Today, Invisalign is a household name and everyone knows what it is, but it wasn’t always this way. The concept of incremental tooth movement is not new, and the inventor of Invisalign did not really invent anything. What he did do was see how technology could be applied to an old method of doing things and leverage the technological advantages to create a new system of accomplishing an old time intensive process.
The way Invisalign, and all clear aligner therapy companies work is through incremental tooth movement. You get a series of clear plastic trays that are incrementally different. Each new aligner progresses from an initial tooth position and bite to a new position and bite, a fraction of a millimeter at a time until the desired tooth positions and bite are achieved. Depending on the required distance of movement and the difficulty of the tooth movement, this may take just a few clear trays or aligners, or it may take a whole bunch of aligners to reach the desired goal.
This type of treatment has been done for decades, and is the same process used with braces, but instead of wires and braces, a clear plastic aligner is used to effect the tooth movement. In the past, when the “aligners” were made out of a semi-vulcanized rubber, braces were much more efficient, comfortable, fashionable, and tasty. The old rubber aligners worked great, but looked like big, black boxing mouth guards and had a distinct tire tread taste.
The fabrication process involved an extreme amount of manual labor from a highly trained technician or the doctor, and it was very time consuming. The original black rubber “Positioners” were thick enough and flexible enough that you did not need a series of them to accomplish the desired tooth movements. The same appliance was worn from start to finish rather than moving from one aligner to the next. The teeth would move gradually, and in a similar fashion in both techniques, but the rubber was more flexible than the plastic and had a better rebound character which allowed it to move the teeth all the way through the programmed range of motion.
The fabrication process was completely different, as there was no such thing as CAD/CAM or computer modeling. For the Positioner (the original aligner), an impression of the teeth was taken, then a plaster model made from the impression. Most people are familiar with dental impressions, although now it is becoming much more common to take a scan of the teeth rather than an impression. The impression produces a physical plaster model, where the scan produces a digital image of the teeth. This digital image may be printed to produce a physical model, so you can get to the same place with either method.
The process for making a positioner is highly time consuming and involved compared to the digital method for clear aligners. Once an impression has been taken, and the plaster model made, this model is then duplicated by hand so there are working models available. One of the working models gets the teeth individually cut off of the model, then the gums reduced and replaced with a wax rim. The wax is then warmed and the teeth replaced in the wax and strategically reset into position to create the ideal bite and alignment. This process is all done by hand, and meticulous precision is needed to achieve the desired result. The models with the reset teeth and wax rims are duplicated so those models can then be used to fabricate the positioner which will ultimately be used by the patient. The positioner is then fabricated and finished, and those models are destroyed in the process. The final positioner is checked for fit on one of the other models that was duplicated from the wax rim model.
The craftsmen who do this are masters at their art. Unfortunately they have been replaced by computer geeks and the virtual models and technology that is currently in use. Fortunately, these craftsmen have the capacity needed to pivot and use their skills in other ways to benefit all of us as patients. Most have embraced the new technologies and upgraded their skills as things continue to change and progress.
With the new technology, what happens today is that the teeth are scanned and a virtual 3D image of the teeth and gums are stored. If a model is needed, it is simply printed and used. The process has changed as the materials and technology has changed. Currently, instead of resetting the teeth in a plaster model, the original digital image is saved and duplicated, and teeth are moved digitally. The computer program will allow the technician to specify the distance of the incremental movements of the teeth in all 3 dimensions. A final tooth setup is done virtually, and based on the incremental movements specified, a series of models is created virtually that progress from the original model to the final setup. Each of these models is then printed and a clear plastic aligner is fabricated. The patient wears each aligner long enough for the plastic to effect the tooth movement needed so the next aligner can continue the process. The teeth should be tracking or moving in harmony with the progression of the aligners, and this process continues until the last aligner is reached. At this point, if the teeth have tracked completely, the intended ideal result would be achieved. If the teeth don’t track completely, or there are some minor discrepancies between the virtual result and the actual result, a new series of aligners will need to be done to refine the actual result. In this case, a new scan of the teeth is done and the process is repeated, but since the teeth are a lot closer to an ideal position, the number of aligners is noticeably reduced.
With Invisalign and all clear aligner companies, it’s the technology and the application of the technology that allows the process to be leveraged and applied to a broad audience. Once it became possible to capture a virtual image of the teeth, and manipulate the image, then print the image so a physical model can be used, it was game over for the manual process. The virtual process is much faster, requires less human intervention, and multiple images can be processed simultaneously.
Zia Chisti is credited with being the first one to recognize the potential for automating the process of moving teeth and started Invisalign. He grew the company and stayed with it for a number of years, but ultimately took his golden parachute and jumped. He took his money and purchased a majority interest in the largest of the customer service call centers and moved them to his home country; Pakistan. For several years, many of us suffered an inability get help from a call center because they couldn’t understand us and we couldn’t understand them. Thanks Zia! Fortunately more companies have moved their customer service in house and back to their home bases and our experience and ability to communicate have both improved.
Invisalign has done a tremendous amount of development while pioneering clear aligner therapy, and have protected their investment with numerous (read; hundreds) patents. For decades they added patents on every minute step of the process and have been successful at destroying their competition through the legal system and multiple law suits for patent infringement. Since they were the only player in the market, they had little incentive to maintain an ongoing R&D system or push the process ahead as new technologies continued to emerge. Their old process was sufficiently effective, and without competition in the marketplace, there was no need to improve while they were protected by their patents.
They were able to maintain control of the market and the status quo until the patents started to expire. There were several months running where Invisalign had 40+ patents expiring every month. This has resulted in the market seeing almost everyone in the dental industry coming out with their own process for clear aligner therapy. The current market place is very competitive and as a result, there have been significant improvements in the processes and materials used. Under pressure, Invisalign has responded and updated their plastics and processes, and remains The major player in this market segment of dentistry and orthodontics.
As the technology continues to improve and the materials develop in tandem with the technology, this doctor predicts that it will not be long before we will have no need of printing a model of the teeth to fabricate the aligners we will be using in the near future. We are currently printing models and pressing the plastic over the model so it adapts to the teeth and attachments. In the future, it is anticipated that materials will be developed so the aligners can be printed directly off the virtual image of the teeth without the need for a physical model. This will be a great advantage for the environment as well as the manufacturers and patients. Less material means less waste and reduced costs, which should make everyone happy.
Materials science is advancing rapidly and they are getting greater and greater control of how to manipulate the properties of the plastics used so they have the flexibility and regidity to move the teeth more predictably and effectively. This will increase efficiency and reduce the time and number of aligners needed to complete treatment. As we print the aligners directly, production will be more efficient, costs will reduce, and so will the wait time when treatment starts or a refinement is needed. Invisalign and clear aligner therapy is a great way to experience orthodontic treatment, and it will only get better as the technology and materials improve!