Stress-Strain Curves for Different Biomineral Composites Stress: response to uniaxial loading Strain: change in size and/or shape in response to stress

The Stiffness of Bone is Strongly Dependent on its Mineral Content Higher mineralization levels also means greater brittleness, therefore, the maximum amount of energy absorbed in long bones occurs at modest levels of mineralization (higher mineralization rates are observed in tympanic bones)

Time Dependence of Interfacial Bond Strengths in Bone Bond strengths change as a function of time due to changes in interfacial area with time and progressive mineralization of interfacial tissues, both of which can affect the elastic modulus & shear strength of the bonded area

Diagram of Mechanical Interlocking Between Bonding Agent and Hard Tissue Implant BONE or DENTIN methyl methylacrylate methyl cyanoacrylate Apparently smooth surfaces are pitted & rough at the microscopic level, which increases the bonded surface area Chemical etching of the hard tissue (e.g., 35-40% H3PO4) is often done to increase surface irregularities prior to bonding of a hard tissue implant

Evolution of Hip Prosthesis Designs

Section Through Femer At Site of Hip Prosthesis Showing Mechanical Interlocking into Cancellous Bone w/o organic matrix 17 0.04 0.006

Changes in Bone Structural Strength with Fixation Plate Rigidity introduction of a load-bearing implant coupled to a previously load-bearing structure leads to atrophy--bone mass near an implant decreases with time due to tissue remodeling