What is an Interdental Lisp?

An interdental lisp is the most common kind of lisp that you could encounter during your child’s early life and language development. It involves an abnormal tongue protrusion between the front teeth causing speech to sound “muffled” or “hissy”. The most common example is a child producing a th sound for s, z and sh sounds.

What are the types of lisps?

There are four different types of lisps with distinct sounds related to tongue placement:

1. Interdental or frontal lisp.

When the tongue protrudes or sticks out between the teeth when making s or z sounds, causing a th sound.

2. Dentalised or dental lisp.

When the tongue rests or pushes up against the front teeth, causing a muffled sound.

3. Lateral lisp.

When extra air flows over the sides of the tongue instead of down the middle, causing a slushy lisp sound.

4. Palatal lisp.

When the tongue tip touches the roof of the mouth (or soft palate) when making s or z sounds, rather than resting behind the teeth. Book a Speech assessment

What causes an interdental lisp?

The short answer is we don’t really know. But there are a few factors that can lead to an interdental lisp and disruptions to learning speech:

• Anatomical issues, such as cleft palate, tongue tie, or misalignment of teeth.
• Prolonged habits, like thumb sucking or dummy use, pushing the front teeth forward.
• Hearing loss, which affects speech development.
• Some cognitive difficulties which are known to impact speech development.

When do children’s interdental lisps typically start?

Interdental lisps usually occur before four years, which is when a child typically fully develops the s, z and sh sounds. If the lisp persists beyond seven years, it’s recommended that you reach out to a speech pathologist for an assessment.

What should I look for?

If your child produces a th sound for s or z sounds, like “thebra” for “zebra”, it’s likely that they have an interdental lisp. It could also be helpful to observe your child and note whether their tongue protrudes between their front teeth while making these sounds. If your child has a prolonged habit of thumb sucking, dummy use, or issues with their teeth, this could be another sign of an interdental lisp.

How is an interdental lisp diagnosed?

An interdental lisp is usually diagnosed by a speech pathologist after they do a comprehensive assessment on your child. This normally includes analysing their speech sounds, oromotor skills, hearing and general observations, and parent interviews. Gathering more information allows your speech pathologist to make an accurate diagnosis.

• A speech sounds assessment allows your speech pathologist to assess the types of speech your child finds difficulty in. For an interdental lisp, this would be s, z, or sh
• An oromotor assessment provides more information about your child’s muscle movement for speech, testing for strength and accuracy.
• It is strongly recommended that your child’s hearing is also checked, since children need good hearing to receive feedback about their speech and correct it.
• Through observations and case history interviews, your speech pathologist can also look out for any red flags indicating the presence of an interdental lisp, such as prolonged thumb sucking, teeth issues, tongue thrust, etc.

How is an Interdental Lisp Treated in a Child?

An interdental lisp is usually treated in speech therapy sessions through articulation therapy. This gives your child the space for intensive practice to help them correct the way their mouth moves to say the sound. Usually, your speech pathologist will work with your child to discriminate between different sounds and then practice producing the sounds in syllables, words and sentences. Early intervention is recommended so that the habit is not reinforced, making it harder to treat.

How can I help my child with an interdental lisp?

Give your child auditory and visual feedback so that they can be aware of the difference between the sounds they’re making and the sounds you’re making. For example:

• “I heard a th. Let’s try that again, ‘zebra’.”
• “Look where my tongue is, it goes behind my teeth!”

It’s important that your child has regular practice correctly producing the sound. book a speech assessment

What are the long-term effects on an interdental lisp if left untreated?

Long-term effects may include:

• Lowered speech clarity.
• Communication barriers.
• Negative impact on literacy.
• Negative impact on academic success.
• Negative impact on social interactions, as they are less likely to be understood by other children.
• Lowered self-esteem.

When Should I Speak With a Speech Language Pathologist?

You should reach out to a speech language pathologist for help if you notice and hear that your child is consistently unable to produce s, z or sh sounds. If you suspect your child has a lisp, a speech language pathologist can recommend treatment tailored directly to your child. Most lisps can be treated successfully through early intervention and speech therapy. If your child’s lisp is identified at an older age, it becomes harder to treat. It’s still recommended that you start speech therapy sessions and begin working on correction techniques as soon as possible.