Q: My client lowers the jaw too much when he speaks, and he has a frontal lisp. He tends to clench the jaw when I tell him to hold the jaw up. I may have taught him this when using a bite stick to position the jaw. Not sure what to do now.

As you have discovered, making a strong crushing bite on a firm object is not what he needs.  The term “jaw stability” does not mean “jaw rigidity.”

Our clients need to learn how to hold the jaw high position that is still flexible.  The jaw moves in a very small subtle up-down pattern during speech. It does not clench.

I teach this with a firm flexible straw instead of a bite stick. Place the straw between the molars on one side along the length of the dental line.  Have the client bite gently into the straw, and then lower the jaw again all the while holding on to the straw with the molars.

This will teach him the very small movements the jaw needs to make––a little higher for /s/ and a little lower for the vowels.

The jaw moves in big up-down oval-shaped patterns during chewing, but it moves in very small up-down patterns during speech.  A chewing activity could help him experience the gross motor pattern, and the straw then can help him feel it in the small, restricted range of jaw movements needed for speech. — Use a mirror throughout so he can see what’s going on.

Many therapists are trying to teach “jaw strength” but strength of the jaw muscles have nothing to do with speech.  The motor pattern is what needs to be taught––the soft, gentle, very small up-down movements the jaw makes during speech.