I've heard babies can start getting teeth up to a year. My older two started getting them at 4 months but my youngest is going to be 11 months on the 28th and JUST got his first tooth a couple of weeks ago.
I wouldn't be worried at all. DD didn't her first tooth until she was almost 13 months old and she got a ton at once then. I was concerned and asked her pedi about it at her 12 month appointment, but he said as long as they started cutting teeth by about 15-18 months old then it's normal.