Clear aligners

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Clear aligners
A clear plastic device in the shape of teeth
An Invisalign aligner

Clear aligners, also known as clear-aligner treatment, are orthodontic devices that uses incremental transparent aligners to adjust teeth as an alternative to dental braces. They are sold under various brand names including ClearCorrect and Invisalign.

A 2014 systematic review concluded that there is insufficient evidence to determine the effectiveness of these therapies.[1] Opinion is that they are effective for moderate crowding of the front teeth, but are less effective than conventional braces for several other issues.[n 1] In particular they are indicated for "mild to moderate crowding (1–6 mm) and mild to moderate spacing (1–6 mm)," in cases where there are no discrepancies of the jawbone. They are also indicated for patients who have experienced a relapse after fixed orthodontic treatment.[3]

Clear-aligner treatment involves an orthodontist or dentist taking a mold of the patient's teeth, which is used to create a digital tooth scan. The computerized model suggests stages between the current and desired teeth positions, and aligners are created for each stage. Each aligner is worn for 20 hours a day for two weeks.[4] These slowly move the teeth into the position agreed between the orthodonist/dentist and the patient. The average treatment time is 13.5 months.[5]


A 2014 systematic review concluded that there is insufficient evidence to determine the effectiveness of these clear aligners.[1] Opinion is that they are likely useful for moderate front-teeth crowding. In those with teeth that are too far forward or backward, or rotated in the socket. The aligners are likely not as effective as conventional braces. More cases of relapse of the anterior teeth have been found with Invisalign compared with conventional braces.[2] A 2013 Cochrane review found no high-quality evidence with respect to the management of the recurrence of lower-front-teeth misalignment following treatment.[6]

Clear aligners are more noticeable than lingual braces, but are probably more comfortable. They can be removed, which makes cleaning of the teeth easier, and they are faster for the dentist to apply.[2]


3D representation of a person's teeth in the Invisalign software

Treatment begins with taking x-ray, photographs, a bite registration, and polyvinyl siloxane impressions of the person's teeth and gums. The dentist/orthodontist completes a written evaluation that includes diagnosis and treatment plan.[7][8][9][10] Dental impressions are scanned in order to create a digital 3D representation of the teeth.[8][9] Technicians move the teeth to the desired location with the program Treat, which creates the stages between the current and desired teeth positions.[9][10][11] Anywhere from six to forty-eight aligners may be needed. Each aligner moves teeth .25 to .33 millimeters.[4][7]

A computer graphic representation of the projected teeth movements, created in the software program ClinCheck, is provided to the doctor and patient for approval or modification before aligners are manufactured.[7][9][11] The aligners are modeled using CAD-CAM (computer-aided-design and computer-aided-manufacturing) software and manufactured using a rapid prototyping technique called stereolithography.[8][9] The molds for the aligners are built in layers using a photo-sensitive liquid resin that cures into a hard plastic when exposed to a laser.[8] The aligners are made from an elastic thermoplastic material that applies pressure to the teeth to move into the aligner's position.[11][12][13] Patients that need a tooth rotated or pulled down may have a small, tooth-colored[14] composite attachment bonded onto certain teeth.[11] More attachments can make the aligners less aesthetically pleasing.[9] Reproximation, (also called interproximal reduction or IPR and colloquially, filing or drilling), is sometimes used at the contacts between teeth to allow for a better fit.[15][16]

Each aligner is intended to be worn 20 hours a day for two weeks.[4] On average the treatment process takes 13.5 months.[5] Treatment time varies based on the complexity of the planned teeth movements.[4] The aligner is removed for brushing, flossing and eating. Once the treatment period has concluded, the patient is advised to continue wearing a retainer at night for the foreseeable future.[citation needed]

When the Invisalign system was first developed, many of the aligner manufacturing processes were carried out by hand, and computer technicians had to modify each tooth in the computerized model individually.[8]


Woman wearing a clear aligner

Align Technology[edit]

Invisalign is manufactured by Align Technology, a multinational medical-device company headquartered in San Jose, California. The company was founded in 1997 by Zia Chishti. Chishti conceived of the basic design of InvisAlign while an adult orthodontics patient. During his treatment with a retainer intended to complete his treatment, he posited that a series of such devices could effect a large final placement in a series of small movements. He partnered with Kelsey Wirth to seek developers.[7][8][17]

Invisalign was approved by the Food and Drug Administration in 1998, and sales began in the U.S. in 1999.[2][9] $140 million in venture capital was raised from 1997 to 2000, and another $130 million in an initial public offering in 2001. As of 2014, according to Align Technology, 2.4 million people around the world had been treated with Invisalign, and 80,000 dentists had been trained how to use it.[2]

Orthodontists were resistant to adopting Invisalign at first, in particular because the founders had no orthodontic credentials or expertise, but the product became popular among consumers.[7] In 2000 Align Technology planned a $31 million television advertising campaign that The New York Times said would be "the most aggressive consumer advertising plan the dental profession has ever seen."[18] The company raised about $140 million in funding over four rounds from 1997 to 2000.[18][19] $130 million in additional funding was raised in 2001 through an initial public offering on NASDAQ.[17][20] By 2001, 75 percent of the 8,500 orthodontists in North America had been trained on the Invisalign system.[17][21] That same year, Align Technology made Invisalign available to general dentists following a class-action lawsuit that alleged making the system available only to orthodontists resulted in unfair competition for dentists.[17][21]

