Tooth (years)

Average Lenth of crown (mm)

Average Length of Root (mm)

1st evidence      of calcification

Crown done (yrs)

Age of emergence in oral cavity(yrs)

Root Done (yrs)

Mandibular 3rd molar

7.0

6.5

7-9

12-16

17-21

18-25

Maxillary 3rd molar

11.0

11.0

8-10

12-16

17-21

18-25
mm = millimeters, yrs = years
Table 2: Average Length of Crown and root (millimetres) and Chronology of development of maxillary and mandibular third molars (years) by Wheeler RC et al.