When my son was younger, I asked this question also. He got his first two bottom teeth at 2 months, then no more until about 8 months. He is now just getting in his two year molars. (He is 27 months old). From what I was able to gather . . . (1) dentists seem to disagree on whether bone age and teeth are related. Some say they are, others say they are not. (2) I spoke with three dr.s and 2 dentists, as well as friends and family, they all said the parents dental history is the key factor. e.g. If mom or dad got teeth early, child will probably get teeth early. If mom or dad got teeth late, child will probably get teeth late. (3) There seems to be a very wide range of when kids get their teeth. Because I was concerned about my son, I looked at and talked to everyone I could. Each child seemed to have a different time of getting teeth in. I will be very interested to hear what others found out. Good luck Yong Yan. Try not to worry.