1.1 History of Clear Aligners

1.1.1 Early Beginning

Recent advances in technology have allowed many inventions that were previously only thought of to become a reality. Such is the case with clear aligners whose history began at the start of the 20th century.

These early retainers were developed by Hawley and others and made from Vulcanite and gold.

Rubber was first used in 1924, when Orrin Remensnyder developed the ‘Flex‐o‐Tite’,¹ a device that was meant to stimulate gums through home use combined with toothpaste, and was therefore convenient for periodontally compromised patients.

On approval the patent, Remensnyder described that the device might cause small teeth movements, using the expression ‘orthodontic appliance’ to describe it on his second patent for the device.²

Twenty years later, in 1946, Harold Kesling was responsible for developing what he called the ‘Tooth Positioner’, a device made from Vulcanite meant to prevent relapse after orthodontic treatment.

This, alongside variations from other orthodontists, was considered a gold standard for several years, in which black vulcanite was the preferred option.

By using the tooth positioner, Kesling suggested ‘major tooth movements could be accomplished with a series of positioners by changing the teeth on the setup slightly as treatment progresses. At present this type of treatment does not seem to be practical. It remains a possibility, however, and the technique for its practical application might be developed in the future’.

In 1963 when Shanks developed a technique for producing mouth guard style transparent retainers, with a machine capable of producing them. In 1964 Nahoum patented his ‘vacuum formed dental contour appliance’, while other orthodontists such as Ponitz³ faced problems in different designs such as heating capability or plastic needs.

Up to this time these devices were used to stabilize the results of previous orthodontic treatment but were also used for minor corrections to the position of the teeth.

At the end of the 1980s, Elasto devices were developed that were made from highly flexible silicon that could be used for either one or two teeth quadrants.⁴ Tooth movements were possible thanks to several set‐ups that were built in different plastics, depending on the clinician’s needs, after fixed appliances.

In 1994, Sheridan developed an aligner system,⁵ which he called ESSIX, using clear, polymeric shell appliances with thermoplastic divots to reposition teeth, which was meant to solve minor anterior malpositions. In 1997, together with Schwartz, they standardized this by patenting a system that would be implemented in many dental offices until now, an ‘in‐office’ vacuum system.

1.2 Origins of Align Technology

At the end of the 1990s a computerized aligner system was developed in the USA with promising features: namely, Invisalign, created by two Stanford students, Zia Chishti and Kelsey Wirth.

Zia Chishti was an orthodontic patient that found out that his own clear retainer might be applicable to the whole orthodontic treatment, as it might be able also to move teeth and avoid metal braces. This reasoning led to why they both started the Company, partnered with some other students in their campus, Apostolos Lerios and Brian Freyburger, who were responsible for the Computer Aid Design part of this start‐up.

They then developed a software to design incremental stages of retainers to straighten teeth in a campus laboratory. In 1998, they got Food and Drug Administration (FDA) approval, and were then able to sell their product to the orthodontic community, which was resistant to this radical change, mostly owing to the lack of orthodontic experience of its founders.

In 2000, they raised $140M from venture capital companies and this allowed them to start a $31 million TV campaign that same year. In 2001, the Company went public, raising an additional $128M on NASDAQ.⁶

During this time, consumers drove more than 70% of the American Orthodontists to be trained in the system.⁷ That same year, Align Technology made Invisalign available to general dental practitioners, arguing that offering it only to orthodontists would be considered unfair competition by dentists.

By then, Align Technology was spending most of its revenues on advertising, and losing about $18 million per year,⁸ which led cofounders Wirth and Chishti to resign from Align Technology before 2003.

After a cut in advertising to one‐third of the original, the company grew from 80,000 patients treated in 2002 to 175,000 in 2004, while receiving awards for its stereolithography techniques, medical design and fast growth. In addition, the company finally achieved a profit for the first time in 2003.

In 2004 the FDA cleared expanded labelling for Invisalign and removed the permanent dentition requirement, making possible the launching of Invisalign TEEN and widening clinical applicability to include more complex cases and increase the age band for treatment.

In 2005, the Harvard School of Dental Medicine required for the first time that its orthodontic graduate students complete Invisalign certification before they graduated.⁹

1.3 Early Clear Aligner Manufacturers

Although most patented innovations have been developed by Align Technology, other companies have been working on new functionalities since the beginning of the century.

Orthoclear

• Founded in 2005 by Zia Chishti, one of the Invisalign system founders, based in Pakistan, ended its operations in 2006 after a corporate agreement with Align Technology that followed litigations related to trademark.

ClearCorrect

• Founded in 2006 in Texas, it was developed by one of the practitioners using Orthoclear, after it ended its operations, to be able to finish his patient treatments not using the Invisalign system, offered to old Orthoclear customers.
• This was made in collaboration with a technician working with plaster models. In 2008 they digitalized the process and were able to produce larger series of aligners, which they sent to the orthodontists together with the plastic models made for every movement.
• The Company was acquired in 2008 by Straumann group, together with some other companies with previous experience in the field to build an aligner system driven by this international holding.

Orthocaps

• Founded in 2006 in Germany by Khan, this system has a ‘method of combining two different soft aligners for day and night time use’. These two types differ from one another in both their composition and the amount of pressure they exert. This innovation is called the TwinAligner system.

Inman aligner

• Developed by a dental technician, Donal P. Inman in 2000 in Florida, it was initially for minor alignments and finally widely used by general practitioners for veneer preparation in a simple and more affordable way than other aligner brands.

1.4 Align Technology Development

Align Technology claims an investment over $1000M, which has made them a leader the clear aligner market over 20 last years, with more than 900 patents currently issued at the time of writing.

This progress has been possible thanks to an increasing clinical and engineering team that has been involved with many innovations over the years, such as: