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A calibration model for in-line API determination was developed based on Raman spectra collected during hot-melt extrusion. This predictive model was validated by calculating the accuracy profile based on the analysis results of validation experiments. Furthermore, based on the data of the accuracy profile, the measurement uncertainty was determined. Finally, the robustness of the model was evaluated. A Raman probe was implemented in the die of a twin-screw extruder, to monitor the drug concentration during extrusion of physical mixtures containing 15, 20, 25, 30 and 35% (w/w) metoprolol tartrate (MPT) in Eudragit(®) RS PO, an amorphous copolymer of acrylic and methacrylic acid esters with a low content of quaternary ammonium groups, which are present as salts. Several different calibration models for the prediction of the MPT content were developed, based on the use of single spectra or averaged spectra, and using partial least squares (PLS) regression or multivariate curve resolution (MCR). These predictive models were validated by extruding and monitoring mixtures containing 17.5, 22.5, 25.0, 27.5 and 32.5% (w/w) MPT. Each validated concentration was monitored on three different days, by two different operators. The β-expectation tolerance intervals were calculated for each model and for each of the validated MPT concentration levels (β was set at 95%), and acceptance limits were set at 10% (relative bias), indicating that at least 95% of future measurements should not deviate more than 10% from the true value. The only model where these acceptance limits were not exceeded was the MCR model based on averaged Raman spectra. The uncertainty measurements for this model showed that the unknown true value can be found at a maximum of ±7.00% around the measured result, with a confidence level of 95%. The robustness of this model was evaluated via an experimental design varying throughput, screw speed and barrel temperature. The robustness designs showed no significant influence of any of the process settings on the predicted concentration values. Raman spectroscopy proved to be a fast, non-destructive and reliable method for the quantification of MPT during hot-melt extrusion. From the accuracy profile of the MCR model based on averaged spectra, it was concluded that for each MPT concentration in the validated concentration range, 95 out 100 future routine measurements will be included within the acceptance limits (10%)., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Study Design: Controlled in vitro trial., Objective: To study vertebral strength in relation to cement augmentation technique after vertebroplasty and to assess the influence of the biomechanical compression model on postoperative results., Summary of Background Data: In the treatment of osteoporotic vertebral fractures, the role of vertebroplasty has been well established. Biomechanical compression models thus far used, compressing vertebrae by only 25% of their initial height, did not show a correlation between cement augmentation volumes and postoperative compression strength. In these studies, even very small volumes of cement seem effective. However, these models may not realistically simulate clinically relevant osteoporotic wedge fractures. We hypothesize that, in clinically relevant osteoporotic wedge fractures, postoperative vertebral body strength is strongly dependent on endplate-to-endplate cement augmentation., Methods: Twenty-five intact osteoporotic cadaver vertebrae were obtained (10 lumbar, 15 thoracic). In 21 vertebrae, anterior wedge fractures (AO type A1.2) were created by controlled external force, with preset height reduction by 35%. After height reconstruction, 9 vertebrae were augmented endplate-to-endplate and 12 vertebrae were partially augmented with polymethylmethacrylate (PMMA). Another 4 vertebrae were compressed by only 25%. Posttreatment strength and stiffness of the vertebrae were determined by a compression test identical to the pretreatment compression protocol., Results: In the 35% compression group, posttreatment strength was significantly decreased in vertebrae that were partially augmented with cement compared with the endplate-to-endplate augmented group (767 +/- 257 N vs. 1141 +/- 325 N, P < 0.01). Postoperative strength amounted 106% +/- 27% of preoperative strength values in the endplate-to-endplate augmented vertebrae, compared with 65% +/- 18% in the partially augmented vertebrae (P < 0.001). In the 25% compression group, results in height restored and augmented vertebrae were similar to the nontreated vertebrae., Conclusions: Endplate-to-endplate PMMA augmentation restores the biomechanical properties of vertebrae in clinically relevant anterior wedge fractures. Our preliminary data suggest that biomechanical models with only 25% compressive deformation unlikely form a good model to assess the mechanical effects of cement augmentation in osteoporotic fractures.

