Orthodontic Articles & News by Dr. Scott Frey

Taco Bell addict. Board Certified Orthodontist at Hatcher & Frey Orthodontics. Click here to Facebook me / Stalk me on Instagram

Understanding Invisalign’s SmartStage Technology

April 8, 2017 by Scott Frey Leave a Comment

What is SmartStage Technology?

Invisalign’s newly developed SmartStage technology is helping make orthodontists’ prescribed movements much more predictable using pre-activated attachments and unique aligner forming features. Currently, you will be alerted to SmartStaging in the comments section of your ClinCheck when it is being utilized. However, the behind the scenes functioning of SmartStage seems to be a tough concept for many people to grasp so I feel that it warrants some additional attention. Below is an example of what a SmartStaged movement looks like in your digital set-up:

By compiling treatment data from what now extends into the millions of cases, Invisalign is now taking into consideration the optimal path of tooth movement, as prescribed by the orthodontist, when modifying the shape of the aligner. This allows for more precise aligner activations to be delivered at a given stage.

This is a lot like shooting clay pigeons. You never shoot at the clay……You have to calculate the flight line and lead target before pulling the trigger. Invisalign is employing this same concept with SmartStage to arrange for a “successful collision” between the tooth and the aligner at any given stage. This means more ideal force systems, better tracking of aligners, and faster treatment with Invisalign.

*Image Courtesy of Duck Hunt

All Hail Our Robot Overlords

April 7, 2017 by Scott Frey Leave a Comment

The Impending Robot Apocalypse

The Promethean Myth that we will end up creating a technology that will destroy us appears to be deeply engrained in our human psyche. More and more I am beginning to hear orthodontists say, “the machines are getting smarter, and pretty soon, they’ll come for us.” I prefer not to operate on superstition.

If we are being honest, automation is a problem that we all love to have because it frees us up to do more vital and productive things in our businesses and lives. Greater efficiency through automation is the essence of why we train our orthodontic teams and develop our own clinical systems. It seems to me that the intuitions we have about machine learning, Invisalign, algorithms, automation, etc. are somewhat poorly formed. Technology exists to augment our abilities, not to replace them.

In orthodontics, and in just about every industry, we will need to learn to embrace our non-human co-workers, who will be gathering data and helping us direct patient care. Humans and computers are good at very different things, and a healthy give and take between man and machine will become standard operating procedure.

Artificial intelligence is not the end of the specialty, it is a source of empowerment. However, it is our responsibility to adapt and take advantage of the opportunities ahead.

Evaluating Invisalign Tracking & Attachment Flash

April 5, 2017 by Scott Frey 4 Comments

Checking Invisalign Attachments & Flash

The use of Invisalign attachments are an important part of achieving the best results with Invisalign, so it is essential that these attachments are properly placed and that their integrity is checked during the course treatment. They shouldn’t be worn down, chipped, or missing to work effectively. The tried and true way of visualizing the attachments has always been to air-dry the teeth completely. However, when you use composite materials, like Ivoclar’s Tetric EvoCeram Shade T, that blends in with the teeth correctly it becomes more difficult to assess attachment placement and how they are holding up throughout treatment.

A simple trick to better visualize attachments in order to remove excess material around the attachments and assess their overall shape, is to use a handheld black light. Under natural light, restorative composites are designed to match with the surrounding tooth structure. However, under a fluorescence-inducing UV light, subtle (and sometimes not so subtle) differences in fluorescent qualities between the attachment materials and the tooth become apparent as seen in the diagram below.

Being able to adequately visualize what is the attachment and what is the tooth helps make cleanup after attachment placement that much faster. Below is a before and after example, with Tetric EvoCeram composite attachments, showing how efficient flash cleanup is when using a black light to aid in visualization.

Evaluating Aligner Tracking

If there is any question about how the attachments are tracking relative to the ‘pockets’ on the aligners, again a black light works well. Below is an image showing poorly tracking teeth and attachments not correctly inside the aligner pockets using a black light.

If you have patients who frequently work under black lights, you may get complaints regardless of the material used. There will be some slight discrepancy between the fluorescence of the tooth and that of the attachment material, but under these circumstances, you will want to select a material that isn’t as obvious under black light as others. 3M ESPE’s Filtek Supreme line of composites has been shown to perform very similar to natural tooth structure under UV light, so that composite is a good option.

Traditional Attachments vs Aligner Optimization

April 4, 2017 by Scott Frey Leave a Comment

Common Sense Invisalign Mechanics

I always get a good chuckle when I hear ‘flat-earthers’ proclaim things like “optimized attachments don’t work.” This position is anti-science, and ironically sounds a lot like the now completely debunked claim that “Invisalign doesn’t work.”

