First thing that is to be done is to get your crooked teeth treated. Now with the dentures on it is not possible for orthodontic treatment. Either you get a bridge or implants. So, it is suggestive to visit a prosthodontist and get your teeth manually checked before you plan a visit to orthodontist for the treatment. For more info visit the link...http://www.identalhub.com/articlecategory-braces-21.aspx