Soft tissue, mechanical properties

Resilient Diners. Resilient liners reduce the impact of the hard denture bases on soft oral tissues. They are designed to absorb some of the energy produced by masticatory forces that would otherwise be transmitted through the denture to the soft basal tissue. The liners should adhere to but not impair the denture base. Other critical properties include total recovery from deformation, retention of mechanical properties, good wettability, minimal absorption of... 

The PGS obtained by Wang and coworkers was a kind of thermoset elastomer with the Young s modulus of 0.282 0.025 MPa, a tensile strain of at least 267 zE 59.4%, and a tensUe strength was at least 0.5 MPa. The mechanical properties of PGS were well consisted with that of some common soft tissues. Although PGS is a thermoset polymer, its prepolymer can be processed into various shapes by solving it in common organic solvents such as 1,3-dioxolane, tetrahydrofuran, isopropanol, ethanol, and iV,M-dimethylformamide. Porous scaffolds can be fabricated by salt leaching. 

In all types of PHAs, P4HB is of the most interest because it was used in the degradable scaffold that resulted in the first successful demonstration of a tissue-engineered tri-leaflet heart valve in a sheep animal model. Its copolymers with PHB and polyhydroxyoctanoate (PHO) are also promising in tissue engineering because of their nontoxic degradation products, stability in tissue culmre media, and the potential to tailor the mechanical and degradation properties to match soft tissue. 

Schiraldi et al. [64] have developed this kind of material by combining silica particles and pHEMA. pHEMA is a biocompatible hydrogel that has been widely studied in the past decades due to its chemical-physical structure and mechanical properties. It has been widely used in ophthalmic prostheses (contact or intraocular lenses), vascular prostheses, drug delivery systems and soft-tissue replacement [65]. These authors have shown that by incorporating silica nanoparticles, the resulting hybrid material is highly biocompatible and promotes bone cell adhesion and proliferation of bone cells seeded on it.1 ... 

In contrast, through eons of evolution Nature has come up with many biopolymers that can combine important mechanical properties including strength, toughness, and elasticity. For example, sUks (Oroudjev et al. 2002), cell adhesion proteins (Law et al. 2003), and connective proteins existing in both soft and hard tissues such as muscle (Kellermayer et al. 1997 Rief, Gautel, et al. 1997 Marszalek et al. 1999 Li et al. 2000), seasheUs (Smith et al. 1999), and bone (Thompson et al. 2001)... 

Silver, F. H., Biological Materials Structure, Mechanical Properties, and Modeling of Soft Tissues, New York University Press, New York, 1987. 

In contrast to soft biologies, whose mechanical properties primarily depend upon the orientation of collagen fibers, the mechanical properties of mineralized tissues, or hard biologies, are more complicated. Factors such as density, mineral content, fat content, water content, and sample preservation and preparation play important roles in mechanical property determination. Specimen orientation also plays a key role, since most hard biologies such as bone are composite structures. For the most part, we will concentrate on the average properties of these materials and will relate these values to those of important, man-made replacement materials. 

Tissues are composites of macromolecules, water, ions, and minerals, and therefore their mechanical properties fall somewhere between those of random coil polymers and those of ceramics. Table 6.1 lists the static physical properties of cells, soft and hard tissues, metals, polymers, ceramics, and composite materials. The properties listed in Table 6.1 for biological materials are wide ranging and suggest that differences in the structure of the constituent macromolecules, which are primarily proteins, found in tissues give rise to the large variations in strength (how much stress is required to break a tissue) and modulus (how much stress is required to stretch a tissue). Because most proteins are composed of random chain structures, a... 

Cancellous bone is a very porous material, with an average density of 1.3gcm, implying a porosity of nearly 35%. In practice, the density lies between 5 and 95% varying gradually between cortical and cancellous regions. The pore size distribution is bimodal. The pores are elongated and filled with soft tissues that include bone marrow, blood vessels, and various bone-related cells. It is the overall porosity and the pore size distribution that mostly control the mechanical properties of bone. 

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