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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

Accuracy of iRecord vs Invisalign Scans

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iTero Element ScreeniRecord Scan Accuracy

Many of you have probably heard that you should always use the dual scan capability on the iTero when scanning for appliances or 3D printed models because the iRecord scans are “less accurate.” I have heard this as well so naturally, I raised this question with the iTero engineers on a call last week discussing their scanning technology and development timeline.

As it turns out, there is no difference in data capture or in accuracy between the iRecord and Invisalign scans. However, up until recently, voids were not visualized on the iRecord scans, while voids have always been displayed on the Invisalign scans. Since gaps in data were not being displayed with standard iRecord scans, scans were being submitted with lots of voids and the software was having to compensate for these lower quality scans. Many orthodontic labs were receiving these files as well giving them a false impression about relative scan qualities between intra-oral scanners.

Fortunately, this issue has been fixed by recent updates for the Element scanner, but most doctors are completely unaware about these changes and how to insure that they are activated. To activate the data alerts on the iRecord-only scans, simply hit the toggle to the upper left of the dental arch selector. There is a similar toggle to the lower left of the dental arch selector that activates and inactivates the colors scans as seen in the image below.

Turning on Voids and Color
Turning on Voids and Color

As you can see when the voids are colorized they are far easier to see, and you can much better assess scan quality before submission. Without the color in the image below on the left, smaller voids and especially inter-proximal voids could be easily missed.

iRecord Scan With and Without Voids
iRecord Scan With and Without Voids

When the scan is in full color mode as opposed to the standard greyscale scanning mode, the voids will appear blue rather than red.

iRecord Voids With and Without Color
iRecord Voids With and Without Color

It is important to note that these updates (and will be the case other future software updates), are only available on the iTero Element scanner. Thus, if you are scanning for iRecord models on either then 1st Gen or 2nd Gen iTeros you will want to use the dual scan mode or very carefully review the scan quality before submission.

3D Printer Maintenance – Bottom Up Printers

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3D Printer MaintenanceCaring for Your 3D Printer

One of the benefits of ‘bottom-up-and-peel’ style 3D printers is that they tend to have fewer mechanical parts that require attention. However, all 3D printers requires proper care and maintenance to continue humming along well and turning out accurate prints. When you purchase and unbox your new printer you’ll receive some additional instructions from the manufacturer about upkeep, but here are some good rules to follow when caring for key components in these types of machines.

Maintaining Resin Tanks

Bottom-up printers require a peel step between each layer to release the freshly cured layer from the build window at the bottom of the resin tank (typically made out of silicone) so over time the material on the build window will being to ‘cloud’ significantly and require replacement. How long the resin tank lasts is a factor of the build window material, the properties of the resin, and the number of peel steps that occur over a particular region on the build window.  The build windows in the Form2 resin tanks are rated for 5000 peel steps with their V3 resin, so the rough math is one resin tank per resin cartridge (you want to keep them paired off) to maintain high quality prints.

Clean and Dirty Curing WindowsYou can extend the lifetime of your resin tank by printing with the largest acceptable layer thickness (Z Res) without compromising accuracy (100microns for orthodontic models), and by varying position of your prints on the build platform to more evenly utilize the build window. The Form2 dashboard can help you watch for even utilization by showing you a heat map of your prints on that particular resin tank as you can see below. Once they integrate this data into the PreForm software it will be even more useful.

Resin Tank Heatmap Form2It goes without saying that you should handle the resin tanks while wearing gloves and avoid touching the curing window. Fingerprints, dirt, or any smudges that could interfere with the light transmission through the curing window will negatively impact your prints. If you were to accidentally smudge the underside of the curing window, you must clean it using Novus 1 acrylic cleaner on a paper towel or microfiber cloth.

Isopropyl alcohol should not be used on any of the acrylic surfaces because it can cause cracking, and no chemical cleaners should ever be used on the inside of the resin tank since it could impact print resins. The resin tanks are more of a disposable item so cleaning the inside is largely unnecessary. If bits of cured resin were to find their way into the resin tank due to a failed print, you should filter them out by pouring the resin through a 190 micron paint filter.

Mirrors and/or Projector Lens

High quality optics are important for accurate and successful 3D printing, so you will need to avoid introducing dust or dirt into the machines and be careful not to smudge optical surfaces with residual resin or oils from your hands. The optics deck on many newer 3D printers are sealed to help avoid dust getting in, but either way you should keep the lid closed on your printer as much as possible to keep dust from getting in.

While changing resin tanks or in the even of a failed print, the mirrors and/or projector lens should be inspected to make sure they are in fact clean. If they were to become dirty, a damp microfiber cloth or compressed air dusters can be used to clean their surface.

