According to the American Association of Orthodontists (AAO) glossary, Orthodontics and Dentofacial Orthopedics is the specialty which includes the diagnosis, prevention, interception, guidance, and correction of mal-relationships of the developing or mature oral and facial structures (figure 1). Orthodontics is actually more about overseeing and managing facial development and jaw relationships, and less about aligning crooked teeth. This article will discuss the vital role the orthodontist plays, for better or for worse, in understanding, screening and managing the patency of the human airway and the long term effects of that management on sleep disordered breathing (SDB) such as obstructive sleep apnea (OSA) when this information is considered (or not considered) in orthodontic treatment.
Since the early 19th century, the relationship between airways and facial structure has been studied1. 2. 3. People became interested, because breathing is a function of craniofacial anatomy (Figure 2).
One of the most famous theories in craniofacial biology is The Functional Matrix Theory postulated in the 1960’s by Dr. Melvin Moss4. It states that soft tissue and airway guide hard tissue, because the need to breathe supersedes all other factors which may influence growth. As 3D imaging technology continues to improve, the research is becoming increasingly clear and abundant, that the way we breathe during our growing years deeply affects how our face grows and conversely, our facial patterns and shapes produce our airway anatomy, thus influencing the way we breathe. It’s a bit of the chicken-or-the egg(?) scenario. Which came first? The truth is the 2 are tightly intertwined and as owners of craniofacial anatomy, no one is better positioned to manage airway development than orthodontists.
The upper human airway is known as the pharyngeal airway or pharynx (figure 3) , divided into thirds: the laryngopharynx positioned inferiorly, the oropharynx in the middle and nasopharynx right above (figure 4) .
Several investigators have recently studied the relationship between pharyngeal airway shape and different facial patterns using cone beam computerized tomography (CBCT), a highly accurate method for airway assessment. The results are changing the landscape of orthodontics as we know it. Recently, Drs Dan Grauer and William Proffit at the University of North Carolina compared non-growing patients, categorizing their facial types into convex profiles (Class II), straight profiles (Class I), and concave profiles (Cl III), and then measured the pharyngeal dimensions to see if a possible correlation exists between the 3 different facial categories and airway size. The results of the study concluded that there was a statistically significant difference between airway dimensions and the facial type: Cl II (receded lower jaws) patients had the smallest airways, followed by the CL I (straight profiles), and then CL III faces (strong lower jaw) had the largest airways. In other words, small mandible correlate to small airways, and large jaws correlate to large airways5.
A similar study by Abdelkarinm, et al, found even stronger correlations between facial patterns and minimal cross sectional areas (MCA) of pharyngeal airways. MCA is important because it represents the “bottle neck” of the airway and thus the risk for an airway obstruction problem such as obstructive sleep apnea. This study was particularly important because it correlated facial pattern with risk factors for obstructive sleep apnea (OSA). Abdelkarim concluded the following6:
- Pharyngeal airway volume was largest in the Cl III patients –those with the strongest mandibles or most forward lower jaw position, followed by Cl I patients – normal mandible posture, and then the last or worst were the Cl II patients with the weakest lower jaw position, known as mandibular retrognathism
- These results indicate that the anteroposterior (front-back) dimension of the oropharyngeal airway space is affected by different skeletal patterns of the mandible. In conclusion, the mandible seems to be the biggest determinant of the airway size.
- The pharyngeal airway should be evaluated in patients with mandibular retrognathism (small lower jaws), especially in severe cases
- If relevant snoring or OSA symptoms are present, consideration of a sleep study, including polysomnography (PSG), can be beneficial for specific Class II malocclusion patients with noticeable mandibular retrognathia
A recent study conducted at Case Western Reserve University by Dr. Martin Palomo reached similar conclusions7.
Various methods exist for the treatment of obstructive sleep apnea. They include from weight loss (the least invasive, but arguably the most difficult), positional therapy (sleeping on one’s side, not one’s back), nasal decongestants, CPAP, oral appliances, soft tissue ENT surgery known as UPPP, hard tissue jaw surgery in the form of orthognathic surgery known as maxillomandibular advancement (MMA) or mandibular advancement (MA) surgery and finally, as a last resort, a tracheotomy or tracheostomy. Several controlled institutional based studies have compared the efficacy of some of these above mentioned methods and have found that MMA has the best outcomes for OSA when compared to CPAP and oral appliances. A few studies have even found success rates of 100% using MMA as measured through sleep studies and looking at AHI (Apnea Hypopnea Index) compared to CPAP and oral appliances8, 9, 10, 11 (figure 5 & 6).
