In Vitro Mechanical Properties of a Calcium Silicate Based Bone Void Filler

Abstract

The objective of the paper is to investigate the mechanical and the handling properties of a novel injectable bone void filler based on calcium silicate. The orthopaedic cement based on calcium silicate was compared to a calcium phosphate cement, Norian SRS from Syntes Stratec, with regard to the working (ejection through 14 G needle) and setting time (Gillmore needles), Young’s modulus and the flexural (ASTM F-394) and compressive (ISO 9917) strength after storage in phosphate buffer saline at body temperature for time points from 1h up to 16 weeks. The calcium silicate cement is composed of a calcium silicate powder (grain size below 20 µm) that is mixed with a liquid (water and CaCl2) into a paste using a spatula and a mixing cup. The water to cement ratio used was about 0.5. The calcium silicate had a working time of 15 minutes and a setting time of 17 minutes compared to 5 and 10 minutes respectively for the calcium phosphate cement. The compressive strength was considerably higher for the calcium silicate cement (>100 MPa) compared to the calcium phosphate cement (>40 MPa). Regarding the flexural strength the calcium silicate cement had high values for up to 1 week (> 40 MPa) but it decreased to 25 MPa after 16 weeks. The phosphate cement had a constant flexural strength of about 25 MPa. The results show that calcium silicate cement has the mechanical and handling potential to be used as high strength bone void filler.