By Anthony Deluke, DDS, Specialist in Orthodontics
Patients and parents today expect orthodontic professionals to review their needs more comprehensively than ever before and deliver care addressing the entire spectrum of oral-facial function. Our responsibilities and task lists have therefore grown: Treatment must integrate cone beam imaging research, staging, and collaboration along with targeted biomechanical choices for comprehensive skeletal, dental and muscular improvement with normalized airway, speech and masticatory functions. The resulting comprehensive approach is what we now know as functional matrix-focused orthodontics.
More than 50 years ago in 1962, Dr. Melvin Moss articulately postulated the functional matrix theory as an explanation beyond simple genetics for growth and the etiology of dysfunction in the oral-facial complex. Today, adult patients and the parents of young patients likely have never heard of the functional matrix, but their knowledge of treatment options and the varied approaches to orthodontic care has increased dramatically due to information available on the internet. Patients desire esthetic improvement, as always, but they also expect improved or corrected total orofacial function.
Artificial intelligence is likely to continue and accelerate the trend toward increased dental knowledge among patients and their parents. Practitioners must therefore understand recent changes in treatment plans with consistent respect for the functional matrix.
Moving to the Matrix
Traditional orthodontic care largely prioritized occlusion and cosmetic goals. Practitioners saw their task as “fixing crowded teeth, improving occlusion and making better smiles.” Malocclusion was largely viewed as primarily genetic in etiology. In this regard, facial-bone growth was viewed as immutable and predetermined by a patient’s genetic blueprint. Most orthodontic care was considered “camouflage therapy” to cover up the underlying skeletal dysplasia. The primary exceptions included a first phase of orthodontic care attempting to improve or at least mitigate the effects of abnormal growth, followed by patients planning for orthognathic surgery.
Airway-focused orthodontics moves us partly into functional matrix-based treatment. Treatment plans have changed along with a growing acceptance among dental professionals of the concept that “form follows function,” which serves as a brief definition of the functional matrix hypothesis.
The interest in and clinical understanding of the causative basis for malocclusion is correctly shifting away from genetics to a disturbed myofunctional environment. The modern perspective demands a shift to include comprehensive evaluation of the functional matrix. The frequent and common problem of relapse from traditional orthodontic care, as well as common temporo-mandibular joint and airway problems, decreases as a result.
A specific, singular treatment focus can be on the airway. Patients likely benefit from their care providers simply considering occlusion and esthetics, but we would again be failing if we did not examine the rest of the functional matrix, both during the initial diagnosis and treatment planning and during treatment, where progress records and clinical findings must be examined to be certain the elements of the functional matrix are improving rather than worsening. The additional perspective gained by prioritizing research and the latest clinical case reports on improving the airway can change many aspects of care, including treatment timing, referrals, staging and appliance selection. Providers may need to prioritize different goals and include surgical, restorative and myofunctional therapy stages in their comprehensive treatment plans.
Simulation Vs. Reality
The change in perspective orthodontic practitioners must embrace will require considerable and persistent effort in this specialty area of dentistry, as well as all of dentistry. The time has come for functional matrix-focused comprehensive dental treatment planning.
In dental school, students are conditioned early by a focus on restorative care. The field adopted a “chief complaint” and “problem-focused philosophy” from the medical education model: Replace or repair the broken tooth, eliminate infection and halt or reverse periodontal disease. Today, patients’ expectations are that care providers will improve their healthy lifespan, rather than simply fix singular, acute dental problems. Practitioners must remain aware of and incorporate the different perspectives gained from focusing on the functional matrix. Treatment planning in modern orthodontics requires continuously examining every change we plan. It is not enough to focus on the obvious clinical or imaging change; we must focus on the impact the change is likely to have on the functional matrix. Using the newest and evolving digital tools can help us collaborate as teams, sharing opportunities to plan and execute complex care.
