Strong and Macroporous Calcium Phosphate Cement: Effects of Porosity and Fiber Reinforcement on Mechanical Properties

Published

December 1, 2001

Author(s)

Laurence C. Chow

Abstract

Because of its excellent osteoconductivity and bone-replacement capability, self-setting calcium phosphate cement (CPC) has been used in a number of clincal procedures. For more rapid resorption and concomitant osseointegration, methods were desired to build macropores into CPC; however, this decreased its mechanical properties. The aims of this study, therefore, were to use fibers to strengthen macroporous CPC, and to investigate the effects of the pore volume fraction on its mechanical properties. Water-soluble mannitol crystals were incorporated into CPC paste; the set CPC was then immersed in water to dissolve mannitol, producing macropores. Mannitol/(mannitol + CPC powder) mass fractions of: 0,, 10, 20, 30, and 40 % were used. An aramid fiber volume fraction of 6 % was incorporated into the CPC-mannitol specimens, which were set in 3 mm x 4 mm x 4 mm molds and then fractured in three-point flexure to measure the strength, work of fracture, and modulus. The dissolution of mannitol created well-formed macropores, with CPC at 40% mannitol having a total porosity of a 70.8% volume fraction. Increasing the mannitol content significantly decreased the properties of CPC without fibers (analysis of variance; p <0.001). The strength (mean standard deviation; n = 6) of CPC at 0 % mannitol was (15.0 1.8) Mpa; at 40% mannitol, it decreased to (1.4 0.4) MPa. Fiber reinforcement improved the properties, with the strength increasing three-fold at 0 % mannitol, sevenfold at 30 % mannitol, and nearly fourfold at 40 % mannitol. The work-of-fracture increased by 2 orders of magnitude, but modulus was not changed as a result of fiber reinforcement. A scanning electron microscopy examination of specimens indicated crack deflection and bridging by fibers, matrix multiple cracking, and frictional pullout of fibers as the reinforcement mechanisms. . Macroporous CPCs were substantially strengthened and toughened via fiber reinforcement. This may help extend the use of CPCs with macropores for bony ingrowth to the repair of larger defects in stress-bearing locations.

Citation

Journal of Biomedical Materials Research

Volume

57

Issue

No. 3

Pub Type

Journals

Keywords

calcium phosphate cement, fiber reinforcement mechanisms, fracture resistance, hydroxyapatite, macropores, strength, Dentistry

Citation

Chow, L. (2001), Strong and Macroporous Calcium Phosphate Cement: Effects of Porosity and Fiber Reinforcement on Mechanical Properties, Journal of Biomedical Materials Research (Accessed July 27, 2024)