MDS AIPGDEE preparations B-IDS : Which of the following factors concerning retention and resistance for single unit crowns are false?

Which of the following factors concerning retention and resistance for single unit crowns are false?

a. Over tapering of the opposing axial walls can be corrected if a band of several millimeters of tooth structure can be prepared circumferentially with a restricted taper of approximately 6 degrees.
b. As taper increases, the free movement of the restoration will do so likewise, and reduce the retention.
c. Molar crowns are more retentive than premolar crowns of similar taper.
d. A 7/8 crown with grooves has more retention than a complete crown with no grooves.

Ans D It is false statement: Is a true statement. Over tapering of the opposing axial walls can be corrected if a band of several millimeters of tooth structure can be prepared circumferentially with a restricted taper of approximately 6 degrees. It is probably unnecessary to further modify the preparation to compensate for the areas of excessive reduction in the occlusal third.