Vortex extrusion (VE) is a severe plastic deformation technique which is based on the synergies between high strain accumulation and high hydrostatic pressure. Such a high amount of pressure places a mandate to seek the method for investigation of the load under processing conditions. For this, kinematically admissible velocity field and upper bound terms based on Bezier formulation are developed in order to investigate relative pressure in the VE process. Effects of reduction in area, relative length, twist angle, and friction factor in power dissipation terms are systematically analyzed. It is demonstrated that the increase in twist angle, area reduction and friction factor in the VE process increases the relative pressure, which the rates of these increase vary with twist angle. Moreover, the effect of the relative length is different in various frictional conditions. Results of conventional extrusion (CE) are in good agreement with those found by Avitzur for the effect of slug length and friction factor on the relative extrusion stress.

Physical modeling of extrusion process has been studied to obtain qualitative and quantitative information. To observe the flow pattern during the process the plasticine specimen was made with layers of different colors (dark and light). The strain distribution was obtained by measuring the thickness of the plasticine layers and considering the axi-symmetric formulations. The stress distribution and subsequently the extrusion load were computed according to the strain distribution. To model the real frictional effect several ring compression tests have been performed. In order to verify the validity of the modeling data, a similarity study between plasticine and Al 2024-T4 was made. The load obtained by this technique was compared with the results of ANSYS modeling and slab method analysis.

Hot-melt extrusion is one of the most widely applied processing technologies in the plastic, rubber and food industry. Today this technology has found its place in the array of pharmaceutical manufacturing operations. Melt extrusion process are currently applied in the pharmaceutical field for the manufacture of a variety of dosage forms and formulations such as granules, pellets, tablets, suppositories, implants, stents, transdermal systems and ophthalmic inserts. This review article in detail describes the melt extrusion equipment and process. Industrial application of this process along with specific areas on pharmaceutical industry is illustrated. This article concludes with the overview of published examples of the melt extrusion process.

A 39-year-old man with a medical history of hypertension, type I diabetes mellitus (HbA1c: 7%) and 3 components penile prosthesis for erectile dysfunction refractory to medical treatment implanted 9 years before, presented at the Urology Department. He reported an extrusion of the prosthesis through the urethral meatus avoiding spontaneous urination (Figure). Three months before during an intense sexual intercourse (“ cowboy sex” syndrome), the patient had pain in the penis and latter the prosthesis started to appear through the meatus. The function of the prosthesis had been successful during these years. A physical examination showed one cylinder through the meatus without inflammation or infection signs (no pus collection). . .

Background. Crown lengthening is a procedure that is done to increase the supra gingival tooth structure which permits esthetic restoration of the tooth without violating the biological width. Several techniques are available for this purpose including post core with crown, surgical crown lengthening, and orthodontic extrusion. Each technique has its indications, advantages, and disadvantages. This article will review each method precisely. Methods. Surgical crown lengthening is a traditional method which is mostly done by apically repositioned flap after bone recontouring to establish new biological width. However, this bone reduction may damage the bony support of the adjacent teeth resulting in compromised function, loss of interdental papilla, as well as open embrasures. Orthodontic root extrusion is a technique based on principles of osteophysiology and continuous orthodontic forces. The objectives of forced eruption are preservation of biological width, exposure of sound tooth structure, and provision of high esthetics particularly in anterior region. Therefore, it is the preferred mode of crown lengthening avoiding the negative consequences of surgical CL. Results. Orthodontic forced eruption is a minimally invasive treatment option for reestablishing biological width and it does not affect esthetic, nor does it interfere with the periodontal support of the adjacent teeth. This approach also would balance the crown root ratio which leads to a more stable hard and soft tissue results. More than this, in the anterior section orthodontic root extrusion provides gingival alignment with no interference with the periodontium of the neighboring teeth. Conclusions. Forced eruption is mostly indicated in the anterior region of the dentition where esthetics is of major concern. Posteriorly in the dental arch, surgery crown lengthening may be more appropriate because flared molar roots may present proximity problems if extruded, and esthetic is of less important.