The old mindset of Invisalign treatment was to deliver the desired forces by modifying the shape of teeth with attachments, creating nothing more than a crude handle to push on. The solution then to any bio-mechanical problem was to add more attachments and/or bigger attachments based on a visual inspection of the apparent force vectors. However, it should be common knowledge to any trained orthodontist that a visual method of determining forces, while seemingly obvious, leads to faulty conclusions and frustration. Unfortunately, many people still approach Invisalign bio-mechanics in this way.

Data-Driven Force Systems

Invisalign’ s optimized attachments and optimized force systems, like SmartStage, do not function in nearly the same manner as traditional attachments. Instead of just a handle, Invisalign’s optimized element use unique aligner-forming features and pre-activated attachments to deliver custom force systems based on individually prescribed tooth movements. As a result, smaller attachments can be utilized and less teeth require attachments. This technology would not be possible without Align’s extensive treatment databases, which allow for aligner bio-mechanics to be better examined on a massive scale and without visual bias.

Data-driven force systems, developed by data analysis of thousands of cases using well controlled selection criteria, will always trump the arbitrary conclusions made by any one person and the comparatively small sample size they have to draw on. If you use Google as your search engine, you already know that big data makes all the difference.

As a speaker for Invisalign, it would be convenient for me to turn attachment selection into a mysterious process where I alone am in possession of “secret knowledge” that has been denied to everyone else, but that is not how science works. Continuing to promote the use of traditional attachments when an optimized solution exists is simply not science based, and advocating the use of an inferior clear aligner product.

Orthodontists’ personal struggles with optimized attachments are simply the result of inadequate clinical systems for attachment placement and a failure to seat key aligner forming features during treatment. This seems to occur regardless of experience level.

Without consistent seating of aligner features throughout treatment the optimized attachments cannot not deliver the prescribed forces. You can see what I am talking about with regards to poor placement in the diagram below.

The Importance of a Skilled Orthodontist

With Invisalign’s algorithms helping orthodontists to provide more efficient force application, we are freer to design better smiles and better bites for our patients. It still takes a significant amount of input from a skilled orthodontist to properly plan optimal movements and the final alignment if you are going to deliver the best outcomes for your patients. However, when it comes to attachment planning, our role is now to audible between optimized approaches rather than being forced to design attachments from the ground up.

3D Printing Resins for Digital Orthodontics

April 1, 2017 by Scott Frey Leave a Comment

Selecting the Appropriate Resin

For a 3D printer to be useful to your orthodontic practice, it needs to be capable of producing dental models, appliances, and other essential objects. Thus, you’ll need the right resin materials on hand for your fancy new printer to do it’s job effectively.

The important thing to understand is that resins are custom formulated and printer specific, so you can’t exactly use a generic resin and resins typically cannot be used between different brands of printers, though there are occasional exceptions. Manufacturers will also have a number of different resin options for orthodontists to select from, and you’ll have to choose different resins based on the desired print resolution, print color, and whether or not the resin material should be bio-compatible. Selecting the appropriate resin for the job comes down to how the prints will end up being used.

Resins for Orthodontic Models

When it comes to selecting a print resolution for orthodontic models, and in turn the appropriate resin for that resolution, 100microns is more than enough detail to produce high quality models for diagnostic purposes, retainers, or other appliances. You can always choose to print at a higher resolutions if you desire, it will just take a lot more time to print. When submitting printed models for board ABO board certification, it is recommended by the ABO that you submit the highest quality prints (<30micron resolution) for grading.

Naturally, printed orthodontic models turn out best when they are printed using an opaque material, so it is easy to see fine details across the models. Most 3D printer manufacturers in the dental space seem to think that we like colors that resemble yellow dental stone, so with many companies you’ll get some form of beige or yellow-stone type resin as an option. With my Juell Flash OC printer we use the taupe colored resin, and both Sean and I prefer the standard grey resin for our Form 2 printers.

Colored resins get their color from pigment particles which have different chemistry than resin, so they won’t dissolve in the material, unlike other components. Particles with similar chemistries like to group up, so one of the potential challenges with using pigmented resins is keeping these particles from clumping together and settling. Depending on the resin formulation and type of printer, some manufacturers are able to insert additives to the resins that will help keep the colored particles separated. Other resins may require you to shake the container before adding resin to the vat, or to stir the vat to prevent settling if the printer has been inactive for some time.

