HIP (Hamular Notch Incisive Papilla) MOUNTING: IMPORTANT POINTS TO RECONSIDER

By Clayton A. Chan, DDS

The mandibular and cervical head mechanism PROPRIOCEPTIVELY responds to subtle occluding contacts (distal facing or mesial facing) of the teeth. The occlusal plane and its orientation to the cervical neck and base of the skull also proprioceptively responds to each individual occlusal form and incline plane in total as well as how the occlusal plane is designed in an attempt to seek a balance of forces between the teeth, joints and musculature of the temporalis, masseters and even more so with the suprahyoid/digastricus and the semispinius cervicalis, capitus, trapezius, scalene, levator scapula muscles. Teeth and the occlusal plane do not function independently from the supporting musculature.

Classic HIP mount with fence post and incive pin.

Many technicians still don’t get it, thinking that it doesn’t matter if the doctor Rx/presribes a case for HIP or Fox plane mounting, because they believe they are artists and can customize any occlusal plane to any orientation of the maxillary case with a curve of Spee and make it look esthetic. That may seemly be true superficially, but they fail to realize the clinical outcomes dentist may or may not be aware of. Here are just a few important factors:

1) They fail to recognize that when asked to exccentuate the curve of Spee with the HIP mount that they are just excentuating the negative proprioceptive responses of the mandible to function posteriorly off the neuromuscular trajectory. As the maxillary posterior first and second molar occlusal tables begin to tip posteriorly they begin to act as distalizing forces to the opposing mesially facing lower occlusal tables of the opposing dentition.

2) When building the case to HIP, the lab technicians all admit that the upper posterior crowns are shorter with longer looking lower posterior crowns. This is not just against golden proproptional crown to root ratio principles, but further contributes to abnormal vector of musculo-occlusal forces (abnormal form leads to abnormal function) since the occlusal plane tends to be flatter and does effectively support an isotonic perpendicular closure path of the mandible to support a normalized head posture, thus…

3) A relapse of the closing path will naturally occur over time posterior of an optimized NM trajectory with an accompanying upward head tilt tendency further confirming a level occlusal plane with accompanying relapse of musculo-occlusal signs and symptoms (UNRESOLVED)!

The laboratory technicians all know the truth about the mounting problems and occlusal plane design problems they have with HIP! They admit that it produces odd crown length ratios for years. But may not realize the impact it has on the patients subtle proprioceptive responses to the musculature of the mandible and head and neck posture.

Since they fail to openly admit this to doctors they knowingly and or unknowingly contribute to confusion to the learning dentist, thus confusion in the ranks of our dental profession.

Every doctor has choices and will chose what is best for themselves as well as for their patients. I can only share what I am aware of. Perhaps it may make a difference to some.

Time is a real tester of concepts and principles. It is unrelenting and the TRUTH WILL PREVAIL. You don’t have to take my word for it. Your patients will let you know and the evidence will become obvious in time. It’s a matter of one’s awareness.

For further reading see: Fox Plane and HIP Mounting Considerations Blog

Neuromuscular Dentistry

Skull Orientation, Fox Plane vs. HIP Occlusal Plane Relationships

by Clayton A. Chan, DDS

When considering the “HORIZONTAL GAZE” for each of these skulls one will note that picture “A” skull could have the head tipped slightly more downward to improve a level eye gaze which would increase the occlusal plane angle relative to the horizontal table approaching what I would consider a better more anatomical relationship.

The pictures of the 2 skulls with both physiologic and pathologic head postures will go a long way to clarify the issues of the relevance of the Optimized use of the Fox Plane vs. the HIP mount.

Seeing the bigger picture and correlating these key principles to earths gravitational forces and cervical muscular balance works best and compliments the clinician's cosmetic treatment when a clear and balanced understanding of these foundational occlusal plane concepts are presented in an unbiased manner.

We cover the clinical and laboratory aspects more extensively in our Level 6 Occlusion Connections training.  I hope many of you would consider coming to our OC courses to learn "why and what I do" to help my esthetic/TMD cases.  It is impossible to convey all these great concepts in just a short posting.

