In search of the etiology of malocclusions — a common discovery technique is proposed

Dr. John Hayes discusses why finding the ideal treatment approach for any condition is identifying the cause

Background — calls for action

Consider the following three statements from eminent orthodontic educators as “calls for action” for more research into the etiology of malocclusions:

  1. “I hate open bites! I don’t understand their etiology, I don’t understand why they don’t self-correct, I don’t seem to be able to be able to identify the diagnostic features that are really important, I really don’t know the best methods to treat them, and even worse, I don’t know how to successfully retain the correction.”1
  2. “I predict you will be hesitant to promise long-term closure of the open bite, even if the patient agrees to follow through with any treatment approach you recommend.”2
  3. “To this day, we pretend to be ‘scientific’… and have replaced extraction with a host of popular but largely ineffective substitutes, each with a labored, after-the-fact ‘scientific’ rationale. As long as nobody dies from anchorage loss and permanent retention, this clear violation of the tenets of science may seem to have little practical significance; however, it imposes a penalty that threatens the status of the specialty: It argues that there is little in the way of a market for evidence, the work product of ‘the schools.’ ”3

The causes of most malocclusions are generally understood by orthodontists to be unknown. The “calls for action” suggests a need for the discovery of the etiology of malocclusion — in this instance, anterior open bite (AOB).

Consider the advantages if orthodontists were able to treat a patient’s malocclusion with confident knowledge in the efficacy that their treatment is based on science. There may be those who would argue that the effort to discover etiology is a waste of time — that things are well enough left alone. It may even be argued that there is no such thing as the etiology of a malocclusion — “AOB happens.” However, it should be reasonable to hold that every malady has a cause.

It should be evident that if the cause of any malady (medical or dental) were to be unknown — that the treatment “cure” for the malady would be at best palliative. We should also be aware that this malady is not a diagnosis — it is a symptom of something gone wrong.

The study of the etiology of malocclusions has on been on a back burner with a low flame. Through the years, those who deserve credit for keeping the flame going include the following notables: Drs. Kingsley, Lundstrom, Brodie, W. Price, Harvold, Vanarsdall, and Musich.

Orthodontics is not alone with unknowns — for example, in medicine, there are many maladies that have unknown etiologies, and research may be ongoing. Medical patients may be acutely aware that their particular malady and their treatment is a question mark.

What to do?

This commentary is a call for action for a different approach to problem solving. Commendable efforts have been undertaken in the past with the hope that AOB could be treated efficiently with lasting stability by way of a particular technique or regimen; we are unaware if this has proven fruitful.

We should follow Dr. Kim’s reasoning: “The ideal treatment approach for any disease [malady] is identifying the etiology, understanding the pathophysiology, and removing the etiology.”4

A corny story from the agricultural industry

A major agricultural supplier of corn seed to farmers was attempting to invent a seed that would be more disease resistant. Their greenhouses grew thousands of cornstalks.

On the day the corn was to be harvested, one scientist happened to note that one plant yielded cobs 20% larger than the others. Size was not the purpose of the original research; however, the large cobs were noticed because the scientist’s mind was open to discovery. The larger cobs were an outlier. and they could eventually turn out to be a bonanza for the company and for farmers after further testing.

A true medical story5

In 1929, a 47-year-old Scottish researcher presented a paper in front of his medical research club in London. A little over a year earlier, he had noticed something he had never seen before — the streptococcus culture was being liquefied by some fluffy white mold that had apparently settled in out of the air onto his culture dish.

Although he continued to believe in his discovery, there were many dead ends, and the project languished because it did not fit with universal belief at the time that disease was best cured by way of inoculation.

Nine years later — in 1938 — a couple of new researchers happened to come across his 1929 paper. Eventually, Alexander Fleming got his due respect in 1945 with a Nobel Prize along with the two researchers who followed up on his discovery. This discovery is another example of the recognition of an outlier.

