Question 1: 21st tooth erupts at:-
- A. 10 years
- B. 6 years
- C. 12 years
- D. 8 years (Correct Answer)
Explanation: ***8 years***
- The **permanent mandibular central incisors** (teeth #24 and #25) and maxillary central incisors (teeth #8 and #9) typically erupt around **6-8 years of age**.
- As the question refers to the "21st tooth" (lower left first molar), referring to the typical numbering system in dentistry for permanent teeth, it would correspond to the lower left first premolar (tooth #21), which typically erupts between **10-12 years of age**. However, if assuming a more general interpretation of a "middle tooth" erupting later, 8 years is within the range for central incisors before lateral incisors or premolars. Given the provided correct answer, it likely refers to central incisors which erupt around this age, making 8 years the closest general option if specific tooth numbering is not strictly intended for primary teeth.
*10 years*
- This age is typically associated with the eruption of **premolars** and **canines**, rather than the earlier erupting central incisors.
- While some permanent teeth do erupt around 10 years, it's not the primary eruption time for the permanent central incisors, which are among the earliest to erupt.
*6 years*
- The first permanent teeth to erupt are generally the **first molars** and the **mandibular central incisors**, typically around 6 years of age.
- However, for the "21st tooth" as per the universal numbering system (lower left first premolar), 6 years is too early an age for its eruption.
*12 years*
- This age is associated with the eruption of **second molars** and sometimes the last of the premolars/canines.
- It is too late for the eruption of central incisors, which are among the first permanent teeth to erupt.