Orthodontic tooth movement is carried out by mechanical stimulation and has many stages of influence. The initial changes are provoked within seconds of loading a cell (immediate); the next stage involves messengers that produce longer term consequences within 1-3 hours (intermediate) and require proteins to be manufactured. The final stage requires possible nuclear consequences in terms of changes in gene expression. All these effects allow teeth to move without excessive damage. In addition the loading of bone in particular has a significant impact in ensuring viability. This presentation will review the previous data on tooth movement and identify what significant advances have occurred with regard to advances in our knowledge.