Introduction

The 1973 the Nobel Prize in Medicine and Physiology was awarded to Tinbergen, von Frisch and Lorenz for pioneering work in the science of ethology [1]. Ethology involves investigation of certain behaviors under natural conditions using the scientific method to evaluate its application to improved functions. Lorenz defined the term fixed action patterns as instructive characteristic responses that would occur in the presence of identifiable stimuli reliably invariant within the species. In the ethological method a behavior measured response to a stimulus does not necessarily emphasize evolutionary adaptability, but the significance of the behavioral process. Ethologists not only query the “why” of functions but, “What are their consequences?”

Ethology is basically the science of watching, wondering and testing. It usually involves fieldwork or in this case clinical observation. Human beings are unique among mammal species by having a combined airway and foodway. The pharynx, being unsupported by bone is flexible and collapsible. As a result, adult humans cannot breathe and swallow at the same time. The positive consequence is the development of speech. The negatives are the possibility of choking and obstructive sleep apnea (OSA), a disorder in which the tongue during sleep intermittently collapses on the pharynx to restrict breathing. OSA is a relatively new disease [2]. Its pathophysiology was only recognized within the past 50 – 60 years. As its numerous morbid health consequences have been scientifically determined and technology developed to objectively measure its phenomenology, its diagnostic prevalence has multiplied in huge numbers. Continuous Positive Air Pressure (CPAP) has been shown to be a near universally effective treatment modality, but uncomfortable, bulky and having reduced patient adherence. Surgical procedures such as uvulo palato pharyngoplasty, tracheotomy, tonsillectomy and adenoidectomy have had less than satisfactory results and low acceptance. OSA has also been found amenable to treatment by dental protheses, many of which have high patient adherence but are currently not as robust a treatment modality as CPAP. Dentists in effect, align and stent mouth parts to maintain optimal airway patency in the pharynx, an anatomic structure contiguous to, but actually not in the mouth. It is known that the diameter and volume of the pharynx can be dilated and stented by appliances that reposition various parts of the oral apparatus. This nocturnal dilation and stenting is dependent on complex coordination of the interaction between the local bony architecture, neural, muscular, vascular, ligaments, cartilaginous disc and soft tissue.
Pharyngeal airway dilation and stenting is accomplished by the complex inter-reaction between at least seven neurological/anatomic factors:
Pharyngeal airway dilation and stenting is accomplished by the complex inter-reaction between at least seven neurological/anatomic factors:

1. Create optimal space for the tongue in the mouth

2. Advance the tongue anteriorly

3. Advance the mandible anteriorly

4. Stretch the mylohyoid muscle

5. Lower the mandibular position

6. Advance the hyoid bone anteriorly

7. Change the alignment of the masticatory muscles [3].

[3]

SlantSlant In an anterior stabilized interarch jaw registration an acute angle seen between the plane of the mandibular teeth relative to the plane of the maxillary teeth and narrower at the posterior than anterior is referred to as slant. The ethologist looks at slant and asks, “Is this a fixed action pattern that is invariant?” “What are its consequences?” “Is this a behavior that is modifiable?” “Can understanding slant affect the registration of the interarch jaw position for an intraoral sleep appliance?”