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Evaluating the Cervical Spine and Head

By Clayton A. Chan, D.D.S.

The antero-posterior (AP) posture of the head in relation to the cervical spine can be determined by a vertical plumb line from head down to the dorsal portion of the thoracic spine. (Most restorative, orthodontic and TMD dentist don’t pay attention to this aspect of head posture). Garry has reported measuring the neck curvature using a plumb line to the deepest curvature of the posterior of the cervical neck region to determine the distance and degree of forward head posture.(1)   Optimal distance according to Racabado is 6 cm.(3, 4)

Racabado further defined normal cervical lordosis and normal craniovertebral relationships based on cephalometric measurements. A line that connects the posterior nasal spine to the basi-occiput is called the McGregor’s plane. The odontoid plane (OP) is a line that extends from apex to the anterior inferior angle of the odontoid process.  A normal measurement of the posterior-inferior angle at the intersection of McGregor’s plane and OP is 101 degrees +/- 5 degrees (96-106 degrees). A distance between the basi-occiput to the posterior arch of the atlas is 4-9 mm (less than 4 mm indicates cranio-vertebral compression).(3, 5)

For more information and details read more: Chan, C.A.: Evaluating the Cervical Spine and Head, page 15-19.

Finding the Occlusal Plane

Many clinicians abroad have determined and confirmed that the occlusal plane has a great influence on the functional articulation and esthetic aspects of stomatognathic system.  Clinicians have recognized that the occlusal plane should be at a right angle to the occlusal forces for stability of the occlusion, head and neck musculature; perpendicular to the long axis of occlusal forces produced by an optimal cervical posture and an optimized mandibular closing trajectory (path).  Many neuromuscular minded dentist have falsely been misled to believe that the occlusal plane is flat or parallel relative to horizontal level.  This is in fact a wrong teaching that defies natures bio-physiologic and anatomical design for health.

Note: Hand held diagnostic model casts oriented into a maximum intercuspal position is not sufficient to establish natures “true” occlusal plane orientation. Determining a physiologic dimensional relationship of the upper to lower model casts (vertical, antero-posterior, frontal, pitch, yaw and roll) is crucial if one desires to minimize mandibular to maxillary jaw torque during function. Reproducing nature’s occlusal plane orientation with the model casts using the Modified Fox Plane technique per Chan assists the dentist and lab to replicate what is in the patients mouth.  Read more: “Mounting the Diagnostic Case Using the Fox Plane”.

The inclination of the occlusal plane (IOP) is one of the key factors governing occlusal balance. (6)  Determination of inclination of the occlusal plane is an important step before construction of full arch restorative and full denture type cases. Evaluating and assessing the bilateral occlusal plane of the maxillary arch for symmetry, balance and form is desirable to meet the demands of function and appearance.  Anteroposterior IOP is typically determined with a device called the Fox occlusal plane, (7)  which is commonly positioned parallel to Camper’s plane or can be used to capture the occlusal plane slope by orienting the Fox plane (modified according to Chan) parallel to the horizontal level (the floor) and patient’s head positioned at level using bite recording material.(8)     Ear bows or face bows have been traditionally been used in the gnathologic arena to register the steepness and tilt of the occlusal plane using the auditory meatus, nasion and orbitale as reference points.

Note: Radiographic images of before restorative treatment, progress (stabilized mandible at optimized mandibular position) and after (finished restored occlusal plane at optimized mandibular position). All images were recorded with the patient’s head position (“unposed” purposely – not at Frankfurt plane) to determine how the mandibular occlusal positioning can effect the occlusal plane and head posture. Initial radiographic shows a flatter occlusal plane relative to horizontal level (red line), patient’s head is slightly tilted upward with neck strain. As the patient is stabilized with an improved gneuromuscular occlusal position the head and cervical/neck also changes orientation relative to horizontal level. Patient’s neck pain is resolved using a lower fixed bonded orthotic over the existing restorative dentistry.  Final imaging shows improved occlusal plane (angled relative to horizontal level.  Patient no longer complains of neck and shoulder pain. To read more about this case and  “What Angle is the Occlusal Plane Relative to Horizon”

Flat Maxillary Cast Mountings

Maxillary cast mounting and orientation is critical in phase II diagnosis and treatment.  Maxillary cast that are mounted in a manner that depicts a flat to upward slope anteriorly (e.g. classic HIP – hamular notch, incisive foramen, flat mount) often times will unknowingly build in pathologic vector of forces due to an abnormal occlusal plane orientation.

• This will lead to toothy looking smiles, especially in the second bicuspid molar region and will also result in vertically taller mandibular posterior clinical crowns.
• A curve of Spee is often compromised and minimal due to inadequate space between the desired occlusal plane and tooth preparation during laboratory waxing and crown fabrication.
• To compensate for this the clinician will need to be more aggressive in maxillary posterior occlusal prep reduction which can lead to pulpal infringement and endodontic therapy.
• Skewed crown to root ratio in both the upper and lower arches will be present making arch and crown form lacking in natures anatomic proportions.

