Clear aligners and tooth scanners are the two parts of a treatment often called invisible braces. Clear aligners are thin, transparent plastic trays that fit over the teeth and move them, a little at a time, into a straighter position. They are an alternative to metal braces. Each patient gets a series of aligners, made to fit their own teeth from a 3D scan of the mouth. The scan is taken with a tooth scanner, called an intraoral scanner.
The scanner is a wand about the size of an electric toothbrush. The dentist moves it around the teeth, and its camera takes thousands of images in a few minutes. Software joins the images into a 3D model of every tooth and the gums. Before scanners, the dentist pressed a tray of soft putty onto the teeth to take an impression, which many patients find unpleasant.
From the model, treatment planning software works out how each tooth must move. It divides the whole movement into small stages, usually no more than about a quarter of a millimetre per tooth at each stage. An orthodontist, a dentist who specialises in straightening teeth, checks the plan on screen, adjusts it and approves it. The software also shows the patient an animation of how the teeth will look at the end.
Then each stage is made. A 3D printer prints a resin model of the teeth as they should be at that stage. A sheet of clear plastic is heated and pressed over the model, and a machine trims it along the gum line. This is mass customisation with 3D printing: the factory makes millions of aligners, and no two are the same.
Consider a 23-year-old college student in Mangaluru with crowded front teeth. Her scan is taken at a dental clinic, which books her visits through practice management software. Her plan needs 20 stages for each jaw. She wears each aligner for about 22 hours a day, and changes to the next one every 10 days. So the treatment takes about 200 days, or roughly seven months, with a check-up every few weeks. If a tooth does not move as planned, the dentist takes a new scan, and the software makes a revised set of aligners.
The same scan is useful elsewhere in the clinic. Dental CAD/CAM uses it to design crowns. The printing is done in the aligner maker's own factories, or by on-demand manufacturing companies. In India, a course of aligners costs from about one lakh to several lakh rupees, and it must be prescribed by a dentist.