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.