Electrochemical dissolution of nickel-titanium instrument fragments in root canals of extracted human maxillary molars using a small reservoir of electrolyte.

AIM: To evaluate the viability of the electrochemical dissolution of fragments of fractured NiTi instruments in root canals of extracted human maxillary molars, using two electrodes and the solution restricted to a small reservoir coupled to the pulp chamber. The primary hypothesis was that this method enables the reduction of fragment volume and re-establishment of the root canal path with a size 08 K-file, both in simulated canals and in extracted human maxillary molars. METHODOLOGY: Fragments of F1 ProTaper instruments were polarized in simulated root canals and in distobuccal root canals of extracted maxillary molars using a new method, with the solution restricted to a small acrylic microcell coupled to each resin block or pulp chamber. Two electrodes were used, where one was kept in contact with the intracanal fragment and another was positioned in the solution present in the acrylic microcell. After the tests, a size 08 K-file was used passively to verify the possibility of bypassing the fragment, which was also confirmed by radiographic analysis. Micro-CT analysis of the teeth was used before and after fragment dissolution to evaluate the volume, length and porosity of the fragments. The D'Agostino-Pearson normality test was used to verify the distribution of the data. A paired t-test (P < 0.05) was used to compare the volume, length and porosity of the fragments before and after the dissolution tests. RESULTS: After dissolution, all fragments could be bypassed with a size 08 K-file in both simulated canals and in extracted teeth. The dissolution process did not result in significant reduction of neither the fragment length nor the fragment porosity. However, it resulted in a significant reduction of fragment volume (paired t-test, P < 0.05). CONCLUSION: The electrochemical dissolution of fragments of NiTi files in root canals of extracted human maxillary molars using two electrodes, and the solution restricted to a small reservoir coupled to the pulp chamber resulted in a significant reduction of fragment volume. The re-establishment of the root canal path with the passive insertion of size 08 K-files was possible in all samples after the tests, both in simulated canals and in extracted teeth.

Analysis of two meteorite fragments (lunar and martian) using X-Ray microfluorescence and X-Ray computed microtomography techniques.

Meteorites have been arousing the curiosity of mankind since antiquity. However, the interest in these objects goes far beyond mere curiosity in the study of such materials, which has great importance due essentially to the information they can provide. The importance of studying meteorites is associated about the earliest conditions and processes during the formation and earliest history of the solar system. So, in this study, the characterization of two meteorite fragments was performed using X-ray computed microtomography (micro-CT) and X-ray microfluorescence (micro-XRF). These techniques were used for their non-destructive characteristics and the ability to provide information about the structure and composition the meteorites. The micro-CT images showed encrusted structures within both samples. However, while in Lunar meteorites spheroidal structures very similar to small grains internally grouped in clusters were found, in the Martian meteorite a very peculiar structure was identified. Besides that, the micro-CT it was also possible to evaluate the different density materials that compose the samples. The micro-XRF results accounted for the presence of the elements Si, Ca, Ti, Cr, Mn, Fe, Ni and Sr in the Lunar sample, as well as of Si, S, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Sr and Y in the Martian sample. The results obtained are effective for the characterization of meteorites, proving thus that it is possible to obtain important information about the chemical composition, as well as about the distribution and the internal structure of these materials, evaluating aspects such as density and porosity.