Superior Drummer 2 |TOP| Crack 14

Figure 18 shows the stages of the impact test. Upon impact, one can see elastic deformation (indentation and elastic bending), which is followed by the formation of cracks and ultimately complete penetration. As seen in the last frame for the foamed sample (t = 10.5 ms), the crack propagates in the same direction as the flow path during mold filling. Since fibers are predominantly aligned with the flow, the sample is more resistant to failure due to bending in this direction [42]. Figure 19 illustrates the anisotropic microstructure and how fibers in plane B-B are normal to the load direction in the outer regions where stresses are highest. In this plane (B-B), the matrix will carry most of the load near the part surface leading to an earlier failure, most likely due to debonding. This mode of failure is known as transverse cracking [66,67].

Crack propagation was evaluated using micro-CT scans. Figure 20 shows examples of the secondary cracks formed perpendicular to the main crack direction. The presence of the foam core can have different effects on the crack propagation behavior due to hindrance caused by air cells. This can force the crack to undergo a tortuous path, which reduces the extent of crack propagation. In some cases, the crack can deviate from a straight path by following a weaker path generated by large cells and changes in fiber density [68]. For example, Figure 20 (left) shows the upper crack avoiding a high FC region caused by undispersed fiber bundles. In other cases, cells can relieve the high stresses at the tip of the crack and stop crack propagation [69,70].

Additive manufacturing, also called 3D printing, is the process of building up a three-dimensional (3D) object from computer-aided-design (CAD) models through a layer-by-layer fabrication process [16,17,18]. Here, the CAD design is converted to a stereo-lithography file (stl-file) to describe only the surface geometry of the 3D design. The software of the 3D printer converts the stl-file into two-dimensional layers stacked on top of each other [19,20]. Complex geometries can be built in this way while using a variety of materials, depending on the method employed. The successive deposition of layers is a relatively slow process and is, therefore, still limited in terms of quantity. Some benefits of using additive manufacturing techniques are the increase in design freedom and flexibility and the reduction in material waste and production cost [21]. A notable drawback is the reduced mechanical performance of 3D-printed polymer objects, which has been, until now, generally lower than conventional processing methods. This decrease in properties is mostly due to reduced adhesion upon stacking of the layers [22,23]. Reduced consolidation can stem from characteristics of the feedstock material or from defects arising from the fabrication process, such as porosity due to incomplete fusion, keyhole porosity, residual stresses, and warping, amongst others [24,25,26,27,28,29,30]. In the following section, the different additive manufacturing approaches are presented, together with process-specific challenges and limitations. Currently, additive manufacturing is utilized for the processing of polymers, metals, and ceramics [18,31,32,33,34,35,36,37]. Regarding polymers, the focus of the present review is several amorphous and semi-crystalline polymers that are readily processed through 3D printing, such as acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polycaprolactone (PCL), polyether-ether-ketone (PEEK), Polyamide (PA12), polyethylene terephthalate (PETG), polyvinyl butyral (PVB), etc. However, most are regarded as commodity plastics. Due to the aforementioned limitations, additive manufacturing of polymers has been utilized mainly for rapid prototyping and case-specific applications, for example, prosthetics for medical applications or custom engineering components [35,38,39]. However, there is a recent tendency for additive manufacturing to move from a method for rapid prototyping toward the manufacturing of functional parts aimed at high-end engineering applications. Toward that end, the addition of polyolefins, such as polypropylene and polyethylene, to the palette of standard materials used for 3D printing will be highly beneficial, as they are readily used for high-end applications due to their superior mechanical properties and chemical resistance.

Reagan's new "anti-terrorist" bills are aimed in two directions: First, to step up U.S. intervention to put down the revolutionary struggles of the peoples. And second, to crack down on the struggles of the American people against such U.S. aggression abroad.

A key element in Reagan's latest "anti-terrorist" bills is a number of draconic laws to crack down on the mass struggles at home against U.S. aggression and in solidarity with the oppressed peoples fighting for their liberation from the U.S. imperialist yoke.

