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Where Speech-language Pathologists find ideas, activities and materials.

Interdental Lisping

What is it?

Interdental lisping is when the tongue protrudes between the front teeth when producing /s/ or /z/, resulting in a “th” sound.  The /s/ becomes a voiceless “th”, as in “think”, and the /z/ becomes a voiced “th”, as in “those”.  Interdental lisping, also be known as “frontal lisping”, is a normal developmental phase that some children go through.  Because of this, if a person continues this pattern of speech past the age when most have outgrown it (around 4 ½ years old), his speech may be perceived as juvenile.
What about other interdental sounds?

Other sounds may be produced with a protruding tongue as well.  Most commonly, lingual protrusion during the “sh”, “zh” (as in “equation”), “ch” and “j” sounds may accompany the interdental lisping of /s/ and /z/.

In addition, lingual alveolar sounds (i.e., /t/, /d/, /n/, /l/) that should be produced with the tongue on the alveolar ridge may be produced with the tongue protruding between the front teeth.


What can I do to work on interdentalized /s/ and /z/?

1.   Establish auditory discrimination

2.   Provide focused auditory input.

3.   Get correct production of /s/ in isolation.

4.   Move through the hierarchy of production levels (syllables, words, phrases/sentences, reading activities, and conversational speech) with the sound in each position.  Note:  For lisping, I prefer to start with /s/ in the initial position.

Check out our sets and individual materials for practicing correct /s/ and /z/ sounds.


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