In post and core preparation must:
- A. Extend to contrabevel.
- B. Extend to full length tooth preparation.
- C. Take same shape of natural tooth.
- D. Take shape of preparation abutment.
- E. A & d. ***
- F. A & b.
- G. D & c.
- H. B & c.
The correct answer is: E. A & d. Here's why:
- Extend to contrabevel (A):
This is true. The post-core preparation should extend slightly into the contrabevel to provide anchorage and resistance to rotational forces.
- Extend to full length tooth preparation (B):
This is false. The post portion shouldn't reach the full length of the tooth preparation. It should leave some healthy dentin at the bottom for the core buildup.
- Take same shape of natural tooth (C):
This is false. The post-core preparation doesn't necessarily need to mimic the natural tooth shape. It should primarily focus on providing adequate mechanical retention for the post and core.
- Take shape of preparation abutment (D):
This is true. The post-core preparation should adapt to the shape of the prepared abutment to ensure a good fit and minimize stress on the remaining tooth structure.
Therefore, both A and D are required, making E the correct answer.
Other Options:
The other options are incorrect because:
- F. A & b: Option B is false as explained above.
- G. D & c: Option C is false as explained above.
- H. B & c: Option B is false as explained above.
