Teeth "float" in the socket, held in place by the periodontal ligaments. The periodontal ligament acts as shock absorber for your teeth.
Applying pressure to a tooth causes it to move. If the pressure on a tooth is intermittent or short lived the movement is temporary. Chewing won't cause a tooth to change it's position. When the pressure on a tooth is gentle and consistently applied, the body react to this pressure by activating the cells which cause bone to remodel. Thumb sucking or a tongue thrust will cause the teeth to move because the pressure is gentle and consistent.
If the pressure on the tooth is too heavy, the tooth will resist movement.When heavy pressure is applied to a tooth, the blood which surrounds the tooth in the periodontal ligament is forced out. Some cells build bone, some cells resorb bone.When there is no blood flow in the periodontal ligament the result is pain (ischemia related) and the cells needed for movement can't function properly.
Any given tooth has an ideal force which will promote its most rapid movement.
This basic biology is important because orthodontic treatment has to be consistent with these 'rules'.
Braces are the handles that are attached to teeth. The wires which connect the braces provide the force needed to apply the pressure needed for tooth movement.
We'll talk more about the importance of wires and bracket design in a later post.