In this year's election none of the presidential candidates are worth voting for. But we do not have to content ourselves with choosing which of these representatives of the capitalists will crack the whip over our heads for the next four years. We can strike out on another path, the path of building the independent movement of the working class, the path of organizing a real struggle against Reaganite reaction.

For several years now, a major crisis has been brewing in the northwestern Indian state of the Punjab. In June the crisis exploded. The central government of Indira Gandhi launched a massive military crackdown against the Sikh nationalist movement. Over a thousand people were killed and the state has been put under military occupation. The blows of the Indian government have fallen not just upon the Sikh nationalists but also against the Sikh masses generally.

With the improved macro- and micro-designs, dental implants enjoy a high survival rate. However, peri-implant bone loss has recently emerged to be the focus of implant therapy. As such, researchers and clinicians are in need of finding predictable techniques to treat peri-implant bone loss and stop its progression. Literature search on the currently available treatment modalities was performed and a brief description of each modality was provided. Numerous techniques have been proposed and none has been shown to be superior and effective in managing peri-implant bone loss. This may be because of the complex of etiological factors acting on the implant-supported prosthesis hence the treatment approach has to be individually tailored. Due to the lack of high-level clinical evidence on the management of peri-implant bone loss, the authors, through a literature review, attempt to suggest a decision tree or guideline, based on sound periodontal surgical principles, to aid clinicians in managing peri-implantitis associated bone loss. © 2011 Wiley Periodicals, Inc.

To present a literature review on implant overdentures after a brief survey of bone loss after extraction of all teeth. Papers on alveolar bone loss and implant overdentures have been studied for a narrative review. Bone loss of the alveolar process after tooth extraction occurs with great individual variation, impossible to predict at the time of extraction. The simplest way to prevent bone loss is to avoid extraction of all teeth. To keep a few teeth and use them or their roots for a tooth or root-supported overdenture substantially reduces bone loss. Jaws with implant-supported prostheses show less bone loss than jaws with conventional dentures. Mandibular 2-implant overdentures provide patients with better outcomes than do conventional dentures, regarding satisfaction, chewing ability and oral-health-related quality of life. There is no strong evidence for the superiority of one overdenture retention-system over the others regarding patient satisfaction, survival, peri-implant bone loss and relevant clinical factors. Mandibular single midline implant overdentures have shown promising results but long-term results are not yet available. For a maxillary overdenture 4 to 6 implants splinted with a bar provide high survival both for implants and overdenture. In edentulous mandibles, 2-implant overdentures provide excellent long-term success and survival, including patient satisfaction and improved oral functions. To further reduce the costs a single midline implant overdenture can be a promising option. In the maxilla, overdentures supported on 4 to 6 implants splinted with a bar have demonstrated good functional results.

PURPOSE To present a literature review on implant overdentures after a brief survey of bone loss after extraction of all teeth. MATERIALS AND METHODS Papers on alveolar bone loss and implant overdentures have been studied for a narrative review. RESULTS Bone loss of the alveolar process after tooth extraction occurs with great individual variation, impossible to predict at the time of extraction. The simplest way to prevent bone loss is to avoid extraction of all teeth. To keep a few teeth and use them or their roots for a tooth or root-supported overdenture substantially reduces bone loss. Jaws with implant-supported prostheses show less bone loss than jaws with conventional dentures. Mandibular 2-implant overdentures provide patients with better outcomes than do conventional dentures, regarding satisfaction, chewing ability and oral-health-related quality of life. There is no strong evidence for the superiority of one overdenture retention-system over the others regarding patient satisfaction, survival, peri-implant bone loss and relevant clinical factors. Mandibular single midline implant overdentures have shown promising results but long-term results are not yet available. For a maxillary overdenture 4 to 6 implants splinted with a bar provide high survival both for implants and overdenture. CONCLUSION In edentulous mandibles, 2-implant overdentures provide excellent long-term success and survival, including patient satisfaction and improved oral functions. To further reduce the costs a single midline implant overdenture can be a promising option. In the maxilla, overdentures supported on 4 to 6 implants splinted with a bar have demonstrated good functional results. PMID:25177466 2b1af7f3a8