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Objectives The purpose of this study was to investigate the suitability of the Bend and Free Recovery (BFR) method as a standard test method to determine the transformation temperatures of heat-activated Ni-Ti orthodontic archwires. This was done by determining the transformation temperatures of two brands of heat-activated Ni-Ti orthodontic archwires using the both the BFR method and the standard method of Differential Scanning Calorimetry (DSC). The values obtained from the two methods were compared with each other and to the manufacturer-listed values. Methods Forty heat-activated Ni-Ti archwires from both Rocky Mountain Orthodontics (RMO) and Opal Orthodontics (Opal) were tested using BFR and DSC. Round (0.016 inches) and rectangular (0.019 × 0.025 inches) archwires from each manufacturer were tested. The austenite start temperatures (A s ) and austenite finish temperatures (A f ) were recorded. Results For four of the eight test groups, the BFR method resulted in lower standard deviations than the DSC method, and, overall, the average standard deviation for BFR testing was slightly lower than for DSC testing. Statistically significant differences were seen between the transformation temperatures obtained from the BFR and DSC test methods. However, the A f temperatures obtained from the two methods were remarkably similar with the mean differences ranging from 0.0 to 2.1 °C: A f Opal round (BFR 26.7 °C, DSC 27.6 °C) and rectangular (BFR 27.6 °C, DSC 28.6 °C); A f RMO round (BFR 25.5 °C, DSC 25.5 °C) and rectangular (BFR 28.0 °C, DSC 25.9 °C). Significant differences were observed between the manufacturer-listed transformation temperatures and those obtained with BFR and DSC testing for both manufacturers. Significance The results of this study suggest that the Bend and Free Recovery method is suitable as a standard method to evaluate the transformation temperatures of heat-activated Ni-Ti orthodontic archwires.

The purpose of this investigation was to study the effect of stress and phase transformation on the corrosion properties of a superelastic nickel-titanium orthodontic wire.The phase transformation profiles of superelastic nickel-titanium (Sentalloy, GAC International, Bohemia, NY) and beta-titanium (TMA, Ormco, Orange, Calif) archwires were analyzed by using differential scanning calorimetry. The force/deflection behavior of the wires at 37 degrees C was measured in a 3-point bending test per modified American Dental Association specification no. 32. Electrochemical testing consisted of monitoring the open circuit potential (OCP) for 2 hours followed by polarization resistance and cyclic polarization tests on archwire segments engaged in a 5-bracket simulation apparatus with bend deflections of 0.75, 1.5, or 3 mm in artificial saliva at 37 degrees C. Nondeflected segments were also tested. Sentalloy was additionally examined for bending and corrosion at 5 degrees C, where it exists as martensite and is devoid of stress-induced phase transformation. OCP at 2 hours and corrosion current density (i(corr)) were analyzed by using ANOVA and Tukey tests (alpha = .05) (n = 10 per deflection).Significant differences (P0.05) in OCP with deflection were found for the TMA and the Sentalloy wires at 5 degrees C, but not for Sentalloy at 37 degrees C. Significant differences (P0.05) in i(corr) with deflection were also observed. All 3 wire groups had their lowest mean i(corr) values when not deflected. The i(corr) for superelastic Sentalloy (37 degrees C) peaked at 0.75 mm deflection before the wire's stress-induced phase transformation point and then decreased with further deflection and transformation. The i(corr) values for TMA and Sentalloy at 5 degrees C, both of which do not undergo phase transformation with deformation, continuously increased from 0 to 1.5 mm deflection before decreasing at the 3.0-mm deflection.Stress increased the corrosion rate in nickel-titanium and beta-titanium orthodontic wires. Alterations in stress/strain associated with phase transformation in superelastic nickel-titanium might alter the corrosion rate in ways different from wires not undergoing phase transformation.

