This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
In the cast restoration, cusp protection is mandatory when: 
Select and explain. 
A. The lesion depth is ⅓  to ½ the intercuspal distance, B. The lesion depth exceeds ½ the intercuspal distance, C. The lesion width is ⅓  to ½ the intercuspal distance, D. The lesion width  exceeds ½ the intercuspal distance
D: The lesion width  exceeds ½ the intercuspal distance
Answer: D: The lesion width  exceeds ½ the intercuspal distance 
Explanation: Indications:

If the width of the lesion is 1/3 to 1/2 the intercuspal distance - cuspal protection is to be considered.
If the width of the lesion exceeds 1/2 the intercuspal distance - cuspal protection is mandatory.
If the length:width of the cusp is more than 1:1, but not exceeding 2:1 - cuspal protection is to be considered.
If the length:width of the cusp is more than 2:1 - cuspal protection is mandatory.
When there is a need to change the dimension, shape and interrelationship of the occluding tooth surfaces.

MDS Prep Bytes( Cast Restoration – Onlay)