Mechanical Performance and Metallurgical Features of ProTaper Universal and 6 Replicalike Systems.

INTRODUCTION: This study aimed to compare the ProTaper Universal (PTU; Dentsply Maillefer, Ballaigues, Switzerland) system with 6 replicalike instruments regarding instrument design, mechanical performance, and alloy characteristics. METHODS: New rotary instruments (size 20/.07v) of PTU and 6 replicalike systems (EdgeTaper [EdgeEndo, Johnson City, TN], U-File [Dentmark, Ludhiana, India], Go-Taper Universal [Access, Shenzhen, China], Super Files [Flydent, Shenzhen, China], Multitaper [Proclinic Expert, Besançon, France], and Pluri Taper [Bestdent, Shenzhen, China]) (n = 329) were selected and evaluated regarding their design, mechanical performance, and metallurgical characteristics. The results were compared using the nonparametric Mood median test and 1-way analysis of variance with the significance level set at 0.05. RESULTS: Replicalike instruments were similar to PTU regarding design, maximum torque to fracture (P > .05), and ratio of nickel and titanium elements. Scanning electron microscopy revealed differences in the geometry of the tip and finishing surfaces. Time to fracture of Go-Taper Universal (50.0 seconds) was similar to PTU (44.0 seconds) (P > .05), but the U-File (63.5 seconds), Edge Taper (87.5 seconds), and Super Files (130 seconds) showed significantly higher values (P < .05). The highest maximum torque was observed in the Super Files instrument (P < .05), but no statistical difference was noted among the other instruments (P > .05). The angle of rotation before rupture of the Multitaper (574°) and Pluri Taper (481°) was higher than PTU (354°) (P < .05). Differential scanning calorimetric analysis showed clear differences on the transformation temperatures among the tested instruments. The R-phase start and finish temperatures of PTU were 11.0°C and -18.0°C, respectively. CONCLUSIONS: Overall, replicalike instruments were similar to PTU regarding the torsional resistance, geometric design, and near equiatomic proportions of nickel and titanium elements. In 3 of the 4 mechanical tests, the EdgeTaper (torque, angle of rotation, and bending load) and Go-Taper Universal (time to fracture, torque, and angle of rotation) systems were similar to PTU.

Microanalytical Study of Ancient Gold Jewelry: Mediterranean Impact on the Early Iron Age Technology in Southwestern Iberia.

The gold technology in Iberia underwent an important development during the Early Iron Age (EIA) following the arrival of new technological skills from the Mediterranean region, including the use of filigree, granulation, and brazing. This work presents the microanalytical study of EIA gold jewels (22 spherical beads and four tongue pendants) recovered from three graves in southern Portugal. The set of jewelry, showing an extraordinary stylistic resemblance, was characterized by optical microscopy, micro energy-dispersive X-ray spectrometry and scanning electron microscopy with X-ray microanalysis to establish the alloy composition and production techniques. The pieces show a close technological relation, making use of artificial gold alloys with different amounts of silver (c. 40 and 25%). The decorative styles include different types of filigree (solid wires and hollow wires), while the joining techniques comprise brazing with Au-Ag-Cu solders and, probably, sintering. In spite of those technological and stylistic features, clearly pointing to a Mediterranean influence, the absence of granulation suggests an indigenous workshop where exogenous technologies/decorations were not yet fully integrated in the manufacture of such luxury items.

Effects of Long-Term Aging in Arsenical Copper Alloys.

Archaeological materials present unique records on natural processes allowing the study of long-term material behaviors such as structural modifications and degradation mechanisms. The present work is focused on the chemical and microstructural characterization of four prehistoric arsenical copper artifacts. These artifacts were characterized by micro-energy dispersive X-ray fluorescence spectrometry, optical microscopy, scanning electron microscopy with X-ray microanalysis, micro-X-ray diffraction and synchrotron radiation micro-X-ray diffraction. Cu3As is the expected intermetallic arsenide in arsenical copper alloys, reported in the literature as exhibiting a hexagonal crystallographic structure. However, a cubic Cu3As phase was identified by X-ray diffraction in all of our analyzed archaeological artifacts, while the hexagonal Cu3As phase was clearly identified only in the artifact with higher arsenic content. Occurrence of the cubic arsenide in these particular objects, suggests that it was precipitated due to long-term aging at room temperature, which points to the need of a redefinition of the Cu-As equilibrium phase constitution. These results highlight the importance of understanding the impact of structural aging for the assessment of original properties of archaeological arsenical copper artifacts, such as hardness or color.

Multifocus optical microscopy applied to the study of archaeological metals.

Studies on cultural metal artifacts can benefit greatly from microscopy techniques. The examination of microstructural features can provide relevant information about ancient manufacturing techniques, as well as about corrosion/degradation processes. In the present work, advantages of the use of multifocus imaging techniques in optical microscopy for the study of archaeological metals are presented. An archaeometallurgical study of a large collection of bronzes demonstrates the possibility of a microstructural study with no need for sample removal, which is a great advantage in the study of cultural objects. In addition, the study of mounted samples illustrates the advantages of the multifocus technique in the examination of particular corrosion features, with the possibility of three-dimensional reconstructions.

An efficient non-mediated amperometric biosensor for nitrite determination.

In this paper we propose the construction of a new non-mediated electrochemical biosensor for nitrite determination in complex samples. The device is based on the stable and selective cytochrome c nitrite reductase (ccNiR) from Desulfovibrio desulfuricans, which has both high turnover and heterogeneous electron transfer rates. In opposition to previous efforts making use of several redox mediators, in this work we exploited the capacity of ccNiR to display a direct electrochemical response when interacting with pyrolytic graphite (PG) surfaces. To enable the analytical application of such bioelectrode the protein was successfully incorporated within a porous silica glass made by the sol-gel process. In the presence of nitrite, the ccNiR/sol-gel/PG electrode promptly displays catalytic currents indicating that the entrapped ccNiR molecules are reduced via direct electron transfer. This result is noteworthy since the protein molecules are caged inside a non-conductive silica network, in the absence of any mediator species or electron relay. At optimal conditions, the minimum detectable concentration is 120 nM. The biosensor sensitivity is 430 mA M(-1) cm(-2) within a linear range of 0.25-50 microM, keeping a stable response up to two weeks. The analysis of nitrites in freshwaters using the method of standard addition was highly accurated.