Why do some children have a lisp?

How do you correct a lisp in 5 year old that appears to be caused by an overbite? Is there something that can be done by a dentist or must you wait until old enough for braces?

my son is 13 he still says s like sh please help

You are correct that most children do outgrow a lisp because it is a developmental error. The best thing to do is model the correct phoneme (sound) productions and not over-correct them. I watched the YouTube video b/c I am a speech pathologist and I thought he did a very good job explaining. The most important thing to consider is when these sounds are developmentally appropriate. For example, I don't work on /s/ in a child in Kindergarten, unless they have already had therapy for other sounds. Then, I will work on the next sound b/c they are at risk for having additional speech sound errors. I think that some people don't know what sounds are developmentally appropriate. There is a variety of research done that is variable. I use a chart compiled from a variety of the previous research. I will try and post it here for you all to see if I can figure out how to do attachments :).

i dont understand post more

Here is a link to an excellent video on youtube that is packed with information on this topic. A Speech Pathologist explains what needs to occur in the mouth during accurate /s/ production. There is also a demonstration of a couple of techniques that develop stimulability of the /s/ sound.

http://www.youtube.com/watch?v=Jc8jEvC7jHs

I also had to go to speech therapy when I was young, as I could not say the "r" sound. I still remember the worst words to try to pronounce: "squirrel" and "car", which sounded like "squawal" and "caaw" (I would over-pronounce other sounds to try to make-up for the "w" sound!).

I was never embarrassed attending speech therapy class. I think I was so young, it was just another class and I do not recall any of my friends knowing about it. I do not remember actively hiding it, either. I DO still remember by speech therapist teacher, who would create silly hairdos with my long braids while I practiced our lessons...I thought she was so cool! :-)

As an adult, I am able to say my "r's", but if I am in a stressful situation, that "r" is the first sound that I am most likely to stumble on! The worst was trying to pronounce our Realtor's company: "Roy Wheeler", and I would constantly say "Woy Wheeler" or over-compensate and say "Roy Reeler".

Oh, and to the dismay of my mother, my younger sister also picked up the "r" lisp, which was further proof that siblings really do learn more from each other, than from other friends...and even parents! I still think it's funny that of all the people in my sister's life that spoke the "r" sound well, she copied my wrong pronunciation of it. So, Susan, in case your son does need a speech therapist when he's older...you may as well assume that all three of your children may have the same lisp, and start saving up! :-) ha ha! (sorry---I'm just teasing you. I just found out my son inherited my awful teeth and extreme overbite problem, which means braces, headgear, etc...so we're starting to save now!)

I agree that the lisp in little kids is kinda cute. I think our son is actually saying his "r" sounds, but he may have trouble with other sounds in a few years (as miscortes said, when his front teeth fall out...and he just got them!.)

A lisp is a functional speech disorder that involves the inability to correctly pronounce one or more sibilant consonant sounds, usually s or z.

Answer.com provides the following as the description of lisping.
Lisping is a speech disorder characterized by the inability to correctly pronounce the sounds of s or z, known as the sibilant consonants. Usually th sounds are substituted for the sibilants. The word "lisp," for example, would be pronounced "lithp" by someone with this speech disorder.

Many children lisp at certain stages of speech development, especially when they lose their front primary teeth. Lisping is, therefore, sometimes called a developmental phonetic disorder. Frontal or interdental lisp is produced when the tongue protrudes through the front teeth when teeth are missing and is the most familiar type of lisp. Sibilant production may be interfered with in a number of other ways as well. These are all classified as lisping and include excessive pressure by the tongue against the teeth, the tongue held too far back along the midline of the palate, and a "substitute hiss" produced in the throat or larynx.

The following is provided by Ehow.com and provides information about how to correct the lisp in children.

Find a speech-language pathologist in your area. This language specialist can diagnose the cause of your lisp and determine the therapy you need to overcome the impediment.

Step2
Understand the factors that can cause a person to speak with a lisp. A person with a long tongue is more likely to lisp; the tongue interferes with proper annunciation. Young children who learn sounds incorrectly may lisp; they can be re-trained with speech therapy.

Step3
Familiarize yourself with the main kinds of lisping. In an Interdental "s" lisp, the individual makes a "z" sound when trying to say words with an "s." The opposite is true with someone who has an Interdental "z" lisp. People who attempt to make the "s" and "z" sounds often make a "th" sound instead. Other common letters associated with a lisp are "l" and "r."

Step4
Expect a language assessment at your first appointment with a speech-language pathologist. The therapist will take a history, examine your mouth and sample your speech for evaluation. She will then offer a particular speech therapy that is customized to your situation. Practicing certain words and sounds diligently will increase proper speech.

I actually had a problem with my speech when I was growing up. When I was in kindergarten, I attended speech therapy because of the 'th' sound for an 's' sound. It did not take long but I soon learned from speech therapy. The only bad thing was I thought I was 'uncool' being in speech class. It was harmless though and I have not had issues later in life with the 'th' sound.