Hi Anne,
I am happy to hear you are having this problem addressed – dental infections can be very painful. It sounds like you are on the right track. Oral antibiotics should be sufficient to treat or prevent infection in a situation like this. If you are noticing that it is looking worse or your dog has a reduced appetite or activity level, you may want to ask your vet to re-assess the tooth. If you want to try something topical, your veterinarian can likely provide you with an oral hygiene rinse for dogs (containing chlorhexidine usually). It is important that you do not use human mouthwash, and I would suggest consulting your vet before doing anything outside what they have recommended.
Wishing your dog a happy recovery!
Dr. Kim Hester