Laurie,
The ridging of the nipple is from excessive compression, usually the
result of tongue instability.  You feel that as chewing on a digital
suck exam.  The tongue instability can be positional (too shallow a
latch) or from low tongue tone or a short or anteriorly placed lingual
frenulum.  Compressing the breast with the jaws rather than the tongue
is less efficient.  This is a setup for a gassy, colicky, uncomfortable
baby when coupled with timed breastfeedings.  I would assess the tongue
function and latch further, then encourage mom to follow baby's cues as
to when to switch breasts, if at all.  I have posted a lot on the
subject of tongue function and stability, you can do an archive search
on my email address...
--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]