Downward Sloping Maxillary Cast Mounting

Maxillary cast mountings that show a natural downward sloping occlusal plane incline (e.g. modified Fox plane level mount according to C. A. Chan) allows for balanced vector of muscular and occlusal forces due to a more physiologic plane orientation that matches an optimized cervical, head and craniomandibular posture.

• Softer natural smile line leads to a more pleasing esthetic smile.
• Less posterior occlusal prep reduction in either maxillary or mandibular arches is required.
• Easy to develop a curve of Spee.
• Crown to root ratio tends to be closer to natures golden proportions.

References:

1. Garry, JF: Upper Airway Compromise and Musculo-skeletal Dysfunction of the Head and Neck (MSD), 1977.
2. Yee, D: Weight of the human head.  Department of Anatomy and Histology, University of Sydney, Australia. danny.oz.au/anthropology/notes/human-head-weight.html. December 13, 2006.
3. Tilley, L and Hickman, DM: TMD-An Upper Quarter Condition. Anthology of ICCMO. Vol. V. 1995.
4. Racabado, M: Physical Therapy and Dentistry: An Overview, J of Craniomandibular Practice, 1982; Vol. 1, pp46-49.
5. Racabado M: Dentistry I. Racabado Institute for Carniomandibular and Vertebral Therapeutics, Atlanta: Institute of Graduate Health Sciences, 1984.
6. Ogawa T, et al.:  Inclination of the occlusal plane and occlusal guidance as contributing factors in mastication. J Dent. 1998 Nov;26(8):641-7.
7. Trubyte (Fox) Occlusal Plane Plate: Dentsply International, Trubyte, Occlusal Fox Plane Item #92232, (800) 877-0020.
8. Chan, CA: Architecting the Occlusal Plane. Aurum Ceramic Continuum. Vol. 10, Issue 2, May 2006.

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

Neuromuscular Dentistry

Filed under: Diagnosis and Neuromuscular Treatment, Fox Occlusal Plane, Full Mouth Reconstruction, HIP Plane, Neuromuscular Dentistry, Occlusion, Optimized Bite™, Posture by Clayton A. Chan, D.D.S.
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by Clayton A. Chan,  D.D.S., M.I.C.C.M.O.

There are 4 main categories of dysfunctional mal occlusions that requires special attention when designing and managing the lower removable orthosis in the treatment of the TMD suffering patient.

The correction of malformations of the jaws and skeletal structures involving the masticatory system is especially important when attempting to preserve as well as restore optimal function of the skeletal system, its articulations and associated structures, including the trigeminal system.  Clinicians who treat these 4 main problematic types must recognize in the diagnostic phases what structural, biochemical and emotional factors are involved to effectively treat and resolve the various musculoskeletal occlusal symptoms.

Micro occlusal management of the orthosis (orthopedic jaw realignment device) and training is required of the TMJ dentist at the highest levels to properly address the proprioceptive occlusal signaling and communication that occurs with the TMD patient who experiences various levels of occlusal awareness and at the same time present with cervical dysfunction, TMJ primary disorders, Class II Division 2 dental mal alignments and or Anterior open bite problems.

Resolving any one of these or a combination of these problems can challenged the TMJ treating clinician if they are not familiar with sound protocols.  The following is a general guide as to what work up and protocols may be necessary in addressing the needs of the dysfunctional TMJ/TMD patient.

Optimized Bite
When I mention “Apply gnathological principles when managing the Optimized bite” I am referring to the detailed proprioceptive mechanics that the trained dentist must pay attention to during all jaw movements.  Based on a sound Optimized Bite position (GNM) which can only be best achieved with jaw tracking technology and TENS combined gives the  best results.  Using just the Myomonitor TENS alone is not sufficient even in the best of trained clinicians since visual observations alone can not obtain consistency in precision and objective reliablity when attempting to establish a starting lower to upper jaw relationship.  This is crucial if success is desired.

Additional adjunctive support maybe required within the medical and dental community to obtain a successful resolution. Establishing an Optimal physiologic mandibular position is critical to TMJ therapy. Micro occlusal management is of key importance of the TMJ pain patient is going to experience a calming of the muscles since it is clearly recognized within the TMD community that occlusion can effect the masticatory muscles responses either positively or negatively.

When there are are subtle occlusal imbalances in the bite which can contribute to jaw torque, the muscles of the jaw, head, neck and shoulders can strain and cause severe pain, further disrupting the central nervous system.

