L. Esposito

The effect of Teflon coating on the resistance to sliding of orthodontic archwires

Teflon is an anti-adherent and aesthetic material. The aim of this study was to evaluate, in vitro, the influence of Teflon coating on the resistance to sliding (RS) of orthodontic archwires. For this purpose, Teflon-coated archwires were examined using frictional resistance tests by means of a universal testing machine and compared with conventional uncoated wires. Twelve types of archwires with round and rectangular sections (0.014, 0.018, and 0.018 × 0.025 inches) and of different materials (stainless steel and nickel-titanium) were tested with two passive self-ligating brackets (SmartClip™ and Opal(®)) and one active self-ligating bracket (Quick(®)). Each archwire-bracket combination was tested 10 times under 8 simulated clinical scenarios. Statistical comparisons were conducted between the uncoated and Teflon-coated archwires using Wilcoxon and Mann-Whitney tests, and linear regression analysis. For all bracket-archwire combinations, Teflon-coated archwires resulted lower friction than the corresponding uncoated archwires (P < 0.01). The results showed that Teflon coating has the potential to reduce RS of orthodontic archwires.

Hyper-IgE syndrome: dental implications

Hyper-IgE syndrome (HIES) is a rare multisystem disorder with both immunologic and nonimmunological features. It is characterized by extremely elevated IgE serum levels, eczema, and recurrent skin and pulmonary infections. Dental anomalies are often included, such as retention of deciduous teeth together with ectopic eruption or noneruption of permanent teeth. Severe susceptibility to caries and mycotic infections, insufficient transversal diameter of the palate, mucosal plaques, and fissures typically located on the tongue and on the palate are often present. The aim of this study was to review the literature and to report a 6-year observation of 6 patients with HIES (aged 8-39 years) with focus on their oral problems and the treatment provided. The importance of the role of the dentist both in early diagnosis of this syndrome and in monitoring oral conditions was stressed. The dentist can prevent infective complications and intercept the development of malocclusion with a reduction of the need for complex treatment.

InAs/GaAs Sharply Defined Axial Heterostructures in Self-Assisted Nanowires

We present the fabrication of axial InAs/GaAs nanowire heterostructures on silicon with atomically sharp interfaces by molecular beam epitaxy. Our method exploits the crystallization at low temperature, by As supply, of In droplets deposited on the top of GaAs NWs grown by the self-assisted (self-catalyzed) mode. Extensive characterization based on transmission electron microscopy sets an upper limit for the InAs/GaAs interface thickness within few bilayers (≤1.5 nm). A detailed study of elastic/plastic strain relaxation at the interface is also presented, highlighting the role of nanowire lateral free surfaces.

Self-assisted GaAs nanowires with selectable number density on Silicon without oxide layer

We present the growth of self-assisted GaAs nanowires (NWs) with selectable number density on bare Si(1 1 1), not covered by the silicon oxide. We determine the number density of the NWs by initially self-assembling GaAs islands on whose top a single NW is nucleated. The number density of the initial GaAs base islands can be tuned by droplet epitaxy and the same degree of control is then transferred to the NWs. This procedure is completely performed during a single growth in an ultra-high vacuum environment and requires neither an oxide layer covering the substrate, nor any pre-patterning technique.

High-Yield Fabrication of Entangled Photon Emitters for Hybrid Quantum Networking Using High-Temperature Droplet Epitaxy

Several semiconductor quantum dot techniques have been investigated for the generation of entangled photon pairs. Among the other techniques, droplet epitaxy enables the control of the shape, size, density, and emission wavelength of the quantum emitters. However, the fraction of the entanglement-ready quantum dots that can be fabricated with this method is still limited to around 5%, and matching the energy of the entangled photons to atomic transitions (a promising route toward quantum networking) remains an outstanding challenge. Here, we overcome these obstacles by introducing a modified approach to droplet epitaxy on a high symmetry (111)A substrate, where the fundamental crystallization step is performed at a significantly higher temperature as compared with previous reports. Our method drastically improves the yield of entanglement-ready photon sources near the emission wavelength of interest, which can be as high as 95% due to the low values of fine structure splitting and radiative lifetime, together with the reduced exciton dephasing offered by the choice of GaAs/AlGaAs materials. The quantum dots are designed to emit in the operating spectral region of Rb-based slow-light media, providing a viable technology for quantum repeater stations.

Characterization and Effect of Thermal Annealing on InAs Quantum Dots Grown by Droplet Epitaxy on GaAs(111)A Substrates

We report the study on formation and thermal annealing of InAs quantum dots grown by droplet epitaxy on GaAs (111)A surface. By following the changes in RHEED pattern, we found that InAs quantum dots arsenized at low temperature are lattice matched with GaAs substrate, becoming almost fully relaxed when substrate temperature is increased. Morphological characterizations performed by atomic force microscopy show that annealing process is able to change density and aspect ratio of InAs quantum dots and also to narrow size distribution.

Terapia ortodontico-chirurgica: protocollo virtuale 3D tramite TC cone beam

Riassunto Obiettivi Verificare la precisione di un protocollo di programmazione ortodontica prechirurgica virtuale e confrontarlo con quella di un protocollo non virtuale. Materiali e metodi Lo studio ha compreso 7 pazienti: 3 sono stati sottoposti a un protocollo di programmazione virtuale, i restanti 4 al protocollo tradizionale. Effettuate le scansioni tridimensionali dei modelli delle arcate dei pazienti, mediante un software dedicato e stata valutata l’aderenza tra le immagini digitali delle situazioni prechirurgiche e quelle dei rispettivi set-up. Sono stati inoltre considerati i valori di massima deviazione positiva e negativa, deviazione media e deviazione standard forniti dal software per le varie sovrapposizioni. Risultati L’analisi dei valori considerati non ha evidenziato differenze statisticamente significative tra le due metodiche di programmazione. Conclusioni Dallo studio si evince che l’affidabilita dei due protocolli e equiparabile. Cio che cambia e la quantita delle informazioni ricavabili, la ripetibilita della procedura e la velocita con la quale questa viene eseguita.