Welcome to the forum Smoothie, sorry to hear your guinea is not well.
Did the vet say that the molars were actually overgrown? What were/are his actual symptoms - is there any dribbling (drooling), any odour/stale smell to the mouth? There are at
least two potential issues I see here:
1) Incorrect treatment which can actually do more harm than good, and it then makes me wonder about whether the diagnosis was accurate enough;
2) Sore mouth.
The "sore mouth" could be down to sore patches on the tongue or cheeks if the molars
were overgrown, or an oral fungal infection may be to blame (sometimes symptoms are the same as dental problems and there may be no white spots visible in the mouth to suggest the condition, and it may occur alongside dental problems).
Both possibilities - continued dental issues and sore mouth - would cause the pig to go off his food in the first place and both may still be prevalent at the moment. I would recommend treating with Daktarin Oral Gel for three weeks to rule out an oral fungal infection, it is available from chemists/pharmacies (although they won't sell it to you if you say it is for a guinea pig!); it can also help with sores caused by overgrown molars, although there is something more specific that can be used if this is spotted as the more specific problem.
How much Critical Care are you feeding him each day, and how often? Is his weight stable (noted by daily weight checks)?
Would you be willing to speak on the phone to someone who does know a lot about guinea pig dentistry? If so, drop me an email at
[email protected] and I'll pass the details on.
I know there is a rodentologist in County Mayo; she's french-speaking, and I'm not sure if she'd be able to examine and treat dental issues as I've not dealt with her myself, but maybe worth considering contacting at some point?