Which plane is referred to when checking for incisal alignment in horizontal occlusion?

The correct choice focuses on the relationship between the occlusal plane and the alignment of the incisors in horizontal occlusion. The occlusal plane is crucial because it is the plane formed by the biting surface of the teeth, particularly the posterior teeth, which helps in assessing how the upper and lower incisors align when the mouth is closed.

In horizontal occlusion, evaluating incisal alignment involves ensuring that the incisal edges of the upper and lower front teeth are appropriately aligned with respect to the occlusal plane. This plane allows clinicians to determine if the incisors are positioned correctly in relation to one another and to the overall dental arch. Proper alignment is essential for both functional biting and aesthetic outcomes.

The other planes mentioned, while important in dental assessments, do not specifically address the incisal alignment in the same way that the occlusal plane does. The palatal plane, for instance, is related to the maxillary arch, and the facial plane is more associated with the overall facial profile. The mandibular plane, which relates to the position and orientation of the mandible, is not primarily concerned with incisors. Therefore, the occlusal plane is the reference plane that is directly relevant for checking incisal alignment.