I despair really. I tried SO hard with ds1, and he hated it and needed sitting on, though after getting orange toothpaste he got better - he still had a tiny bit of decay. And the dentist's nurse told me off for trying to make him open his mouth in the surgery! Which made me feel awful.
Then with ds2 I took the laid back approach, partly on the grounds of that telling off, particularly as most of his diet consisted of actimel and breast milk but he ended up with a lot of decay and had four extractions 
The way the dentists speak to you as a mother of a child with tooth decay was something I'll not forget in a hurry.
THAT is the reason I force ds3. I can't go through that again, I really can't, and children with tooth ache are not happy. Though ds2 only had one abscess on each side, once, they took the other two out in case.
I felt so sorry for him and so completely ashamed. I hate forcing a child to do anything, I really do, and it isn't in my repertoire normally but with this I can't think of another way.
I just hope it is very temporary. Also I do not hurt him - he knows it doesn't hurt, he just wants to exert control, and sometimes he thinks it is funny to resist.
I don't know any other way. I really don't. And he very rarely has sweets, no juice worth a mention, breast fed still, he drinks water or milk usually.