Build Platform

Build platforms are extremely resilient and rarely need to be replaced during the lifetime of your printer. As long as there aren’t sharp bits sticking out from part removal/resurfacing that may puncture the silicone curing window in the tank, there is no need to replace the build platform, but they should be cleaned throughly with a cloth between prints. Chemical cleaners should not be used on the build platform to avoid introducing them into the resin during printing.

General Upkeep

Although this would be rare in an orthodontic lab, if the resin sits for longer periods of time it may need to be gently mixed to avoid settling of particles with some types of resins. In the Form2, you can simply remove the wiper and gently sweep it left and a right to make sure the resin is mixed. It is a good idea not to mix it while in the machine in case of a spill so you should remove the resin tank prior to mixing. Outside the machine, you should keep the resin covered as much as possible.

Although isopropyl alcohol is used to wash printed parts and remove residual resin and is readily available, it should not be used to clean any of the acrylic parts on the machine like the hood or resin tanks. The isopropyl alcohol will crack the acrylic over time. Instead these acrylic surfaces should be wiped down with an acrylic cleaner like Novus 1 on a paper towel or microfiber cloth.

Trouble with Transparency Under the Sunshine Act

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Sunshine ActTime for Transparency

In order for fellow orthodontists, as well as the general public, to adequately assess for conflicts of interest and general bias, all monetary contributions from companies and organizations made either directly or indirectly to doctors must be publicly disclosed in some fashion. The Physician Payments Sunshine Act, passed in 2010, was an attempt to provide greater transparency; however, the law doesn’t adequately cover all streams of income that can flow from manufacturers and distributors. This means that many doctors are on the honor system to provide this information and it allows for some to keep the origins of their income concealed.

Each year, the previous year’s data for Open Payments is submitted from manufacturers by March 31st, and they allow a 45 day process for dispute and review before the information is published to the Open Payments Database on June 30th. If you are interested, these payments made directly to doctors can be looked up for anyone you are curious about using the Open Payments Data Search Engine. Our concern however are the payments that are going unreported and do not appear on the site.

While the Sunshine Act requires medical product manufacturers to disclose to the Centers for Medicare and Medicaid Services (CMS) any payments or other transfers of value made to physicians or teaching hospitals, transfers of value that are made to a third party that isn’t a doctor or teaching hospital do not need to be disclosed creating the potential for abuse. 

Clever individuals and groups are able to essentially ‘launder’ money provided by companies through educational organizations, industry magazines, educational grants for meetings or forums, vendor fees at the same meetings, internet groups, etc. because these entities do not have reporting requirements under Sunshine regardless of whether or not the entities are owned by a doctor or a group of doctors. In the instances where these entities are doctor-controlled, once the money goes in they are able to reroute the funds to themselves, pay it out to affiliated doctors or speakers, or pass the funds between other organizations and groups that are aligned with their interests and working towards the same end. Furthermore, preferred pricing on products extended to key accounts are not adequately disclosed.

Naturally, we are beginning to see more and more organizations like this popping up with affiliated doctors organizing themselves into what can only be described as “mutual admiration societies” to help establish credibility and coordinate promotional efforts. Since the industry money is being ‘cleaned’ by passing it through or amongst these entities first, these doctors can also technically deny that they receive compensation from these companies, and without them opening their books completely it essentially impossible to distinguish funds that are provided by manufacturers from those that are earned by other means (ticket sales, membership fees, etc.). They are basically on the honor system to disclose any potential conflicts of interest.

There are plenty of other forms of bias out there that can cloud research and recommendations, but financial conflicts are an extremely important disclosure to make. The dilemma we now face as a specialty is that we simply may not be able to get straight answers from the types of entities we have outlined here on the sources and extent industry financing the receive. Therefore, we must consider the information flowing from these organizations, and their affiliated doctors, with increased skepticism and challenge. 

In the interests of greater transparency, we list all disclosures of any financial relationships our doctors have either directly or indirectly with companies or any of the entities in question on our Speakers page under the About tab.

Introduction to Selective Laser Sintering

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SLS 3D Printing TechnologyWhat is SLS?

