Rocklone - I was going to ask if it did stop the hay-dunking but you answered that.
You don't necessarily have to have them done EVERY year. But it sure doesn't hurt to have them checked out. Then again, your vet may check your horse and say - there may be an issue - we need to re-check/possibly do ANOTHER float in 3-6 months.
And some vets have different opinions as to how often they need to be done and whether or not a horse needs to be sedated. A good vet will base both on the horse AND the horses' owner and how they both re-act and interact w/ one another. YES, hopefully there is a vet tech with the vet to help do the job, but I've still seen owners off to the side so upset that it upsets their pet - a lot.
A sedative can reduce that interaction as well as making "an ugly procedure" more pleasant. Some mini's take a lot more sedative to be effective than full size horses do. A horse receiving "outside" stimulus such as an overwrought owner OR construction work next door, will also take more sedative because they "fight" it... And some horses/vets/owners simply don't need/want the sedative.
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Several of my experiences -
When I had a hoof abcess treated on our first Shetland stallion, the vet gave him two doses of sedative - no affect. I can't read the receipt anymore to tell you how much of two different products he gave him - it was in 1995. BEFORE he'd do another, he had me sign a pretty extensive waiver as he couldn't guarantee that he'd EVER WAKE back up from it. He exclaimed that "AJ" took more than one of the Bison down the road (several times AJ's size). Surprise - he went down suddenly and was out just long enough for the procedure and then was AWAKE - none of that "out of it" period that most go thru when waking up from a sedative. Surprisingly, each consecutive year after that, he required less sedative each time to make him "sleepy" for any procedure - to include stitches in his pastern, exam to check his broken hip, teeth floats...
In 2000, our Hackney pony mare just seemed off. Not chewing sideways, not acting painful - but just "off". She had lost weight and we hadn't entered summer yet. The vet looked her over, listened to what I had to say and checked her out. Did TPR, checked gut sounds, checked legs for lameness. Wasn't finding anything. Asked when we'd last floated her and it hadn't yet been a year... But she got out the speculum and the mare had a broken, partial molar in her rear right lower jaw. The vet is feeling around and suddenly, in surprise, says - "OMG - the other 1/2 is embedded in her cheek and scar tissue has OVERGROWN it!!" We didn't have to do a "float" per say - but both halves of that broken tooth were removed - and it did require sedative (I wouldn't have allowed it w/o it) and some work as well as healing time after the procedure.
I've had 4 shetland ponies (plus had the teeth done on boarder's mini) teeth done w/o sedatives this year and 6 done with. 2 of them, imo, needed to have it. Both mares were older, both had had their teeth done in the past but this was a new practice/vet for us, neither behaved badly or moved about BUT he also didn't use a speculum. Personally, I don't like seeing all the blood that followed the/his procedure & I'm not squeamish in any way, shape or form (a later exam showed that he'd missed the teeth several times and their rear gums were "hamburger"). It would have been easier on these two older mares (23 & 24 yrs old) if they'd had at least a speculum to hold their mouths open for easier access and I plan on having them sedated next time as well (by a different vet - tho in same practice). Both girls went off feed for over a month - while I treated their mouths to epsom salt rinses daily - before they healed and ate right. Neither was eating badly before floating.
My old vet, the one whom I worked with for 7 years, now uses power tools to do floats. She's done in minutes! It's AWESOME. She has done extra courses for dental work over the years. The ponies have always done well for her and I've been happy (with dental work). We had several that off and on were done every 6 months due to issues that changed w/ seasons, hay & feed... ON the other hand, we've checked some and I've gladly skipped them that year! Currently, work w/ 3 different vet practices to get our pony's teeth taken care of.
I've never met an equine dentist... And here in NC, they have to be licensed as a vet before they can perform any kind of dental procedures that require/need sedation.