Teeth grinding but he doesn't seem to be in pain?

I'm a new bunny owner, I just got a holland lop a couple weeks ago and he's just about 11 weeks old now. I had to take him to the vet three days ago because it seemed like he was on the verge of having a URI, so while he was getting checked out by the vet, she noticed his top incisors were far too long so I had them filed down for him - and on top of that, he broke off one of his bottom incisors! Anyway, since he had them filed down, he's been grinding/chattering his teeth but he doesn't look like he is in pain? Right now he's flopped over beside me taking a nap and I can hear him grinding them slightly. So I don't know if any of you have had something similar happen. Is he maybe still just getting used to the shorter teeth? He's eating fine and everything else seems to okay. I might just be a bit too paranoid :|

With rabbits there are two different types of tooth grinding. There is contented tooth purring that usually sounds more like light chattering of their teeth, and there is grinding their teeth in pain which often is a harder harsher sound and will most often also be accompanied with other signs of pain such as sitting hunched up in a corner and not moving, lack of appetite, drop in body temp, frequently changing positions like laying down and getting right back up repeatedly, or other uncharacteristic behavioral changes. If he is eating and pooping normally and is laying down and seems relaxed when he is doing this, then my guess would be it is contented tooth purring he is doing. But if you aren't sure, it would probably be a good idea to contact your vet.
http://www.dummies.com/how-to/content/knowing-when-your-rabbit-needs-emergency-treatment.html

I'm sure your vet will have mentioned it, but you will need to keep an eye on the teeth as it's likely they may need trimming again in a few weeks, especially with the one tooth broken. A couple things that can help with incisor tooth wear and may help delay when the next trim is needed, are things like apple branches(pesticide free) where they have to use the incisors to strip the bark off, and timothy hay cubes where the incisors are used to chew down the blocks. It might be worth trying them out to see if they help at all. Here's a bit of info on teeth problems in rabbits that may be helpful to look at.
http://www.medirabbit.com/EN/Dental_diseases/Differential/D_problems1.htm

Did the vet find that your bun did have a URI and did he get antibiotics for it if so?

Thank you for the dental help!! I'll get him some apple sticks and timothy hay cubes then! She was saying it's possible he'll need frequent trimming but hopefully that isn't the case :/

She said it was possible he was at the beginning stages of getting a URI/snuffles. I told her how he sneezed twice and his nose was slightly damp but his discharge was clear. She said that his lungs and heart sounded fine and there was no crusting yet but she put him on baytril for 21 days just to be safe. So far he hasn't sneezed again and his nose isn't as damp anymore, but when I wipe with a tissue occasionally, I cans see it's still not completely dry.

Also regarding your comment on the apple sticks - does it have to strictly be apple? Because I have a lemon tree..would that yield the same results?

Not sure that citrus is rabbit safe, don't think it is. Apple, willow, hawthorn, pear, are some rabbit safe woods. No pitted fruit like peach, plum, etc. If you can't get safe branches, the hay cubes may work well and you can get them at most pet stores or online. It's possible as he continues to grow, that the teeth problems will correct themselves.
http://www.medirabbit.com/EN/GI_diseases/Food/Branch/Branch_en.htm

With the URI, a good place to check for continued nasal discharge is on the inside of their front paws, as that is how they will usually wipe their nose. If it's crusty or matted at all, then likely the nose is still runny. Hopefully the abx clears it up, but sometimes it can take a month or more of the antibiotic, as URI's can be quite difficult to clear, and sometimes it can be difficult to find the right antibiotic. If he still has a runny nose after this course of abx and it is believed to be due to a URI and not some other sensitivity, you may want to ask the vet about having a culture and sensitivity test done on the bacteria. It can sometimes be inconclusive, but it also may help positively identify the exact bacterias involved and the best abx to fight it.

Another consideration with nasal discharge when it is clear and not thick and white or colored, is that sometimes an environment change such as being in a new home, can sometimes cause some nasal discharge, especially when a rabbit is coming from a cool environment into a warm home. Also other things that can cause clear discharge are sensitivities to household chemicals or smells, as well as dusty hay or bedding/litter, or a sensitivity to a particular hay or litter. Sometimes just switching to a different hay/litter can clear these type of things up, like if you use a soft paper litter, try a wood pelleted litter instead. Another cause of a damp nose can be a rabbit that is very hot and trying to cool off. Usually their ears will also be flared and they will be breathing faster and laying down a lot, in which case you need to take active steps to help them cool down.

http://www.medirabbit.com/EN/Respiratory/Bacterial/URI.htm

The change in environment was what I was thinking it might be - especially if it has to do with litter/hay/heat. I started using carefresh a week before he went to the vet, so tomorrow i'm buying wood pellets instead. I also noticed sometimes the hay is dusty so I'll make sure to shake it out more. In terms of the heat - he really likes to lay down on the air vent where the heat comes out of! Is this safe? Could this be the problem?

I wouldn't think the air vent would be a problem in terms of it making him too hot, otherwise he would likely lay somewhere else if it was too warm for him. But it could be contributing to a damp nose as it may be making his nasal passages too dry, which can cause some irritation and discharge as a result. As he gets used to his new environment, this can sometimes just clear up on it's own though.

One thing you are going to want to watch out for with him being on an abx, is this can sometimes lead to reduced appetite. So keep a close eye on his eating and make sure he is eating well. Also watch out for mushy poop or very small hard poop. If you notice any changes in appetite or poop, you should contact your vet.

How experienced do you feel your vet is? Typically baytril is not given to young animals as it can affect their cartilage while still in the growth period, but I'm not exactly sure what they consider the cut off age for bunnies. Certainly at 11 weeks old a rabbit is still growing, though growth will have slowed down a bit by then in small to med. rabbits. Just wondering if this is something your vet considered, as not all vets are particularly rabbit savvy?

The vet I went to deals with rabbits specifically and she has co-owned the animal hospital for many years now, plus one of my friends with a rabbit also goes there. I'm not sure what a small dosage is considered by I'm supposed to give my rabbit 1mL once a day - just going by what I've seen from other forums, it seems like that is a smaller dosage than what others have been prescribed. She told me we would start with the baytril first because the other option was using the culture, but she didn't want to do that yet unless it's needed because he is young?