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    The effect of blue thermal treatment on endodontic instruments and apical debris extrusion during retreatment procedures
    (Wiley, 2019) Yildiz, E. Doganay; Arslan, H.
    Aim To determine the effect of blue thermal treatment on Reciproc (VDW, Munich, Germany) endodontic instruments and the amount of apically extruded debris during retreatment procedures. Methodology Thirty extracted mandibular molar teeth having mesial roots with a degree of curvature less than 20 degrees and having an initial apical size equivalent to a size 10 K-file were selected. The mesial roots of the teeth were removed from the cementoenamel junction to obtain a 15-mm root length. The mesiobuccal canals were prepared to size F2 using the ProTaper Universal system (Dentsply Sirona, Ballaigues, Switzerland), filled with gutta-percha and 2Seal (VDW) using the lateral compaction technique and then randomly divided into two groups (n = 15). The root fillings were removed with one of the following instruments using a crown-down preparation technique: M-Wire Reciproc or Reciproc Blue (both VDW). Apically extruded debris was collected in pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 degrees C for five days to evaporate the distilled water. The data were analysed using the Mann-Whitney U test (P = 0.05). Results Reciproc Blue (1.42 +/- 0.4491 mg) extruded significantly less debris apically than M-Wire Reciproc (2.56 +/- 1.0232 mg) (P < 0.05). Conclusions Blue thermal treatment of Reciproc instruments was associated with less debris extrusion during retreatment procedures.
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    An investigation of rolling element vibrations caused by local defects
    (Asme-Amer Soc Mechanical Eng, 2008) Arslan, H.; Aktürk, N.
    In this paper, a shaft-bearing model is developed in order to investigate the rolling element vibrations for an angular contact ball bearing with and without defects. The shaft-bearing assembly is considered as a mass-spring system. The system shows a nonlinear characteristic under dynamic conditions. The equations of motion in radial and axial directions were obtained for shaft and rolling elements, and they were solved simultaneously with a computer simulation program. Additionally, the effect of localized defects on running surfaces (i.e., inner ring, outer ring, and ball) on the vibration of the balls is investigated. Vibration of rolling elements in the radial direction is analyzed in time and frequency domains. Characteristic defect frequencies and their components can be seen in the frequency spectra of rolling element vibrations. Comparison of the obtained results with similar studies available in literature showed reasonable qualitative agreement.