Occlusal Plane Truth About HIP and the Fox Plane Mounting Techniques

by Clayton A. Chan, D.D.S.
Director and Founder of Occlusion Connections and trained laboratory technician (Dental Technology Institute, Orange, CA)

Key Point: Cosmetic dentistry crown failures can be associated with how the maxillary cast is mounted. HIP mount. Modified Fox Plane Mount.

Few are willing to tell the truth.  Not until doctors begin to mount their own models/cases will they discover for themselves what is the truth of HIP teachings and the truth of the modified Fox Plane.  In the mean time it is easier, simpler and convenient for them to accept what they believe is true since most don’t have time to do their own lab work or investigate on their own.  I investigated and discovered the truth.


Note: Porcelain Empress crowns commonly break and fail due to abnormal HIP mounting techniques.  The Modified Fox Plane according to Chan’s protocol aligns the maxillary to better coordinate with the cervical neck and masticatory muscle dynamics, thus reducing breakage.

Stability of the cranio-mandibular  occlusal relationship is based on the quality of the isotonic muscle dynamics between the cervical neck and upper trapezius, sternocleidomastoid/scalenes, anterior temporalis anterior, masseter, medial and lateral pterygoids and suprahyoid and digastic muscles.  Occlusion plays a significant role between all these muscles, but is only subservient when comes to restorative porcelain cosmetic dentistry.  It is true that occlusion is a major player and dominates over the accommodating muscles and joints.   There comes a time when the habitual worn down dentition is no longer tolerated and signs and symptoms become prominent on ones life, e.g., TMD, crano facial pain symptoms.  At this stage, muscles seek a neutral homeostatic relationship between the teeth/occlusion, joints and muscles.  Finding the corrected balance between the occlusion and muscles is key if the esthetic restorative dentistry is desired,  re-establishing cosmetic harmony and neuromuscular dental health.

All astute cosmetic lab technicians and corporate laboratories recognize that natures orientation of the maxillary cast is angled between 6-14 degrees (C.A. Chan 2007).  Teachings still exists within the TMD and cosmetic restorative dentistry communities perpetuating the false notion that the hamular notch incisive papilla (HIP) mounting technique is a simple and correct means for dentist and technicians to mount the maxillary cast for diagnosis and treatment.  Studies and experience has shown that the classic HIP mount produces a distorted and false orientation (57.6% flat to upward occlusal plane tilt) which is not anatomically correct when the head is level and balanced relative to the horizon. By implementing this technique it perpetuates the masticatory muscles are forced to proprioceptive react and will naturally cause the cervical neck muscles and head to respond by tilting the head slightly upward with a corresponding posteriorizing response by the mandible. This does not support physiologic balance of the occlusion, thus leading the occlusal system to unwanted occlusal strains (e.g., tooth sensitivity, toothaches, unwanted root canals, crown breakages, muscle fatigue).  Because of this distortion, technicians will often use their artistic discretion to mount  the maxillary cast model by eye rather than using the HIP mounting technique prescribed by the dentist and re-orient the cast to overcome this obvious distortion, especially when doctors request their patient casts to be mounted to the HIP mount.  Because technicians realize the HIP is not accurate, symmetry bites and a frontal smiling photograph are requested and required to give the technician extra information to correct the problems seen with the HIP mounting technique. Dentist are informed correctly and politically by their lab that the HIP mounting, symmetry bites and photographic information supplied by the cosmetic minded dentist will be evaluated and the lab will choose what records they will use to mount their cases. Inevitably the HIP mount will be ignored and the frontal facial smile photos and or any symmetry may be used to mount the case if found helpful. This shouldn’t be! Lab technicians should receive from their dentist accurate mounting recordings to specifically guide the technician as to how best to mount the maxillary casts without the lab technician jury rigging the mounts according to what the artistically perceive it correct. The fact that this has been going on for over 11 years is an indication that HIP has failed and is not working!


Note: Technicians know that this is not how nature intended the maxillary cast to be mounted. They also know by experience if they wax and finish the case to this mount it will lead to a very tooth looking smile. The case will have to be redone and corrected according to the eye of the technician. This is not what any patient or doctor really desires.


Note: HIP mount produces a toothier looking smile due to the flatter more visible second bicuspid and first mesial buccal cusp of the first molar region.

WHY I AM THE ONLY ONE to tell doctors the truth about how the occlusal plane is really oriented:

Lab technicians who have come to study and learn our teachings about the modified Fox Plane mounting have recognized our methods make the most sense and are practically implemented into their labs behind the scenes.  No lab has ever said what we are teaching and advocating is wrong.  If they have, they are speaking political talk and are not telling the dentist the truth.  The fact of the matter is that they know what we have taught works and makes logical sense than the HIP concept, especially for those who understand cranio-mandibular posture, orthopedics, TMD, cosmetic restorative dentistry and orthodontics.

