Hey,
As was stated, if you lost one the likelihood of losing the other is pretty great. Infections of the mouth, can in their severest case, affect the bone area, maxillary and mandible, and other parts too, causing lose of teeth. In its mildest state, the infection can be treated using some topical meds, like Neosporin antibiotic oinment, and a rinse or flush, like Hydrogen peroxide, or Povidine (Betadine), diluted to a light colored tea with water. If the severity of the infection is not known, a visit to the vet is warranted, particularly, if you have no prior experience with treating Stomatitis, which again, is usually secondary to something underlying, like a URI.
A visit will likely run you about 100 dollars, but in the end you will save your gtp, and get it on the road to recovery, and the knowledge gained on how to best treat this is indespensible.
Drugs used to treat Stomatitis and URI:
Amikacin, Baytril, Ceftazidime, Cipro and recently, Tylosin. These meds are only obtainable from a Vet and the latter, can be purchased from an online source. However, do not attempt treatment without being shown properly by a Vet.
-Angel
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"Until we lose our self, there is no way of finding our self."
-Henry Miller.