Pediatrics Growth, Development, and Behavior 5eae03b7 Eruption of 1st molar permanent tooth occurs at the age of: A 4-5 years B 6-7 years C 7-8 years D 8-10 years High-Yield Explanation b. 6-7 years(Ref: Nelson's 20/e p 1768-1771, Ghai 8/e p 11)Permanent dentition begins at 6 years and is completed by 12 years (except for 3rd molar).