Invisalign is a very well known system of moving teeth but some people do not know how Invisalign works. First, here are some facts about Invisalign.
Align Technologies, Inc was founded in 1997 and their first sale was in July 1999. By April 2009, they had treated their one millionth patient. Two million patients were treated in November 2012 and in March 2015, their 4 millionth patient had been treated. As you can see, Invisalign has been excepted by orthodontists as a way to treat malocclusions. With the advent of computers, digital scanners and 3d printers, Invisalign active clear aligner treatment is possible.
The advantages of active clear aligner treatment is numerous. First, the appearance. Treatment can be performed without unsightly braces. Secondly, good oral hygiene is easily maintained. Third, a better controlled movements can occur verses braces. Finally, the cost is about the same as traditional braces. The largest disadvantage is patient compliance. If you don’t wear the aligner 22 hours per day, your teeth will not move and you’re wasting time and money.
What can Invisalign not do? Invisalign has a hard time correcting anterior-posterior discrepancies. If you have a large overjet, which is a horizontal measurement from the incisal edges of the lower teeth to the upper incisors, you have to wear elastics or in some cases, a fixed appliance to get rid of the excessive overjet. Class II correction is more difficult with Invisalign.
I’ll go through the sequence of how Invisalign is used to move your teeth.
You need a Good Digital Scan of Your Teeth
After orthodontic records are taken. An accurate representation of the dental arches are needed. You have to have an very detailed digital model of the occlusal surfaces to fabricate the aligners. This can be accomplished in a couple of ways. One way is to take a polyvinyl siloxane (PVS) impression which is very accurate and has fine detail of the gum tissue and teeth. A tray is used with PVS impression placed into the tray, then in the mouth. Once the impressions are completed, they are shipped in a box to Align Technologies, Inc. Once they get to their processing plant, the impressions are digitally scanned. Any defects in the impression will show up in the scan and may cause Invisalign to ask for another new impression.
iTero – Invisalign’s Digital Dental Scanner
The other option besides a PVS impression is a digital dental scanner. Invisalign has it’s own scanner called iTero. The dental scanner has a wand that is placed in the mouth and a point cloud is made by laser or by strobe lights. The assistant has to pass the wand over the teeth watching the monitor for an accurate scan. Once the scan is done, the point cloud is saved as a STL file and the digital scan is sent to Invisalign via the internet. The scan is faster and more accurate than a PVS impression. Look at the picture below of the scanned premolar. Notice that the surface is a series of small triangles.
Your orthodontist creates on Invisalign’s web portal, an account for the patient and a prescription describing what movements need to occur.
Once the scans of dental arches are complete, an Invisalign tech will digitally separate each tooth in the digital scan, along with it’s gum tissue so they can move each tooth separately in the computer. A technician then, with the guidance of an orthodontist, will move each tooth per each aligner to go from malocclusion to a corrected occlusion. Align Technologies has developed and perfected their own propriety software systems to move your teeth accurately. There are a few companies like Orchestrate 3D that provides in-house software to an orthodontist so that the orthodontist can move the teeth prior to aligner fabrication. This would by-step Invisalign completely but place more work on the orthodontist. It places more work in the orthodontists’ lap, which they may not want to do. Below is a picture of Orchestrate 3D’s software where each tooth has been segmented in the STL file.
Once Invisalign’s tech is satisfied with the sequence of movements, they send a ClinCheck to your orthodontist. A ClinCheck is a graphic representation of the movements of your teeth from the first tray to the last. Watch the animation below. Your orthodontist reviews the ClinCheck and can make changes to it. Once the ClinCheck is approved, Invisalign starts making your aligners.
Once your orthodontist has your aligners, they will phone you and set up an appointment to fit your aligners and begin the process. At your first appointment, they will place attachments if indicated by the treatment plan. Attachments are composite resin placed on the front surface of the tooth to help move the tooth. Look at the picture below. The circle indicates attachments. They come in different shape and sizes.
Once the attachments have been placed, your orthodontist will seat your first aligner. They will give you specific instructions on how to wear the aligners and how often to change them. Usually, an aligner is worn 22 hours out of 24 and changed every two weeks. They are not worn when you eat your meals. As you progress from one aligner to the next your teeth are slowly being moved into their new correct positions. \
During treatment, your orthodontist may have to create space between your teeth. This is called Interproximal Reduction (IPR). If you look at the picture above, you will see .5 mm in seven different locations where IPR will be performed during treatment on this patient. This does not hurt the teeth and helps create space to accomplish the movements needed.
Finally, when you get to your last aligner, you will be fitted with a retainer to hold the teeth in their new positions. Congratulations, you have created a better smile.
Consult with an orthodontic specialist to find out if Invisalign is a good match to correct your malocclusion. Find a specialist at the American Association of Orthodontists website my clicking here (http://mylifemysmile.org).
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