A lisp is a speech impediment that inhibits to proper pronunciation of certain sounds. In some patients it is possible for a lisp to develop when they begin wearing Invisalign because it alters the amount of spacing in their mouth. This will vary from patient to patient as some patients will have no issues with a lisp developing while other may. You can talk to our dentists if you have any issues or have any questions about problems that arrises after using Invisalign.