Background information

It should help to know that malocclusions were rare prior to the early 1800s. Our analysis of old and prehistoric museum skulls prior to the 1800s reveals universally well-formed arches, well-aligned teeth, Class I occlusions (tending with prehistoric skulls to become Class III subsequent to excessive occlusal wear), and slight-to-moderate curve of Spee with obvious lifelong dental stability.6,7,8

Those facts should also suggest that malocclusions are mostly caused by something environmental, something that apparently started to change beginning in the late 1700s to early 1800s. (To be clear, very old skulls of 10,000-plus years BP, for example, reveal space distal to the 12-year molars — and today, given several millenniums of natural selection, that space is no longer present — so we expect wisdom teeth to become impacted — that is a genetic change that leads to later crowding as the wisdom teeth attempt to erupt.)

Over the years, mixed inheritance has been proposed for crowding (Kingsley 1880, Case 1908, and others) — small jaws/large teeth; however, one would expect this to be equally offset by patients with large jaws and small teeth.

Application of a discovery technique to malocclusions

Lightman detailed the discovery process for what he considered the 23 high points of 20th-century discovery.5 “The urge to discover, to invent, to know the unknown, seems to be so deeply human that we cannot imagine history without it.” “In some cases, sheer brilliance leads to discovery. In others, the required ingredients include circumstance and luck.”

A technique proposed for the discovery of etiology is not a new idea — it is what Lightman might call creating the circumstances for success along with some luck9:

  1. Read every research manuscript with case studies on AOB that includes failed results: what was done and what was not done — draw some conclusions.
  2. Read every study on AOB that purports successes: what was done and what was not done — draw some conclusions.
  3. Consider the outliers in the treatment of one’s own AOB cases — those cases where treatment seemed easier and also those cases where treatment was intractable; consider posttreatment stability or instability; consider periodontal stability or instability; evaluate any “patterns” in cases that work and where it does not work.
  4. “Cherry-pick” those patients from the cases that seem to work out.
  5. Evaluate the “cherry-picked” results for their cephalometric similarities along with measured arch harmony or disharmony.8
  6. Group those cases into a pilot study.9,10
  7. The etiology of the malady can be proposed for further study.

(Incidentally, the etiology of Class II malocclusions might also benefit from this discovery technique (refer to Moyers, et. al.’s, landmark paper that discusses the six horizontal types [symptoms] and five vertical types [symptoms] of Class II malocclusions. The 11 possible etiologies were left for future discovery.)10

Time for an RCT?

It is well accepted that a medical randomized controlled trial (RCT) is among research with the highest degree of validity. Medical RCTs can be accomplished most easily when a virus or bacteria is the etiology; when the double-blind requirement is feasible; when results can be evaluated over time spans that are also feasible among other strict requirements.11 RCTs are only real RCTs, when and if an etiology can be proposed and tested.

Unfortunately, the medical RCT design does not fit well with orthodontic treatment research for a several reasons:

  1. The double-blind requirement is problematical.
  2. The etiology of the malocclusion is not yet known.12-15
  3. Malocclusions are not caused by a virus or bacteria.
  4. Routine patient orthodontic care requires periodic adjustments at each visit.

A medical RCT requires that patients are not to receive additional treatment interventions while in the study. Accordingly, a medical RCT design and an orthodontic “RCT” are not the same thing.

If it is desired to proceed with the necessary compromises of an orthodontic “RCT,” the following is an outline:

  1. Prospectively select 100 early AOB subjects (7 to 10 years old).
  2. Stratify the subjects equally into two groups (treatment and controls) based on severity of AOB; age; sex; and most importantly, the proposed AOB etiology.
  3. Treat the one cohort (as appropriately suggested from the pilot study).
  4. Observe the control group and treatment groups through age 18.
  5. Accept the fact that the untreated controls have been left behind and likely cannot be caught up.


