Introduction of porosity to calcium phosphate scaffolds for bone repair has created a new challenge when measuring bioresorption in vitro, rendering traditional outcome measures redundant. The aim of this study was to identify a surrogate endpoint for use with three dimensional (3D) scaffolds. Murine RAW 264.7 cells were cultured on dense discs of -tricalcium phosphate in conditions to stimulate osteoclast (OC) formation. Multinucleated OC were visible from Day 6 with increases at Day 8 and Day 10. Resorption pits were first observed at Day 6 with much larger pits visible at Days 8, 10 and 12. The concentration of calcium ions in the presence of cells was significantly higher than cell free cultures at Days 3 and 9. Using linear regression analysis, Ca ion release could account for 35.9% of any subsequent change in resorption area. The results suggest that Ca ion release is suitable to measure resorption of a TCP ceramic substrate in vitro. This model could replace the more accepted resorption pit assay in circumstances where quantification of pits is not possible e.g. when characterising 3D tissue engineered bone scaffolds.