I just replied to you on an older post and I'm glad you made a new one that will probably be seen by more members! So sorry your pig is having dental issues... teeth problems are no fun and they can be challenging.
First off, how experienced is your vet with guinea pig teeth? Sometimes vets do see guinea pigs without actually having much experience or much recent training and can end up exacerbating problems by missing things, cutting teeth too short, etc. Most North American vets who have more knowledge with small animals bill themselves as 'exotic' vets or 'pocket pet' vets. Vets with a lot of experience with rabbit teeth are good to know as well, as the issues are not exactly the same but they are similar. If he's offering a referral to a specialist who does more small animal dental procedures, frankly I would take it! You don't have to say yes to imaging or anything else invasive/prohibitively expensive, but a second opinion from someone who sees more of these problems is probably really worthwhile.
Usually slanted incisors in front do result from a problem further back.... problems usually start at the molars and move forwards. Sometimes molar spurs can form that trap the tongue or cut up the cheeks, sometimes abscesses cause pain while chewing, which leads pigs to favour the other side and leads to overgrown teeth and spurs. It can take time for these abscesses to puff up, though they can be painful before that. I would daily run your hands along his jawline to feel for any lumps that aren't supposed to be there. They can puff up in a remarkably short period of time! I would also add that sometimes a vet can miss molar changes at first glance. Pigs tend to keep food to chew over at the back of their mouth to keep chewing on, which can hide the molars. He should be able to get a good view if he anesthetized the pig and looked really closely while they were out, but if he just looked in the back with an otoscope while your pig was awake and squirmy and then just treated the incisors, it's possible something was missed.
Weight maintenance is important, so you should weigh daily. If he isn't maintaining weight, there is a sticky note about how to supplementally feed a piggie at the top of the page. It's important to keep the gut going to maintain his health while you figure out the teeth. It's also worth asking the vet about pain relief... a lot of pigs manage pain poorly and simply won't eat if it's sore, no matter if it leads to them wasting away. A painkiller may make him a lot more willing to chew food if he's literally just so sore eating that he's discouraged from even trying.
I hope some of this helps and I hope you're able to find a fix for him, he's a cute little guy!
