PubMed · 5336845
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H Boersma. 1967. A method for making dental casts with cold-curing polyester resin.. https://doi.org/10.14219/jada.archive.1967.0436
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PURPOSE: To compare neodymium:YAG (Nd:YAG) laser effects on acrylic, silicone, and poly(methyl methacrylate) (PMMA) intraocular lens (IOL) polymers. METHODS: Ten Nd:YAG laser exposures were produced in each of 6 implantation-quality acrylic (Alcon MA60BM), silicone (Staar AQ1016), and PMMA (Alcon MC60BM) IOLs under identical conditions. Each polymer type was irradiated at 6 power settings (0.3, 0.5, 1.0, 1.5, 2.0, and 3.0 mJ) and at 2 focal points (midpoint of lens optic and on the posterior surface to which a cellophane membrane was affixed). The linear extent of the damage was measured using light microscopy. Specimens exposed to 1.0 mJ were processed for scanning electron microscopy. RESULTS: The damage threshold (> or = 5 microns depth) was 0.3 mJ for silicone and 1.0 mJ for acrylic and PMMA IOLs. At the clinically relevant power levels, 1.0 to 2.0 mJ, the depth of damage in the acrylic polymer was 11.9 to 30.5 times less than the depth in the silicone polymer. Similarly, the depth of damage in the PMMA polymer was 5.4 to 52.6 times less than the depth in the silicone polymer. The morphologic pattern of damage in the silicone IOL showed a deep, irregularly configured trough with meandering tendrils. Acrylic IOL damage morphology consisted of an ameboid-shaped entry site without radiating fractures and mild posterior penetration. Poly(methyl methacrylate) IOL damage consisted of a shallow focal trough with radiating fractures. CONCLUSIONS: The silicone IOL polymer had the lowest threshold for laser-induced damage and greater linear extension of damage than the PMMA and acrylic IOL polymers. Poly(methyl methacrylate) and silicone polymers exhibited collateral damage or ejected particulates adjacent to the entry site, whereas the acrylic polymer showed a discrete locus of damage.
The influence of propylene glycol (PG) on the in vitro penetration of diclofenac sodium (DFS) through a synthetic membrane and abdominal rat skin from carbopol gels was investigated using Franz-type diffusion cells. The combined effect of isopropyl myristate (IPM) and PG was also evaluated. It was found that the penetration through the synthetic membrane was well described by the Higuchi model. The gel containing 40% PG showed the highest release rate, indicating that a releasing maximum exists for PG content which provides the fully solubilized drug in the vehicle. When using rat skin as the barrier, the penetration rate was controlled by the membrane. DFS flux decreased with increasing PG content of the gels due to an increase of the drug affinity to the vehicle. A cosolvent action of PG was evident. However, the combination of PG and IPM resulted in a synergistic enhancement of DFS flux. Maximum enhancing activity was obtained from gels containing 40% PG, which yielded an enhancement ratio of about 8. Increasing IPM content from 3 to 5% increased the flux and decreased the lag time taken to reach a steady-state level.