Missing teeth usually result in unattractive spaces. Opposing and adjacent teeth can drift into the space to create further problems. Orthodontic treatment involves moving all teeth into correct position, and creating proper space to facilitate replacement of the missing teeth. In certain situations, it is possible to close the spaces and avoid having to replace teeth.
Impacted teeth don't have sufficient space to erupt. Orthodontic treatment involves creating space to allow the impacted tooth to erupt.
Ectopic teeth are teeth, which develop in the wrong position. In most cases, an ectopic tooth can be moved into the correct position with braces.