Home About us Contact
|
Home About us Contact | ||
|
|
||
Cyclic Mechanical Loading (cyclic + mechanical_loading)
Selected AbstractsDomain Switching Under Cyclic Mechanical Loading in Lead Zirconate TitanateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Soodkhet Pojprapai (Imlao) The domain-switching behavior of lead zirconate titanate (PZT) during mechanical cyclic loading between 10 and 150 MPa was investigated by in situ time-of-flight neutron diffraction. The domain-switching behavior was represented by a change of the pole density distribution during cycling. With increasing number of cycles, domain switching becomes saturated, correlating with a decrease in the rate of remnant strain accumulation in the stress,strain curve. Moreover, a relationship was demonstrated between the macroscopic strain and that developed from ferroelastic domain switching. The contribution of ferroelastic strain to the macroscopic strain was calculated from an orientation average of the domain switching distributions and the c/a ratio. The results show that nearly 80% of macroscopic strain arises from ferroelastic domain switching during mechanical cyclic loading. [source] High-Turnover Periprosthetic Bone Remodeling and Immature Bone Formation Around Loose Cemented Total Hip JointsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2001Michiaki Takagi Abstract Aseptic loosening and periprosthetic osteolysis are the major problems awaiting solution in total hip surgery. The clinical investigation focused on the analysis of periprosthetic bone remodeling to clarify one important key event in the cascade of periprosthetic connective tissue weakening and osteolysis around loose artificial hip joints. Twelve acetabular bone samples adjacent to granulomatous synovial-like membrane of loose hip prosthesis were retrieved at revision surgery and processed for Villanueva bone staining for morphological observation and bone histomorphometric analysis. Eight well-fixed bony samples were used as control. Although osteoclastic surface and eroded surface by osteoclasts were evident in the periprosthetic bone from loose hip joints (p = 0.003 and p = 0.027), increased osteoid/low-mineralized bone matrix (p < 0.001) and osteoid width (p < 0.001) also were significant findings in structural analysis. In addition, not only elevated mineral apposition rate (MAR; p = 0.044) but also increased mineralizing surface (p = 0.044) and bone formation rate (BFR; p = 0.002) in loose periprosthetic bones were shown in dynamic data analysis. These results were confirmed by precise morphological observation by confocal laser scanning microscopy. Active coupling of bone formation and resorption and increased osteocytes with abundant bone canalicular projections were found in combined with the presence of immature bone matrices (osteoid and low-mineralized bone areas) in periprosthetic bones from loose hip joints. These results indicated that active osteoclastic bone resorption and/or defective bone formation are coupled with monocyte/macrophage-mediated foreign body-type granuloma in the synovial-like interface membrane of loose hip joints. Thus, this unique high-turnover periprosthetic bone remodeling with bad bone quality probably is caused by the result of cellular host response combined with inappropriate cyclic mechanical loading. The fragile periprosthetic bone may contribute to hip prosthesis loosening. [source] Effect of cyclic mechanical loading on osteoclast recruitment in periodontal tissueJOURNAL OF PERIODONTAL RESEARCH, Issue 1 2010K. Nozaki Nozaki K, Kaku M, Yamashita Y, Yamauchi M, Miura H. Effect of cyclic mechanical loading on osteoclast recruitment in periodontal tissue. J Periodont Res 2009; doi: 10.1111/j.1600-0765.2008.01193.x. © 2009 The Authors. Journal compilation © 2009 Blackwell Munksgaard Background and Objective:, It is well accepted that cyclic mechanical loading induces osteoclastogenesis in periodontal tissue, but its molecular mechanisms are not well understood, in part because of a lack of appropriate models. In this study, we investigated a novel device that allows cyclic mechanical loading to be performed in a well-controlled manner. Furthermore, by employing this model, the effect of cyclic loading on osteoclast recruitment in the periodontal tissue was described. Material and Methods:, By using a newly developed device, the cyclic loading of 20 n (reference loading corresponding to the fracture hardness of dietary pellets) and two excessive loadings (i.e. 30 and 40 n) were applied to maxillary right molars in rats for up to 7 d, and osteoclast recruitment in the periodontal tissue was evaluated by analyzing relevant marker proteins using immunohistochemistry. Results:, Osteoclastogenesis was induced by day 3 within alveolar bone subjected to a compression force of 30 n. With both 30 and 40 n loadings, cells that were positive to for tartrate-resistant acid phosphate, receptor activator of nuclear factor-,B ligand and osteoprotegerin were significantly increased in the alveolar bone/periodontal ligament in a time-dependent manner. Conclusion:, A new device was developed that allows various levels of cyclic mechanical loading to be exerted. By using this device in rats, early events of osteoclast recruitment in the periodontal tissues were observed with excessive loadings in a time-dependent manner, indicating the usefulness of this model. [source] | ||||||||||