Hi Linda,
What about brushing her teeth at a different time? If it's a part of her bed-time routine, she may see this a signal that the day is over and she is resisting. Mix it up a bit.
I agree with Rebecca, make it fun and goofy. Katelyn resisted a bit when she was Hope's age, but now she is fine. However, she does have a preference on who brushes her teeth. Most of the time she prefers to have dada brush her teeth. If he's not around then she'll allow me to do it, but if he's there she wants him to do it.
Try having dad brush her teeth (if he's available) and see if this makes a difference. Also try to me calm about it, kids sense our anxiety and react accordingly.
It is very important to take care of our babies teeth even from a young age. York Region has dental clinics where you can take your babies to get checked if you are worried about their teeth. I used them for Katelyn when she was 13 months and they were great. If you are interested, you can call York Region Health Connection for more info.