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.
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. 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.
Align Technology was in a legal battle with the makers of a competing product, OrthoClear, from early 2005 until September 2006. 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.
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.
Advantages and disadvantages
The most obvious advantage of the treatment is cosmetic: 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, which are commonly worn by children and adolescents. In addition, the aligners are marketed as being more comfortable than 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, for example the effects on the gums and supporting tissues. Almost all other types of orthodontic treatment will cause the roots of teeth to shorten (root resorption) for most patients, and demineralisation or tooth decay occurs in up to 50% of patients 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.
Aligners should be removed to eat, drink, to clean the teeth, or to have them checked by the clinician. Because patients are able to remove the aligners, there are no restrictions on foods that could damage the appliances. Computerized treatment planning is compulsory as part of the Invisalign protocol. As with other forms of orthodontic treatments that incorporate a computerized plan, this allows the prospective patient to review the projected smile design, learn how long the treatment is likely to take, compare different plans, and make a more educated decision about whether or not to use Invisalign.
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, while Invisalign takes between 12–18 months. In a much smaller study 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.
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 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.
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. 
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. 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. 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.
In a systematic review of the literature, published in the Journal of the American Dental Association in 2005, 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. 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. In the USA, 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". In a comparison of outcomes between the two approaches, Kuncio et al. 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 Djeu and colleagues had similar findings to Akhlaghi above and concluded that "Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts". They felt that "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, work at NYU/Buffalo University by Dr Omar Fetouh in 2009, where 67 patients were studied, 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 posttreatment 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 Braces group. The study concluded that "Invisalign can treat mild cases of malocclusion (DI <5) as efficiently, if not better, as braces."
The treatment price is often more than traditional braces. Treatment price is set by the dentist or orthodontist, although the cost of treatment varies considerably by doctor. Doctor fees are usually determined by complexity and length of treatment. In the U.S., treatments range in price from $3,000 to $9,000, depending on geographic location. For example, in northwest Ohio, the case of a patient with a mild overbite and several teeth that needed to be turned cost $5,580.00 in 2008 (for a 13-month treatment).Whereas in Utah, the cost of Invisalign may only be $4700. Braces would have cost $5,225.00 (if the express treatment were available, it would have been $4,300). It is important to remember that costs vary from case to case. In Europe, the treatment price ranges from €3,000 to €7,800, depending on case complexity and length while Australia provides a price ranging from $5000 to $9000.
In Jordan, the treatment price is fixed for all cases and is JOD2,000.
An orthodontist, or general dentist, begins by taking dental impressions, x-rays and photographs of the patient's teeth and sending them to Align Technology. The impressions are put through a CT scan from which a computer creates a three-dimensional model. The information is sent to Costa Rica and is manipulated by non-dentist and non-orthodontist lay persons who individualize the teeth in the computer model and move them to their final position as prescribed by the orthodontist. Custom software then simulates the movement of the teeth in stages. The orthodontist reviews the simulation online using Align Technology's ClinCheck via a web browser and approves or modifies the treatment. Once approved, a plastic resin aligner is manufactured for each stage of the computer simulation and shipped to the orthodontist.
Attachments are sometimes bonded to teeth that need to be rotated or moved more than other teeth. Patients can expect as many as fourteen attachments. They are tooth-colored and made of composite material ( material is also used to fill cavities). Elastic wear (rubber bands) are also used to move the teeth forward or back relative to the jaw, thus accomplishing anterior or posterior corrections or intrusions and ectrusions. Reproximation, (also called Interproximal Reduction or IPR and colloquially, fileing or drilling), is sometimes used at the contacts between teeth to allow for a better fit. 
Average treatment time is about one year, again depending on the complexity of the treatment. Simple treatments (minor crowding, minor spacing) may be as short as twenty weeks—this is known as the "Invisalign Express" program. Although the aligners are removable, they must be worn at least 20 to 22 hours per day to avoid delaying the treatment process. If they are not worn consistently, treatment time will increase.
After the regular aligner or braces treatment is complete, retainers composed of a similar plastic material are usually required to be worn, at least at night.
Like other orthodontic systems, the patient has some flexibility. The final position of the teeth is not completely determined by the last aligner. If the patient wants to change the end position because the actual position is not optimal, new aligners are ordered, which are usually included in the originally quoted cost, called a 'Refinement.'
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