Objective Nickel–titanium orthodontic wires have various temperature-dependent phases. The purpose of this study was to investigate temperature-dependent corrosion characteristics of shape memory, superelastic, and nonsuperelastic orthodontic wires. Methods Four orthodontic wires were investigated: 27 and 40 °C copper Ni–Ti (superelastic and shape memory, respectively), superelastic Ni–Ti, and nonsuperelastic Nitinol Classic. Differential scanning calorimetry (DSC) was used to confirm phase/temperature behavior of the wires. Sectioned halves of as-received archwires were assessed electrochemically in artificial saliva at 5, 24, 37, and 45 °C. Open circuit potential (OCP) was monitored for 2 h followed by polarization resistance and cyclic polarization tests. Results DSC results showed Nitinol was primarily martensitic-stable whereas NiTi, 27 °C CuNiTi, and 40 °C CuNiTi possessed austenite-finish temperatures of approximately 19, 21, and 38 °C. The OCP of the CuNiTi wires was significantly greater than NiTi and Nitinol but no apparent trend in values was apparent with regard to temperature or phases present. Corrosion current density ( i corr ) increased with temperature for all wires, but not all were equally influenced. The two lowest austenite-finish temperature wires (27 °C CuNiTi and NiTi) approximately tripled in i corr from 37 to 45 °C. Greater incidence of pitting was observed in the CuNiTi wires. Significance This study showed the corrosion rate of various nickel–titanium wires increase with temperature and different phases present may influence corrosion rate trends.

This research determined the effect oxidation, as that occurs during porcelain firing, has upon the corrosion parameters of Pd-based ceramic alloys and how it may relate to Pd allergy. The 20 h open circuit potential (OCP), 20 h corrosion rate (Icorr), and anodic polarization (E-i) curves of 11 commercial Pd alloys were measured in a phosphate buffered saline solution. The alloys were divided into the following four groups based upon composition: PdGa(Ag), PdCu, PdAg, and AuPd and tested in both as-cast and oxidized conditions. In both the as-cast and oxidized conditions, the OCP of Ag-containing Pd alloys is significantly lower than non Ag-containing high-Pd alloys. The OCP of all alloys increased after oxidation. With regard to corrosion rate, the Ag-containing alloys showed a decrease in Icorr with oxidation. In contrast, three of the four non Ag-containing high-Pd (>or=74 wt%) alloys exhibited a higher Icorr. A comparison of the anodic polarization curves showed only the alloys containing larger amounts (>or=16 wt%) of Ag displayed a notable difference between as-cast and oxidized states. Oxidation as required during porcelain-fused-to-metal device preparation alters the electrochemical characteristics of the alloys studied. This alteration may be of importance with regard to their potential for Pd allergy.

To compare as-received copper-nickel-titanium (CuNiTi) archwires to those used in patients by means of differential scanning calorimetry (DSC). Also, the thermal or phase properties of 27 degrees C, 35 degrees C, and 40 degrees C CuNiTi archwires were studied to ascertain if their properties match those indicated by the manufacturer.Six wires of 27 degrees C, 35 degrees C, and 40 degrees C CuNiTi were tested as-received, and six each of the 27 degrees C and 35 degrees C wires were examined after use in patients for an average of approximately 9 and 7 weeks, respectively. Segments of archwire were investigated by DSC over the temperature range from -100 degrees C to 150 degrees C at 10 degrees C per minute.There were no significant differences between as-received and clinically used 27 degrees C and 35 degrees C wires for all parameters (heating onset, endset, and enthalpy and cooling onset, endset, and enthalpy), except the 27 degrees C wires exhibited a significant decrease in the heating enthalpy associated with the martensite-to-austenite transition after clinical use. The heating endsets (austenite finish temperatures) of the 27 degrees C and 35 degrees C wires were within 2 degrees C of those claimed by the manufacturer, but the 40 degrees C wires were found to be nearer to 36 degrees C than 40 degrees C.Clinical use of CuNiTi wires resulted in few differences when compared with as-received wires analyzed by DSC. Two temperature varieties of CuNiTi are reasonably within the parameters of those identified by the manufacturer.

