Perhaps part of the reason the idea that “a dog’s mouth is cleaner than a human’s mouth” came to be so widely believed is that we don’t typically swap diseases with our dogs when we swap saliva. You are not going to get the flu from a dog kiss, but you might get it from kissing a human loved one.
Most of the bacteria in your dog’s mouth are not zoonotic, which means you probably won’t get a disease from a big old doggy kiss. There are exceptions to this. Dogs that are fed a raw diet are at an increased risk of contracting salmonella, which can be spread to humans, and you really don’t want to share kisses with a dog that regularly raids the litter box.
In other words, kissing your dog is less risky than kissing another human
Good luck out there!