<prompt> Eruption of 1st molar permanent tooth occurs at the age of:4-5 years6-7 years7-8 years8-10 years  <response>: b. 6-7 yearsRef: Nelsons 20e p 1768-1771, Ghai 8e p 11Permanent dentition begins at 6 years and is completed by 12 years except for 3rd molar. 