Search Results (5)

The fracture of nickel–titanium (Ni-Ti) instruments during root canal instrumentation leads to compromised outcomes in endodontic treatments. Despite the significant impact of instrument facture during a root canal treatment, there is still no universally accepted method to address this complication. Several previous studies have shown the ability of a Neodymium: Yttrium–Aluminum–Perovskite (Nd: YAP) laser to cut endodontic files. This study aims to determine safe irradiation conditions for a clinical procedure involving the use of a Neodymium: Yttrium–Aluminum–Perovskite (Nd: YAP) laser for removing fractured nickel–titanium files in root canals. A total of 54 extracted permanent human teeth (n = 54) were used. This study involved nine distinct groups, each employing different irradiation conditions. Groups 1 s, 3 s, 5 s, 10 s, and 15 s simply consist of irradiation for 1, 3, 5, 10, and 15 s, respectively. After identifying the longest and safest duration time, four additional groups were proposed (labeled A, B, C, and D). Group A was composed of three series of irradiations of 5 s each separated by a rest time of 30 s (L5s + 30 s RT). Group B consisted of three series of irradiations of 5 s each separated by a rest time of 60 s (L5s + 60 s RT). Group C consisted of two series of irradiations of 5 s each separated by a rest time of 30 s (L5s + 30 s RT), and group D consisted of two series of irradiations of 5 s each separated by a rest time of 5 s (L5s + 5 s RT). In all groups, during the rest time, continuous irrigation with 2.5 mL of sodium hypochlorite (3% NaOCl) was carried out. The variation in temperature during irradiation was registered with a thermocouple during irradiation with different protocols. The mean and standard deviation of the temperature increase was noted. The calculation of the temperature was made as the Δ of the highest recorded temperature at the root surface minus (−) that recorded at baseline (37°). Additionally, scanning electron microscopy (SEM) was used after irradiation in all groups in order to assess the morphological changes in the root dentinal walls. The Nd: YAP laser irradiation parameters were a power of 3W, an energy of 300 mJ per pulse, a fiber diameter of 200 µm, a pulsed mode of irradiation with a frequency of 10 Hz, a pulse duration of 150 µs, and an energy density of 955.41 J/cm². Our results show that the safest protocol for bypassing and/or removing broken instruments involves three series of irradiation of 5 s each with a rest time of 30 s between each series. Furthermore, our results suggest that continuous irradiation for 10 s or more may be harmful for periodontal tissue. Full article

MXene materials have shown numerous useful mechanical and electronic properties, and have been found to possess nice potential in the field of optical modulation. Here, we fabricated a MXene Cr₂C saturable absorber by the liquid-phase exfoliation method, and systemically analyzed the surface morphology and nonlinear properties of the Cr₂C sample. Applying the Cr₂C saturable absorber as a Q-switch in a thulium-doped yttrium aluminum perovskite (Tm: YAP) laser, the shortest single pulse was obtained with a width of 602 ns under an absorbed pump power of 3.3 W at a repetition rate of 55 kHz with a T = 1% output coupler. The maximum output power was obtained with a T = 5% output coupler at a repetition rate of 58 kHz. The obtained maximum pulse energy and peak power were 3.96 μJ and 4.36 W, separately, which reveal that the MXene Cr₂C can be applied as a promising modulation material in the near-infrared pulsed lasers. Full article

The sensitivity of luminescence thermometry is enhanced at high temperatures when using a three-level luminescence intensity ratio approach with Dy³⁺- activated yttrium aluminum perovskite. This material was synthesized via the Pechini method, and the structure was verified using X-ray diffraction analysis. The average crystallite size was calculated to be around 46 nm. The morphology was examined using scanning electron microscopy, which showed agglomerates composed of densely packed, elongated spherical particles, the majority of which were 80–100 nm in size. The temperature-dependent photoluminescence emission spectra (ex = 353 nm, 300–850 K) included Dy³⁺ emissions in blue (458 nm), blue (483 nm), and violet (430 nm, T 600 K). Luminescence intensity ratio, the most utilized temperature readout method in luminescent thermometry, was used as the testing method: a) using the intensity ratio of Dy³⁺ ions and ⁴I_15/2→⁶H_15/2/⁴F_9/2→⁶H_15/2 transitions; and b) employing the third, higher energy ⁴G_11/2 thermalized level, i.e., using the intensity ratio of ⁴G_11/2→⁶H_15/2/⁴F_9/2→⁶H_15/2 transitions, thereby showing the relative sensitivities of 0.41% K⁻¹ and 0.86% K⁻¹ at 600 K, respectively. This more than doubles the increase in sensitivity and therefore demonstrates the method’s usability at high temperatures, although the major limitation of the method is the chemical stability of the host material and the temperature at which the temperature quenching commences. Lastly, it must be noted that at 850 K, the emission intensities from the energetically higher levels were still increasing in YAP: Dy³⁺. Full article

Ceramic matrix composites (CMCs) are promising materials for high-temperature applications. Environmental barrier coatings (EBCs) are needed to protect the components against water vapor attack. A new potential EBC material, YAlO₃, was studied in this paper. Different plasma-spraying techniques were used for the production of coatings on an alumina-based CMC, such as atmospheric plasma spraying (APS) and very low pressure plasma spraying (VLPPS). No bond coats or surface treatments were applied. The performance was tested by pull–adhesion tests, burner rig tests, and calcium-magnesium-aluminum-silicate (CMAS) corrosion tests. The samples were subsequently analyzed by means of X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Special attention was paid to the interaction at the interface between coating and substrate. The results show that fully crystalline and good adherent YAlO₃ coatings can be produced without further substrate preparation such as surface pretreatment or bond coat application. The formation of a thin reaction layer between coating and substrate seems to promote adhesion. Full article

Two new types of oxide fibers, namely, those of single crystalline yttrium-aluminum perovskite YAlO₃ (YAP) and two-phase YAlO₃-Y₄Al₂O₉ (YAP-YAM), have been grown by the internal crystallization method. The fibers of the second type retain their strength at temperatures up to 1000 °C. Their effective strength in a molybdenum matrix reaches about 600 MPa at a temperature of 1400 °C. Full article