Q: My client lets air come out the side of his mouth when he makes Th. It’s not a big deal, but it is noticeable and distracting.

This could be classified as a minor lateral lisp. The client is lacking the firm push of the side of his tongue against his side teeth that would prevent the airstream from staying midline.

I would use a straw. Place one end of the straw outside the central incisors and tell him the air needs to go only there.

Then shift the straw to one side of his mouth and the other, outside the teeth, and show him that he has air escaping to the one side.

Tell him he needs to push the side of his tongue harder (upward or sideways) to seal it against the side teeth so the air does not sneak out that side.

I might do some negative practice too. Practice making the air come out the sides on purpose, first one side and then the other, and then at midline. [Side-Side-Middle… Side, side, middle… Side, side, middle…] until he gets the hang of it.

Then offer him a decision to make. Ask him, “Do you want to make your TH in the middle like everyone else? Or do you want to make it come out the side like you are doing now?”

This is a little tricky! Your client may choose the side “Because it makes me different” or “Because it makes me stand out.” Keep in mind that you will have to accept his decision whatever it is. And dismiss him if he wants to keep it like it is. Tell him you will check with him in a month, and again next year, to make sure he still wants to keep it that way. Tell him he can come back to speech any time if he decides to change it.