For many years orthodontics depends largely on mechanical factors. In reality, orthodontic tooth movement is a biologically mediated process. Bone cells and the plastic nature bone are the key factors in orthodontic tooth movement. Therefore future orthodontics will increasingly become biologically correct consequently, patient-friendly. The target of future orthodontics should be on the bone cells. This book reviews the modulation of orthodontic treatment by different biological modulators and presents an experimental study on rat to investigate the possibility of using strontium ranelate drug as modulator of orthodontic tooth movement. Strontium ranelate represents a new generation of oral antiosteoporotic agents able to stimulate bone formation by osteoblasts and to inhibit bone resorption by osteoclasts. On the basis of results arrived, the experiments concluded that the local injection of strontium is a promising approach for enhancing both orthodontic anchorage and retention