The ease with which we can visualize simulated orthodontic treatment in three-dimensional images and the fact that we can so easily make changes to a simulation is an example. The ability of all parties to immediately share, store and discuss cases can improve care delivery, but it can also lead to complacency. Patients do not always respond in the ways we see in simulations, and our treatment planning should never be reduced to thinking, “the simulation looks good, so we can print aligners and start treatment.” Commercial interests may promote the easy, fast and visible results obtained by their products, but multiple obstacles can stop us from achieving the ideal simulated results.
Learning from the examination of relapse, for example, is critical. Relapse is a reliable indicator of a disturbed functional matrix. We must respond to relapse in our patients’ dental history by determining the abnormal forces in the myofunctional, orofacial environment and planning for their resolution and/or modified retention.
Observing abnormally slow orthodontic movement of the teeth during treatment offers another, similar clue. Again, it is usually the case that the functional matrix is imbalanced. Aligners have been found to reduce open bites with greater success than braces. It’s likely that abnormal, negative forces from a tongue thrust are reduced while an aligner is being worn over occlusal and incisal edges, so movement of the teeth is more predictable.
Let’s consider another wearing-compliance possibility, which not only would change the functional matrix but also alter the simulated results we reviewed before ordering aligners. Perhaps an adult patient is not able to wear aligners because of an unrevealed thumb-sucking habit. The patient might have to remove one or both aligners to begin going to sleep and occasionally forget to put them back in, resulting in zero or reduced nighttime wear. Indeed, such a case has been observed; fortunately, the adult patient, sensing her care provider’s bewilderment that she was not progressing normally with full braces, asked if her thumb sucking could be a problem.
Other concerns that might be less obvious would be a new or worsened persistent tongue-between-teeth (TBT) swallow of saliva or a new or worsened vertical rest position and mouth breathing. In either case, the “new” or “worsened” conditions would introduce possible changes to the functional matrix. Consider, for example, the possible effect of months of wearing a rapid palatal expander with the screw dramatically reducing tongue space. It’s virtually certain the patient would adopt a more abnormal swallow and lowered resting tongue posture.
Perhaps in the future, expansion using only aligners (avoiding RPEs) will be considered the most desirable treatment to avoid worsening of the resting tongue position and swallow and negatively impacting the functional matrix. It’s not hard to imagine, with improvements in aligner materials, attachments, wearing protocols and other changes, that radiographic studies may someday demonstrate comparable skeletal expansion effects among aligners and all other appliances available. Such a change could simplify design and refine redesign, creating the opportunity to deliver two or even three phases of expansion, in contrast to the more difficult placement of traditional RPE designs and less patient friendly miniscrew-assisted rapid palatal expansion intervention.
We now understand that facial-skeletal growth and change is not solely determined by genetics, but also influenced by long-term musculoskeletal forces. Treatment of malocclusion cannot be simplified to the mechanics that are most efficient to tip, rotate, intrude or otherwise move a tooth. Treatment of the functional matrix with an initial assessment of how abnormal the condition is and what improvement is reasonable to expect is necessary.
Many early dental school educations narrowed practitioners’ focus to restorative care. The loss of teeth was more prevalent before fluorides and routinely available dental care, and dental education responded to that societal need. The teaching of restorative care is technique sensitive, with little to no room for a teaching style that encourages trying an approach, re-evaluating to see how the patient responds and refining the treatment plan. Our societal model for restorative dental care has deep roots in a “fix it or pull it” mentality.
The Matrix Focus in Practice
Let’s review a hypothetical functional matrix-based case. Imagine a patient suffering from a deficient airway and the following adaptations to mouth breathing. The individual presents with the abnormal postural rest position of a forward protrusion chin positioning, unconsciously developed to allow the patient to live with difficulty breathing easily through the nose. The chin is protruded by tilting the crown of the head backward (as if looking above) to effectively shift their mandible forward relative to the upper cervical vertebrae (opening the upper airway). Adopting a head and neck posture displaying excessive curvature of the cervical vertebrae from thrusting the chin forward to help open the airway is common. Flaccid lip musculature and narrow nares become observable due to the long-standing mouth breathing.
