I have a 7 year old gelding who has just started head tossing when contact is made with the bit in his mouth, specifically when asking for the back -- I ride Western and ask for a back by taking the slack out of the reins, releasing the pressure each time he gives me a step. We've been working on making this cue less and less so I don't think I'm using a heavy hand.
It's the same bit he's ridden in for the past three years and he's been perfectly peachy with it all along until now. This leads me to think it's something with his teeth. He had a few sharp points ground down last year -- overall his mouth was in good shape. He's in good weight and eating just fine but he still has his wolf teeth.
Are there any visual inspections I can do to pinpoint a possible issue before calling a dentist out to give him a more thorough exam?
ETA: Maybe the wolf teeth are finally coming out on their own and that's his issue?
How do you know he still has wolf teeth? If he does they should be pulled. Why weren't they pulled before? If it has been a year since the last float he almost certainly need his teeth floated also.
The dentist's receipt that came with his other papers when I purchased him said he still had his wolf teeth. That receipt was dated two years prior to when my vet at the time floated him and she confirmed that he still had them once his mouth was opened up (she also said his mouth was in great shape and had only developed a couple of points between floats, but nothing major, hence my thought to go longer between floats). She was of the opinion that "if it ain't broke, don't fix it," ie, if the wolf teeth weren't bugging him, no need to pull them. So unless they've fallen out on their own, he still has them.
Start by having them pulled. A horse should always have them pulled before a bit is placed in the mouth. You may want to consider finding a different vet for dental care as her advice is far from the norm. If you told your vet he is ridden without a bit I could see saying leave them but that would be the only reason.
It's rare to find a 7 year old that lasts more than a year between floats. Wolf teeth rarely fall out after the 2nd premolar sheds and that took place for your horse 4 1/2 years ago. If it ain't broke don't fix it doesn't cut it when it come to horses mouths. It's sounds like you vet has no interest nor knowledge when it comes to equine oral care. You need another opinion and remember... your best choice may not be a doctor.
I agree with everyone else, his wolf teeth have to come out and someone recommending otherwise has no business in his mouth.
I also agree that he should have his teeth done annually (at least). Often enough that the dentist/vet doesn't find much that needs to be done. You should not wait long enough between floats for those little points and ridges to turn into something bigger. A horse done regularly with a good dentist/vet shouldn't have any "issues" with their mouth; that's why we have the service done in the first place! A lack of problems does not mean go longer between visits.
Yes, the head tossing could very likely be caused by oral discomfort.