Read more: Four Types  of Neuromuscular Dysfunctional TMJ Challenges

Neuromuscular Dentistry

Filed under: Diagnosis and Neuromuscular Treatment, Neuromuscular Dentistry, Neuromuscular Education and Training, Occlusion, TENS by Clayton A. Chan, D.D.S.
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by Clayton A. Chan, DDS, Las Vegas, NV

Aesthetic Orthopedic Rehabilitation  .  Craniomandibular-facial Pain Dentistry  .  International Dentistry

Today, the cosmetic dentistry and beauty industry has over the years increased the publics awareness of beautiful smiles.  Who doesn’t want to have a great smile?  Brighter and whiter looking teeth to enhance and change the yellowish, worn down look of chipped front teeth, crooked teeth, oversized teeth, dark undesirable spaces that can be distractors from achieving the look, appearance and sense of confidence that may be necessary for an improved self esteem or the extra dental boost to move up into the ranks of a higher paying job perhaps because of a better looking smile?  Beware!

Altering one’s look may seemingly be appealing through dental marketing and cosmetic dental ads.  Cosmetic dentistry could be simple for some, but it may not be that easy for others.  Those individuals that may seemingly have a good bite and desire to improve the appearance of their teeth just a tad more to perfection may find themselves going down a nightmarish path of pain, frustration and despare.  Be cautious, because if you are one of those patients who has had previous retractive orthodontics, feels bite changes after having your teeth cleaned and polished and you have the ability to feel the thinnest of a human air between your teeth (5 microns), you may be just one of those individuals that requires a high level of dental accuracy when you need any dentistry done on your teeth or bite.

If you have a bite that already is not stable, you have a history of previous tooth sensitivity issues,  missing teeth (especially in the bicuspid and molar regions), you have a restricted narrow arch form with minimal overject and over lap of your front teeth….get ready.  If  your dentist doesn’t realize the detailed importance of how your teeth must function and how they must smoothly glide and move across one another free of any interferences when chewing or grinding your teeth after they have been lengthed to improve the short and worn down loo…..that is where your TMJ and temporomandibular joint dysfunction (TMD) troubles and pain can begin.

Words of Wisdom

• Make sure your cosmetic dentist understands what TMJ is all about and has the ability to treat it bio-physiologically if problems arise.
• Make sure your dentist has experience in treating TMD pain problems after he/she performs your cosmetic dentistry restorative treatment with veneers, porcelain restorations, implants and fillings.  (Dentist who are attempting to perform comprehensive levels of cosmetic arch dentistry must be trained and understand a higher level of occlusion and neuromuscular dentistry than those who are trained in habitual bite dentistry.
• If you find yourself to be a detailed person and can feel a human hair between your two front teeth, make sure your dentist is as equally detailed and aware of your level of detail.  Ask your dentist what level of thin marking paper he/she uses when checking the patient’s bite.  Some dentist use 100 micron, 80 micron, 60 micron articulating paper.  That may not be adequate for you if you are a 5-10 micron detailed aware patient.  Reason: If your dentist checks your bite with thicker marking paper, everything will look like it is marking correctly when bringing the teeth together when in reality you need to have a finer marking paper of possibly 10-13 microns to identify the detailed prematurities left when placing a new filling or new crown.
• Do not let your dentist convince you after dental treatment that you are suppose to get use to your new bite when they have given you new filling(s) and crown(s).  If your bite feels different and off, it most  likely is off and not correct.  Don’t let it go!  If you procrastinate and think that the high marbly feeling in your bite is going to go away and you find that it doesn’t it will continue to cause the tooth or teeth to become pressure sensitive, sweet sensitive, mobile, ache and in some cases a combination of all of the above.  If the tooth becomes achy sometimes the dentist will prescribe a root canal.  That could have been avoided if the bite was properly managed and check in a detailed manner.
• If you came to the dental visit with no bite problems that you were  aware of then you should leave the dental office with no bite problems….unless you had an unstable and uneven bite from the start.  If so, your dentist should have recognized it and you should inform your dentist that you have a bite problem.  The problem is most individuals and dentist don’t  even know the various occlusal signs and symptoms to look out for to avoid the dental mishaps that can contribute to TMJ problems after routine dentistry is performed.  You don’t have to be hurting to have occlusal signs and symptoms.
• Ask your dentist to check your bite in a sitting up supine positon before you start any dental treatment that requires any alteration to your biting surfaces of  your teeth, fillings and crowns.
• Ask your dentist to complete a proper TMJ muscle palpation examination.  Tender muscles of the head, face, lower jaw, neck  and shoulders are often related to an imbalanced bite.
• Make sure your dentist understand how strained muscles are a result of occlusal prematurities in the bite.
• A few follow up visits will be necessary to refine any occlusal biting imbalances after restorative dentistry.  If you have to return numerous times over and over again, something is wrong!  Either your muscles, jaw joints and/or your bite is a very unstable making it challenging for you andyour dentist resolve your problem.  Make sure your dentist is a detailed operator, especially if you discover that you are a demanding, high level precision type of person.

Neuromuscular Dentistry

Filed under: Bite Optimization, Cosmetic Dentistry, Fox Occlusal Plane, Full Mouth Reconstruction, HIP Plane, Neuromuscular Dentistry, Neuromuscular Education and Training, Occlusion, Porcelain crowns, Posture, TENS, Veneers by Clayton A. Chan, D.D.S.
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