Anatomical Lower Or-tho'sis

by Clayton A. Chan, D.D.S.

The Science of Aligning Body Parts to Improve Function
"Pl. ortho'ses [Gr. orthosis making straight] an orthopedic appliance or apparatus used to support, align, prevent, or correct deformities or to improve the function of movable parts of the body." - Dorlands Medical Dictionary, 26th Edition.

This is what my Anatomical Lower Orthois looks like for most of my patient's. It is made from a 2.5 mm bisacryl clear shim base formed over a lower cast. It is then overlayed with a lab processed orthodontic acrylic and later hand carved anatomically to match the patient's occlusion. I usually do this myself. Fabrication Time: Approximately 4 hours.

Webster's dictionary defines a Splint as a "material or device used to protect and immobilize a body part". Masticatory muscle proprioception requires the most exquisite repositioning of any body part if optimal rest and function is to be achieved. Splinting implies an immobilization which is exactly opposite of the desired criteria for physiologic occlusion. A law of muscle physiology is that any obstacle to muscle action initiates excitement of muscle.

I am a firm believer of orthosis therapy, especially for any patient experiencing joint derrangement, masticatory muscle dysfunction and or pain. Most TMD pain comes from muscles that are restricted. A lower removable anatomically orthosis allows for freedom of entry to and from the established terminal contact position (myocentric) where the internal and external muscles of the jaw have freedom to move as well as rest properly. The anatomical lower orthosis specifically supports optimal disc and condylar positioning within the glenoid fossa, acknowledging the unwanted clicking and popping symptoms.

Indications for an Orthosis
Indications for an orthosis are many and are varied. "A fixed reconstruction is in a true sense a permanent orthosis." - Jankelson, R. In this blog, an orthosis is refered to as a lower anatomical removable appliance used to align and support the mandible in an occlusal position that sustains relaxed musculature and optimal function.

1. Provisional deconditioning of the TMD/TMJ/MSD symptomology of the patient. Deprogramming the muscle engrams via low frequency Myomonitor TENS allows the establishing of physiologic rest to identify a starting point to reference the neuromuscular bite registration.
2. Provisionally repositions the patient's jaw to identify both the anterior vertical as well as the posterior vertical dimension. Additionally, a very important aspect which is often overlooked is the anteroposterior relationship of the lower jaw to the upper jaw to anticipate final reconstruction and facial esthetics. It is essential that the orthosis be worn to establish muscle comfort to begin a pain free testing period of 3 months off medications prior to any finalizing restorative therapy. CMS (Computerized Mandibular Scanning/Jaw Tracking) and EMG (Electromyography) documenting jaw functioning ability and muscle status are objectively measured to determine a suitable occlusal position after 4-6 months or longer to prove stability and comfort.
3. An orthosis can be used as an intermediate holding appliance during orthodontic/orthopedic treatment of dysfunctional patients needing definitive orthodontic care. The appliance in those cases can be used as the "ORTHOPEDIC MATRIX" to help guide the clinician to the finalized treatment position via modification of the orthosis and verticalization techniques to assist in periodontal, bone, ligament and tissue remodeling and development.
4. The orthosis can be used for those patients who teeter on borderline dysfunction and are on the edge of clinical symptomology. Some of those patient's may decide to wear the appliance on an "as need basis" since orthodontics and or complex restorative treatment may pose an economic or emotional impossibility. Some may be able to wear the appliance at night time only and go about their daily activities symptom free.
5. The orthosis can also be used as a nightguard to reducing clenching and bruxing. Noctural stresses can be greatly reduced by providing a neuromuscular position free of any interferences and noxious proprioception. True clenchers are poor, high risk candidates for fixed reconstruction rehabilitation or orthodontics unless the pelvis and sacro-iliac region is properly aligned to support an aligned cervical neck (Atlas C1) with a balanced occiput. Any imbalance in the postural system will contribute to unresolved clenching actions and abnormal forces.

The orthosis is designed to distribute even forces through out the mouth to give balance and support to the complete body to allow it to function and rest optimally. It can be worn 24/7 with proper home care.

My Personal View
The lower anatomical orthosis is my appliance of choice! It is the one appliance I use for all my TMD patients who exhibit masticatory dysfunction,pain and joint derrangement. I keep it very simple, yet sophisticated! I don't use night time appliances or day time appliances to confuse the patient. My patients wear only one appliance, no day or night time appliance, just like they don't have day time teeth and or night time wearing teeth. I design the orthosis so it does what it is suppose to do both antomically and functionally in the mouth. My patient's love it, having tried numerous kinds of appliances (uppers, lowers, soft, hard, anterior positions, anterior discluders, jigs, shims, flat plane, even some so called NM appliances, etc. etc. and etc.). Another KEY is finding the correct bite position!


The Clincians Responsibility
If the clinician understands how to properly design, adjust, modify and deliver the orthosis appliance properly, the patient should report that the lower removable anatomical "orthosis feels better in than out!" Patient's that cannot wear the appliance comfortably will naturally take it out and not resolve optimally. I do not believe the patient has to get use to something that does not feel right in their mouth. The clinician must take the proper time to make the orthosis feel right. 


There are simple things that can be done by the laboratory and the dentist to make the appliance feel totally comfortable....but that is for another blog posting.... see Orthotic Central.