The History of Clear Aligners

Let's take a look at the history of clear aligners therapy the over past 60 years.

• 1940s: Positioners were first used to straighten teeth by prominent and influential orthodontist Dr H.D. Kesling. His treatment was known as "positioner-based orthodontic therapy."
• 1960s: Developments in tools and materials enabled doctors to create the thin, clear, plastic aligners we're familiar with today. In the late 1950s when Dr Henry Nahoum was the Chairman of the Orthodontic Program at Columbia University in New York, he began experimenting with thin sheets of plastic and introduced thermoforming into the orthodontic world. He invented the vacuum thermoformer, which is still in common use today. In 1964, Dr Nahoum published his developments in the New York State Dental Journal.

The key benefits of his invention included:

1. Cosmetic "invisible appliance"
2. Clear translucent films/sheets (0.1-0.4" thicknesses)
3. Patients could eat with the appliance
4. Habit breaking appliance
5. Could be modified for use with headgear
6. Uses in restorative dentistry, periodontics

• 1990s: Aligned Technology introduced clear aligners to the mass market. 

1. In the late 1990s, many advertisements condemned fixed appliances as being antiquated and compared them to the horse and buggy. This marketing claim was rather brash and clinicians took exception particularly when the evidence of comparability and treatment outcomes was non-existent. 
2. Consumer marketing led the public to have certain expectations for clear aligners. People expected that they simply wore a series of aligners and their malocclusions would be corrected. Many people were disappointed to learn that they were not good candidates for clear aligner treatment at the time, revisions were necessary, treatment often took longer than planned and complaints to dental boards were rather common.
3. Following the false promises to antiquate fixed appliance therapy, clinicians asked for evidence. Digital orthodontic aligner companies lost value and stocks in these companies were in the $1 range. However, a constant that remains today is the public's desire for an esthetic removable orthodontic appliance. Innovative clinicians saw the potential and got behind the concept of aligner treatments and began to advance concepts of biomechanics, setups and staging. The initial indication for aligner therapy was a post-orthodontic relapse and only minor crowding.

How did the clear aligners improve?

→ A better understanding of how they work: From the original indication of post-orthodontic relapse and minor crowding, numerous clinicians began to study how aligners work and overcome limitations with auxiliaries such as attachments, buttons and elastics. The literature showed case reports of complex treatments, then extraction treatments, hyperdivergent skeletal patterns, and even orthognathic surgery treatments combined with aligner treatment. Scientific reports of the accuracy of tooth movement did not emerge until 2009. This table shows 3 studies which looked at the various types of tooth movement and the differences between movement by tooth type and began to paint a picture of which teeth would be more or less amenable to tooth movement with aligners.

→ A better understanding of the appliance: Clinicians began to critically evaluate what aligners could do well and what they didn't do as well. This better understanding of the appliance and identification of problems led to the creation of solutions Let's discuss key points that the historic literature has taught us.

• 1945: Aligners are rooted in the concept of tooth positioning appliances which was introduced in 1945. The appliance is one-piece construction. This is by design as it was the intention to not only seat individual teeth into the appliance but to seat them in a specific occlusion. Splitting the appliance into an upper and lower would greatly lessen this latter ability. Another aspect of the tooth positioning appliance is the exercise regimen that came along with it. Patients were instructed to repeatedly bite heavily and clench into the appliance over a period of 15-20 minutes, 3-4 times per day to get results.

• 1961: Dr Burnie Bunch 1961 showed the effects of combined orthodontic positioner treatment during the orthopaedic treatment of scoliosis. In this treatment, an orthopaedic device was used which exerted tremendous tensile forces between the hips and under the mandible. As you can see in the photograph the patient was cast into this apparatus so compliance was rather mandatory. The forces forced the teeth to seat into the positioner and Dr Bunch was able to treat moderately complex malocclusions using a series of tooth positioners to provide respective increments of tooth movements.

Conclusion: Kesling and Bunch's findings of the importance of the occlusion and seating forces to this day are under-utilized. Seating the aligner is critical for success. Many clinicians dispense Chewies along with the aligners but it is important to have a regimen ala Kesling to exercise and ensure continuous seating of the teeth into the aligners.

So, does the aligner plastic move the teeth or is it the constant seating of teeth into the appliance that makes it work? Likely both mechanisms are at play but constant seating of the appliance has a larger role than the effect of plastic exerting forces on teeth to move them.