I know for cats it IS better for kidneys because it provides more moisture and cats don't drink enough, not sure about dogs. It's think the whole dry food scrapes plaque off of teeth idea has been proved wrong. Many dogs don't even chew their food enough for that to make a difference and the trouble spot on a dog's tooth is up by the gums, animals generally get gum disease, not cavities so if the dry food is all smashed up before it reaches the gums it's not doing any good. Now wet food sticking to teeth does not make sense to me, why would wet stick to teeth more than dry? If a dog did chew his food dry food would quickly be wet and I can't see that there could be a difference, it's like saying pudding sticks to your teeth more than crackers. As far as fillers it depends on the food but I know if you look at most of the nasty brands you'll see the wet food is a lot more meat based than the dry because fillers are used to bind kibble together. Now most of this is stuff I learned in regards to cats as the people I discuss cat stuff with are very pro wet food and many feed all wet, they have researched and had experience in feeding all wet and have not had teeth issues.
I honestly don't think there is a big difference between the two in dogs (there is in cats) and if your dog has an easier time eating wet then it should be fine but if her teeth are hurting you should take her to the vet to have her teeth checked out.
There are many good foods, some are not senior, they are All Life Stages which means they can be fed to any age dog.
Innova
EVO
Canidae
California Naturalhttp://www.chazhound.com/forums/newreply.php?do=newreply&noquote=1&p=1112516
Chazhound Dog Forum - Reply to Topic
Eagle Pack Holistic
Solid Gold
Timberwolf Organics
Merrick (some people have complained of quality control though)
Fromm
That's all I can think of right now, I might have missed a few but it's a good list of things to try, make sure you read the can to see that it's for All Life Stages or a Senior formula.