Corrosion resistance assessment of nickel-titanium endodontic files with and without heat treatment.

OBJECTIVES: The aim of this study was to evaluate the corrosion resistance of heat-treated (Reciproc and WaveOne) and non-heat-treated (ProTaper and Mtwo) superelastic nickel-titanium endodontic files when immersed in a 5.25% sodium hypochlorite solution. MATERIALS AND METHODS: Anodic polarization curves were obtained with potential sweeps that began at the open circuit potential or corrosion potential (Ecorr). The pitting potential (Epit) was identified on the anodic polarization curve as the potential at which a sudden increase in current was observed. The micromorphology of the 28 tested files was analyzed before and after the electrochemical assay using scanning electron microscope (SEM). The data were analyzed using 1-way analysis of variance with the post hoc Bonferroni test (for Ecorr) and the Student t-test for independent samples (for Epit). RESULTS: The mean Ecorr values were 0.506 V for ProTaper, 0.348 V for Mtwo, 0.542 V for Reciproc, and 0.321 V for WaveOne files. Only WaveOne and Protaper files exhibited pitting corrosion, with Epit values of 0.879 V and 0.904 V, respectively. On the SEM images of the ProTaper and WaveOne files, cavities suggestive of pitting corrosion were detected. CONCLUSIONS: Signs of corrosion were observed in both heat-treated and non-heat-treated files. Of the evaluated files, WaveOne (a heat-treated file) and ProTaper (a non-heat-treated file) exhibited the lowest corrosion resistance.

Evaluation of Root Perforation Treatments with Mineral Trioxide Aggregate: A Retrospective Case Series Study.

This study aimed to evaluate the long-term clinical success of the use of mineral trioxide aggregate (MTA) as a sealant material in root perforation treatments. Therefore, the dental records of 53 patients were analyzed, and treatment data was collected (age, gender, tooth location, jaw, presence or absence of radiolucent lesion, fallow up time and final radiographic/clinical assessment). All procedures were performed by a single specialist. Two examiners analyzed three radiographs from the records of each patient and classified the treatments as successful or unsuccessful. Data was analyzed statistically using parametric chi-square (P≤0.05). The examiners classified 69.8% of the cases as successful, with a follow-up time of 1-16.25 years (average: 6 years). The presence of initial radiolucent lesion was observed in 79.2% of the teeth, with a higher index of treatment in maxillary teeth (62.3%). However, the majority of successful cases were located in the maxilla (73.0%), while most unsuccessful ones were located in the mandible (62.5%) (P=0.014). There was no statistically significant difference regarding presence of previous lesions in successful (75.7%) and unsuccessful cases (87.5%) (P=0.330). In the present study, root perforations sealed with MTA had a success rate of 69.8% within 1-16.25 years. The presence of initial injury did not influence the prognosis, and maxillary teeth presented a higher success rate.

Surface Changes Of WaveOne™ and Reciproc® Instruments after Using Three Times for Preparation of Simulated Curved Canals with and without Glide Path.

Introduction: This study evaluated the occurrence of morphological changes on the surface of the instruments WaveOne™ and Reciproc® when used in the preparation of simulated curved canals with and without glide path (generated with the Pathfile™ system), after the first, second, and third uses. Materials and methods: Sixty-four resin blocks, which simulated curved root canals, were used and instrumented with a variety of instruments, grouped according to manufacturer and conditions of simulated canal preparation. Simulated canals were instrumented with WaveOne™ (GW1 group) and Reciproc® (GR1 group) according to manufacturers' recommendations, respectively. In contrast, GW2 and GR2 groups' simulated canals were submitted for construction of glide path with the PathFile™ system before the use of WaveOne™ and Reciproc® instruments, respectively. Each instrument was used three times; after each use, each instrument was analyzed by using scanning electron microscopy (cervical, middle, and apical thirds of the instrument) in order to characterize the occurrence of changes (fracture, twist, and crack). Data were described using means and standard deviations. We used generalized linear models to compare differences between factors (region, manufacturer, glide path, and number of uses). SPSS-15 software was used, with a significance level of 5%. Results: Without glide path, WaveOne™ instruments tended to fracture more frequently (P=0.003), twist more frequently (P=0.05), and crack more frequently (P=0.022), with increasing use, with statistically significant differences. With glide path, both WaveOne™ and Reciproc® instruments cracked less frequently (P=0.001); Reciproc® instruments did not exhibit superficial changes, such as fractures and/or twists. Conclusion: In this in vitro study Reciproc® instruments exhibited superior performance, compared with WaveOne™ instruments, particularly when glide path with the PathFile™ system was used; both instruments may be used, safely, three times to prepare curved canals.