Attacking an old adversary: A new paradigm

Nasomaxillary complex deficiency is closely associated with many of the most complex challenges encountered in dentistry, both currently and historically: the treatment of temporomandibular disorders, craniofacial orthopedic irregularities, dental malocclusion, and sleep disorders. The American artist, George Catlin, first associated dental and facial malformations with mouth breathing in his 1861 book entitled, The Breath of Life Or Mal-respiration: And Its Effects Upon the Enjoyments & Life of Man [1]. The existence of this document was brought to the attention of Dr. Edward Angle, who had it reprinted in 1925. In his forward, Dr. Angle referred to the artist, stating, “In his belief that some forms of malocclusion of the teeth and facial deformity are due to mouth breathing, we only know too well Mr. Catlin to be entirely correct” [2]. Catlin’s work had fallen into obscurity at the beginning of the twentieth century; however, Angle [3] noted in his 1911 textbook, Malocclusion of the Teeth, “As the evil effects of mouth breathing are so pronounced, how important it becomes that it should have thorough and prompt attention from the most skillful rhinologist only, and that normal nasal respiration be established, otherwise the work of the orthodontist must be futile”.

Since the time of Catlin and Angle, an extensive list of ingenious dentists have attempted countless mechanisms, persistently applying traditional mechanistic force systems to the developing craniofacial structures, attempting optimization of Cranio-Facial-Respiratory Complex (CFRC) growth and development. Most of these efforts have yielded widely variable, unpredictable, and often disappointing outcomes. Orthodontic treatment failure spawned an increased focus on orthognathic surgery, with accompanying risk and uncertainties, as an alternative attempt to correct craniomandibular imbalances.

Where are we now with CFRC diagnostic and treatment regimens? My perspective is not positive, but here I go: 1) Most diagnostic tools routinely in use are very subjective; 2) Most current cephalometric schemes likely underestimate CFRC parameters; 3) Functional appliance therapies are often effective in children but not in adult patients; 4) Repositioning of teeth, including removal of teeth to accommodate CFRC deficiency; 5) Use of cervical and reverse headgear apparatus in attempt to redirect CFRC growth and development; 6) CFRC expansion techniques, orthodontic or orthognathic, directed to modification of the dentoalveolar structures or craniofacial bones (often, we do not know or understand the actual effects); 7) orthognathic surgery; and 8) contributions of otolaryngology, which also suffer subjective uncertainty of diagnosis and treatment planning for CFRC conditions.

Our continuing dilemma remains the lack of research and development of techniques, which can achieve predictable, efficient, and non-invasive Cranio-Facial-Respiratory Complex three-dimensional development of individualized and optimized phenotype expression for correction of craniomandibular imbalances. However, there are reasons to be optimistic. Innovative diagnostic and treatment concepts are presently evolving that focus on the possibilities of known growth and development of neurobiology rather than traditional mechanistic force systems. These concepts have their origins in the work of pioneers of postnatal human growth and development, such as Dr. Julius Wolff’s “Wollf’s Law” [4], Dr. H. Frost’s “Mechanostat Theory” [5], Dr. Melvin Moss’s “Functional Matrix Theory” [6], and Dr. Donald Enlow’s “Counterpart Principle” and “V Principle” [7]. Although none of these concepts completely elucidate craniofacial growth and development in and of themselves, in combination, they point to the future for significant advances in our understanding and treatment for CFRC disorders. I am compelled to point out that the concepts of Wolff, Frost, Moss, and Enlow were never taken up for their practical value by orthodontists, a conundrum noted by these authors. This draws attention to something fundamentally wrong with the orthodontic field, which myofunctional therapy can exploit.

Myofunctional therapy is non-iatrogenic, holistic, safe, and essential for achieving optimal treatment of the Cranio-Facial-Respiratory Complex orthodontic, craniofacial orthopedic, airway, and temporomandibular disorder conditions. The term, “myofunctional therapy,” was coined by E.B. Lisher [8] in 1934 in reference to techniques developed by Alfred P. Rogers [9,10] from 1918 to the late 1930s. However, by the 1950s, these techniques had become obscure [11]. Nevertheless, practitioners’ efforts continued culminating in the adoption of the American Speech-Language-Hearing Association position paper in 1991 [12] as official policy of the ASHA. Thereafter, there has been a significant growth in numbers of myofunctional therapy practitioners and techniques. Although myofunctional therapy has been adopted as a tool that clearly has improved treatment outcomes for many CFRC conditions, there are challenges. Quality research on the efficacy of different techniques and procedures remains lacking. I had the pleasure of attending a week-long international myofunctional therapy conference. My biggest single takeaway from this experience was that no real research was presented to recommend one therapeutic approach over another. It reminded me of the persistent centric relation-centric occlusion (CR-CO) controversy within dentistry. The most significant myofunctional failure I have observed is more to the point of this editorial. Can myofunctional therapy achieve predictable, efficient, and non-invasive Cranio-Facial-Respiratory three-dimensional development to individualized and optimized phenotype expression? My answer: sort of. Predictability is very problematic. Not surprising, considering the wide prospect of known and unknown factors, anatomical, behavioral, neurological, and cultural, that impact even the “best” myofunctional treatment approach. Regardless of how dramatically it may improve many CFRC conditions, myofunctional therapy does not currently offer a solution to the persistent problem of maxillary anteroposterior deficiency. That said, it is an important component of a new CFRC treatment paradigm.

I suggest that the most exciting opportunities lie in the emergent science of signaling. The concept of signaling is a fundamental principle guiding current understanding of functional flows of biologic systems. Biologic signaling is complex and pertains to interactions between molecules, cells, ecologic systems, and even species. Introduced decades ago, signaling has now taken a preeminent role in the research of all biologic systems, including CFRC growth and development. Of particular interest to clinicians involved in the treatment of CFRC disturbances are those that occur postnatally and, therefore, have potential for positive modification. Thorough appreciation of biologic signaling pathways, especially of the structures composing the craniofacial complex, is essential for attaining competency within the field of orthodontics, and I maintain in the fields of temporomandibular disorders and sleep disorders as well. Of particular emphasis to clinicians are the hard tissues comprising the craniofacial regions, teeth, and bones. Development, growth, and function of other craniofacial structures and tissues, such as muscles, neural tissues, and pharyngeal structures as well as spaces, such as the airway, are also of major interest and must be considered due to their influence structurally, functionally, and developmentally on the growth, size, and form of the skeletal elements of the face and jaws [13].

Significant advances in the genetic and epigenetic basis of craniofacial development, of which biologic signaling is an essential component, are advancing rapidly [14]. Many therapeutic options based upon molecular concepts of craniofacial growth and development are available to clinicians now, but more research must be done to establish predictable, efficient, and non-invasive Cranio-Facial-Respiratory three-dimensional development to individualized and optimized phenotype expression for correction of craniomandibular imbalances. My hope is that your interest, support, and participation in this new paradigm will be stimulated by these few comments.