SLS stands for Selective Laser Sintering. This 3D printing technology uses a laser to harden and bond (sinter) small grains of plastic, ceramic, glass, metal, or other materials to build a 3D dimensional structure inside a hot chamber with the temperature just under the material’s sintering point. During the SLS process, the laser traces the pattern of each cross section of the 3D design onto a bed of powder. After one layer is built, the bed lowers, a roller transfers new powder to the sintering bed as needed, and another layer is built on top of the existing layers. This process is repeated until the object is complete, at which point it must be uncovered from within the un-sintered powder, and cleaned before it is ready for use. The SLS process is visualized in the diagram below:

Selective Laser SinteringSLS printers can use a wide range of materials including metals, always in powder form, but most often they are polyamides (Typically PA12, like Nylon) that can have additives including materials like glass and aluminum to change properties such as color, strength, flexibility, stiffness etc.

SLS Build VolumeSince the product lies in a bed of powder, one of the major benefits of SLS is that it doesn’t require the support structures that many other additive manufacturing technologies use to prevent the design from collapsing during production. With no need for support structures, this technology is suitable for interlocking parts, moving parts, living hinges and other highly complex designs. You can also utilize the build volume more effectively than with SLA.

Although the use of powder provides a few advantages by serving as a support medium, the powder also raises some safety concerns. Breathing apparatuses and ventilation need to be considered, depending on the type of material.

In the future, SLS technology will likely have some applications in orthodontics because of the unique material options and the fact that it is capable of producing intricate and highly durable parts. However, the post-processing time required to uncover the prints is significant so there is less benefit to producing objects where SLS will not save your significant assembly time.

Refinement Rates are Meaningless

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Airplane Speed TapeLow Refinement Rates Are Meaningless

Back when goopy PVS impressions were required for Invisalign case submissions and additional aligners, case refinements and mid-course corrections were a substantial encumbrance.

The PVS impression process was extremely time consuming, less accurate (than a scan), and highly technique sensitive. All Invisalign attachments needed to be removed to avoid distortion or locking-on of the PVS material, which put force systems and elastics on hold, and it sometimes took a few tries to capture a suitable set of impressions that could be mailed to Invisalign. As a result, additional aligners became something to be avoided at all costs and low-refinement rates became a focus of early Invisalign treatment. The problem with this philosophy is that great results cannot be achieved in fixed appliances without some detailing the archwires or adjusting bracket positions. Additional aligners for the orthodontist to make adjustments are just as important to the outcome in Invisalign.

One can very easily drop their refinement rates by accepting lower quality treatment finishes, but this is not a worthy goal and the lack of consistent finishing which many orthodontists bemoaned in the past was certainly due to this approach to case refinements. Thankfully, all of this is now a moot point with intra-oral scanning technology. Attachments can now remain on during the scan, and the resulting impressions are faster, more enjoyable to patients, and far more accurate.

Orthodontists don’t have a crystal ball, and the suggestion that we currently have the means, or the data, to be able predict the patient’s biologic response to movements and thereby avoid refinements predictably is simply false. Furthermore, there is zero scientific evidence to suggest that individual tooth overcorrections lead to better treatment stability. Adjustments are simply a necessary part of good orthodontic treatment.

Over-activated force systems are absolutely necessary in a broad sense for leveling, expansion, etc., but this is an entirely different concept. These over-activations also require refinement to be able to properly transition into retention from the final .stl files. Such force systems are why I refine most patients, and, done correctly, these adjustments should not result in extended treatment. In the consecutive treated sample I posted the other week, I averaged 1.4 refinements per patient (because we are going to do what it takes to deliver the best result), but the average treatment length for this sample was only 13.6 months and not much different to my treatment time for braces.

Our focus as specialists needs to be on our craftsmanship. If that requires making adjustments with either fixed appliances or Invisalign along the way, then we should not be cutting corners in order to pretend that we are being more efficient.

Look Out Labs Change is Coming

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Orthodontic Lab TechThe Future of Orthodontic Labs

3D printing and computer aided design (CAD) tools are making orthodontic lab work easier to bring in-house and streamlining manufacturing by reducing the number of physical steps required to make appliances. This technology will significantly change how orthodontic care is delivered and the role orthodontic labs play in the marketplace.

To be able to assess the impact this will have on orthodontic labs themselves, we need to understand first the overall breakdown of the lab work they are currently performing. We were able to compile data from 8 orthodontic labs, ranging in size from one man operations to very large labs consisting of 100+ lab technicians, which gives us a pretty good sampling of the products produced by traditional orthodontic labs across the US.

