This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2017, Subject name: Forensic Medicine
21st tooth erupts at:- 
Select and explain. 
A. 6 years, B. 8 years, C. 10 years, D. 12 years
A: 6 years
Answer: A: 6 years 
Explanation: Eruption is defined as the superior pa of crown of the tooth appearing level with the surface of the alveolar bone.Temporary dentition: total 20 number of teeth, stas at 6 months till 2 years.Permanent dentition: total 32 number of teeth, stas at 6 years completed by 17 - 25 years.1st to erupt is molar 1 (M1) and last to erupt is molar 3 (M3).21st teeth refers to 1st permanent tooth, which erupts at 6 years.