In the early 2000s, Align Technology was spending nearly all of its revenues on marketing and advertising, and losing about $18 million per year.[22][23] Cofounders Wirth and Chishti resigned from Align Technology in 2001 and 2003 respectively,[24] with Thomas Prescott replacing Chishti as CEO in March 2002. Prescott re-focused the company on North America and cut the marketing budget to about one-third its original size.[22][23]

The Invisalign system grew from 80,000 patients in 2002 to 175,000 in 2004. It won several awards for stereolithography, medical design and fast growth. Align Technology was profitable for the first time in 2003. In 2005 the company expanded into Japan, and acquired General Orthodontic, an orthodontics firm that supported doctors prescribing the Invisalign system. Later that year the Harvard School of Dental Medicine began requiring that its orthodontic graduate students complete Invisalign certification before they graduate.[22]

The Invisalign Express 10, which uses 10 aligners, was introduced in 2005.[25] Invisalign 1.5 was released in 2009. It was followed by Invisalign G3 in 2010 and G4 in 2011. Invisalign G3 and G4 were designed for more complex treatments. An Invisalign Express 5 version, which uses 5 aligners, was introduced in 2012.[26] In February 2014, Align Technology released a G5 product designed to treat deep bites.[27]

Support, software engineering, pre-production and administrative functions are done from Align Technology's headquarters in California. The manufacturing of Invisalign aligners is performed in Mexico[17] and treatment plans are created in Costa Rica. Align Technology also operates separate subsidiaries in Hong Kong and Australia that sell Invisalign in their respective markets.[28] Align Technology provides training and certification to doctors.[9][29]

In 2007 the Academy of General Dentistry approved Align Technology's Program Approval for Continuing Education (PACE) program.[citation needed] The company also created the AlignTech Institute, which provides educational resources to doctors.[28] In March 2011 Align Technology acquired Cadent System, Inc., a dentist firm, for $190 million.[30]


Zia Chishti was ousted from Align Technology in 2002. In 2005 he developed Orthoclear, a similar product, which resulted in several legal disputes involving allegations of patent infringement, false advertising, defamation and trademark infringement. The case was settled in 2006.[24][26][31] Align paid OrthoClear $20 million and OrthoClear agreed to end its operations.[26][32]


ClearCorrect, LLC, based in Round Rock, Texas, was established in 2006. The company distributes its product throughout the United States, and in 2011 was named the fastest-growing health company in America by Inc. magazine.[33][34]

ClearCorrect was founded in Houston, Texas, by Willis Pumphrey, Jr., a dentist.[35][36] In 2001 Pumphrey started using Invisalign.[37][38] He decided to switch to OrthoClear, because of the way OrthoClear manufactured its aligners and because of its reduced lab fees.[39] When manufacture of Orthoclear ceased, Pumphrey had 400 patients in treatment. With no other options available, he started his own company to complete his patients' clear aligner treatment.[40]

Society and culture[edit]


The litigious history in the clear aligner market prompted ClearCorrect to be proactive in addressing patent issues between itself and Align Technology. Align had previously filed a complaint with the U.S. International Trade Commission against OrthoClear Inc., In the end an agreement was made between Align and OrthoClear in which Align paid OrthoClear $20 million for its intellectual property and OrthoClear agreed to stop accepting cases in the United States.[38]

In 2009 Align Technology began to require that doctors prescribing Invisalign complete at least ten cases per year and ten hours of training in order to maintain their Invisalign provider status. In January 2010, 20,000 doctors had their certification suspended for not meeting the requirements, but a class action lawsuit regarding providers that paid for training under the original rules resulted in some certifications being re-instated.[41]

In February 2009, ClearCorrect filed a declaratory judgment against Align Technology. ClearCorrect claimed that some of Align’s patents were invalid, and thus ClearCorrect’s product did not infringe on Align’s patents.[40] ClearCorrect voluntarily dismissed the suit in April 2009, after Align stated to the court that it had no intention of suing ClearCorrect for patent infringement.[40][42]

On February 28, 2011, Align Technology filed two lawsuits against ClearCorrect. Align alleged that under California’s Unfair Practices Act, that ClearCorrect sold products for a price below the average production cost, with the purpose of "destroying competition in the market for clear aligner systems." Align also claimed that ClearCorrect infringed eight of Align's patents.[43]

On May 12, 2011 ClearCorrect filed a countersuit against Align Technology, denying allegations that it is infringing on Align patents. In the countersuit, ClearCorrect alleged that Align's allegations are invalid and accused Align of patent misuse and double patenting. The countersuit cited much of the evidence raised in Align's previous patent case against Ormco, which resulted in a federal court ruling that 11 of Align's patent claims were invalid.[44]



  1. ^ Daniel A. Kuncio (The New York State Dental Journal), 2014: "Invisalign has been proven to resolve moderate anterior tooth crowding predictably, but treatment outcome studies have highlighted Invisalign’s weaknesses compared to conventional braces in treating anterior-posterior discrepancies, large rotational movements and the extrusion of teeth. More post-treatment relapse of anterior dental alignment has also been found in Invisalign cases."[2]


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Further reading[edit]