Introduction The purpose of this study was to compare the in vitro torsional stress characteristics of Twisted Files (TFs; SybronEndo, Orange, CA) with 2 milled files of a similar cross-section: EndoSequence (Brasseler USA, Savannah, GA) and ProFile Vortex (DENTSPLY Tulsa Dental, Tulsa, OK). Methods File sizes of 25/.06 and 30/.06 from the 3 file types were compared (n = 20/group). Torsional stress resistance was evaluated by measuring the torque in grams per centimeters and the angle of rotation (°) required for instrument separation with the use of a torsiometer instrument. The fractured files were examined using a scanning electron microscope to look at deformation and fracture surface characteristics. The data were analyzed with analysis of variance to determine statistical differences. Results The 3 file types showed a statistically significant difference in both the maximum torsional stress and the angle of rotation before failure. TFs displayed the least amount of torsional stress resistance and the highest angle of rotation. The 30/.06 size files of all 3 types withstood more torsional stress than the size 25/06 files of the same type. Within each file design, there was not a statistically significant difference in angular rotation between the 25/.06 and 30/.06 groups. The scanning electron microscopic analysis of all 3 file types revealed dimpling near the center of rotation on the fractured surface indicative of torsional stress. Conclusions The novel techniques used in manufacturing TFs do not make them more resistant to torsional stress as compared with milled nickel-titanium endodontic files of a similar cross-sectional design.

Background/Objectives: Because polymer-based materials typically exhibit viscoelastic properties, the objective was to determine if commercially available, aesthetic, fibre-reinforced composite archwires maintain continuous forces without undergoing force decay when deflected continuously. Materials/Methods: Quasi force decay was evaluated by comparing three-point bending profiles of nickel–titanium (NiTi) and fibre-reinforced composite archwires (BioMers) prior to and after 30 days of continuous deflection of either 1 or 2mm. Paired t-tests or non-parametric signed rank tests were used to statistically compare pre- and post-deflection bending forces. A control group consisting of wires not subject to the 30-day constant deflection was tested to check whether the initial testing altered the second three-point bend test. Results: Significant ( P < 0.01) differences in the pre- and post-deflection deactivation force delivery were most evident in the composite 2mm deflection group and all of the NiTi groups. The composite 2mm deflection group failed to deliver consistent forces as the majority of the wires experienced crazing during the 30-day deflection period. The decrease in force delivery in the NiTi groups may be attributed to the small standard deviations. Conclusions: The composite 1mm deflection group demonstrated that fibre-reinforced composite archwires are able to deliver a consistent force after 30 days of deflection. However, the clinical applicability of these fibre-reinforced composite archwires may be limited as they are unable to sustain deflections of 2mm without experiencing crazing and loss of force delivery. Limitations: Clinical efficacy of the aesthetic, fibre-reinforced composite orthodontic archwires remains to be observed.

The orthodontic profession is constantly seeking to improve and optimize the aesthetics of orthodontic wires since the introduction of aesthetic brackets. Nickel-titanium (NiTi) wires since their introduction to orthodontics (Andreasen and Hilleman, 1971) have been extensively researched in vitro and are used as an initial levelling and aligning archwire because of its properties of springback and superelasticity (Burstone et al. , 1985; Miura et al. , 1986; Leu et al. , 1990; Bishara et al. , 1995; Bradley et al. , 1996; Biermann et al. , 2007; Berzins and Roberts 2010). Aesthetic wires are usually either coated NiTi wires or composite wires of reinforced polymers. Shape memory polymers have wide application in space technology and are being used currently in medicine and industrial applications (Jung and Cho, 2010; Hu et al. , 2012). These wires have enormous potential for clinical application in orthodontics, and polyphenylene, a self-reinforced polymer composite, is close to being introduced to orthodontic practice (Burstone et al. , 2011; Goldberg et al. , 2011). However, these wires are still at the experimental stage. A fibre reinforced polymer is in clinical use (BioMers Products, LLC, Jacksonville, FL, USA) that is manufactured using a pultrusion process with a photo-cured resin (Gopal et al. , 2005); however, these wires may be more likely to crack during bending and have been shown to deliver less consistent forces compared with alloy wires (Chang, 2012). The coated wires, which are currently available, either have an epoxy resin, polytetraflouroethylene (Teflon; Neumann et al. , 2002), or a low reflectivity rhodium coating (Iijima et al. , 2012) applied to the surface. Atomized Teflon particles are used to coat the wire using clean compressed air as a transport medium, which is then further heat treated in a chamber …

