Hydrogels and bone cements

Medicine. The polymethacrylates have been used for many years in the manufacture of dentures, teeth, denture bases, and filling materials (116,117) (see Dental materials). In the orthodontics market, methacrylates have found acceptance as sealants, or pit and fissure resin sealants which are painted over teeth and act as a barrier to tooth decay. The dimensional behavior of curing bone-cement masses has been reported (118), as has the characterization of the microstmcture of a cold-cured acryUc resin (119). Polymethacrylates are used to prepare both soft and hard contact lenses (120,121). Hydrogels based on 2-hydroxyethyl methacrylate are used in soft contact lenses and other biomedical appHcations (122,123) (see Contactlenses). 

Boesel, L. F., Mano, J. F., Elvira, C., San Roman, J., Reis, R. L. (2003). Hydrogels and hydrophilic partially degradable bone cements based on biodegradable blends incorporating starch. In E. Chiellini (Ed.), Biodegradable Polymers and Plastics. Kluwer Academic, Dordrecht. 

To end, we must emphasize that methacrylates in medicine are made use of in diverse areas including bone and dental cements (109), and as surface modifiers to prevent or delay process of rejection (110), and that each commands a formidable literature. The reader should also be aware of the considerable effort which has been directed towards a phenomenological and theoretical understanding of the solution and swelling properties of synthetic hydrogel and polyelectrolyte polymers (111-116). 

Hydrogels And Hydrophilic Partially Degradable Bone Cements Based On Biodegradable Blends Incorporating Starch... 

Hydrogels and Hydrophilic Bone Cements Based on Starch... 

This principle can be applied to bone cements. After polymerization of the (hydrophilic) monomer inside the femoral cavity and insertion of the prosthesis, the hydrogel would start absorbing water, due to the same constraints referred to above, fixing the implant in place. Since the bone cement must fulfil some minimum requirements in terms of mechanical properties, the combination of hydrophilic and hydrophobic (MMA) monomers will allow for the tailoring of water uptake and, consequently, the mechanical properties of the system. 

Since there are acrylic monomers hydrophilic enough to form hydrogels (e.g., acrylic acid (AA), HEMA,...) they could be incorporated into the bone cement formulation without changing the polymerization system, using the same initiator and activator. On the other hand, different acrylic monomers could be selected to tailor the extent of water uptake of the system or even to impart some additional behaviour, like pH- or temperature sensitivity. 

Dynamic mechanical analysis (DMA) is a suitable technique that allows the characterisation of the solid-state rheological behaviour of materials, including biomaterials , in a broad temperature and frequency ranges. Specifically, this technique has been used in the characterisation of bone cements or hydrogels ". Such materials display usually an anelastic behaviour and DMA is able to monitor the complex mechanical modulus (E = E + E where E" is the storage modulus and E is the loss modulus, and the complex compliance (D - D - iD ). The loss factor, tan 6 = EVE = D D , measure the damping capability of the material. 

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