mouthguard lisp

The lisp you get when you talk while wearing a mouthguard

Person 1: You got your mouthguard for ufc?
Person 2: Yeth, I have my mouthguard for uf -thea. And I covered it in Vatheline.
Person 1: please take out your mouthguard.
Person 2: (takes out mouthguard) Sorry, mouthguard lisp.