ECerS 2011 - Oral abstract

Oral 370

Tuesday 21 June, 10:50 - 12:20, Room: 307

Session: Bioceramics

Presentation type: Oral

Title: Optimization of alpha-tricalcium phosphate cement setting

Author(s): Irbe Zilgma¹, Linda Vecbiskena¹, Dagnija Loca¹, Daina Vempere¹, Liga Berzina-Cimdina¹

^1]Riga Technical University, Latvia

E-mail (First author): zilgma.irbe@rtu.lv

Presenter: Irbe Zilgma

Calcium phosphate biomaterials enjoy great success as materials for bone augmentation and regeneration. Calcium phosphate cements harden inside living tissue and take the form of defect as well as have small crystal size (compared to calcium phosphate ceramics) that can contribute to faster resorbtion and replacement with healthy tissue. Setting is a highly important property of calcium phosphate cements for successful clinical application. Calcium phosphate cements should remain in paste form after mixing at ambient temperatures long enough to allow implantation. After implantation calcium phosphate cements must harden rapidly to avoid cement washout.
Cements investigated in this work are alpha-tricalcium phosphate cements that form calcium deficient hydroxyapatite after setting. The goal of this work was to investigate the processes during calcium phosphate cement setting and to evaluate possible setting control methods. Calcium phosphate cement setting is highly dependent on concentration of phosphate ions, initial pH of the liquid phase and additives used. The influence of setting time modifying additive is also dependent on initial liquid phase pH.
If no setting time modifying additives are used, the fastest setting occurs at pH 7 (setting time 7 min at 21°C with 0.5 M of phosphate ions in liquid phase). If initial liquid phase pH is 9, setting is too long for clinical use (more than 20 min at 37°C with 0.5 M of phosphate ions). If initial liquid phase pH is less than 5, setting is almost instantaneous (at 21°C with 0.5 M of phosphate ions). By varying amount of citric acid and tartaric acid in initial liquid phase it is possible to increase or decrease the alpha-tricalcium phosphate cement setting time. It was suggested that in order to adjust cement setting, the composition of initial liquid phase has to be altered.
Methods used for setting time control also influence other properties of calcium phosphate cement - mechanical strength and release rate of drugs that may be incorporated in cement. Compressive strength is higher if initial liquid phase pH is lower than 7. This is due to increased conversion of starting material to calcium deficient hydroxyapatite.