Lateral Lisp, Missing Teeth, and Malocclusion

By Pam Marshalla

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.


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.


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.


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.


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.

6 thoughts on “Lateral Lisp, Missing Teeth, and Malocclusion”

  1. hello. My 14 month old is still without a single tooth. I am so scared and began to wonder if her lack of teeth will impair her speech? at present she says, mama, dada, droder, ball and baby…but is there anything I should be doing with regards to early intervention? My doctor tries to assure me that it is normal and that he’s known of 19 month old babies without teeth. I don’t want to expose my daughter to an xray just yet. Please advise.

    1. Lack of teeth affects speech only in very minor ways at this age. Relax and let things unfold naturally. Seek the advice of a local SLP and use her to help you monitor the child’s speech over the next 6-12 months. That means to have her take a quick look at her no more than once per 1-2 months. This is not therapy, it is a series of little check-ups. If the therapist feels that things are going awry then consider therapy. I do not think you will need it unless the lack of teeth is a signal that there is something much bigger going on developmentally.

  2. Mam,
    mine front two teeths are quite large and,
    moreover, the “right front teeth” has protuded out too,
    mam,kindly guide me any treatment….
    I live in India by the way….loved your site too much…

  3. I have a student who has been referred for a speech evaluation secondary to lateral lisp. Since the referral and before I was been able to test, her parents had her two front teeth pulled. Wondering what you would do: wait to test until her teeth come in? Or start therapy working on compensating for the structural deficit until the teeth come in?

  4. I have a fifth grade student referred for a “lateral lisp” and it somewhat follows the above scenario. I did the straw test and the airflow was coming out the front, but also out the sides. She has a pronounced overbite and only demonstrates distortions (lateral sounding) for /s/ and /z/. I just want to clarify based on what you reported that a malocclusion such as an overbite could impact only /s/ and /z/ and not the other sibiliants? Also the straw test could result in airflow directing out the front as well as side but this is due to the malocclusion and not a lateral production error? Thanks in advance for any feedback!!

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