Were cultures done on the bacteria in the mouth? That’s the best way to narrow down what antibiotic should be prescribed as many are resistant to various antibiotics. I had a similar issue with a retic a couple years ago and was prescribed Fortaz (ceftazidime) and Metacam for pain management.
Between 5 vet visits which included an X-ray, culture, and a surgery I spent about a grand on that animal in medical costs alone over 5 months. Best of luck and hope you get something figured out soon
Sent from my iPhone using Tapatalk