Here's some information from kellymom.com (a lot of the information refers to toddlers, but the principles should still work for you!):
Teeth scraping, uncomfortable latch, or indentations on your nipple tissue from the teeth is not all that uncommon. It seems to be worse for most moms right when the teeth first cut through, and before they have a chance to wear down some and become less sharp. Babies may also change their latch a bit when they get new teeth, as nursing can feel different to them with the new teeth. With time, baby will learn to nurse better with the new teeth and you won't be so aware of them. Here are some suggestions that have helped other moms:
* With an older baby, the weight of the baby can cause baby's mouth and teeth to "drag down" on the breast tissue. See if you can position baby so that her weight is supported well. Use pillows or a chair with arm rests to support her as much as you can. When she is nursing on the left side, bring her bottom in a little bit closer and vice versa. Don't let her nurse in a position that lets her weight and gravity cause her mouth to pull down on your breast and nipple. Try moving her body slightly in different ways (higher, lower, side to side, etc.) till the pressure on your breast is lessened.
* Latch baby on and position her head so that it is tilted back more to get the pressure of the top teeth off your breast. For example, if baby is nursing in the cradle position on the left side, bring her body toward the right a bit. This will bring baby's chin up, with her head a bit cocked back, and that moves the pressure of baby's top teeth off the top of the nipple. Don't let her chin rest on her chest.
* Some other ways to get baby's head tilted back more: ask your child to look at you while she nurses, or hold a book up high to read to your child and have her look at the book.
* When you support your breast with 2-4 fingers underneath and thumb on top, push in against the chest wall with your index finger just before offering the breast. This will cause the nipple and areola to point down more, so that they don't rub against baby's upper teeth. This technique is often suggested for moms who have nipple soreness due to their nipples rubbing up against the roof of baby's mouth.
* Ask baby to open WIDE and show her with your own mouth. Tell her that it hurts mommy and ask her to try again until it feels better.
* A generous application of lanolin before and after feeding may be helpful, as will rinsing your nipples with cool water after feedings. When babies are teething they produce more saliva which can be irritating to nipple tissue. If baby is eating solids, sometimes food particles left in the mouth can also irritate nipple tissue, so it may help to rinse out baby's mouth or give baby a sip of water prior to nursing.
* Any time you experience soreness, go back to the basics of latch just as you did in the early days.
* It's also possible that some of the tenderness is a result of ovulation or an impending menstrual period. Many moms of older babies are more bothered with latch on and baby's teeth during these times.
(
http://www.kellymom.com/bf/older-baby/biting.html#scraping)
Hope that something in there is helpful for you!