The increase in line on the enamel of tooth can be useful in determining age. This method is called

Gustafson's method: the age can be determined from the erupted permanent teeth and from the degradation changes in them. Boyde's method: in developing teeth, it is claimed that the deposition of dentine and enamel takes place by layers after the formation of neonatal line in the deciduous dentition. These are called incremental lines. So, microscopically measuring the incremental lines the age of the fetus or infant can be calculated in days. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr. PC IGNATIUS PAGE NO 81, 83.