T Eliades is a Professor and Director of the Clinic of Orthodontic and Paediatric Dentistry, University of Zurich, Switzerland.
Aim: To evaluate the viscoelastic properties of two experimental BPA-free and one BisGMA-based orthodontic resin composite adhesives for bonding fixed retainers.\r\n\r\nMaterials & Methods: A commercially available BisGMA-based (TXA: Transbond LR) and two Bisphenol A-free experimental adhesives (EXA and EXB) were included in the study. The viscoelastic behaviour of the\r\nadhesives were evaluated under static and dynamic conditions at dry and wet states and at various temperatures (21, 37, 50oC). The parameters determined were shear modulus (G), Young\'s modulus (E) under static testing and storage modulus (G1), loss tangent (tan δ) and dynamic viscosity (n*) under dynamic testing. Statistical analysis was performed by 2-way ANOVA and Bonferroni post-hoc tests (α=0.05).\r\n\r\nResults: For static testing, a significant difference was found within material and storage condition variables and a significant interaction between the two independent variables (p<0.001 for G and E). EXA demonstrated the highest G and E values at 21oC/dry group. Dry specimens showed the highest G and E values, but with no significant difference from 21oC/wet specimens, except EXA in G. Wet storage at higher temperatures (37oC and 50oC) adversely affected all the materials to a degree ranging from 40-60% (p<0.001). For dynamic testing, a significant difference was also found in material and testing condition groups, with a significant interaction between the two independent variables (p<0.001 for G1 and n*, p<0.01 for tan δ). Reduction in G1, and n* values, and increase in tan δ values were encountered at increased water temperatures. \r\n
Ana Pagan obtained the degree in Biology from University of Murcia. She has completed her PhD from the same University at the age of 28 years, with a research stay at the Division of Nutrition and Metabolic Diseases, LMU University, Munich, Germany. She works as a postdoctoral researcher in the Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA, Murcia, Spain), in the Department of Biotechnology, with premier biomaterials in tissue engineering.
Silk fibroin has been largely studied in tissue engineering due to its excellent physical and biological properties. Based on this regard, we have developed a new biomaterial consisting on high performance fibers produced directly from the silk glands of silkworms (Bombyx mori) called silkworm gut fibers (1). This novel biomaterial could be a potential solution in tendon and ligament repair, as these are very common injuries and the traditional surgical reconstruction including auto/allograft and ligament prostheses implants can involve several complications. With this aim, we have braided the silkworm gut fibers, in order to explore the possibility to create a consistent scaffold for ligament repair. \r\nThe production of the silkworm gut fibers is based on a traditional procedure that consists of immersion the silk glands in an acidic solution and a subsequent stretching. We evaluated the mechanical properties of 3 silkworm gut fibers weaved in three-strand braids. The biocompatibility assay was also performed by seeding bone marrow adult human mesenchymal stem cells (ahMSCs) on the braided material. 7, 14 and 21 days after seeding, adhesion and proliferation of the cells were studied by SEM and MTT assay, respectively.\r\nOur results showed a good and remarkable mechanical strength, with Young’s modulus values of 80 ± 20 MPa and an ultimate strength of 18 ± 2 MPa. Moreover, cell adhesion and proliferation were excellent, the cells appeared well spread and attached to the silkworm gut fibers surface, connecting to neighbouring cells and organizing a monolayer over the braided material at day 21 post-seeding (Figure 1).\r\nWe conclude that silkworm gut fibers combine good mechanical and biological characteristics to be considered a potential biomaterial in tissue engineering applications.\r\n