Anna-
Anything is possible including a thick labial (upper lip) frenulum.
These are not often a problem but I have heard of some cases where they
can be.  Does the bottom lip flange or are they both restricted?  I would
also look into chiropractic and cranio-sacral therapy to be sure that all
of the nerves and muscles are working properly.

Sarah

Sarah Friend Barnett   LLLL, IBCLC
Bronx (New York City), NY  -  [log in to unmask]
" You are not obliged to finish the task,
 neither are you free to neglect it."       R. Tarfon