Cone beam computed tomography study of apical root resorption induced by Herbst appliance

Objective This study evaluated the frequency of root resorption during the orthodontic treatment with Herbst appliance by Cone Beam Computed Tomography (CBCT).Material and Methods The sample comprised 23 patients (11 men, 12 women; mean ages 15.76±1.75 years) with Class II division 1 malocclusion, treated with Herbst appliance. CBCT was obtained before treatment (T0) and after Herbst treatment (T1). All the dental roots, except third molars, were evaluated, and apical root resorption was determined using the axial guided navigation method. Paired t-tests and Wilcoxon T Test were used to compare the dependent samples in parametric and nonparametric cases, respectively. Chi-Square Test with Yates’ correction was used to evaluate the relationship between apical root resorption and gender. Results were considered at a significance level of 5%.Results Apical resorption was detected by CBCT in 57.96% of 980 roots that underwent Herbst appliance treatment. All patients had minimal resorption and there was no statistical significance between the genders.Conclusion CBCT three-dimensional evaluation showed association between Herbst appliance and minimal apical root resorption, mostly in the anchoring teeth, without clinical significance

Understanding the Origins of Bacterial Resistance to Aminoglycosides through Molecular Dynamics Mutational Study of the Ribosomal A-Site

Paromomycin is an aminoglycosidic antibiotic that targets the RNA of the bacterial small ribosomal subunit. It binds in the A-site, which is one of the three tRNA binding sites, and affects translational fidelity by stabilizing two adenines (A1492 and A1493) in the flipped-out state. Experiments have shown that various mutations in the A-site result in bacterial resistance to aminoglycosides. In this study, we performed multiple molecular dynamics simulations of the mutated A-site RNA fragment in explicit solvent to analyze changes in the physicochemical features of the A-site that were introduced by substitutions of specific bases. The simulations were conducted for free RNA and in complex with paromomycin. We found that the specific mutations affect the shape and dynamics of the binding cleft as well as significantly alter its electrostatic properties. The most pronounced changes were observed in the U1406C∶U1495A mutant, where important hydrogen bonds between the RNA and paromomycin were disrupted. The present study aims to clarify the underlying physicochemical mechanisms of bacterial resistance to aminoglycosides due to target mutations

PS18kh: A New Tidal Disruption Event with a Non-axisymmetric Accretion Disk

We present the discovery of PS18kh, a tidal disruption event discovered at the center of SDSS J075654.53+341543.6 (d ≃ 322 Mpc) by the Pan-STARRS Survey for Transients. Our data set includes pre-discovery survey data from Pan-STARRS, the All-sky Automated Survey for Supernovae, and the Asteroid Terrestrial-impact Last Alert System as well as high-cadence, multiwavelength follow-up data from ground-based telescopes and Swift, spanning from 56 days before peak light until 75 days after. The optical/UV emission from PS18kh is well-fit as a blackbody with temperatures ranging from T ≃ 12,000 K to T ≃ 25,000 K and it peaked at a luminosity of L ≃ 8.8 × 10 erg s . PS18kh radiated E = (3.45 ± 0.22) × 10 erg over the period of observation, with (1.42 ± 0.20) × 10 erg being released during the rise to peak. Spectra of PS18kh show a changing, boxy/double-peaked Hα emission feature, which becomes more prominent over time. We use models of non-axisymmetric accretion disks to describe the profile of the Hα line and its evolution. We find that at early times the high accretion rate leads the disk to emit a wind which modifies the shape of the line profile and makes it bell-shaped. At late times, the wind becomes optically thin, allowing the non-axisymmetric perturbations to show up in the line profile. The line-emitting portion of the disk extends from r ∼ 60r to an outer radius of r ∼ 1400r and the perturbations can be represented either as an eccentricity in the outer rings of the disk or as a spiral arm in the inner disk. 43 -1 50 50 in g out