Clear, Removable Dental Braces
Sometimes, innovation comes as a flash. That happened to Zia Chishti, a student at Stanford Business School, when his orthodontist replaced his metal braces with a removable plastic brace that kept his teeth aligned. If plastic braces could put pressure on teeth to keep them from moving, he wondered, why couldn't a series of retainers push and rotate them into position.
Chishti knew many adults and older teens felt self-conscious wearing metal braces. Like other users, he was not allowed to eat hard, chewy, and sticky foods that might snap, bend, or get stuck in the wires. And he had to brush extensively after every meal to remove food from the metal.
Within two years, Chishti and three other Stanford graduate students, two of them engineers, founded Invisalign. They faced steep biomedical engineering challenges. First, they needed a way to predict tooth motion so they could build the series of 30 or so molds that would progressively force teeth into alignment. This led to the creation of software to model tooth and jaw movements. At first, Invisalign could only handle simple alignments, but as its database grew, it broadened its capabilities.
Invisalign also needed a way to make its incrementally aligned trays so that they would fit precisely over each individual's teeth. Its original process had patients bite down on a putty-like material to create a mold. Then it poured plaster into the impression to create a model, which it digitized by scanning it with a laser. Using this model, computers used 3D printing to produce a model of the teeth at each step of the treatment. It then heat-formed the patient's rigid plastic retainer over each 3D model.
Technology has continued to evolve. Retainer materials have grown stronger and no longer "relax" after weeks of use. Dentists replaced putty with hand-held scanners that generate CAD models on the spot, and Invisalign has begun creating retainers directly from those models.
The result is biomedical engineering that is hidden from about one million new patients every year. They see only the simplicity and flexibility of their new invisible brace.