In this chapter, we focus on methods of accelerating orthodontic tooth movement that attempt to change the biological response. The focus of all these methods is to increase the number of osteoclasts. These approaches fall in different categories—first, approaches that try to stimulate osteoclastogenesis through local or systemic application of different chemical factors; second, approaches that focus on applying different physical stimuli that can increase the number of osteoclasts if used during orthodontic treatment; and third, approaches that rely on increasing natural inflammatory reactions in response to trauma without any chemical or physical stimulants. It should be emphasized that, despite some disagreement about the initial trigger factor that starts the cascade of events leading to bone resorption and tooth movement, all approaches agree that osteoclast activation is the main rate-controlling factor in orthodontic tooth movement.