The average data by appliance category for the labs surveyed is represented below:

Appliance Type AVERAGE
Hawley Retainers 45.4%
Spring Retainers 4.4%
‘Invisible’ Retainers 3.3%
Fixed Lingual Retainers 3.0%
Functionals 2.4%
Occlusal Splints 2.0%
Expanders 11.6%
Habit Appliances 1.0%
Space Maintainers 3.8%
Class II Correctors 6.4%
Clear Aligners 6.6%
Tooth Positioners 4.5%
Indirect Bonding 2.0%
Other (Study models, Mouth guards, etc.) 3.7%

Among the data, there were some other interesting findings:

  • As the size of the lab decreased, the product mix shifted heavily towards Hawley retainers. Large labs would top out at about 20% Hawleys where as some single person labs saw 90%+ in Hawleys.
  • Indirect Bonding and Class II Correctors (Herbst & MARA) were non-existent until you got into the larger commercial labs.  
  • Expanders, both fixed and removable, topped out in the medium size labs before decreasing with the larger labs. This may be due to them being combined with Class II Correctors, rather than being listed separately as an expander.
  • Tooth positioners were also non-existent until you get into the larger labs in the market.  Most of the universities are not utilizing tooth positioners anymore, thus small labs are not getting the demand to carry the product.

The appliances that are least technique sensitive to fabricate and those where significant advantages are gained by shifting work into the digital space are going to be most impacted by 3D printing. This will disproportionately affect the larger labs and primarily concerns ‘invisible’ retainers, study models, clear aligners, occlusal splints, and indirect bonding, which account for 13.9% of lab work performed by orthodontic labs based on the averages in our sample. Spring appliances may also be impacted if they are being done for tooth movement, since may doctors may opt to produce clear aligner in-house as an alternative. The appliances that will be least affected in the short term will be soldered and banded appliances since the advantages from 3D printing that would drive adoption aren’t as significant until such appliances can be directly printed.

How Orthodontic Labs Will Adapt

Given the significant impact that 3D printing technology will have on orthodontics in general, orthodontic labs will be forced to adapt. There are several ways in which we will see them changing their model:

  • Providing supportive digital services so practices can outsource their digital workload and storage. The practice would then have the option of either manufacturing the physical appliance in-house, or having the lab fabricate and ship the appliance as they do now. Some labs have already begun to implement this. Ideally, the global economy would be leveraged to have the digital tasks performed overnight to increase productivity.
  • Manufacturing and marketing direct-to-consumer products, either on their own or in partnership with other companies. Since these labs already have the infrastructure in place to manufacture and distribute products, this may be a natural transition.
  • Offering training services, both on-site and online, for in-house orthodontic lab technicians.
  • Focusing on products less affected by 3D printing. However, this is more of a delay tactic than a solution.

Invisalign Releasing Extended Payment Terms

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Extended PaymentsExtended Payment Terms

It is important for orthodontists to offer flexible financing arrangements to help make great orthodontic care more accessible to patients. Unfortunately, due to the lab fee, many doctors have felt that they can be as flexible with in-house financing terms when using products like Invisalign. We have already shown that orthodontists don’t need to charge more for Invisalign or be less flexible with financing, but the upfront costs of the lab fee are about to become even less of a concern because Invisalign will begin rolling out extended payment terms on their lab fees to doctors.

This will allow doctors to provide even greater flexibility in their financial arrangements with patients, and will help to make treatment more affordable for families. Initially, this program will only be available to Invisalign’s Top 1% and Elite level providers so if you aren’t a Top1% or Elite doctor and you feel excluded, time to treat more patients with Invisalign….

The rest of this post, including details on the extended payment terms, is available only to orthodontists and orthodontic residents registered with the Ortho Cosmos…..

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Print Farm Starter Kit

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3D Printer Shopping3D Printer Shopping

Most of the companies and their reps selling 3D printers have been working in the dental space with restorative dentistry and implant dentistry and have not yet adapted to the substantial differences that exist with orthodontics. Additionally, the margins on the actual 3D printers are razor thin so companies will push items like expensive UV curing boxes (with huge profit margins) when post-curing may not be indicated and when inexpensive UV light boxes for nails salons may suffice.

Orthodontists are in need of greater clarity on what you should or should not buy to begin integrating 3D printing in your practice, so we put together a shopping list.

Print Farm Essential Items

1 x Formlabs Form2 3D Printer (Complete Package is $3499)

  • All the 3D printers we tested for accuracy in printing orthodontic models demonstrated the requisite precision for orthodontic indications; however, the Form2 was the most cost effective and has a wide range of resins available so it makes a good starter 3D printer.
  • With the Form2 you can predictably build 20 dental models vertically per day (two prints of 10 models), which easily translates to 300 models a month on 1 Form2 printer. As your needs grow, you can gradually scale up your capacity by adding printers to your print farm. Having a print farm also provides redundancy so if one printer goes down you have a back up.
  • The complete printer package includes a Resin cartridge, Resin Tank, Build Platform, Finish Kit, and One Year Warrantee

2 x Matte Grey V3 Standard Resin Cartridges (1 included with printer package, $149 for additional)

  • Cartridge system for easy switching between different resins.
  • This resin has highly accurate curing properties and is perfect for dental models.
  • One cartridge will print about 50-70 dental models depending on size, so we recommend getting two.

