Formation of Macropores in Calcium Phosphate Cement Implants

Published

February 1, 2001

Author(s)

Shozo Takagi, Laurence C. Chow

Abstract

A calcium phosphate cement (CPC) was shown to harden at ambient temperatures and form hydroxyapatite as the only end-product. Animal study results showed showed that CPC resorbed slowly and was replaced by new bone. For some clinical applications, it would be desirable to have macropores built into the CPC implant to obtain a more rapid resorption and concomitant osseointegration of the implant. The present study investigated the feasibility of a new method for producing macropores in CPC. Sucrose granules, NaHCO₃, and Na₂HPO₄ were sieved to obtain particle sizes in the range of 125 m to 250 m. The following mixtures of CPC powder (an equimolar mixture of tetracalcium phosphate, Ca₄(PO₄)₂O, and dicalcium phosphate anhydrous, CaHPO₄) and one of the above additive granules were prepared: control-no additive; mixture A-0.25 mass fraction of sucrose; mixture B - 0.25 mass fraction of NaHCO₃; mixture C - 0.25 mass fraction of Na₂HPO₄; and mixture D - 0.33 mass fraction of Na₂HPO₄. Cement samples were prepared by mixing 0.3 g of the above mixtures with 0.075 mL of the cement liquid (1 mol/L Na₂HPO₄). After hardening, the specimens were placed in water for 20 h at about 60 C to completely dissolve the additive crystals. Well-formed macropores in the shapes of the entrapped crystals were observed by scanning electron microscope (SEM). The macroporosities (mean standard deviation; n = 6) expressed as volume fraction in % were 0, 18.9 1.7, 26.9 1,6m 38,3 4.4 and 50.3 2.7 for the expressed as volume fraction in % were 0, 18.9 1.7, 26.9 1.6, 38.3 4.4 and 50.3 2.7 for the control, A, B, C and D, respectively. The diametral tensile stremgths (mean standard deviation; n=3) expressed in Mpa were 10.1 0.7, 3.7 0.3, 2.4 0.2, 1.5 0.5 and 0.4 0.1, respectively, for the five groups. The results showed that macropores can readily be formed in CPC implants with the use of water-soluble crystals. The mechanical strength of CPC decreased with increasing macroporosity.

Citation

Journal of Materials Science-Materials in Medicine

Volume

12

Issue

No. 12

Pub Type

Journals

Keywords

anhydrous, biomaterials, calcium phosphate cement, dicalcium phosphate anhydrous, hydroxyapatite, macropores, self-hardening cement, tetracalcium phosphate cement

Citation

Takagi, S. and Chow, L. (2001), Formation of Macropores in Calcium Phosphate Cement Implants, Journal of Materials Science-Materials in Medicine (Accessed May 7, 2024)