Objective. The corrosion of high-Pd dental alloys, depending on their composition, is postulated to be associated with dealloying and electroformation. The aim of this study was to obtain additional information to support these postulations. Methods. The corrosion characteristics of two commercial high-Pd alloys, Naturelle (79Pd–10Cu–2Au–9Ga wt%) and Rx 91 (54Pd–37Ag–9Sn), and their elemental components were evaluated in a phosphated buffer saline (PBS) solution. Indium, a common element in high-Pd alloys, was also included. The corrosion characteristics measured for each material were the 24 h open circuit potential (OCP) and the potentiodynamic anodic polarization curve. Additionally, the surface composition of the two alloys, before and after immersion corrosion in PBS for 2 months, was analyzed by X-ray photo electron spectroscopy (XPS). Results. Of the pure metals, Ga had the most electroactive OCP followed in order by In, Sn, Cu, Ag, Au, and Pd. The anodic polarization data showed all base metals to be unstable in PBS. The electroformation of AgCl was evidenced in the polarization curve of pure Ag. Both electrochemical characteristics of the PdCu-based alloy were very similar to that of pure Pd. The PdAg-based alloy displayed corrosion behavior resembling that of Ag. XPS data showed that the corrosion of the PdCu-based alloy was associated with a decrease in surface content of Cu and Ga but an increase in Pd and Au. The PdAg-based alloy surface during corrosion showed a decrease in Sn, an increase in Ag, and an unaltered Pd content. The behavior of the PdCu-based alloy is attributed to the operation of a galvanic interaction that causes dissolution of base metals and surface enrichment with primarily Pd. Dealloying, Ag-enrichment, and AgCl formation are thought to have contributed to the observed behavior of the PdAg-based alloy. These mechanisms are consistent with data from published ion release studies. Significance. The allergenic potential of any Pd alloy is dependent on its propensity to develop a Pd-rich surface and thus release Pd +2 ions. The present study, though limited, has shown that electrochemical characteristics, namely OCP and polarization curves, can be used to identify such alloys. Further studies are warranted to evaluate the widespread applicability of these characteristics in distinguishing between Pd alloys that are biologically safe and those that are not.

Objective . Alloys based on AgMn are being evaluated in our laboratory for their possible use as an alternative to Type III dental alloys. They respond to heat treatment and develop hardness values comparable to that of Type III alloys. The objective of the present research was to evaluate their corrosion characteristics. Methods . The three experimental silver-based alloys of the following composition (at%): (1) 63Ag37Mn, (2) 60Ag35Mn5Au and (3) 60Ag35Mn5Pd, were tested in their peak-hardened condition. Following 0.5 h open-circuit potential (OCP) measurement of each alloy in a phosphated buffer saline (PBS) solution, its current–potential profile was generated by the cyclic voltammetry technique within −1300 and +200 mV (SCE) at 1 mV s −1 . In a separate test, the OCP of each alloy was monitored over a 24 h period. Results . Each of the three alloys showed ennoblement of their OCP over time due to dissolution of Mn and consequent enrichment with Ag (Au or Pd). At 24 h, the two ternary alloys were the most noble followed by the binary alloy. With respect to the cyclic voltammetry, oxidation of Ag was noted during forward scans at around 0 mV. The reverse scan was associated with a reduction current peak between −37 and −128 mV. The values for this peak, which is a measure of Ag oxidation, were highest (11.5 mA cm −2 ) for the binary alloy followed by the Au- (2.9 mA cm −2 ) and Pd-containing (0.04 mA cm −2 ) alloys, respectively. This indicates that, for equivalent concentration, Pd is more effective in reducing Ag corrosion than Au. Significance . Alloys based on the AgMn system are as hard as Type III dental alloys. Information on the corrosion characteristics of the AgMn-based alloys presented here is of value in further development of this alloy system.