To discover the latest and most up to date information on GNEUROMUSCULAR Dentistry and the latest in Dental Continuing Education CLICK:

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http://www.occlusionconnections.com/

Neuromuscular Dentistry

Fox Plane and HIP Plane Mounting Considerations

by Clayton A. Chan,  DDS

The leveling of the maxilla, the managing of the maxilla relative to a proper oriented head and cervical neck, and the concern of a proper occlusal plane are steps toward idealizing the finishing of the restorative case in a phase II treatment.  Leveling of the maxillary plane relates to both function and esthetics.

© 2009 Clayton A. Chan, DDS. All Rights Reserved.

Red dots = HIP reference line. Depending on how the clinician and technician chooses to mount the maxillary cast (classic HIP with fence post and Incisive pin (level) or Modified Fox Plane (angled)) will affect how much tooth reduction is necessary to accommodate the same curve of Spee.

Managing the GAP on an optimized trajectory regardless of cants and roller coaster occlusal planes either on the upper or lower arches using an orthotic based on a HIP or Fox plane technique is of little significance in phase I treatment. All that is basically required to assist in bringing normalacy to the dysfunctional head and neck system is the agreed upon physiologic GAP that is established on a proper trajectory. A lower orthotic placed between two distorted and skewed arches certainly fills in the missing components of occlusion to help relate the upper and lower arches together and with good anatomical occlusion has shown to help in maintaining the neuromuscular myo-trajectory, improving head levelness (from pathologic upward tilt to a physiologic leveled head tilt).

Many clinicians have observed these head re-orienting responses with their patients regardless of Fox Plane or HIP techniques, because the Fox and or HIP does not come into play during the Phase I stabilization phase. It becomes a factor when moving into the Phase II level of esthetic restorative finishing of the case as it relates to crown root ratios and smile lines. If the lab “truthfully and honestly” managed and maintained the classic HIP mounting position from start to finish of the case, the dentist will routinely see shorter upper posterior crowns and longer lower posterior crowns. This is not anatomically correct. This will often cause the labs to cheat the upper crown fabrication, by reorienting the maxillary cast, since the upper posterior preps will not have sufficient occlusal reduction (based on this mount) especially in the second molar regions. Because of this lack of occlusal prep height reduction the lab is forced to remount and alter the cast from the original HIP mount to accommodate the lack of occlusal height reduction. (This is what the labs don’t tell the dentist!) The lower crowns will show, routinely, a longer (higher) crown (crown root ratio) and does not reflect proper golden proportional relationships. We strive for golden proportioned anteriors (tooth width ratios and gingiva to gingiva relationships), yet the posterior uppers and posterior lowers are distorted in crown lengths ratios (a failure of the classic HIP concept!) and not evenly balanced in their upper to lower posterior crown lengths (another failure).

With the Fox plane technique the crown to root ratios in the upper and lower posterior regions are more proportional and reflect a better even distribution of crown to root ratios of both upper and lower posteriors (closer to golden proportions) due to a proper maxillary cast orientation due to a proper occlusal plane set up (see picture above).

Consider the same curve of Spee used in both situation.  Different crown root ratios of upper and lower teeth will result depending on which method is used to mount the maxilla.

 If you choose HIP, make sure you reduce the prep sufficiently so the lab doesn’t have to alter the maxillary mounting occlusally! Don’t be surprised if the lower posterior crowns look longer, the upper posterior crowns shorter and the upper first molar to second bicuspid region looks a bit more toothier.

If the HIP is the method of choice in Phase II restorative, make sure the lab doesn’t alter your mount during the finishing of the case. Over the years they all tend to cheat this step and don’t tell dentist that they altered the mount to accommodate the occlusal plane. The clinician can always confirm the HIP mount by telling the lab that you will be checking the maxillary prepped cast with the finalized porcelain crowns on the prep dies in place at the HIP mount referenced to the table before crowns delivery! Make sure they don’t change or alter the HIP mount if you chose to do so!

The dividing of the crown ratios between the upper and lowers (as seen in the diagram above) will vary depending on the maxillary cast orientation technique. Doctors and technicians have choices! We all need to understand these concepts thoroughly to make the proper choices for our patients.

For more information read Fox Plane Mount, Occlusal Plane

Neuromuscular Dentistry