  • Abnormal muscle forces induce abnormal occlusal forces and contribute to porcelain (restorative) crown fracturing and breakage.  When the restorative dentistry is designed to a flat maxillary occlusal plane (HIP) restorations fatigue and break due to skews and strains of abnormal vector of forces between the cervical neck, shoulders and abnormal upward head posture that is induced to cause forces on crowns and the surrounding periodontal structures in the mouth.  Read more on Full mouth reconstruction
  • The facts and science supports Occlusion Connections™ (OC) teachings regarding  our modified Fox Plane teachings.
  • Few corporate big labs are willing to share the actual facts and truths as to how they really mount the maxillary casts for their doctors because if they do they are worried that it will rock the political boat and relationships they have with major speakers who continue to teach these concepts that are not scientifically proven.  If the associated labs speak the truth they will be reprimanded for speaking the actual plaster bench mounting lab realities.
  • Labs really don’t believe HIP (hamular notch-incisive papilla) is correct nor physiologic.  They may tell the doctors they do, but in reality they know behind the scenes that their lab does not finish the final full mouth arch cases to classic HIP mounting.
  • If labs technicians speak out and tell the truth,  they are fearful they will lose their jobs.
  • Lab technicians realize HIP is not cosmetically correct, so they quietly and behind the scene change the pitch of the maxillary cast without telling the doctors when mounting arch esthetic cases in order that the case can be successful.  This has been going on for years.  Labs don’t like to redo the laboratory work, neither do they like to be blamed for the failures.  The reality of the matter is that most cosmetics dentist who endorse the HIP cosmetic are miserably unschooled and lack laboratory savy and understanding of the abnormal postural dynamics that effect the patient who is the recipient of these kind of misleading teachings and concepts.
  • If corporate labs expose the truths of HIP to their cosmetic dental clients they know they will be reprimanded for not speaking the party line by those in charge of teaching the HIP concept.
  • Corporate and small lab technicians are willing to put up with with the status quo and are willing to perpetuate the doctor confusion and teachings since they know that most dentist are lazy and will not check the final porcelain crown mountings as to verify how the maxillary restoration casts was actually mounted (HIP mounted or angled mounted).
  • Labs don’t really care about what occlusal mounting philosophy is taught, because they know from their experience they are going to mount the maxillary cast and fabricated the final restorations in a manner that visually makes sense to them regardless of what method is taught to the doctors.  What makes sense to them is  what I have been advocating for years and they all know it.
  • All labs know that the HIP concept is not correct and doesn’t make sense.  Rather than argue with doctors who were taught and brainwashed to believe it is correct they go ahead and wax up the full mouth case to HIP to satisfy the novice doctor initial inspection/prescription,  but in the final fabrication of the crowns they secretly and quietly change the mount to the modified Fox Plane mounting angle to improve the smile profile and esthetics without informing the cosmetic dentist.
  • Lab technicians when asked if they mount these cases to HIP will give the impression to the unlearned doctor that they do, but in reality they don’t because they know from  experience that it has been  proven to be unesthetic and and the case is doomed to fail.
  • Dentist don’t really care and or worry about whether  the case is mounted via the HIP or Fox Plane mounting when they see how beautiful the smile line appears and the cosmetics, until something dramatically bad happens, such as numerous crowns breaking and failing on a single case when the case is mounted to HIP.
  • Dentist do not routinely check the laboratory mountings of their  cases – they only worry if the  porcelain fits in the mouth and is the right shade and shape to meet the needs  of their patient.
  • Conscientious lab technicians have come to me time and time again to tell me these truths and facts from all around North America.  They are the unspoken hero’s in the cosmetic dentistry arena.  Doctors often take the credit for the beautiful smiles that the lab technicians actually created.


Note: Cephalomatric tracing showing an angled occlusal plane relative to horizontal level. Also, shown is the correlating cranio-odontoid angle relative to the cranial base and cervical spine. Left cephalometric tracing is based on the classic HIP mounting. Right cephalometric tracing is based on the modified Chan Fox Plane technique.

Am I really the only one to share these obvious truths?

Many technicians share the views, perspectives and beliefs I have shared with you on this website blog.  More and more dentist are recognize the ease and simplicity of taking the modified Fox Plane recording.  Dentist have validated it’s clinical usefulness and common sense approach that has been missing in the dental profession about this matter of establishing a proper occlusal plane of restorative reconstruction procedures.  It just makes sense!

Scientific dental literature proves that the HIP concept is not correct (false premise that the occlusal plane is level, parallel to a horizontal level).  Here is just one simple example that a recent dentist shared with me regarding Occlusal angle influences smile attractiveness: http://www.drbicuspid.com/index.aspx?Sec=sup&Sub=cos&Pag=dis&ItemId=308768&

I have written and extensive scientific article: Chan, CA: A Review of the Clinical Significance of the Occlusal Plane: Its Variation and Effect on Head Posture: Optimizing the Neuromuscular Trajectory – a Key to Stabilizing the Occlusal-Cervical Posture.  International College of Craniomandibular Orthopedics (ICCMO) Anthology VIII, 2007.

Other Related Articles written by Dr. Clayton Chan:

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

The Leader in Neuromuscular Dentistry