Last century’s research on the biology of tooth movement has led to the prevailing compression-tension theory. Here we present scientific evidence that supports a novel theory to explain the biology of tooth movement: Biphasic Theory. According to this theory a Catabolic Phase, during which osteoclasts resorb bone at both compression and tension sites, precedes and overlaps an Anabolic Phase, which restores alveolar bone to its normal levels. Furthermore, when evaluating this biological response it becomes clear that both animals and humans show a saturation of this response beyond which additional force fails to elicit this response and therefore, no additional tooth movement can occur. In this webinar we will discuss the clinical implications of these advances in understanding the biology of tooth movement and how they can be used to modify our biomechanics to optimize orthodontic treatment.