Firstly, my sincere apologies for my ignorance of basic geography, & failure to read your details. I wouldn't take kindly to be taken as from a different country with very marked cultural differences, history, & even some aspects of language, either!!
I hope you understand that my "heart was in the right place", in trying to spare you some of the distress we have encountered.
To your rabbit's teeth. Now you know about the "lay out" of rabbit teeth, you can see how I found it so difficult to understand how 1 molar could grow as long as an incisor, without propping the jaw so widely open, your poor bun wouldn't have been able to eat at all for ages!
One possibility was that there was no opposing upper molar. This
may need different long term dental management from the situation of opposing molars.
Another possibility, is that there were large spurs at the sides of the molar making it much wider & "bigger" & it only had the
appearance of being longer in the narrow mouth cavity at the back.
I don't know the answer, but hopefully, you have more questions for your vet.
It's so good that your bun is a good hay eater, because this is needed for normal tooth wear as well as gut motility. I strongly recommend simple pain relief for about 3 days after dental work to help your bun return to eating comfortably ASAP
I truly believe that each bun is different. The standard signs of developing dental problems are very gradual eg. subtle changes in dietary preferences, gradual decrease in fluid intake, which are best seen in the litter tray.
A reduction in poop number & size can indicate reduced food intake which predisposes to gut motility problems. I've briefly touched on urinary calcium issues. We get to know our buns in time!
My only other tip happened by chance, & has proven to be invaluable in monitoring "litter contents" closely. It may not be possible in your "set up" or your bun may not "take to it." Thumper designed his own toilet arrangement & won't use anything else! There is a photo on:
http://forums.rabbitrehome.org.uk/showthread.php?t=200448&page=4 #38 "Introducing Thumper".