Strength and Chemical Stability Due to Aging of Two Bone Void Filler Materials

Injectable resorbable bone cements for bone void fillings are gaining in interest. The materials resorb in vivo with loss of void filling capacity and strength as a consequence. The objective with this study is to qualitative determining the dissolution behaviour for a calcium sulphate and a calcium phosphate cement as function of storage time in different storage medium and correlate to their strength development. Experiments were performed on a calcium phosphate based cement, Norian SRS, and a calcium sulphate based cement, MIIG X3. In the resorbtion study, the materials dissolution at different pH (3, 5 and 7) was compared over a period of 11 weeks. The materials compressive and biaxial flexural strength was measured after aging in phosphate buffer saline for up to 12 weeks. The proposed qualitative method to study dissolution behaviour of injectable biomaterials as function of time and medium were evaluated and proved to be useful. Both materials were dissolved after 3 weeks of storage in pH 3. MIIG X3 dissolved faster than Norian SRS at pH 5. At pH 7 both materials were stable over the test period of 11 weeks. For both materials the strength decreases with storage time. Norian had a higher compressive strength than MIIG X3 for the first week, after the first week the compressive strength was similar for the two materials. MIIG X3 showed a higher flexural strength than Norian during the full test period.