The Occlusal Plane: Why HIP Mounting Misleads Dentists

Why the Occlusal Plane Matters in GNM Dentistry — and Why Most Dentists Get It Wrong

Originally published 2009 · Last updated May 2026

The occlusal plane is not just an aesthetic reference — it is a foundational determinant of how the entire masticatory system functions. Getting it right requires both gnathologic principles and objective physiologic measurement.

Determining the correct orientation of the occlusal plane has been a topic of interest amongst restorative-minded dentists.

Two skull mountings on Acculiner table comparing physiologic occlusal plane (Example A, angled HIP) versus pathologic upward-tilted HIP-mounted orientation (Example B) — Dr. Clayton Chan, Occlusion Connections

Bony Landmark References — The HIP Method

Some clinicians have advocated the use of boney landmarks in the maxillary arch as reference points in establishing a correct maxillary arch orientation relative to horizontal level. The two hamular (H) notches and incisive papilla (IP) have been used as a tripoded reference using equal height posts and “fence posts” as a means to mount the maxillary dental case.

Comparing the Two Mounting Examples

As one can see in example B above, the skull base has been accurately referenced to the “HIP” reference marks on the Acculiner mounting table according to instructions. It is evident that the skull is oriented in an upward head tilted orientation. This is not physiologic, but rather would represent a strained and abnormal head posture resulting in the maxillary occlusal plane being incorrectly oriented.

Example A demonstrates a more physiologic skull orientation where the HIP references would actually be angled downward (posterior to anterior) and parallel to the maxillary occlusal plane. The maxillary occlusal plane is angled relative to the horizontal level mounting table. Lateral cephalograms repeatedly confirm this observation when the patient is unposed and presents with no abnormal muscle strain in the masticatory regions, neck and shoulders.