  1. The causes of most malocclusions are generally understood by orthodontists to be unknown.
  2. There is a need for the discovery of the etiology of malocclusions — in this instance, anterior open bite (AOB).
  3. “The ideal treatment approach for any disease [malady] is identifying the etiology, understanding the pathophysiology and removing the etiology.”4
  4. There is a technique that can be used for discovery that is not a new idea. The technique starts with creating the circumstances for the recognition of outliers.
  5. Much malocclusion is of relatively recent origin — a couple of hundred years old. That suggests that the discovery of etiology is feasible.
  6. A medical randomized clinical trial (RCT) is among research with the highest degree of research validity. For several reasons, the medical model RCT is not fully applicable to orthodontic etiology research.
  7. Case studies and pilot studies should not be underestimated in their potential contribution to orthodontic knowledge when there is a need for discovery.

John L. Hayes, DMD, MBA, received his dental degree from the Boston University Henry M. Goldman School of Graduate Dentistry and his orthodontic certificate from the University of Pennsylvania, School of Dental Medicine, Orthodontic Department where he is a Clinical Associate. He continues to research and lecture on the advantages of early interceptive treatment and on the etiology of malocclusions. Dr. Hayes is in private practice in Williamsport, Pennsylvania, with his wife, Sharon, who is also an orthodontist. He can be reached at

  1. Berents RG. Editorial: New vistas in orthodontic research. Am J Orthod Dentofacial Orthop. 2015; 148(5):701-702.
  2. Turpin DL. Online only. Editor’s summary and Q&A: Zuroff JP. et. al., Orthodontic treatment of anterior open-bite malocclusion: Stability 10 years postretention. Am J Orthod Dentofacial Orthop. 2010; 137:302.e1-302.e8.
  3. Johnston LE Jr. Through a glass darkly: Orthodontics in the 21st century. Am J Orthod Dentofacial Orthop. 2015; 147(suppl 5):187-188.
  4. Kim KB. How has our interest in the airway changed over 100 years? Am J Orthod Dentofacial Orthop. 2015;148(5):740-747.
  5. Fleming A. Antibiotics. On the antibacterial action of cultures in penicillium. In: Lightman A. The Discoveries: Great Breakthroughs in 20th Century Science. New York, NY: Pantheon Books; 2005.
  6. Hayes JL. March 8, 2003, PAO Meeting, Philadelphia, PA. Presentation: A Clinical Approach to Identify Transverse Discrepancies.
  7. Hayes JL. Orthodontics. Smithsonian Institution. In: Owsley DW, Jantz RL, eds. Kennewick Man: The Scientific Investigation of an Ancient American Skeleton. Texas College Station, TX: A&M University Press; 2014.
  8. Hayes JL. In search of improved skeletal transverse diagnosis. Part II: A new measurement technique used on 114 consecutive untreated patients. Orthodontic Practice US. 2010;1(4);34-39.
  9. Hayes JL. A new regimen of phase I care applied to anterior open bite—10 case studies: an etiology proposed by the strategy of triangulation. Orthodontic Practice US. 2012;3(3):18-26.
  10. Moyers RE, Riolo ML, Guire KE, Wainright RL, Bookstein FL. Differential diagnosis of class II malocclusions. Part 1. Facial types associated with class II malocclusions. Am J Orthod. 1980;78(5):477-494.
  11. Wapner J. The Solid-Gold Wonder Drug. Scientific American. 2014;311(3)32-33.
  12. Koletski D, Pandis N, Polychronopoulou A, Eliades T. What’s in a title? Assessment of whether randomized controlled trial in a title means that it is one. Am J Ortho Dentofacial Orthop. 2012;141(6): 679- 685.
  13. Hayes JL. Evidence-based orthodontics. Am J Orthod Dentofacial Orthop. 2008;133(5):637-638.
  14. Hayes JL. Design flaws in some randomized controlled trials. Am J Orthod Dentofacial Orthop. 2008. 134(4):466-467.
  15. Hayes JL. Problems with RCT designs. Am J Orthod Dentofacial Orthop. 2009;136(2):143-144.

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