S.B.
I had a similar problem with my son around that age. My son also hated bugs for some reason so I told him there were little bugs he couldn't see in his mouth and we had to brush them out. I would ask him what color buggies were in his mouth and he would say orange or blue and he would open his mouth wide and let me get rid of the buggies. For whatever reason, it worked. It may not work for you son but don't give up. Keep trying! And stick to a routine. That helps. In fact, sometimes I forget and my kids quickly remind me that it's time to brush their teeth. Good luck!