Considered one of the weak links in the total hip replacement (THR), efforts to enhance the interfacial strength between bone cement and ultra-high molecular weight polyethylene (UHMWPE) acetabular cup had been conducted in this laboratory. Following the successful demonstration of high interfacial strengths for our new acetabular component design, the nature of physical, chemical, and thermal property of the compression-molded specimens, including UHMWPE, PMMA/MMA treated UHMWPE, and PMMA has been investigated in this study. Density results from a density gradient column showed that the molding processes and conditions were adequate for complete sintering of UHMWPE and PMMA powders. FTIR-ATR results gave a direct evidence that PMMA did exist in the PMMA/MMA treated UHMWPE matrix. It also revealed a clear diffusion-related behavior across the interface. Under the high temperature and pressure, the UHMWPE powders undergo drastic changes of their morphology and crystalline structures. These changes were examined by differential scanning calorimeter (DSC) which showed a large difference in terms of % crystallinity. The percent of PMMA deposited in the treated UHMWPE was 17.8%, 18.8%, and 24.3% from the analyses of density, FTIR-ATR, and DSC, respectively. Finally, an evidence of diffusive behavior at the interface exhibited diffusion of PMMA occurring across the interfaces between the treated UHMWPE and UHMWPE or PMMA.

In this study was verified accuracy and porosity of denture bases submitted to double cycles of polymerization. Thirty-Six master casts were made in dental stone from the impression of the metal die. They were divided in three groups. Denture bases of conventional acrylic resin were made on the casts of the groups I (GI-control) and II (GII), polymerized in water bath during 9 hours at 73 degrees C, and specific resin for microwave polymerization were made on the casts of the group III (GIII) and cured at 500 W during 3 minutes. Accuracy was verified by the weight of a impression material put between the denture base and cast die under load of 2 Kg. Afterwards, all the denture bases were relined by addition method and those of the group I and II were relined with the same material and polymerization technic. The denture bases of the group II were filled with the same resin, however cured in microwave oven with 500 W during 3 minutes. Accuracy was reevaluated. The porosity was verified by the immersion of the specimens in a solution of permanent black ink and the pores were counted through a stereo light microscope under magnification of 6.3 x. The average and standard deviation obtained for accuracy before and after the relining were respectively: GI: 0.63 +/- 0.02 - 0.66 +/- 0.03; GII: 0.63 +/- 0.03 - 0.68 +/- 0.03: GIII: 0.58 +/- 0.02 - 0.80 +/- 0.05. There was a significant difference (p < 0.05 as tested by Tukey) only for the group III. The average and standard deviation for porosity before and after the relining were respectively: GI: 8.33 +/- 0.63 - 9.25 +/- 0.85; GII: 8.17 +/- 0.98 - 10.08 +/- 1.63: GIII: 5.41 +/- 0.78 - 6.58 +/- 1.02. There was a significant difference (p < 0.05) for the group III before relining. The conclusion is that after relining, the conventional resin cured by water bath or microwaves energy showed a better adaptation, and the highest number of pores.

Next to the presence of (chemical) coupling between filler and resin, filler particle size is important for the mechanical coherence of dental resin composites which are used for posterior restorations. In the range of the current composites a smaller particle size is desirable. The better mechanical coherence for composites with smaller particles found in an in vitro erosive wear test is probably related to the size of food fibres, which are part of the erosive medium. It appears that there is a critical value of the filler particle size (1.3-1.5 microns), under which the food fibres are not able to penetrate in the interparticle space, so the erosive capability of the erosive medium will be reduced.

Hydrophylic porous polymers (HPP) obtained by polymerization of the alpha-cyanoacrylates under contact with solution of the polymeric carboxylic acids has the degree of water absorption up to 50.000 percent. Disclosed are the data on the HPP porosity investigation, water absorptions HPP are not toxic, do not exhibit allergenic and irritative actions, admit introduction of the medicine into HPP. The HPP films and sheets were used in the course of the experiment for treatment of purulent wounds. Their high effectiveness expressed in reduction of the adhesion time by 1.5 to 2 times was established.

