română MEDDOUR BELKACEM, BREK SAMIR, SAOUDI ABDELHAK, BAKHOUCHE HIBAT ERRAHMANE
Abstract
The choice of material for an implant is considered one of the best for successful arthroplasty. The prosthesis implants for knee joints are usually made of metallic biocompatible materials and polymers. However, this work proposes the replacement of stainless steel with zirconia. Zirconia is known for its weak cracking strength; therefore, this paper aims to predict the cracking of the femoral implant made of zirconia. To do so, a pre-crack was created while performing a numerical simulation to determine the stress intensity factor. This procedure is repeated for the incremented length of the pre-crack until the stress intensity factor reaches the fracture toughness value. To extend the investigation, three areas of the femoral implant where the stress concentration could be expected were considered. In all cases, the simulation results showed good zirconia behavior against cracking, and no crack propagation was expected.
Keywords
crack, toughness fracture; zirconia; knee
IOANA GOMOIU, MĂDĂLIN ENACHE, SIMONA NEAGU, ROBERT RUGINESCU, MARIA DUMBRĂVICIAN, ILEANA MOHANU, ROXANA COJOC
Abstract
Mural biocleaning is an ecological method performed with bacterial cells or enzymes and polysaccharides of microbial origin. This process allows the removal of black scales, organic materials used in the previous restoration, and accidental or accumulated organic deposits over time. Lipases produced by the halotolerant bacterium Bacillus sp. BA N P3.3 (E) were used to remove some restoration materials (Paraloid® B72 acrylic resin and Transparent Casein Dispersion) as well as accidental organic deposits (beeswax, sunflower oil, soot) from the surface of the murals. A new bacterial gel (HG) was obtained using a halotolerant bacterial strain. Bacterial lipases were integrated into the bacterial gel (HGE) and then applied to the surface of the frescoes mock-ups for 5 hours and 10 hours. The results obtained in the case of biocleaning with lipases integrated in the bacterial gel were more efficient than those with esterases integrated in Agarart. In a single application step, more than 50% of the existing restoration materials or organic deposits on the frescoes mock-ups were removed. Biocleaning efficiency was evaluated by direct examination and microscopy (optical and scanning electron microscope). The biocleaning of murals with bacterial metabolites is safe, low cost, non-invasive, risk free and very competitive with chemical cleaning methods.
Keywords
halotolerant bacteria, biotechnologies for restoration, bacterial lipases, integrated lipases in halohydrogels, biocleaning with bacterial metabolites.
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Year
2024
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Issue
54 (2)
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Pages
101-107