Objectives: To investigate the mechanism by which silicon released by Pseudowollastonite (psW) exerts an osteogenic effect and to provide an insight into the role that silicon may play in vivo in developing bones. Methods: Fragments of psW were incubated in tissue culture media for up to 48hours. Over this period Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to measure the extent of material dissolution and the kinetics of silicon and calcium release. Results: Normal bone nodule media contains <1mg/ml silicon and 58mg/ml calcium but after 48 hours incubation with psW the media contained 56mg/ml silicon and 155mg/ml calcium. There was also a reduction of phosphorous from 33mg/ml to 10mg/ml during this period. Silicon and calcium were added to osteoblastic cells at 50mg/ml and 100mg/ml respectively - similar to that released from psW incubated in vitro. The speed of bone nodule formation increased and total number of nodules formed was 100X that seen in control cultures. Increased calcium and silicon is associated with raised levels of alkaline phosphatase, osteocalcin and elevated cell metabolic activity. Using Scanning Electron Microscopy (SEM) it is possible to detect elevated levels of silicon in areas undergoing mineralisation in the dentin in new born rat teeth and 3 month-old rat humerus in a narrow band within the growth plate region approximately 3 times above that of surrounding tissues. Using high-resolution analysis it will be possible to identify the precise region of highest silicon concentration and thus gain more information regarding the cellular processes involving silicon. Conclusions: The results suggest that silicon and calcium released from psW is responsible for much of the biological activity of this material. Silicon may have an important role in mineralisation as determined by its presence in the growth plate of the humerus and developing dentin – both regions undergoing active mineralisation.