Resins for Indirect Bonding Trays & Occlusal Splints

With the appropriate lab software, 3D printers also allow for orthodontic appliances to be printed directly without having to use a physical model. The same minimum resolution requirement of 100 microns applies with direct printed appliances, though many bio-compatible resins are only designed for printing at higher resolutions.

It should be fairly obvious that when printing indirect bonding trays & occlusal splints, we’d want to select a clear resin material, but since you are also printing medical devices in this case, be sure to use a resin that is bio-compatible. Some companies offer a somewhat flexible resin to print indirect bonding trays, but this less accurate and can make full seating of the tray less predictable, especially if a team member mishandles the softer tray. In the case of both occlusal splints and indirect bonding trays, you will be better served by printing in a clear, rigid material as in the image below.

Switching Between Resins

Since different resins will be required for different orthodontic indications, another important consideration in purchasing a 3D printer and designing your workflows is how easily you are able to changeover between materials. Some companies like FormLabs, with their cartridge based system and stackable resin tanks, make this process extremely easy, but you may find this difficult with other printers. Top-Down style 3D printers like the Juell Flash OC from Park Dental Research make it especially difficult to change resins, so they are best designed for high capacity printing of a singular material.

Stop Letting OrthoChats Pick Your Pocket

March 31, 2017 by Scott Frey Leave a Comment

It seems like every time I turn around there is yet another company looking to siphon money from doctors’ pockets. Little by little we buy into the promises they make and we wonder when the cost of running a practices became so high.

The latest case of insidious overhead creep comes in the form of outsourced live chat on your website to companies like OrthoChats and OrthoEngage.

Whether or not live chat on your website is useful is not something that we need to debate. The issue that I have in contracting with these companies is they…..

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Biocompatible Resins for 3D Printing in Orthodontics

March 29, 2017 by Scott Frey Leave a Comment

When Do I Need to Use a Biocompatible Resin in Orthodontics?

Biocompatibility is required by the FDA for the manufacture of any ‘medical devices’ that will come into direct contact with the skin or oral tissue. Dental and orthodontic models that are used to fabricate clear aligners, or other appliance do not have to be printed with bio-compatible materials.

Direct printed indirect bonding trays, occlusal splints, denture bases, or other printed items that qualify as a medical devices and will come into direct contact with tissue should be printed using a bio-compatible resin.

Currently, bio-compatible resins for use in orthodontics are manufactured by FormLabs, Stratasys, and Envisiontec just to name a few suppliers.

What Does It Mean for A Resin to be Bio-compatible?

Typical 3D printed materials undergo ASTM International standards testing to evaluate material properties like tensile strength, flexural modulus, etc. However, bio-compatible materials must undergo a completely separate set of tests that are according to ISO standards, which can get expensive very quickly. These tests can cost upwards of $100,000 per resin, depending on the medical or dental indications for the resin.

There may not actually be any material difference between standard resins and bio-compatible resins from the same company; however, to produce medical devices with a resin, for the company be able to assert ‘medical claims,’ and to market directly to the dental and medical market the ISO testing is mandatory.

To be classified as a bio-compatible materials, 3D printed resins will undergo biologic evaluation according to ISO 10993-1: 2009 to address cytotoxicity, genotoxicity, and delayed hypersensitivity, and USP plastic class VI, which includes the test for irritation, acute systemic toxicity and implantation.

Resins may also undergo additional ISO testing for certain material properties pertinent to their intended use. For example, a bio-compatible dental resin might undergo ISO 20795-1:2013 testing, which applies to denture base polymers where the manufacturer might be making advertising claims regarding impact resistance.

What to Ask A Sales Rep for 3D Printers?

March 26, 2017 by Scott Frey Leave a Comment

When comparing 3D printers, the first you’ll want to do is get the spec sheet for the printer and review a sample orthodontic model. Be sure and find out the resolution at which they printed the sample and which resin they used.

The spec sheet should have almost all the information you need listed on it, but you may need to ask some additional questions for clarification. I have grouped by printer what information you’ll need to gather. The rest of the stuff that the sales reps will throw at you is just fluff.

