IntroductionDental practitioners are exposed to different occupational hazards during the course of their professional activity, such as physical, chemical, biological, ergonomic factors. The ergonomic hazards, caused by strained posture and prolonged repetitive movements, can induce musculoskeletal disorders. It occurs in 54–93% of dental professionals and involve the spine, shoulder and hand-wrist tract. Through a systematic review of international literature, we analyzed specific ergonomic risk factors and preventive measures of musculoskeletal disorders in professional dental activity.MethodsThis systematic review is coherent with the PRISMA statement. The scientific research on the major online databases was based on the following keywords: dentist, prevention, ergonomic, dentistry, musculoskeletal, neck pain, posture, ergonomics, work and occupational. The studies included in this review focus on disorders related to ergonomics and on the most effective preventive measures to be adopted. No restrictions were applied for language or publication type. We excluded reports not related to ergonomic prevention in dentistry, reports of minor academic significance, editorial articles, individual contributions, and studies published in scientific conferences.ResultsOnline research indicated 4188 references: PubMed (2919), Scopus (1257) e Cochrane Library (12). We excluded 3012 of these, because they were unrelated to ergonomics theme and 187 due to duplication. From the remaining 989 studies, 960 papers did not meet inclusion criteria and they were excluded. Therefore, we analyzed 29 articles, including 16 narrative reviews and 13 original article. The main risk factor for the development of musculoskeletal disorders found in our analysis is static posture adopted during work, highlighted in 87.5% of reviews and 84% of original articles. With regard to preventive measures, 75% of the reviews highlighted the importance of stretching after each working session and at the end of the working day, while 61.5% of the original articles emphasized the use of modern and ergonomic instruments.DiscussionThis review showed that static postures are strongly responsible in the etiology of musculoskeletal disorders. The awkward postures more frequently identified among dental professionals are: extreme forward-head and neck flexion; trunk inclination and rotation towards one side; lifting one or both shoulders; increased curvature of the thoracic vertebral column; incorrect positioning of the lower limbs with thigh-leg angle of less than 90°. It is really important to use of a modern workstation with appropriate ergonomic supports. Among the preventive ergonomic measures, literature has widely recognized the role of physical activity and of a neutral and balanced posture. The present review has some limits: a large part of the selected studies did not have a high methodological quality score and an inadequate statistical analysis.

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In the last few years, nonregular reinforced concrete (R/C) slabs have become more popular in buildings and bridges due to architectural or functional requirements. In these cases, an optimum design method to obtain the ultimate load capacity and the minimum reinforcement amount should be used. For simple R/C slabs, the yield-line method is extensively used in engineering practice. In addition to strength, the “true” failure mechanism is also obtained by identifying the parameters that define it and minimizing the collapse load. Unfortunately, when the mechanism is too complicated to be described or defined by several parameters (e.g., in slabs with complicated geometry), the method becomes more difficult because the system of nonlinear equations becomes harder to solve through traditional methods. In this case, an efficient and robust algorithm becomes necessary. In this paper, a structural analysis of R/C slabs is performed by using the yield-line method in association with a zero-th order optimization algorithm (the sequential simplex method) to avoid calculating gradients as well as any derivatives. The constraints that often limit these parameters are taken into account through the exterior penalty function method, leading to a successful solution of the problem. Considering that the direction of each yield-line is sought by minimizing the ultimate load and finding the parameters defining the collapse mechanism, another parameter concerned with the direction of an orthotropic reinforcement grid is introduced. In this way, the number of unknown parameters increases, but aside from obtaining the ultimate load and the parameters defining the collapse mechanism, the solution also finds both best and worst reinforcement orientations.