Use of technopolymer clasps in prostheses for patients due to have radiation therapy.

Patients with large oral defects as a result of a maxillectomy procedure, who are due to have postoperative radiotherapy, need to have the density of the defect restored to ensure standardised radiation distribution. This is achieved with various types of boluses that often require tissue surface positioning stents to help support them. Traditional metal-clasp retained stents were discarded as the clasps caused backscatter of the radiation beams. A radiolucent material was needed to retain these prostheses. Dental D, an acetal resin was used in the fabrication of a positioning stent. It was assessed in terms of ease of manufacture, cost, fit, retention and radiolucency. The material was found to be more costly and time-consuming to manufacture than conventional metal-retained acrylic resin prostheses, but its radiolucency made it ideal for use in patients during radiotherapy treatment. Future studies will determine if the long-term strength of the material will allow the clasps to be used in a definitive prosthesis and thus help offset the initial time and costs.

Model-based rational strategy for chromatographic resin selection.

A model-based rational strategy for the selection of chromatographic resins is presented. The main question being addressed is that of selecting the most optimal chromatographic resin from a few promising alternatives. The methodology starts with chromatographic modeling,parameters acquisition, and model validation, followed by model-based optimization of the chromatographic separation for the resins of interest. Finally, the resins are rationally evaluated based on their optimized operating conditions and performance metrics such as product purity, yield, concentration, throughput, productivity, and cost. Resin evaluation proceeds by two main approaches. In the first approach, Pareto frontiers from multi-objective optimization of conflicting objectives are overlaid for different resins, enabling direct visualization and comparison of resin performances based on the feasible solution space. The second approach involves the transformation of the resin performances into weighted resin scores, enabling the simultaneous consideration of multiple performance metrics and the setting of priorities. The proposed model-based resin selection strategy was illustrated by evaluating three mixed mode adsorbents (ADH, PPA, and HEA) for the separation of a ternary mixture of bovine serum albumin, ovalbumin, and amyloglucosidase. In order of decreasing weighted resin score or performance, the top three resins for this separation were ADH [PPA[HEA. The proposed model-based approach could be a suitable alternative to column scouting during process development, the main strengths being that minimal experimentation is required and resins are evaluated under their ideal working conditions, enabling a fair comparison. This work also demonstrates the application of column modeling and optimization to mixed mode chromatography.

Comparative study of strong anion exchangers: structure-related chromatographic performances.

Chromatographic performances are highly influenced by operational parameters. New ion exchangers have tailored matrices providing low backpressure and allowing high flow velocity. By systematic frontal analysis and selectivity determination at different flow rates, we suggested an independent evaluation of major anion exchangers to facilitate media selection, and investigated the relationship between (i) surface modification and (ii) chromatographic performances. Structure-extended resins showed higher binding capacities compared to resins with conventional ligands directly attached to the matrix. Moreover, they maintained mainly high capacities even with extremely high flow velocities. Ligand accessibility was therefore largely enhanced, allowing proteins to interact and bind under harsh conditions. High throughput resins can be used for purification of high volume and high concentration feedstock in limited time. This results in higher productivity and could contribute to cost reduction.