Initial Questions You’ll Need Answered

If a software company is selling a printer bundled with their orthodontic software, ask them who actually manufactures their printer. Unless they are manufacturing the printer top to bottom themselves (highly unlikely), they are simply marking up someone else’s printer. If the sales person tries to spin you that their version is special, odds are they are lying to you (you’ll have to verify with the original manufacturer to check). This is the case with Orchestrate3D; you don’t need their software to print, and they are bullshitting doctors by claiming their printer and resin is special. You can buy the exact same printer and resins direct from Park Dental Research for a lot less.
What light source does the printer use? They will tell you whether it is a DLP (and whether they use a commercial DLP projector or a UV-DLP projector), a Laser, or an array of LEDs masked by LCD
Is this a Bottom-Up or Top-Down Printer? You can tell just by looking and it is almost certain that the printer will be a Bottom-Up-and-Peel style printer, but there are a few Top-Down printers in the orthodontic space. Currently CLIP is only available to rent through Carbon3D and are cost prohibitive.
What is your build speed in mm/hr @ 100micron resolution? Again, evaluating build speed in terms of models per hour is too variable to allow for direct comparison. You’ll want to standardize this information.
How big is the build platform? It is important to compare the size of the build platforms. Some like the Envisiontec Vida have a tiny build platforms barely the size of a 3×5 card.
What different resins do you offer? You do not need biocompatible resins to print models, but if you want to direct print occlusal splints, denture bases, or indirect bonding trays some companies (FormLabs, Envisiontec, etc.) offer biocompatible resin materials for those purposes.
What is the cost per liter for resin? Some companies they will obscure the cost of the resin by stating cost per model. Dental arches come in all shapes and sizes so it is hard to directly compare ongoing resin costs without standardizing the information. You’ll typically be able to print 40-60 models per liter of resin.
What is the process to switch between resins? Depending on the design of the printer and the printing vat, it may be challenging to change between different types of resins with certain printers. This could be make or break, if you intend to switch between different types of resins frequently rather than printing models in batches.
What training, installation, and support do you offer? Is this included? Some of the industrial printers have less than user friendly software and hardware so for some 3D printers it can help for them to hold your hand int he beginning. This is an area where you can get them to come down on price if you feel comfortable setting it up yourself.

Questions Specific to DLP-SLA Printers

What is the layer thickness? This will be a range and reflects the Z axis resolution. This number affects surface quality and dimensional accuracy, but to a lesser degree than XY resolution.
What is the pixel resolution of the DLP projector? Verify that their projector is an HD projector in full 1920 x 1080p and isn’t using fewer pixels.
What is the range for your XY Resolution? Most companies are just publishing the low number in the range and your sales rep may not actually know the range.

Questions Specific to MSLA Printers

What is the layer thickness? This will be a range and reflects the Z axis resolution. This number affects surface quality and dimensional accuracy, but to a lesser degree than XY resolution.
What is the XY resolution? For MSLA printers, this will only be one number because there are a set number of pixels in the LCD panel. The only company utilizing this technology in the orthodontic space right now the Structo/4Qube (the US reseller). The pixel size for the Structo/4Qube Orthoform is 97microns; their Dentalform printer offers a higher resolution for crowns, etc.

Questions Specific to Laser-Based SLA Printers

What is the layer thickness? This will be a range and reflects the Z axis resolution. This number affects surface quality and dimensional accuracy, but to a lesser degree than XY resolution.
What is your the minimum feature size? This is roughly equivalent to the laser spot size, but the minimum feature size also takes into account the amount and the extent of resin curing around the peripheral of the laser spot.
What is the pointing precision of your galvos? This number in microns will tell you how accurately they can move the laser and the XY resolution of printed surfaces.

Once you have gathered all the information and pricing for the full 3D printer package and you can make an apples to apples comparison, make sure you evaluate the value based on price per capacity per hour.

What Patients are Saying About Smile Direct Club

March 25, 2017 by Scott Frey 1 Comment

Innovation that helps expand access to care is a great thing for healthcare, so when I saw Smile Direct Club entering the market I was very intrigued. In theory, mail order aligners and at-home orthodontic treatment has the potential to be helpful to a number of patients who otherwise would not be able to see an orthodontist. However, as is the case in many areas of healthcare, corporate greed can often taint a promising approach to treatment.

The inherent problem with Smile Direct Club is that it is not a doctor run organization; it is owned by Camelot Venture Group (Sharper Image, Lens Express, etc.). Their model is not about patient care, it is about profit, and they have been very successful at lobbying state legislatures to allow them to operate without the same oversight provided by state dental boards who’s mission is the protection of the public. Prospective buyers should treat this like any other medical decision and get multiple opinions. They may find that the local orthodontist they know and trust already offers comparable pricing for limited treatment as well as convenient at-home treatment.

There are certainly patients with minor tooth alignment problems who would be great candidates for this type of care model. However, it is hard to tell whether you are actually a candidate for their treatment because SDC provides a financial incentive for dental professionals to approve their treatments so they can ship cases. Additionally, it is extremely difficult for patients to track down reviews of Smile Direct Club, and when you find one it is hard to rule out whether or not it is a fake review or patient story sponsored by the company. Difficulty in gathering valid feedback from customers may stem from the company’s Terms of Service that requires customers enter into an Arbitration Agreement that covers “any dispute regarding the products and services.”

