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A novel miniature mixer called the “Alberta Polymer Asymmetric Minimixer” (APAM) was designed, built and tested. In this study, polymer blends and nanofiber composites were compounded using a total of approximately 2 grams per sample. This mixer has a unique, asymmetric design consisting of a varying clearance between the rotor blade tips and the cup wall, enabling the material to be squeezed, stretched and kneaded in high shear and converging zones. Unlike the few other miniature mixing devices that are commercially available, the APAM has a combination of good mixing capability and complex flow modes required for dispersive flow, and requires minimal sample mass. In this work, the final morphology of non‐reactive blends created in the APAM was similar to that obtained in an internal mixer and in a twin‐screw extruder, and was much finer than that obtained in a MiniMAX™ mixer. The final morphology in reactive blends was comparable for all the mixers. The dispersion of nanofibers is uniform for the nanocomposites blended in the APAM and comparable to the dispersion obtained in the internal batch mixer, whereas for the MiniMAX™, the nanofibers remained in bundles and were not wetted by the matrix polymer. Polym. Eng. Sci. 44:868–879, 2004. © 2004 Society of Plastics Engineers.

Objective: To better understand the mechanics of bracket/archwire interaction through analysis of force and couple distribution along the maxillary arch. Materials and Methods: An orthodontic simulator was utilized to study high canine malocclusion. Force/couple distributions, referenced to the center of resistance (CR) of each tooth, produced by passive ligation brackets and round wire were measured. Tests were repeated for 12 bracket sets with 12 wires per set. Results: Propagation of the force/couple systems around the arch was minimal. Binding was observed only on the teeth adjacent to the displaced canine. For most of the teeth, reduced resistance to sliding of the passive ligation bracket yielded minimal tangential and normal forces at the bracket and contributed to lower moments at CR. Conclusions: Some potential mechanical advantages of passive ligation systems are suggested for the case studied. In particular, limited propagation around the arch reduces the occurrence of unwanted force/couple systems. (Angle Orthod. 2011;81:953-959.)

Introduction. This review is intended to highlight and discuss discrepancies in the literature of the periodontal ligament's (PDL) mechanical properties and the various experimental approaches used to measure them. Methods. Searches were performed on biomechanical and orthodontic publications (in databases: Compendex, EMBASE, MEDLINE, PubMed, ScienceDirect, and Scopus). Results. The review revealed that significant variations exist, some on the order of six orders of magnitude, in the PDL's elastic constants and mechanical properties. Possible explanations may be attributable to different experimental approaches and assumptions. Conclusions. The discrepancies highlight the need for further research into PDL properties under various clinical and experimental loading conditions. Better understanding of the PDL's biomechanical behavior under physiologic and traumatic loading conditions might enhance the understanding of the PDL's biologic reaction in health and disease. Providing a greater insight into the response of the PDL would be instrumental to orthodontists and engineers for designing more predictable, and therefore more efficacious, orthodontic appliances.