Clear aligners, also known as clear-aligner treatment, are orthodontic devices that are a transparent, plastic form of dental braces used to adjust teeth. There are about 27 products available including ClearCorrect and Invisalign.
Clear aligners have undergone changes, making assessment of effectiveness difficult. Experience suggests they are effective for moderate crowding of the front teeth, but less effective than conventional braces for several other issues and isn’t recommended for children. 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.
Clear-aligner treatment involves an orthodontist or dentist, or with home-based systems, the person themselves, 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. These slowly move the teeth into the position agreed between the orthodontist/dentist and the patient. The average treatment time is 13.5 months. Despite patent infringement litigation, no manufacturer has obtained an injunction against another manufacturer.
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. Dental impressions are scanned in order to create a digital 3D representation of the teeth. Technicians move the teeth to the desired location with the program Treat, which creates the stages between the current and desired teeth positions. Anywhere from six to forty-eight aligners may be needed. Each aligner moves teeth 0. 25 to 0.33 millimeters.
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. The aligners are modeled using CAD-CAM (computer-aided-design and computer-aided-manufacturing) software and manufactured using a rapid prototyping technique called stereolithography. The molds for the aligners are built in layers using a photosensitive liquid resin that cures into a hard plastic when exposed to a laser. The aligners are made from an elastic thermoplastic material that applies pressure to the teeth to move into the aligner’s position. Patients that need a tooth rotated or pulled down may have a small, tooth-colored composite attachment bonded onto certain teeth. More attachments can make the aligners less aesthetically pleasing. 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.
Each aligner is intended to be worn an optimal 22 hours a day for two weeks. On average the treatment process takes 13.5 months.
Treatment time varies based on the complexity of the planned teeth movements. 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
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.