MMA/ MA move the jaws forward and consequently enlarge the airway. It should not come as a surprise that MMA/MA are considered the end-all, cure-all of obstructive sleep apnea because it is the only therapy which makes permanent changes on anatomy in non-growing patients. The studies discussed above regarding the relationship between airway size and jaw position explain why this is so5,6,7. Corrective jaw surgery to enlarge airways can be a positively life altering procedure. Not only is life expectancy drastically increased, but also the quality of life can drastically increase as overall health improves/ What’s more, these patients become “CPAP liberated”. However, having one’s facial skeleton repositioned through corrective jaw surgery is invasive, comes with risks, and is by no means a “cake walk”.
All of the above mentioned alternatives to the treatment of obstructive sleep apnea have limitations. What has not been mentioned is perhaps the least invasive, least expensive and most effective approach to OSA (obstructive sleep apnea): PREVENTION in children. Knowing that airways correlate with dento facial patterns, how can we as orthodontists not look at children differently and consider minimally invasive orthodontic therapies during the growing years of the face to help promote forward facial growth consistent with airway development? Just as important how can we continue to design orthodontic treatment plans which violate airways or worse, not consider airway in our orthodontic evaluations?
What this means to orthodontists and patients seeking or undergoing orthodontics is that airways can and should be managed, manipulated or enlarged and orthodontic treatment plans should be designed with this in mind not only to treat to airways, but also, more importantly, to prevent airway obstructive related issues such as obstructive sleep apnea later in life. Figure 7 shows such an example of a pediatric patient suffering from OSA and who through early phase I orthodontic treatment had his airways enlarged and is now sleeping better, breathing better and living better. I know this because not only is he my patient, but also he is my son (figure 7)12.
- Linder-Aronson S. Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. A biometric rhino-manometric and cephalometro-radiographic study on children with and without adenoids. Acta Otolaryngol Suppl 1970;265:1 – 132.
- Linder-Aronson S. Woodside DG, Lundstrom A. Mandibular growth direction following adenoidectomy. Am J Orthod 1986; 89: 273-84.
- McNamara, JA. Influence of Respiratory pattern on Facial Growth. Angle orthod; 1981;51: 269 – 300.
- Moss ML. The Functional Matrix. Functional Cranial Components.
- Grauer D, Cevidanes LH, Styner MA, Ackerman JL, Proffit WR. Pharyngeal airway volume and shape from cone-beam computed tomography: relationship to facial morphology. Am J Orthod Dentofacial Orthop. 2009 Dec;136(6):805-14.
- Abdelkarim, A. A cone beam CT evaluation of oropharyngeal airway space and its relationship to mandibular position and dentocraniofacial morphology. Journal of the World Federation of Orthodontists. . 16 July 2012.
- El H, Palomo JM. Airway volume for different dentofacial skeletal patterns. Am J Orthod Dentofacial Orthop. 2011 Jun;139(6):e511-21
- Holty JE, Guilleminault C. Surgical options for the treatment of obstructive sleep apnea. Med Clin North Am. 2010 May;94(3):479-515.
- Prinsell JR. Maxillomandibular advancement surgery in a site-specific treatment approach for obstructive sleep apnea in 50 consecutive patients. Chest. 1999 Dec;116(6):1519-29.
- Riley RW, Powell NB, Guilleminault C, Stanford University Medical Center, CA. Obstructive sleep apnea syndrome: a surgical protocol for dynamic upper airway reconstruction. J Oral Maxillofac Surg. 1993 Jul;51(7):742-7; discussion 748-9.
- White PD, Wooten V, Lachner J, Guyette RF: Maxillomandibular advancement surgery in 23 pts with OSA syndrome. J Oral Maxillofac Surg 47: 1256, 1989.
- Quintero, JC. (Case Report) Unlocking King Airway, TMJ and Growth with CBCT as the key. OrthoTown, September 2011, Page 70.