So just to be clear, to be registered with the AESD, you merely have to take a 4 week course. And I can't be confident that they would tell you if one of their members had negative complaints as this would reflect negatively on their program. And you said he's using sedation which I will reiterate- ILLEGAL. The choice is yours of course but I want everyone to be very clear as far as what being an "equine dentist" entails.
I'm not trying to poo-poo the program as it seems like a great first step in learning dentistry. I did two 2-week courses (so the same amount of time spent in the AESD program) in dentistry with a DVM who is also an equine dentist and now only practices dentistry and I am a veterinarian and yet I still feel that this amount of training is not sufficient to bill myself as an equine dentist, let alone do more than a simple float. Buyer beware, that is all.