-- Functional appliances
This type of orthodontic tools relies on the forces that are produced by the muscles which help us speak, eat or swallow. By redirecting these forces functional appliances are able to realign the jaw and teeth which have to be repositioned; some of these appliances are removable, others are fixed or bonded to the teeth and others may span across the mouth to leverage the position of the molars to realign the jaw.
-- Fixed appliances
As the name implies these are a set of wires or brackets are directly attached to the teeth in order to correct their position, the most common form of a fixed appliance is referred to as dental braces. These tools work over a set period of time in which he appliance needs to be readjusted to balance of forces that will correct the position of misaligned teeth, this process is also referred to as bone remodeling.
Another good example of the type of orthodontic appliances which are used to prevent teeth from moving back out of their position is called the retainer. The difference between braces and retainers is that braces are used in order to correct and realign the position of the oral structure; retainers on the other hand are used to keep the teeth on the same position after the braces have been removed, dental retainers can be removed and are not as noticeable as braces, they can also be placed on the back of the teeth to make it nearly impossible for someone to tell that you're wearing retainers.
Recent orthodontic tools have been developed in order to get the best from braces and retainers, one of the appliances is referred to as Invisalign, these are virtually invisible braces that can be used to realign teeth without going through the social discomfort that traditional braces may provide, especially in adults.