Objective: To study the effect of water storage on the bending properties of fiber-reinforced composite archwires and compare it to nickel-titanium (NiTi), stainless steel (SS), and beta-titanium archwires. Materials and Methods: Align A, B, and C and TorQ A and B composite wires from BioMers Products, 0.014-, 0.016, and 0.018-inch, and 0.019 × 0.025-inch NiTi, 0.016-inch SS, and 0.019 × 0.025-inch beta-titanium archwires were tested (n = 10/type/size/condition). A 20-mm segment was cut from each end of the archwire; one end was then stored in water at 37°C for 30 days, while the other was stored dry. The segments were tested using three-point bending to a maximum deflection of 3.1 mm with force monitored during loading (activation) and unloading (deactivation). Statistical analysis was completed via two-way analysis of variance with wire and condition (dry and water-stored) as factors. Results: In terms of stiffness and force delivery during activation, in general: beta-titanium was > TorQ B > TorQ A > 0.019 × 0.025-inch NiTi and 0.016-inch SS > Align C > 0.018-inch NiTi > Align B > 0.016-inch NiTi > Align A > 0.014-inch NiTi. Water exposure was detrimental to the larger translucent wires (Align B and C, TorQ A and B) because they were more likely to craze during bending, resulting in decreased forces applied at a given deflection. Align A and the alloy wires were not significantly (P > .05) affected by water storage. Overall, the alloy wires possessed more consistent force values compared to the composite wires. Conclusion: Environmental conditions are more likely to affect fiber-reinforced composite archwires compared to alloy wires.

Various alternatives to metal orthodontic archwires have produced varied successes over the years. This study sought to evaluate the bending properties of fiber-reinforced polymeric composite (FRC) archwires compared with similarly sized nickel-titanium (Ni-Ti) archwires.Two different 0.018-inch translucent FRC orthodontic wires (Translucent Archwire I and Translucent Archwire II) were tested against 0.014-, 0.016-, and 0.018-inch nonsuperelastic nickel titanium orthodontic wires. The wires in each group (n = 10) were evaluated with three-point bending using a universal testing machine. Wire segments were deflected at midspan to 3.1 mm at a rate of 2 mm/min. Loading and unloading slope and modulus were calculated, as were force values during activation and deactivation and elastic recovery.It was found that the 0.018-inch Ni-Ti archwire demonstrated the highest force values at different deflection distances followed by Translucent Archwire II, 0.016-inch Ni-Ti, Translucent Archwire I, and finally 0.014-inch Ni-Ti. 0.016-inch Ni-Ti exhibited the highest modulus value, followed by 0.018-inch Ni-Ti, 0.014-inch Ni-Ti, Translucent Archwire II, and finally Translucent Archwire I. During deactivation, the elastic recovery of 0.014-inch Ni-Ti and 0.016-inch Ni-Ti was significantly greater than Translucent Archwire II.The bending properties of BioMer's FRC archwires were found to be comparable to Ni-Ti, as advertised by the manufacturer.

In the oral environment, orthodontic wires will be subject to thermal fluctuations. The purpose of this study was to investigate the effect of thermocycling on nickel-titanium (NiTi) wire phase transformations.Straight segments from single 27 and 35 degrees C copper NiTi (Ormco), Sentalloy (GAC), and Nitinol Heat Activated (3M Unitek) archwires were sectioned into 5mm segments (n=20). A control group consisted of five randomly selected non-thermocycled segments. The remaining segments were thermocycled between 5 and 55 degrees C with five randomly selected segments analyzed with differential scanning calorimetry (DSC; -100--150 degrees C at 10 degrees C/min) after 1000, 5000, and 10,000 cycles. Thermal peaks were evaluated with results analyzed via ANOVA (alpha=0.05).Nitinol HA and Sentalloy did not demonstrate qualitative or quantitative phase transformation behavior differences. Significant differences were observed in some of the copper NiTi transformation temperatures, as well as the heating enthalpy with the 27 degrees C copper NiTi wires (p0.05). Qualitatively, with increased thermocycling the extent of R-phase in the heating peaks decreased in the 35 degrees C copper NiTi, and an austenite to martensite peak shoulder developed during cooling in the 27 degrees C copper NiTi.Repeated temperature fluctuations may contribute to qualitative and quantitative phase transformation changes in some NiTi wires.

