Clinical and radiographic outcomes of zirconia dental implants-A systematic review and meta-analysis.

peer reviewed[en] OBJECTIVES: For the present review, the following focused question was addressed: In patients with root-analog dental implants, what is the effect of implants made of other materials than titanium (alloy) on implant survival, marginal bone loss (MBL), and technical and biological complications after at least 5 years. MATERIALS AND METHODS: An electronic (Medline, Embase, Web of Science) search was performed to identify observational clinical studies published from January 2000 investigating a minimum of 20 commercially available zirconia implants with a mean follow-up of at least 60 months. Primary outcome was implant survival, secondary outcomes included peri-implant MBL, probing depths (PDs), and technical and biological complications. Meta-analyses were performed to evaluate implant survival, MBL, and PD. RESULTS: From 5129 titles, 580 abstracts were selected, and 111 full-text articles were screened. Finally, 4 prospective and 2 retrospective observational clinical cohort studies were included for data extraction. Meta-analyses estimated after 5 years of loading mean values of 97.2% (95% CI 94.7-99.1) for survival (277 implants, 221 patients), 1.1 mm (95% CI: 0.9-1.3) for MBL (229 implants, 173 patients), and 3.0 mm (95% CI 2.5-3.4) for PDs (231 implants, 175 patients). CONCLUSIONS: After 5 years, commercially available zirconia implants showed reliable clinical performance based on survival rates, MBL, and PD values. However, more well-designed prospective clinical studies and randomized clinical trials investigating titanium and zirconia implants are needed to confirm the presently evaluated promising outcomes

Регулируемый электропривод сталевоза

В данном дипломном проекте был произведен расчет и выбор силового оборудования для электропривода сталевоза грузоподъёмностью 215 тонн. Результатом расчета является выбор электродвигателя постоянного тока; токоограничивающий реактор; тиристорный преобразователь. Для управления электроприводом принята одно-зонная САР, для которой рассчитаны параметры датчиков и регуляторов. Разработаны схемы управления и защит. Расчет переходных процессов электропривода произведен с помощью ЭВМ.In this project, the calculation and selection of power equipment for the electric drive of the lsteel carrier with a lifting capacity of 215 tons was made. The result of the calculation is the choice of a DC motor; current limiting reactor; thyristor converter. To control the drive, a single-zone ATS is adopted, for which the parameters of the sensors and regulators are calculated. The schemes of control and protection are developed. Calculation of transient processes of the electric drive is made with the help of a computer

Effect of Acetonitrile-based crystallization conditions on the crystal quality of vitamin D3

To design an integrated continuous crystallization setup that is directly coupled to a photochemical synthesis in flow, the crystallization of vitamin D3 was studied in detail. Because of the high solubility of the vitamin in the reaction solvent tert-butylmethyl ether, a solvent swap to acetonitrile was necessary. While other methods use a multistep procedure, with the proposed approach, crystalline vitamin D3 can be obtained within one crystallization step. The influence of crystallization parameters, such as the initial concentration of vitamin D3, stirring as well as cooling temperature, rate, and time, on the obtained results in terms of yield, crystal shape, polymorphism, and particle size distribution are discussed in detail