By his own admission, Ryan Weiss’s teeth “needed some work.”
But braces and retainers -- especially the no-show Invisalign variety popular with adults -- are expensive, running more than $5,000. Ouch.
Then Weiss read a now-viral blog post that would change his outlook -- and his smile. The post, written in April 2016, outlined a way mere mortals can design and print their own invisible braces using a 3D printer, promising to help readers “save money, make yourself happier, and stick it to the dental appliance industry, all in one shot.”
Weiss was interested, save for one significant detail: he didn’t have access at the time to an accurate 3D printer. And, because he’d be designing and fabricating something that would go into his mouth, precision and accuracy were paramount.
Then Weiss started a new job with CIC client Envoy AI, which creates artificial intelligence solutions for radiology departments at hospitals and doctors’ offices. With his newfound access to 3D printing at Fab@CIC -- specifically, the Sindoh 3DWOX printer with which he became quite cozy -- he began to build his own set of “Invisalign” retainers.
We sat down with Weiss and asked him how he did it:
What has been your process in working on this project?
I started by taking a mold of my teeth the typical orthodontic way: by making a negative using alginate powder and dental impression molds, followed by a positive casting using "Perfectcast" casting material.
I sent these molds to be 3D-laser scanned at the Artisan's Asylum in Somerville. However, I was soon after given the opportunity to have my teeth professionally scanned in real time by a third-party outfit, and was able to obtain the 3D data from their scan. The second scan was much cleaner than the first, depicting each separate tooth to better ensure accuracy.
Once I had a 3D scan, with all the teeth separated, I imported it into Blender — a very popular free, open-source 3D modeling and animation toolkit. I then animated it from start to finish (ideal state), to my tastes, with an understanding of my teeth's limitations. Something to keep in mind is that in Blender, you can't really do things like pull the teeth down too much, or push them without getting a reverse force just the same. So you have to design the teeth to move with that in mind.
Here's what my Blender models look like:
From there, the rest is very simple. I exported the 3D model at every 10% of the animation from start to the ideal state. I took a guess here with 10% intervals, and if anyone isn't sure the percentage to move -- how many steps they'd need depending on their dental condition -- I suggest estimating based on your animation before printing one, molding an aligner onto it, and trying it out. If it's too tight/hard, reduce the percentage, i.e., increase the steps. One thing to note: when I set the mold density to 100%, the model base tends to swell up too much from the material cooling expansion, impacting the shape of the teeth slightly. To avoid this, I recommend setting the fill density no higher than 85%.
This is the beauty of 3D printing: you get to tune it to your needs, from all aspects. Go, go, DIY!
Another thing to keep in mind is that when printing these teeth sets, I had to tell the printer to thicken the sides of the mold, as the default settings for 3D prints will usually make solid materials hollow inside. When you vacuum-form the actual retainer material onto the 3D prints (which is the next step), the printed molds will heat up a bit. The vacuum process might suck the air out of the 3D mold itself, deforming it, causing the retainer material to mold incorrectly. Here are the settings I use to adjust the wall thickness:
I then export from Blender each of my model stages as a .stl file, then import those into the 3DWOX application. I export the top and bottom sets of teeth as separate models, but import them together within the 3DWOX application, requiring just one print session for both top and bottom, like this:
Then, once I've changed the settings correctly, as above, I save the “G-Code,” which are the basically the raw printer instructions with the settings embedded, and take it to Fab@CIC to print. After about seven hours, the top and bottom set of teeth are ready, I return, remove the model, and scrape it off — always fun.
Here are some of the prints:
Once the molds are printed, the next step is vacuum forming the Invisalign retainer material, which is the plastic stuff you wear, over the molds. A vacuum forming machine and the Invisalign material can both be bought on Amazon. The material I used worked great, and I wouldn't recommend anything thicker than .03 inches.
I place the plastic sheet into the machine, turn on the vacuum-form heat, and wait until the plastic is melted. It should sag about three centimeters or more. More sagging or melting means the plastic will come out thinner and more flexible, which may be necessary if the retainer is too tight or if teeth are too crowded. After about three minutes, when the sag looks good, I place the 3D teeth model into the bottom of the machine, lower the melted plastic onto it with the machine, then hit the vacuum button. This sucks the plastic onto the mold perfectly. After ten seconds or so, I turn it off and let it cool for about 30 seconds. Removing the mold from the vacuum-forming machine can be a little tricky, in which case I run cold water over it.
Here's what comes out of the vacuum-forming machine:
Then, I use a Dremel sander to carve out the teeth to my preferred fit -- a step that takes about 5 minutes per set. You don’t need a Dremel, however; scissors work just as well. Here’s my finished retainer:
Wow -- that is...incredible. How long did it all take? Was it expensive?
All in all, the whole process probably took me about three hours of actual work. This number is so low because it doesn’t include all of the hours of work that would have been required if I had to use a laser scan of my original teeth molds, and then clean up that 3D data. Because I was able to obtain a perfect, ready-to-go scan, I didn't have to do any work there. After that, it took about two hours to design the teeth to ideal. Animating is hardly any work, as Blender will mostly do that for you when you define the start and end positions. From then on, it's just a matter of sending the prints to the printer, and then molding the plastic onto it for each set.
As for the cost, here's a rundown of the total cost of supplies:
Teeth scan: free
“Invisalign” splint material (50-pack): $50
Vacuum-forming machine: $100
Filament for 3D prints: $60 for two rolls, which produce 10 sets (note: must use Sindoh-specific filaments if using the 3DWOX printer)
Total tools and materials cost: about $200
Sounds better than $5,000 for Invisalign, eh?
What's next for this project?
I still have six (out of ten) more sets to print and work through! I generally wear each set for about two to three weeks. Progress is moving pretty fast!
Any tips for someone looking to do a similar project?
The most challenging part is just getting an accurate scan of your teeth. If you can't obtain a professional scan like I did, you can mold your teeth, and send them out to a third party to laser-scan -- but that might run you about $400. I would suggest trying to find a detailed direct 3D scan from a business that might have access to those tools.
Finally, with regards to the teeth design and animation, you can obviously only move the teeth so much in each stage, so be sure to think about what would be comfortable. Fortunately, you can just reanimate and reprint if any sets are too tight, so don’t print all your sets at one time. Also, as I mentioned before, remember that you can't "pull" teeth down (or up, relative to bottom teeth), but rather only side to side. You'll have to play with this a bit, because you can pull, just a tad, in the opportunity presented when the teeth are in a “looser state,” and the retainer can slightly clamp onto teeth (i.e. a slight pull if necessary) — but nothing extreme in that regard.
Open wide and show us how it turned out!
Unbelievable, eh? Fab@CIC is not only helping inventors and startups jumpstart their product development, it’s impacting people’s health. Many thanks to Ryan Weiss for sharing his story -- and fascinating process! -- with us. If you’re interested in fabricating your own set of “Invisalign” retainers or have further questions about the process above, Ryan will graciously accept your inquiries via email: ryan [at] envoyai.com.