Here is the original post, where she does in fact state her horse did not have issues before.
Originally Posted by ilovemyquarter
Hello horse lovers,
I have a problem. My horse has never had any issues with putting the bit in. I have to use treats to get him to open his mouth. He is a quarter horse gelding.
He also had never bitten anyone until I was tacking him up one day and my assitant walked under his head and bit her. I figured it was because I was doing his girth, however he has never had any of these problems.
I started thinking about using bit wraps but I have doubts because those can easily get caught in their throught. He is a beautiful boy and I would never want to hurt him.
to use treats to get him to open his mouth" - have, not had, meaning she has to do so now, not before.
This is why I believe it's a dental issue, not training. Even biting while she's tacking up - could be back pain, muscle soreness, dental related, stomach ulcers. A vet or chiropractor will have to come out to be sure. If all health related issues are ruled out, then
I would begin different training approaches.