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One of the main challenges in additive manufacturing (AM) of medical implants for the treatment of bone tissue defects is to optimise the mechanical and biological performance. The use of post-processing can be a necessity to improve the physical properties of customised AM processed implants. In this study, Ti-6Al-4V coupons were manufactured using selective laser melting (SLM) in two build orientations (vertical and horizontal) and subsequently post-processed using combinations of hot isostatic pressing (HIP), sandblasting (SB), polishing (PL) and chemical etching (CE). The effect of the different post-manufacturing strategies on the tensile and fatigue performance of the SLMed parts was investigated and rationalised by observing the surface topography. Vertically built samples showed higher yield strength (YS) and ultimate tensile strength (UTS) than the horizontal samples, increasing from 760.9 ± 22.3 MPa and 961.3 ± 50.2 MPa in the horizontal condition to 820.09 ± 16.5 MPa and 1006.7 ± 6.3 MPa in the vertical condition, respectively. After the HIP treatment, the ductility was substantially improved in both orientations; by 2.1 and 2.9 folds in the vertical and horizontal orientations, respectively. The vertically built samples demonstrated a superior ductility of 22% following HIP and polishing. Furthermore, chemical etching was found to be the most effective surface post-processing treatment to improve the fatigue performance after HIP, achieving the highest run-out strength of 450 MPa. Most importantly, chemical etching after HIP enhanced the cellular affinity of the surface, in addition to its good fatigue performance, making it a promising post-processing approach for bone implants where tissue integration is needed.

Nanocrystalline (Average grain size ∼200nm) bulk AA2124 alloy was produced through high energy ball milling of microcrystalline powder followed by spark plasma sintering (SPS) at 480°C with a holding time of 10min. The effect of initial particle and grain size on the microstructural evolution as well as on the relative density and mechanical properties of the specimens consolidated through SPS and hot pressing (HP) at the same temperature for 60min was investigated for ball milled nano-powders (NP), as well as as-received micro-powders (MP). Results showed that the NP specimens consolidated with SPS had the highest microhardness values compared to the other specimens despite not achieving full densification. On the other hand, a general increase in density, hardness, and compressive strength was observed for all SPS consolidates compared to HP. The presence of aluminum oxide and its influence on the consolidation process as well as the resulting mechanical properties of the bulk specimens is also discussed.

Playing a musical instrument that loads the masticatory system, such as the violin or oboe, has been suggested to be part of the group of etiological factors for temporomandibular disorders (TMDs). In 2014, a review of literature was published that explicitly focused on the possible association between playing a musical instrument and TMDs. However, though published in 2014, the literature search was performed in 2012, and covered only one search engine, namely PubMed. Therefore, a new comprehensive search of literature was conducted to explore what is mentioned in the English medical literature about the relationship between playing a musical instrument and the presence of TMDs. A PubMed search yielded 23 articles, 15 of which were included in this review. In addition, an extensive search was performed on Google Scholar, which yielded 9 more articles. Of the 24 articles, 11 had a comparative observational study design, and 1 had a pretest-posttest design. These articles were analyzed according to the PICO (patient problem or population, intervention, comparison, and outcome) system. The remaining 12 articles consisted of case reports/case series, literature surveys (2 of which included a case series), and literature reviews, and were only tabulated as brief summaries. While no conclusions could be drawn from these 12 articles, conclusions based on the comparative observational design studies seem to suggest that TMDs and playing a musical instrument are associated. However, no clear-cut conclusion could be drawn as to whether playing a musical instrument is directly associated with TMDs, or whether it is associated only in combination with other factors. More and better research on this topic is needed to better enable counseling, and possibly better treatment, of musicians with TMD complaints.

The grain boundary network evolution of 316L austenitic steel powder during its densification by hot isostatic pressing (HIPing) was investigated. While the as-received powder contained a network of random high angle grain boundaries, the fully consolidated specimen had a large fraction of annealing twins, indicating that during densification, the microstructure evolves via recrystallization. By interrupting the HIPing process at different points in time, microstructural changes were tracked quantitatively at every stage using twin boundary fractions, distribution of different types of triple junctions, and the parameters associated with twin related domains (TRDs). Results revealed that, with increase in temperature, (i) the fraction of annealing twins increased steadily, but they mostly were not part of the grain boundary network in the fully consolidated specimen and (ii) the average number of grains within a TRD, the length of longest chain, and twinning polysynthetism increased during HIPing and (iii) the powder characteristics and the HIPing parameters have a strong influence on the development of grain boundary network. Based on the results obtained, possible alterations to the HIPing process are discussed, which could potentially allow twin induced grain boundary engineering.