Final answer:
The maxillary occlusal rim is aligned parallel to the interpupillary line to ensure the dentures are aesthetically correct and function well.
Step-by-step explanation:
When establishing the plane of orientation, the occlusal portion of the maxillary occlusal rim is parallel to the interpupillary line. This line is drawn between the pupils of the eyes when the patient is looking straight forward and is used to ensure that the dentures will be aesthetically aligned with the eyes and face. The interpupillary line is significant as it helps orient the dental prosthesis in such a way to maintain a natural appearance and proper function.
When establishing the plane of orientation, the occlusal portion of the maxillary occlusal rim is parallel to the Frankfort plane. The Frankfort plane is an anatomical reference plane that connects the external auditory meatus (ear canal) to the infraorbital rim (the bottom of the eye socket). It is commonly used in dentistry and orthodontics to establish a reference point for the orientation of the occlusal plane.