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Invisalign teeth aligner

Invisalign is a proprietary method of orthodontic treatment which uses a series of clear, removable teeth aligners used as an alternative to traditional metal dental braces. As of April 2008, more than 730,000 patients have completed or are currently in treatment.[1]

Invisalign is designed, manufactured, and marketed by Santa Clara-based medical-device company Align Technology, Inc. Align says that over 35,790 doctors are trained to provide Invisalign treatment in the U.S., with 48,130 doctors worldwide.[1] As of January 29, 2008, Align Technology has 1,307 employees worldwide, and has manufactured more than 32 million aligners. The company has 133 patents.[citation needed]

Align Technology was involved in a legal battle with the makers of a competing product, OrthoClear, from early 2005 until September 2006.[2] Zia Chisti, one of the founders of Align, had started OrthoClear to compete against Invisalign. In a complaint filed with the United States International Trade Commission (ITC) on January 11, 2006, Align alleged that OrthoClear utilized Align's trade secrets and infringed twelve Align patents, comprising more than 200 patent claims, in the production of OrthoClear aligners at a facility in Lahore, Pakistan. On September 27, 2006, Align Technology settled its litigation with OrthoClear. OrthoClear has stopped accepting new cases and discontinued its aligner business worldwide. Align acquired all disputed intellectual property. Contrary to some reports, Align did not purchase OrthoClear.[2]

Align Technology is also defending a class action suit on behalf of dentists and orthodontists who were suddenly dropped as approved Invisalign providers because they failed to meet a never-before-mentioned quota requirement. After prescribing doctors paid thousands of dollars each for Invisalign training, Align Technology unilaterally implemented a requirement that every provider start at least 10 new cases a year. The doctors are seeking a refund of the training cost because the training has no utility except in the prescription of Invisalign products.[3]

Treatment process[edit]

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

Once a dentist or orthodontist decides that a patient is a candidate for Invisalign,[4] treatment begins with the doctor taking x-ray, photographs, a bite registration and polyvinyl siloxane impressions of the patient's teeth and gums. Additionally, the dentist or orthodontist completes a six-page form with a diagnosis and treatment plan.[5][6][7][8] Dental impressions are sent to Align Technology and scanned using a computerized tomography scanner which creates a digital 3D representation of the patient's teeth.[8][9] Computer technicians move the teeth to the desired location in a software program called Treat, which creates stages between the current and desired teeth positions for individual aligners.[5][7][10] About six to forty-eight aligners may be needed depending on the patient, with each aligner moving teeth up to .33 millimeters.[6][11][12]

A computer graphic representation of the projected teeth movements is provided to the doctor and patient in a software program called ClinCheck for approval or modification before aligners are manufactured.[6][7][10] 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.[10][13][14] Patients that need a tooth rotated or pulled down may have a small tooth-colored[15] composite attachment bonded onto certain teeth.[10] More attachments can make the aligners less aesthetically pleasing.[7][16] 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.[17][18]

Each aligner is intended to be worn 20 hours a day for two-to-three weeks.[19][20] On average the treatment process takes 13.5 months.[21] Refinements may be ordered by the doctor during the treatment process.[16] The aligner is removed for brushing, flossing and eating.[22] Once the treatment period has concluded, the patient is advised to continue wearing a retainer at night for the foreseeable future.[16]

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

Advantages and disadvantages[edit]


The aligners are completely transparent, therefore far more difficult to detect than traditional wire and bracket braces. This makes the method particularly popular among adults who want to straighten their teeth without the look of traditional metal braces. Due to the removable nature of the device, food can be consumed without the encumbrance of metallic braces.

Clinically, aligners avoid many of the side effects of traditional fixed appliances,[17] for example the effects on the gums and supporting tissues.[23] Almost all other types of orthodontic treatment will cause the roots of teeth to shorten (root resorption) for most patients,[24] and demineralisation or tooth decay occurs in up to 50% of patients[25] because (unlike Invisalign) they cannot be removed for eating and cleaning, and because they prevent accurate x-rays from being taken. Patients "graduate" to a new set of aligners in their treatment series approximately every two weeks. The aligners give less force per week and less pain than do fixed appliances (traditional metal braces). Fixed appliances are adjusted approximately every six weeks and apply greater forces.[26]

Invisalign treatments have been claimed to be quicker than traditional orthodontics. A large-scale study of 408 patients with traditional appliances in Indiana took an average of 35.92 months with a maximum of 96 months,[27] while Invisalign takes between 12–18 months.[17][28] In a much smaller study[29] Invisalign was shown to be faster and achieve straighter teeth than alternatives but relapsed to ultimately get similar results to the traditional appliances examined. The study was considered by the authors, however, to be too small for many conclusions to be statistically significant. Furthermore, this general concept that Invisalign is faster has been challenged by the Invisalign review which points out that there are other brace appliance systems that take half the time, for example by incorporating surgery or temporary implants that insert into the patient's bone, to accelerate the procedure.[citation needed]


Invisalign does not require a cephalometric radiograph. Orthodontists use this type of x-ray to find a treatment for the final angulation of the teeth, keeping in mind the patient's facial profile. Invisalign does not take this into account and does not require a cephalometric radiograph, because an orthodontist plans treatment, not Invisalign (Align Technology).

Like traditional fixed braces, they are largely dependent on a patient's habits and their cooperation. The success of the Invisalign aligners is based on a patient's commitment to wear the aligners for a minimum of 20–22 hours per day, only removing them when they are eating, drinking, or brushing their teeth.

