Sodium Citrate Used to Increase the Strength of Calcium Phosphate Cements for Biomedical Applications

A strengthened cement has been devised specifically for facial reconstructive surgery. Materials Scientists at the University of Birmingham's School of Dentistry have discovered that by adding sodium citrate to the liquid phase, calcium phosphate cement is more than three times stronger.

A new benefit from this discovery is that metal screws can be fitted to the cement, giving a potential for load bearing and fixation devices, for example long bones such as legs and  in jaw surgery.  It is injectable through small needles so can get to inaccessible parts of the body with minimal invasive surgery.  

Calcium phosphate cement has been used since the late 1980s years by surgeons as it sets rapidly and has a neutral pH at body temperature.  However once set, it is a brittle, micro-porous ceramic with a strength less than 50 MPa.  An ideal compressive strength should be above 100MPa, close to the average strength of human cortical bone.

Dr Jake Barralet, lecturer in biomaterials at the Birmingham School of Dentistry explains the application of his research: "Concrete is commonly used to patch holes in bones caused by trauma or disease.  Unfortunately the strength of concrete is generally much lower than that of surrounding bone, making bone grafts difficult.  Adding a small amount of sodium citrate which makes the cement particles pack together better, which combined with pressure to help compaction makes a denser cement with fewer pores.  This strong cement may replace bone in critical, load-bearing sites and improve the patient's recovery and quality of life". 

The research was led by the University of Birmingham's School of Dentistry and the Department for Functional Materials in Medicine and Dentistry, University of Würzburg.  It was published and discussed in the highly regarded Nature Materials journal.  Tom Troczynski in the Department of Metals and Materials Engineering at the University of British Colombia called the idea "simple and brilliant".

Posted May 12^th, 2004