I thought it would be helpful if I could compile patient reviews of Smile Direct Club to make them easier to find. It took me a while, but I did my best to gather a representative sample of SDC reviews from people who actually appear to be verifiable patients of Smile Direct Club. I was hoping for better, but this is what I found.

Patient Reviews of Smile Direct Club

Read C S.‘s review of SmileDirectClub on Yelp Read Bradley B.‘s review of SmileDirectClub on Yelp

Read Samuel T.‘s review of SmileDirectClub on Yelp Read R O.‘s review of SmileDirectClub on Yelp

Read E C.‘s review of SmileDirectClub on Yelp Read Corie K.‘s review of SmileDirectClub on Yelp

Read Jen M.‘s review of SmileDirectClub on Yelp Read Karlyn B.‘s review of SmileDirectClub on Yelp

What Does Resolution Mean for SLA Printers?

March 24, 2017 by Scott Frey Leave a Comment

Resolution and 3D printing

When someone asks the question, what is the resolution of a 3D printer? There’s not a one-number answer. Resolution is a factor of polymerization kinetics, the properties of the photopolymer, and optics of the light source, and your print quality is in turn impacted by the resolution in all three dimensions: the two planar 2D dimensions (X and Y) across the build platform, and the Z dimension (the height). To even begin to have a conversation about 3D printer resolution, you will have to consider at least two numbers: the minimum feature size of the XY plane and the Z-axis resolution (layer height).

Furthermore, the planar (X and Y) and Z dimensions are generally controlled via very different mechanisms, so their resolutions will also be different and they need to be considered separately. There is also no standard that all 3D Printer manufacturers adhere to when discussing their resolution, so you begin to see why there is quite a bite of confusion about what the term “resolution” means in 3D printing.

3D Print Resolution & Minimum Feature Size

The Z-axis resolution, or layer height, for all 3D printers is easily determined and therefore widely reported even though it is less related to the overall output quality, but it is far less important to dimensional accuracy than the XY resolution and minimum feature size.

The XY resolution with DLP-SLA printers will typically be reported as a range and will tell you how small the pixels can be made by focusing the projector. As you’ll remember from our previous post, the DLP projector has a set pixel resolution so the pixels will be larger when focused on a larger surface area. Sometimes manufacturers will only give you the finest resolution and you’ll have to ask for the full range. An accurate spec sheet for printer properties for a DLP printer will look like the below image:

MSLA or LCD-masked SLA printers are a bit different since the XY resolution is determined by how the LCD photomask was manufactured and the size of the pixels on the LCD so you will in fact get a single number and not a range.

In both DLP-SLA and MSLA printers, the relationship between ‘minimum feature size’ and resolution is relatively uncomplicated. Since the layer images are projected, the XY resolution and the minimum feature size are equivalent. However, with laser SLA printers, ‘minimum feature size’ and XY resolution are related, but they are not exactly the same.

Since layers are drawn with laser SLA technology, the XY resolution determined by the pointing precision of the galvos motors (the mirrors that point the laser), and how finely they can move the laser in each layer (finer than 10microns for Form2 printer). While the ‘minimum feature size’ in a laser SLA 3D printer is equivalent to the laser spot size.

This makes comparing the XY resolution of laser SLA printers to DLP and LCD-masked printers challenging, especially considering many manufactures don’t publicize the pointing precision of proprietary galvos. Unlike DLP and MSLA, which have a fixed matrix of pixels relative to the build area, laser-based SLA machines are able to focus the laser beam on any XY coordinate. This means that laser SLA 3D printers using high-quality optics can more accurately reproduce the surface of a part even when the laser spot size is larger than the DLP pixel size.

To illustrate this point about laser SLA, we can examine a dimensional accuracy study for the FormLabs Form2 printer. They examined 84 surgical guides printed with Dental SG resin and compared the printed guides with the original .STLs of the intended models and found dimensional accuracy within ± 100 microns over 93% of the surface area.For orthodontic applications, 100microns is excellent dimensional accuracy. The difference map below shows an example 3D scan of a printed surgical guide using their Dental SG resin overlaid with the original 3D model. Even though the laser spot size of the Form2 is 140microns, you can see the high dimensional accuracy produced in much finer detail than the laser spot size.

Make sure you are comparing apples to apples when examining the resolution of 3D printers for your orthodontic practice. Hopefully, this information should help.