ABSTRACT
To compare the optical properties of hydrophilic and hydrophobic intraocular lenses [IOLs] containing UV-absorber and to determine their chemical composition. Optical properties of different foldable hydrophilic and hydrophobic as well as non-foldable hydrophobic polymethylmetacrylate [PMMA] IOLs were evaluated in three powers of 15, 22 and 25 diopters. Optical properties were measured using UV-VIS [UV-Visible] spectroscopy between wavelengths 200 and 800 nm and chemical structure characteristics were determined by ATR [attenuated total reflectance] spectroscopy. ATR spectroscopy revealed that foldable hydrophilic and hydrophobic IOLs and non-foldable hydrophobic IOLs were respectively composed of hydroxyethylmethacrylate, a copolymer of phenylethylacrylate and phenylethylmethacrylate, and PMMA [in accordance with manufacturer's claim]. Cut-off points of the lenses were found to be around 350-420 nm. Increasing the IOL power from 15 to 22 diopters did not significantly change the cut-off points of foldable hydrophobic IOLs, however a considerable cut-off shift to higher wavelengths was noted when power increased to 25 diopters. PMMA lenses showed a constant cut-off at 400 nm for all power values. The increase in power is associated with absorption of lower energy UV radiation and shift of cut-off points to higher wavelengths in hydrophobic IOLs but with no considerable effect on cut-off points in PMMA IOLs
ABSTRACT
The desirable mechanical properties of nickel-titanium alloy wires have prompted many clinicians to recycle these wires. The purpose of this study was to investigate the changes in mechanical properties of nickel-titanium alloy wires after recycling by electromechanical treatment. In this experimental study, round 0.018 inch nickel-titanium wires [American Orthodontics trademark] were used. For purpose of determining the behavior of samples in mouth, the transformation temperatures of alloy were carried by electrical resistance test. The types of nickel-titanium wires were separated into three groups: 1- as received condition [control wires], 2- treated by low electrical current, 3- treated by high electrical current. Mechanical properties changes were observed by tensile testing. One-way analysis of variance and Tukey HSD [SPSS statistical package] was used for purpose of comparison. The results demonstrated significantly greater remained strains after recycling, but plateau stresses and elastic strain energies of the wires were decreased compared with the control wires. Super elastic property of electromechanical treated nickel-titanium wires is decreased following electromechanical treatments