Unveiling the Magic of Invisalign: A Complete Guide to How it Works and Top Tips
Today I’m writing about Invisalign/clear aligners: pros, cons, dirty secrets, awesome results. Check out this video to see how it works: Clear Aligners Attachments.
A bit of history: The 3D printing of aligners changed the orthodontic field significantly since there was a more discreet way to move teeth. Invisalign was the first-to-market product 25 years ago. The company held over 40 patents for 3D printing of trays and these patents ran out in 2017, which allowed for many other companies to start commercializing the same product. These include Spark, 3M Clarity Aligners, Clear Correct, in-office 3D printed trays, and many more. The term "Invisalign" now is synonymous with "clear aligners," much like "Jacuzzi" with "hot tub". (I wish I was in a hot tub right now...but I digress)
The manufacturing is really cool and went hand-in-hand with the advances in 3D printing 20+ years ago. I use CAD CAM software to program in specific movements that I want on each tooth. Each tooth can move a maximum of 0.25 mm/direction of movement/tray. Then acrylic models of the teeth are 3D printed, with these sequential movements built in. Afterwards, the plastic is melted and sucked down on each model of the upper and lower teeth. Finally, the plastic is trimmed around the acrylic models and the models are removed, leaving a clear tray.
Wearing the trays: The way that the trays work is that they need to be worn 22 hours/day to be able to apply consistent pressure on the teeth. After about a week, the next tray is placed. The trays are taken in and out to eat and drink (except water). You definitely need to take them out to eat but some patients choose to drink with the trays in. The trays will take on the color and flavor of whatever you are drinking. For example, piping hot coffee is not a great idea with the trays in since the hot liquid can distort the plastic but iced coffee through a straw works well.
There is some misleading advertising and misconceptions around wearing the trays for the recommended 22 hours/day. Some companies claim that you can only wear the trays at night to achieve the same movements. This might be true for very small movements (like closing up a hairline space) but physiologic tooth biology does not correlate with these claims. The way teeth move through the jaw bone requires consistent pressure on the teeth for at least 14-16 hours before the bone cells start “working.” The remainder of the hours in the day is when the teeth actually move.
For all of my fellow science nerds, tooth movement occurs with bone resorption on the surface area of the root in the direction of movement followed by bone deposition on the other side. These cells need time for this to happen, especially with more challenging tooth movements, such as rotations. Who knew bone biology was so interesting!? ;) Whew! We got the history and science out of the way.
Clear aligners for Teens and Kids:
While I've done a lot of cases of teens and kids that can comply with wearing the trays, it's not usually my first go-to. It's a challenge for adults to wear the trays 22 hours/day, let alone a teenager that is snacking or eating multiple times or has a lot of sports drinks. The trays get lost a lot at lunch at school or on athletic fields. From experience, I need to switch over about 40-50% of teens from the clear aligners to braces - this adds time and cost and defeats the purpose. For Phase I Orthodontics for kids ages 7-9, I do not usually recommend Invisalign. Kids are transitioning between baby and adult teeth and there are usually multiple rounds of trays that are needed, which leads to a very lengthy treatment time. Braces work a lot faster for the quick goals that we try to accomplish in an earlier phase of treatment. Also, if a child has a jaw constriction or needs an expander, the trays do not have the strength to open the midpalatal suture and do skeletal expansion of the jaw.
Let me go into some pros and cons about clear aligners compared to braces.
PRO: LOOKS. The biggest benefit of clear aligners is the esthetics. Esthetically, the trays just appear a bit more shiny than normal teeth and are definitely more discreet than braces. Even in photos with a flash, the trays blend in well with the teeth.
PRO: COMFORT. The comfort aspect is also a big benefit. Since the trays are changed every week with sequential movements, the pressure on the teeth is incrementally smaller and way more comfortable than braces. Braces are “tightened” all at once and the pressure levels are more initially, making them more uncomfortable.
PRO: EATING! Braces have some food restrictions while the trays are taken in and out to eat, so you can eat whatever you want. The teeth and the trays are easy to keep clean – there is no food that gets stuck in the trays since you are taking the trays out.
CONS: USUALLY SLOWER. Braces, in general, are more efficient at tooth movements. This is also a common advertising push that Invisalign or clear aligners are magically faster. On average, I finish a case with braces about 6 months faster than with aligners. Clear aligners take a long time with the following types of movements:
1) Extruding lateral incisors. Anytime a tooth has to be brought down or extruded, the trays have a hard time “grabbing” the tooth. The lateral incisors are more conically shaped teeth and some patients have small incisors. Even when I place attachments on the teeth to anchor them, it still takes a while. Just for comparison, to extrude a tooth 1 mm with braces would take about 3-4 weeks. To extrude with aligners would take about 3-4 months.
You can see in the photo there is a gap between the lateral incisor and the tray. The technical term for this is that the tooth is “not tracking” or moving how I had programmed it to.
2) Aligning high canines or rotating canines. Canine teeth have the longest roots in the mouth and therefore move slowly.
3) Deep bite correction. The trays by default cover the biting surfaces of the teeth. A deep bite refers to the front overlap of the teeth, which is usually too much, and causes damage on the front teeth by wearing them down. The mechanics to correct a deep bite are to intrude the front teeth and extrude the back teeth. However, like we learned above, it takes a while to extrude teeth.
4) Significant overbite correction. When a patient has a large overbite, there are rubber bands or springs that can be used to correct this. The trays are sometimes not strong enough for this kind of major correction.
5) Premolar rotations. Rotational movements of premolars take a long time, especially in premolars with bifurcated roots.
CONS: WEARING THE TRAYS. It can be a challenge for some patients to wear the trays all the time. It’s a small percentage of patients who really struggle with being compliant with the trays. I completely get it, especially busy teenagers or parents of babies and toddlers (join the party!) – sometimes other priorities take over. Wearing the aligners requires a lot of discipline.
CON: ATTACHMENTS. Most patients will elect to go with clear aligners since they are clear. However, for almost all patients, I need to place attachments or anchor buttons on the teeth to help guide tooth movement. These attachments can discolor a bit over time with coffee, black tea, and curry and might appear yellow. The attachments can also be slightly more visible if I need them on the front teeth.
How to speed up:
I do a lot of combination cases in my office with clear aligners on the upper teeth and braces on the lower teeth to speed up the treatment time. The lower teeth are usually the ones that will crowd up the most over time and need the most straightening. Braces on the lower teeth are much more discreet since our lips rise up when we speak and smile and are not very noticeable. It’s not an option for everyone but we can mix and match to get faster results.
From experience, the biggest motivating factor when patients select one treatment over the other comes down to SPEED (braces) vs LOOKS (clear aligners). The choice is yours. Whatever you choose, the results will be phenomenal 😊
See me today for a FREE consultation in Arlington, VA and we can discuss all options. Call us today: 703-774-3070.