I wrote about getting lingual braces a few years ago in this post. No Northern Ireland orthodontists did linguals at that stage and I traveled to Portlaoise to get treated by Dr. David Hegerty, now based in Midleton near Cork.
It now seems that the Belmont Orthodontics practice in Belfast does lingual braces and also Invisalign invisible straighteners. So if you are looking for invisible orthodontics in Northern Ireland you now have an option 🙂