Imagine the patient undergoes maxillary expansion treatment that effectively increases the total cross- sectional volumetric area of the airway, but no efforts are made to break the habit of mouth breathing. No efforts are made to improve the weak flaccid lip musculature or stop the teeth-apart, open-mouth resting posture. No reeducation effort is made to reverse prior indoctrination that nasal spray, nasal surgery, allergy testing and treatment, or other palliative care is necessary— with the implication that no cure is available. The unsaid message is often that such problems are genetic and, much like height, hair color and eye color, immutable. The patient’s unmet needs therefore result in preventable relapse and the return of malocclusion beginning the moment retainer wear ceases.
Now, let’s imagine functional matrix-focused staging of treatment and consider possible improved outcomes. A hyrax-type maxillary expander creates maxillary expansion, but it does not cease when a crossbite is seen to be corrected or a specific inter-molar arch width is achieved. The expansion is continued until full buccal crossbite can be observed. If two expanders are needed, then consecutive appliances should be planned to achieve the result. In some cases, the patient’s pre-existing deficiency may be so severe that only a smaller screw can be accommodated; in other cases, premature removal results due to cementation difficulties or the patient’s emotional state requiring a pause. These are reasons for further expansion.
An intentional, functional matrix-focused treatment plan would consider the maximum lateral displacement of bicuspids and molars that would displace the buccinators, laterally changing the matrix. The goal would be to create a similar effect to that of the Frankel appliance’s buccal shields facilitating lower arch expansion. Since cone beam studies reveal that only about 30 percent skeletal expansion results from traditional RPEs, 50 percent results from splint style RPEs, and 60 percent results from MARPEs, it is prudent to plan to lose 70–40 percent of observed expansion from the relapse of tooth tipping and alveolar bending. The perception of expansion efforts to overcorrect deficient transverse growth appears exaggerated. Temporary full buccal crossbite occlusal is uncomfortable to see. Despite concern that a telescoping malocclusion may develop, it is not observed clinically due to changes in the functional matrix.
Continuing the functional matrix-focused treatment plan, removal of the hyrax screw obstruction should follow completion of expansion to facilitate a return to normal tongue position after no more than six to 10 weeks of having the screw in place after stopping activations. Providing an ESSIX-style retainer, leaving the palate unobstructed and beginning lip competency nasal-breathing exercises (i.e. taped lips practice) can establish a return to nasal breathing with normal tongue position. The lip-tape nasal breathing exercise will also alert and train the patient to keep the teeth together when he or she feels the tug of the tape as the jaw drops. In cases where patients’ pretreatment swallow and tongue resting position was noted as TBT, the exercise will retrain the swallow. (An exception is in cases of large open bites where the tongue can still fit between the teeth even when clenching.)
Two additional benefits result from including the lip-tape exercise in the treatment plan. The first is due to the distinct possibility that wearing a hyrax expander in the palate for several months may start or worsen a dropping of the jaw and abnormally low or TBT problem. The second benefit is that the lip-tape exercise serves as a functional test to confirm if nasal breathing is possible. This is helpful for borderline decisions whether to expand again or refer the patient to an ENT. Keep in mind that the lip-tape exercise is typically well-accepted when first introduced as a daytime exercise and followed only after success by attempted night wear. If a baseline sleep study is available, it could be repeated, or the patient could be referred to a myofunctional therapist.
Many other waypoints occur along a comprehensive orthodontic treatment plan in which a functional focus may be beneficial. Some of these may be best if always included, and others can be deployed on an as-needed basis. Practitioners can use the new discoveries, advancements and technologies to better tailor treatment plans for maximum patient satisfaction and better clinical results.
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