What is the primary effect of an upward/anticlockwise rotation on the occlusal plane angle?

When considering the effects of an upward or anticlockwise rotation on the occlusal plane angle, the primary impact is a decrease in this angle. An upward rotation means that the posterior aspect of the occlusal plane is positioned higher relative to the anterior aspect. As a result, the angle formed between the occlusal plane and a reference plane, such as the Frankfort horizontal plane, decreases.

This reduction occurs because the posterior teeth are positioned higher, causing a tilting effect on the occlusal plane. Consequently, the overall orientation of the occlusal plane shifts downward, leading to the decrease in the occlusal plane angle. This is significant in orthodontic treatment planning or surgical cases, as it affects the overall dental and skeletal relationship.

In contrast, options indicating increased occlusal height or changes in the ANB angle or the mandibular plane angle represent different outcomes influenced by various factors, rather than directly relating to the primary effect of the upward or anticlockwise movement specifically on the occlusal plane angle.