The need for biomaterials has increased as the world population ages. Calcium phosphate cements (CPC) are highly promising for wide clinical applications due to their osteoconductivity and bone replacement capability.Their low strength, however, limits CPC to only non-stress uses. A literature search revealed no study on fiber reinforcement of CPC. In preliminary studies, the promise for CPC reinforcement was shown with a 2- to 5-fold increase in strength, 6-fold increase in fracture toughness, and two orders of magnitude increase in work-of-fracture. In this project, Aim 1 will use absorbable fibers to strengthen CPC and then to dissolve and create microprocessor vascular ingrowth; the effects of fiber length, volume fraction and fiber-matrix interface will be studied.
Aim 2 vill study the effects of changes in the absorbable fiber properties on the composite properties, and establish predictive equations.
In Aim 3, CPC matrices with wide property ranges will be used to establish the relationships between matrix and composite properties. Non-rigid CPC, fast-dissolution CPC, flow able CPC and macroporous CPC will be studied; models on fundamental structure-property relationships will be determined.
Aim 4 will investigate novel methods to control the macropore formation rate and tailor the strength history of the implant. Faster-absorbable fibers and slow-absorbable fibers will be combined in CPC for a high initial strength. Then the faster fibers dissolve and create macropores for bony ingrowth, while the slow fibers provide longer-term strength. Modeling will be performed to relate the composite property change to that of each fiber.
In Aim 5, absorbable meshes will be used in CPC for strength and then highly interconnected macropores. The effects of mesh thickness and strength changes in immersion will be investigated and predictive equations will be established. Functionally graded multilayer implants will be investigated using mesh and fibers for controlled strength and macropore formation gradient. These studies will: 1) Yield novel composites for Dental and craniofacial repairs with superior strength, self-setting ability, scaffold structures, and capability of resorption and replacement by new bone; (it) Establish microstructural design methods for implants to achieve high strength and toughness with tailored strength history and macropore formation rates; (iii) Provide new reinforcement mechanisms, fundamental composite-constituent relationships, predictive models, and processing guidance to form the basis for a new generation of biomaterials.
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