The system is also somewhat expensive, as conceded by the Align company[citation needed] and can be more expensive than traditional wire and bracket systems.

The aligners must be removed before eating, an advantage and disadvantage depending upon the person. They and the teeth should be cleaned before re-inserting them afterwards. The aligners should always be removed when eating, and also when drinking anything that is not water or any cold, clear, non-sugary liquids. Sugars and other debris could become caught in the aligner causing cavities and other dental problems.

Because the aligners are removed for eating, they could be lost. Invisalign recommends that the patient keep the previous aligners in case this happens. However, Invisalign provides two plastic containers to keep the braces in, so they are less subject to loss or damage.

Certain teeth are slightly problematic for Invisalign aligners to rotate. Some lower premolars with their rounded shape can be difficult for the aligners to grasp and apply a rotational force to, so bonded attachments made from composite material may be required.[30]

Also, due to the nature of the design, Invisalign treatment may require the use of auxiliary techniques for teeth that require vertical movement, such as teeth that are higher in the gum line than other teeth (known as intrusion and extrusion of teeth). The aligners (without composite attachments) work by applying pressure on teeth, whereas teeth that are too low or too high require pulling/pushing to be moved into place. This would require the use of different types and styles of composite attachments called buttons on certain teeth with the use of elastics to accomplish the intrusion/extrusion.[31]

Unlike traditional braces, if a patient grinds or clenches her or his teeth during the day or while sleeping, the aligners can become damaged, however this protects the teeth from damage which would otherwise occur. In practice, however, this problem is very rare and a new aligner can be ordered. Also, similar to traditional metal braces, aligners may cause a slight lisp at the beginning of treatment. This usually disappears as the patient becomes used to the treatment.

The aligners are constructed of implantable-grade polyurethane, and the Align company has acknowledged that, though extremely rare, there may be cases of allergic and toxic sensitivity reactions to Invisalign.[32] Minor symptoms such as sore throat, cough, and nausea have been reported. Due to the nature of the treatment and the need to move the teeth, mouth and jaw pain can be expected when changing aligners. Headaches can also be a disadvantage. In more serious cases, the FDA has received reports of systemic swelling or throat pain that has extended to the upper chest and wind passages requiring emergency medical treatment and discontinuation of the Invisalign treatment.[citation needed] While the Invisalign company provides no information except the MSDS (material safety data sheet) directly to patients or orthodontists, working through the patient's orthodontist Invisalign will make the aligners with several different materials to attempt to reduce toxic or allergic sensitivity.

Should the treatment go off track, or patients fail to keep the aligners in for the required length of time, then the next aligner in the series will not fit, and a new set of impressions and aligners will be necessary, adding to the cost.[28]

Scientific studies[edit]

In a systematic review of the literature, published in the Journal of the American Dental Association in 2005,[33] Drs. Manual Lagravere and Carlos Flores-Mir were unable to draw strong conclusions about the effectiveness of the Invisalign system. They pointed to the need for randomized clinical trials.[33] Since this paper, more studies about the clinical effectiveness have been published; for example in the UK, Dr Paul Humber has analyzed 100 back-to-back Invisalign cases. Assessing the patients after two sets of aligners, he found that 94% of the dentitions had achieved the objectives set.[17] In the US, Akhlaghi and colleagues compared treatment with the Invisalign system with treatment with conventional braces and concluded that "conventional fixed appliances achieved better results in the treatment of Class I mild crowding malocclusions".[34] In a comparison of outcomes between the two approaches, Kuncio et al.[29] reported that the Invisalign group displayed greater relapse saying "the mean alignment of the Invisalign group was superior to the Braces group before and after the retention phase, but these differences were not statistically significant. Therefore, even though the Invisalign cases relapsed more, they appear to have the same, if not better, overall alignment scores." In a larger study[35] Djeu and colleagues had similar findings to Akhlaghi and concluded that "Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts". They wrote "The strengths of Invisalign were its ability to close spaces and correct anterior rotations and marginal ridge heights." They added, "Invisalign patients finished 4 months sooner than those with fixed appliances on average."

Furthermore, in 2009 Dr. Omar Fetouh at State University of New York at Buffalo[36] studied 67 patients, half of whom were treated with Invisalign and half with traditional braces. All cases had Difficulty Index (DI) less than 5 and were treated non-extraction. The post-treatment results were graded using the ABO Objective Grading System. The results show that there was no statistical significant differences between the scores of both groups in treatment alignment (p=0.059), occlusal relationship (p=0.223) and interproximal contacts. The Invisalign group had higher scores in marginal ridges, bucco-lingual inclination, occlusal contacts, and overjet than the braces group. The study concluded that "Invisalign can treat mild cases of malocclusion (DI <5) as efficiently, if not better, as braces."


  1. ^ a b Align Technology Announces Fourth Quarter and Fiscal 2007 Results
  2. ^ a b Align Technology and OrthoClear Complete Definitive Agreement
  3. ^ "Courthouse News Service". 2010-05-14. Retrieved 2013-09-15. 
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Further reading[edit]

  • Align Technology, Inc. (Apr 6, 2000). Straightening Teeth Over the Internet; Thousands of Orthodontists Use Web for First Time to Treat Patients. Press Release.
  • Align Technology, Inc. (Jun 20, 2006). NAD Refers OrthoClear Inc. to FTC. Press Release.

External links[edit]