I did alot of research on these from the internet before I gave them to my daughter.  I have many friends that swear by them but I was not impressed.  Research that I found made them sound kinda scary to use (like kids were experiencing an acid trip) but I broke down one day 'cuz my daughter was in so much pain.  They didn't seem to help as much as tylenol or ibuprofen so I have away teething tablets and stuck with regular pain relievers.