultados, a quantidade de porcelana aderente após os testes era maior (43 por cento - AuPt, 37,7 por cento - NiCr, 35,3 por cento - PdAg) do que nas que apresentaram os piores resultados (Ti - 20,9 por cento). O tipo de fratura foi definido como misto, uma combinação de fratura adesiva e coesiva. As combinações que apresentaram interfaces mais espessas tiveram menores resultados de resistência de união.

Nuevos enfoques en la reconstrucción coronaria del diente endodónticamente tratado (DET) / New approaches in the coronal reconstruction of the endodontically treated tooth (ETT)

Los conceptos referidos a la rehabilitación del diente endodónticamente tratado han cambiado sustancialmente. Se acepta como verdadero refuerzo a la misma estructura dentaria, por lo tanto, los procedimientos que la conserven son de elección. Asimismo, se deben diferenciar las situaciones en el sector anterior y posterior de la arcada dentaria, siendo necesaria en el sector anterior una estabilización mecánica con pernos o potes. Será en cambio, más habitual no utilizar dipositivos intrarradiculares en el sector posterior. La integración de superficies que se consigue con los mecanismos adhesivos, permite más ahorro de tejidos. En tanto que las restauraciones (inlays, onlays, coronas y postes no metálicos) elaboradas con materiales más fácilmente integrables (cerámicos y compuestos) cobran mayor importancia en relación con esta filosofía (AU)

Ligas para amálgama contendo zinco: quando devemos usá-las? / Dental amalgam alloy containing zinc: when should we use them?

O presente estudo teve por objetivo avaliar, por revisäo da literatura, o efeito da inclusäo do zinco nas ligas de amálgama dentário. Para isso, foram analisadas a microestrutura, as propriedades físicas, a corrosäo, a deterioraçäo, fraturas marginais e a citoxicidade do amálgama

Resistência de uniäo entre cerômero e metal: uma comparaçäo utilizando três tipos de tratamento superficial do metal e ciclagem térmica / Bonding ceromer to metal: a comparison using three metal surface treatments and thermocycling

A utilizaçäo de próteses metaloplásticas sempre esteve sujeita a problemas como o desgaste, alteraçöes de cor e infiltraçäo na interface metal/resina. Com o surgimento de novos materiais resinosos com propriedades estéticas e funcionais melhoradas, os problemas originalmente observados parecem ter sido solucionados. No entanto, necessita-se avaliar os possíveis meios de tratamento da superfície metálica a fim de se evitar que o processo de infiltraçäo ainda ocorra nesse tipo de prótese, ocasionando falhas estéticas e funcionais. O objetivo do presente estudo foi de avaliar a resistência de uniäo entre um cerômero e uma liga de níquel-cromo, utilizando-se três tipos de condicionamento da superfície metálica e ciclagem térmica. Confeccionaram-se 66 corpos de prova que foram submetidos a testes de cisalhamento. Os resultados mostraram que a resistência de uniäo variou entre 4,0MPa e 23,3MPa. Além disso, o tratamento com Rocatec apresentou resultados superiores aos outros tratamentos. A ciclagem térmica ocasionou diminuiçäo nos resultados de todos os grupos

Uniäo da cerâmica ao metal: uma comparaçäo utilizando testes de cisalhamento / Bonding ceramic to metal: a comparison using shear tests

Muitos dentistas e técnicos usam cerâmicas dentais com diferentes ligas sem se preocupar com as características de compatibilidade desses materiais. É muito importante para o profissional, conhecer as propriedades das ligas e cerâmicas utilizadas em restaurações metalocerâmicas. O objetivo deste estudo foi de avaliar a resistência de uniäo de uma liga de paládio-prata (Pors-On 4) com três cerâmicas (Ceramco, Noritake e Vita VMK-68) utilizando forças de cisalhamento na interface meta/cerâmica, além de testar a metodologia e as características de manipulaçäo dos materiais estudados. Uma matriz cilíndrica foi utilizada para a preparaçäo dos padrões metálicos, aplicaçäo das cerâmicas e execuçäo dos testes de cisalhamento. Trinta padrões metálicos receberam duas camadas de opaco e duas camadas de porcelana de corpo. Os testes de cisalhamento foram executados em uma máquina de ensaios universal a uma velocidade de 0.5mm/min. Os valores de resistência de uniäo foram: 28.21MPa (Ceramco), 28.96MPa (Noritake) e 24.11MPa (Vita VMK-68). A ANOVA a um critério determinou näo existirem diferenças estatisticamente significativas entre os grupos (p < 0.05). Os resultados mostraram que os três sistemas cerâmicos säo satisfatórios para a utilizaçäo com a liga selecionada