I didn't have a gap filled in my front two teeth, I was missing a tooth next to them. I studied for over a year with pat hession, and also with mike williams a few times. I studied for 2 years with Stephen Jones (former ITG president) also. They have all suggested the same stuff... long tones, lip slurs and arban's. I think I may try and get the front of the tooth filed down a little bit or angled more straight up and down as I can feel it when I play.