I know for a fact that older dogs w/missing teeth will have their tongue sticking out...but Momo sticks his tongue out all the time. It's so darn cute! He has a really long tongue too, so maybe that has something to do w/it. All my other 3 rarely stick their tongue out...he makes up for it lol.
He has a little cut on his tongue, some bug left a stinger on it awhile back & left it like that. Poor baby, he gets into so much naughty trouble lol.