Strange query this but my MS bitch has, in the last week, been almost obsessively licking at her five month old bitch puppy Bea's mouth.
She does it whenever they are relaxing. She never tries to do it to her dog puppy Tom. I have checked Bea over  and cannot see any obvious problem or soreness around her mouth and gums. She seems in excellent health and is quite happy to indulge her mum's odd behaviour sometimes reciprocating so that they look like they are French kissing!
I am just concerned that Rosie, the mum may sense something that we are unaware of. Has anyone else experience of this strange behaviour?

My GSD does it to my 5 1/2 month old pup and sure in a few days you will see that the pups teeth will start falling out and see gaps and blood in her/his mouth.
Don't worry about it they all do it.

Well oddly enough my 5 month old sheltie Isla does it to our rescue JRT (who is about 7).  Gets her long pointy face right into his gums and licks and kisses him in his mouth - rather her than me!!
Snowflake

I have a super book called how to speak dog by  Dr Stanley Coran

his theory for dogs licking other dogs faces is : A pacifying gesture of active submissiveness,acknowledging the dominance of another.As a holdover from the puppyhood. this is also a food request.

Funny thing , this morning whilst walking my two, as soon as we got out I saw them licking each others mouths as they often do, and I frequently wonder why they do this when they first get out.  Is it just excitement?  It does look as though they are saying to each other 'isn't this fantastic'!  lol.

my two do this aswell both of them do it to each other??? there isnt really a submissive one between the two