Me and my boo had the teeth problem too. I just cover my teeth with my lips and open as wide as I can. I suck him while he's still soft and can fit alot in then. Love feeling it grow in my mouth hehe. After he's hard though I just can't make it fit. The head and maybe another inch. Sometimes I can lay on the bed and let my head hang off the edge and can take 4 inches maybe 5. Why it is a sometime thing I don't know. Just is.
Anyway, lips to cover teeth, keep tongue as flat as possible, and get a good angle. That's about all you can do. If it still won't fit... to hell with it. Just fuck her lol