Little did we know that the lisp, a certain speech disorder mostly oriented with either the wrong placement of the tongue when talking or what the professionals call the “reversed swallow†(the act of swallowing through pushing the tongue forward when in fact it should be the other way around), is a dental issue too. Yes, you’re reading it right. Most of the people with lisps have an over bite since they tend to push their tongues forward, thus, the air escaping the sides of the tongue. This “gap†is the reason why people who have lisps tend to pronounce the letter “S†more like “THâ€. Lisps can be corrected (dentally speaking), through braces with orthodontic rubber bands or with the use of headgears (extreme cases).
Photo taken from http://www.kiferdentalspecialist.com