Viscoelasticity soft tissues

Essential requirements for maxillofacial materials are biocompatibility, the capability of shade matching to the surrounding soft tissues, and adequate mechanical properties to provide acceptable clinical longevity. It is desirable that the viscoelastic response and creep compliance of these materials mimic the in vivo force response of these soft tissues under ftmctional loading without undergoing excessive dimensional changes over time. 

Soft tissues subjected to repetitive loading, due to their viscoelastic properties, demonstrate creep and load relaxation. The loss of precision, speed, and control of the neuromuscular system induced by fatigue reduces the abihty of muscles to protect the weakened passive structure, which may explaiu many industrial, cHnical, and recreational injury mechanisms. These results further indicate the necessity of relating clinical protocols to the job and show how short-duration maximal isometric testing alone cannot provide the complex functional interaction of strength, endurance, control, and coordination. 

A wet-chemical method for production of CTS/HAp nanocrystal composites at low temperature has been demonstrated by Murungan and coworkers [140]. Limitations associated with nanoHAp, such as bioresorption and particle migration, can be alleviated by this approach. The rate of bioresorption of nanoHAp was improved by the addition of CTS, and the viscoelastic nature of the composites prevented the migration of particulate matter into the surrounding tissue upon postimplantation. In addition to these, the smoothness of the composites prevents the soft tissues around the implant from damage. 

To mimic the mechanical behavior of the native tissue is a basic assumption to facilitate the biointegration and function of the substitute. Incorporation of fibers to the biomaterial matrix opens the way to inhomogeneity, anisotropy, nonlinearity, and viscoelasticity features. Provided that interfacial binding between matrix and fibers in the composite goes on, mechanical properties could be tailored by varying the amount and orientation of fibers embedded, to suit the purpose applications, whether it s related to hard or soft tissue substimtes. Individual fibers, no matter how small and isolated compared to fibrous structure, could affect mechanical properties. To be effective, fibers principal direction should be considered and controlled. 

Viscoaugmentation Viscoelastic gels used to replace or augment the intercellular matrix of dermal and other soft tissues. [44, 50]... 

Hyaluronic acid is a linear polysaccharide found in the highest concentrations in soft connective tissues where it fills an important structural role in the organization of the extracellular matrix (23,24). It has been used in ophthalmic preparations to enhance ocular absorption of timolol, a beta blocker used for the treatment of glaucoma (25), and in a viscoelastic tear formulation for conjunctivitis (26). The covalent binding of adriamycin and daunomycin to sodium hy-aluronate to produce water-soluble conjugates was recently reported (27). 

Abstract Materials like soft biological tissues undergo large viscoelastic deformations... 

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