Effect of some organic binders on the mechanical strength of hydroxyapatite-based biocements

Abstract

In the present study, aiming to control the setting reaction and to increase the strength of hydroxyapatite-based biocements, gelatin, citric acid and malonic acid, and combinations of them, were used as binders. The mechanical strength of the developed biocements was evaluated after 1 to 15 days of exposure (aging) to air with 100% relative humidity at 37–40 ºC. Especially for the case of gelatin, the mechanical properties of the biocements increased as a function of aging time in the humid environment. In this case, the standard compressive strength increased from ~19 to ~40 MPa, while the diametral compressive strength increased from ~2 to ~12 MPa, between day 1 and day 15 of aging. These values are similar to those reported in the past for HAp-containing biocements added with a variety of organic or inorganic binders. However, the resulting setting times were too long. Thus, it was proposed that crosslinking of gelatin by a suitable chemical agent during the application of the prepared HAp-based biocements could be a potential way to control their handling and setting characteristics, while preserving their good mechanical properties, good biocompatibility, and good solubilization characteristics in the presence of biological fluids.