Principles Of Tooth Preparation Practice Test

What is the ideal convergence angle of a single axial surface?

4 degrees 6 degrees 8 degrees 10 degrees

Correct Answer:

6 degrees

Explanation:

A small, controlled taper on each axial wall is essential for good retention while still allowing the restoration to seat smoothly. For a single axial surface, about 6 degrees of convergence provides the best balance. If the convergence is too shallow, the wall may not grip the restoration enough, reducing resistance to dislodgement. If it’s too steep, the restoration becomes difficult to seat and can bind or cause improper seating. Six degrees gives enough wedging effect to hold the crown in place without creating seating problems, which is why it’s considered ideal for a single axial surface.

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