objective: the aim of this study was to evaluate and compare the effect of dental surface treatment with er:yag , nd:yag ,co2 lasers and sodium ascorbate to recently laser bleached enamel by scanning electron microscope (sem). methods: 15caries-free extracted human third molars were selected for this study. the samples were bleached by heydent jw power activated by diode laser 810 nm. after 7 d...

The present study aims to investigate the residual stresses and surface hardening in ground components caused by the coupled effect of thermo-plasticity and phase transformation. A feasible numerical method was developed to accommodate appropriately the phase transformation in a workpiece experiencing critical temperature variation during grinding. The change of material properties was modelled...

The beam hardening effect is one of the major artifacts of X-ray computed tomography. It not only complicates medical inspection and material analysis, but also influences the accuracy and repeatability of dimensional measurements. Therefore, many efforts have been devoted to develop beam hardening correction methods since the early 1970s. In practice, the combination of hardware filters (pre-f...

introduction: the aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a ytterbium-doped potassium yttrium tungstate (yb: kyw) thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances. method: twelve extracted human premolars were sectioned into crowns and roots along the cem...

background: at the end of fi xed orthodontic treatment, the remnant of adhesive should be eliminated from the tooth surface. the purpose of this study was to compare the effect of three methods of removing adhesive on enamel surface roughness, dental pulp t emperature, and also on the time spent. materials and methods: the brackets on 90 extracted teeth were debonded using bracket removal plier...

A surface hardening technique called “interstitial hardening” has been developed to introduce interstitial carbon atoms into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. The interstitial hardening...

in this study, we have theoretically investigated the effect of electron stopper layer on internal temperature distribution of high performance vertical cavity surface-emitting laser emitting at 1305 nm.  simulation software pics3d, which self-consistently combines the 3d simulation of carrier transport, self-heating, gain computation and wave-guiding, was used. simulation results show that cha...

This study aimed to identify the optimal combination of wavelength and laser pulse density achieve pressure that can induce maximum compressive residual stress at subsurface microalloyed steel. For this, shock peening without coating (LSPwC) was performed on steel samples fundamental (1064 nm) with densities 3, 6, 9, 12 GW/cm2 second harmonic (532 9 GW/cm2. The distributions were studied a dept...