The "Biology" of Tooth Movement
Picture A Your teeth have roots that fit into a socket in the bones of your jaws. The roots do not actually touch the bone. They sort of float in the socket, and are held in place by a ligament - the periodontal ligament.
Picture B Braces put pressure on the teeth. If pressure is placed on a tooth, the ligament gets squeezed (1) on one side, and gets stretched (2) on the other side.
Picture C The squeezing and stretching stimulates your body's cells in the area surrounding the tooth. The cells automatically begin to dissolve bone away where the squeezing is happening (1) and to make new bone where the stretching is happening (2). The human body is pretty amazing!
Picture D If the pressure is constant, over time the bone and ligament will transform itself in the direction of the pressure. Gradually, the tooth winds up in a different spot, with a brand new socket of bone around the root. Interesting...
The pressure must be light. Heavy forces kill the cells and you have to wait around for the body to make new ones. That wastes time.
The pressure has to be constant. If it comes and goes, the body cells never get the message to change things. That is why you are told to wear rubber bands 24/7.
FYI-The teeth have NO IDEA what is pushing on them. The body only knows that there is pressure present. There is no such thing as special braces that make the teeth "move faster"