Adhesives may offer a number of advantages over conventional metal osteosynthesis in the treatment of fractures: ease and speed of fixation are improved, they have the anatomy to anatomically coapt small fragments, and hardware removal is not necessary. A review of the literature was performed to evaluate experiments with collagen and other biologic adhesives, epoxy resins, polyurethane foam, cyanoacrylates, zinc polycarboxylate, polymethylmethacrylates, and fibrin adhesives pertaining to osteosynthesis. Cyanoacrylates, polymethylmethacrylates, and fibrin adhesives are currently being investigated. These agents are tested to evaluate their bone-bonding strength. Cyanoacrylates of biologically tolerated chain length did not develop useful bonding in cancellous bone; they bond well to cortical bone only with meticulous surface preparation. Fibrin adhesives developed only minimally useful bonding. Polymethylmethacrylate developed surgically useful bonding in osteosynthesis where conventional fixation is impossible.

Blood chambers of counterpulsation heart pumps were subjected to a special hydrophilization process in order to reduce the coagulation activity of the surface of poly(methyl methacrylate) (PMMA). The chemical treatment of the surface was carried out in three variants, namely A (ethylenglycol), B (diethylenglycol), C (glycerine) by using concentrated sulphuric acid with subsequent neutralization [12]. Controls were performed with the same pumps made of PMMA but without surface treatment. 30 dogs were used in the experiments.

The denture base which is made from the acrylic resin often occurs the fracture during function, and it is known that this fracture is mainly occured by the fatigue fracture, which is happened by the crack growth from the location of high stress. Until now, the author discussed on the fatigue properties about the specimens with semi-circular notch as the model of the remaining natural teeth, but these results are not easily applied to the design of denture base because the shape of denture base, considering its function and esthetics, is not changed. So, for the improvement of the strength of denture base, the denture base might be used the reinforcement. And, used as a trial the organic fiber as reinforcement, and their effects were investigated from the sides of the bending moment at fracture and the strain distribution occurs the fracture at the posterios palatal area, and its strength is improved 190%. And the fracture of the complete denture happens in general at the location between two central incisors, therefore this problem should be considered as the notched effect. So, reinforcing the lingual part of maxillary anterior teeth using the organic fiber, its strength is improved 53% comparing with the general complete denture. Therefore, the effects of reinforcement were enough appeared, and the improvement of the strength of denture base is very expected in dental use.

The effect of surface protein deposits on the oxygen permeability of polyhydroxyethylmethacrylate ( polyHEMA ) gel contact lenses was studied using: (1) previously worn lenses with protein deposits accumulated in vivo, and (2) new lenses with protein deposited in vitro. The oxygen permeability (Dk) of the protein-deposited in vivo lenses was determined before and after cleaning, and that of the new lenses before and after in vitro protein deposition. For both groups of lenses, the oxygen permeability did not change significantly after either cleaning (in vivo lenses) or protein deposition (in vitro lenses). It is concluded that surface protein deposits on polyHEMA lenses do not alter the oxygen permeability of the lenses.

The physiochemical properties of a hydrogel used as a scleral buckling implant for retinal detachment surgery are described. The new material was prepared by simultaneous polymerization and crosslinking of 2-hydroxyethyl acrylate with methyl acrylate and ethylene diacrylate, in the presence of an inert diluent, ethylene glycol. At equilibrium swelling, the hydrogen absorbed 17% water and had a durometer hardness (DH) of 15 (Shore Durometer A-2). A unique property of this material was its swelling hysteresis; when the gel swollen in 70% ethanol was placed in water, it retained a high level of hydration (75% water) and softness (DH 8), and most of its elasticity and strength as well. Then the swelling decreased very slowly so that the implant reached its ultimate size at equilibrium swelling in ca. 1 year. This property is especially useful in the scleral buckling procedure, in which a soft implant indents the sclera over the detached retina until reattachment is achieved. In addition to this advantage, this hydrogel is more elastic and stronger than available hydrogels of similar softness.