Lateral Lisp, Missing Teeth, and Malocclusion

Q: My client has no incisors and an underbite, and she distorts both S and Z. These errors sound like a lateral lisp, however when I use your straw testing method, there is no airflow coming out the sides, only the front. My colleague tells me that this is a lateral lisp. But how can it be if the air doesn’t come out the sides?

Your colleague is wrong: If the airstream is not coming out the sides (as tested with the straw) then it is not a lateral lisp. A lateral lisp comes out the sides. Period. Thus the term “lateral” lisp. Your client’s phonemes sound lateral, however, due to the missing teeth and the malocclusion. Let me explain.

Incisors

The incisors form a “dental barrier” or “wall” against which the midline airstream of the sibilants strikes. The airstream hits the back of the wall, rebounds, tumbles around, and then exits the mouth. This striking, tumbling, and exiting together all create the strident (fricated) sound.

Missing Front Teeth

When the front teeth are missing, especially when so many are missing, the airstream broadens. The air usually will come out where ever the teeth are missing. This interferes with the sharp sound that should occur, and it gives a broad and sloppy sound to all the sibilants––S, Z, Sh, Zh, Ch, and J. All of these phonemes can end up sounding lateral, but they are not. They are midline according to your straw test.

Malocclusion

A malocclusion causes further distortion of the strident sounds. The anterior dental barrier has to be like a straight wall of teeth against which the airstream strikes before it escapes out the front of the mouth. When there is malocclusion, the front teeth do not meet together correctly. With an underbite, you have a wide anterior-posterior gap. Thus you have additional distortion of the airstream.

Analysis

Your client does not have a lateral lisp. Your client has distortion of the sibilants due to malocclusion and missing incisors. Your client has an articulation problem due to the structural defect. These structural problems cause the sibilants to sound sloppy and distorted.

Treatment

Charlie Van Riper said that when there is a structural deficit, one has two basic options for your path of remediation:

1. Wait for the structure to be fixed with orthodontia or surgery, and then work on the phonemes.
2. Teach the client to compensate for his structural problems by teaching an individual or idiosyncratic oral position. This is the sound he will use until the dental problems are fixed, if they ever will. The compensated sound usually is not a “perfect” sound. It is only “good enough” and “as good as it can get.” This concept has to be taught to the client and his parents so that they don’t think you have failed. There is only so much we can do with a structural problem, and the resultant phonemes are only as good as the structure allows.

Thus, your choices are to wait for the client’s teeth to come in before you worry about how well she says these sounds, or you work on the sounds by teaching her to compensate for her structural deficit.