The purpose of this study was to compare galvanic currents generated by different combinations of commonly used brackets and archwires.As-received stainless steel, nickel-titanium, and beta-titanium wires were coupled to stainless steel and titanium brackets in an artificial saliva medium. The galvanic current and amount of charge transferred for each pair were monitored with a zero resistance ammeter for 10 hours.Two-way analysis of variance (ANOVA) showed a significant difference in charge and galvanic currents when factored for type of bracket (P 0.001), but no significant difference between them when factored by type of wire (P 0.05). Specifically, a brazed stainless steel bracket was significantly greater in charge transferred and 10-hour galvanic current than metal injection molded stainless steel and titanium brackets (P 0.001), which were not different from each other (P 0.05).The method of bracket manufacturing might be of equal or more relevance to galvanic corrosion susceptibility than bracket composition.

Purpose: The purpose of this article is to review basic information about the alloys used for fabricating metal-ceramic restorations in dentistry. Their compositions, properties, advantages, and disadvantages are presented and compared. In addition to reviewing traditional noble-metal and base-metal metal-ceramic alloys, titanium and gold composite alloys are also discussed. Materials and Methods: A broad search of the published literature was performed using Medline to identify pertinent current articles on metal-ceramic alloys as well as articles providing a historical background about the development of these alloys. Textbooks, the internet, and manufacturers' literature were also used to supplement this information. Results: The review discusses traditional as well as more recently-developed alloys and technologies used in dentistry for fabricating metal-ceramic restorations. Clear advantages and disadvantages for these alloy types are provided and discussed as well as the role that compositional variations have on the alloys' performance. This information should enable clinicians and technicians to easily identify the important physical properties of each type and their primary clinical indications. Conclusions: A number of alloys and metals are available for metal-ceramic use in dentistry. Each has its advantages and disadvantages, primarily based on its specific composition. Continuing research and development are resulting in the production of new technologies and products, giving clinicians even more choices in designing and fabricating metal-ceramic restorations.

Objective: The aim of this study was to determine whether the Pd–Cu-based dental ceramic alloys possess any electrochemical characteristics distinguishable from that of other Pd-containing alloys. Of all Pd-containing alloys, this particular alloy group has been linked to frequent incidence of allergy and hypersensitivity reactions. Electrochemical corrosion may instigate these reactions. Methods: Four groups of alloys, Pd–Cu, Pd–Ga-(with and without Ag), Pd–Ag, and Au–Pd, were evaluated by traditional corrosion measurement techniques in a phosphated buffer saline solution at 20°C. The electrochemical characteristics measured were: (1) 20 h open circuit potential (OCP); (2) 20 h corrosion rate (Icorr); and (3) anodic polarization (E–i) curves. Results: The OCP values (232±25 mV ) of the Ag-free Pd–Ga and Pd–Cu-based alloys were higher than and distinctly different from that (144±52 mV ) of the Ag-containing alloys. The Icorr values of different alloys, despite varied compositions, were indistinguishable from one another. The E–i curves of all alloys were essentially similar, with the Ag-containing (>5 wt%) alloys showing a subtle difference in their anodic slope within 100 mV above their corrosion potentials. Significance: The OCP values of Pd–Cu alloys and the Ag-free Pd–Ga alloy are comparable to that reported for pure Pd (239±21 mV ), which indicates that during corrosion these alloys undergo dealloying and consequent Pd-enrichment on their surface. Such a condition is conducive to the release of allergenic Pd++ ions and offers a plausible explanation for the frequent incidence of hypersensitivity reactions associated with the Pd–Cu alloys. The OCP values in other alloys are attributed to dealloying followed by surface enrichment with Ag and/or Au and the possible formation of an insoluble AgCl surface film on the respective alloy surfaces. These events have the potential to suppress or prevent Pd++ ion release. Alloys showing these characteristics have seldom been linked to allergic reactions.