Additional Resin Tanks (1 included with printer package, $59 for additional)

  • The rule is 1 Resin Tank per Resin Cartridge. These stackable resin tanks (with lids – don’t throw these out) that can be easily removed to switch between resins. The printer will come with one resin tank included.
  • Since the resin tank will be partially filled with resin, you will want to keep the resin tanks with a particular cartridge of resin (you can label the lids). Simply remove and cover with their original lid for storage.
  • The silicone curing window on the bottom of the resin tank wears down with each ‘peel step’ and will eventually cloud and require replacement. The silicone window is tested to withstand 5000 ‘peels,’ which means that you will typically need to replace the resin tank after printing through a whole resin cartridge to keep your prints accurate (2 cartridges is sometimes a stretch). You should evenly utilize the build platform and vary your print position so that the silicone curing windows do not cloud pre-maturely.

Finish Kit (included)

  • The Finish kit includes a finishing tray and accessories to remove parts and perform a thorough alcohol wash while maintaining a clean workspace.

PreForm Print Preparation Software (included)

  • Free software that comes with the Form2 printer. Other printers will have similar prep software for their machine.
  • This software will prepare files for printing and optimize them for printing on the Form2. Simply lay out prints on build platform, use the support generating tool, and push to print via WiFi.
  • You will have to physically present to start a print on the printer (needs manual verification that build platform is in place, etc.), but you can utilize the online Dashboard to monitor print progress remotely.

Optional Print Farm Purchases

CAD software

  • Although STL files for dental models can be downloaded and printed without additional software, if you want to make design modifications to the 3D files themselves you will need additional software. This isn’t necessarily something you’ll need to do right away.
  • This includes movement of teeth to stage clear aligner tooth movement, digital bracket removal, fabrication of direct print indirect bonding trays, fabrication of direct print occlusal splint/retainers, modification of tooth and gum surfaces
  • Some options include Orthoanalyze, Orchestrate, Elemetrix.
  • If you elect not to purchase software, you can outsource these CAD services to labs (to remove brackets, etc.) and have them provide the STL files of the final product for printing and digital storage in-house.

Pro Service Plan ($499)

  • Although the Form2 is dead simple to set up and use, the Pro-Service plan can be helpful for orthodontists new to the 3D world.
  • You will get a customized training session to learn in the ins and outs of desktop 3D printing, priority phone and email support, and the ability to hot swap a broken printer (a good idea if you don’t have a second printer)

Orion Pulse Arc Welder & Argon Tank (~$2500)

  • For welding/soldering parts on printed models.
  • Instead of purchasing an expensive laser welder, pulse arc welders offer an effective means of welding on printed models without melting the print. Welds are sturdier than soldering, but are a different technique so it may take some training for your lab technician.

Siliform Separating Medium (~$260 for 8oz)

  • If you are going to be making Hawley retainers or other acrylic based products on the printed models, you will need a separating medium. However, the surface tension on printed models is different than plaster casts and traditional separating mediums won’t work as well.
  • There are certainly a lot of options that can do the job, but the one that we have found to work best has been Siliform. It is not cheap, but it is effective. You can order from Adell Corporation.
  • 3D printing offers more advantages if you are sticking to thermoplastic retainers or direct printed retainers, so you may want to consider modifying your retention protocols.

Biocompatible Resin Cartridges (price varies depending on material)

  • Bio-compatible resins are only needed for printed final products that will be used in the mouth. You do not need a bio-compatible resin to print a dental model that will be used as a working or diagnostic model.
  • Bio-compatible resins are available for use in direct printed IDB trays, occlusal splints, analogs for autotransplantation, surgical guides, etc.
  • The Dental SG Resin ($399) is already available, but the upcoming Dental LT Clear Resin (~$500) will be a better fit for most orthodontic needs.

Form Wash ($499)

  • While you can perform an alcohol wash with the finish kit that is included, Formlabs has created a little alcohol jacuzzi for your finished prints that accepts a full build platform.
  • This is an optional purchase, but it automates the wash process and takes up less counter space than the alcohol baths in the Finish Kit so it may be useful. The agitation of the alcohol will also get a more thorough clean of the printed items in less time. By purchasing an additional build platform you can start another print immediately while the other build platform is being washed.

UV-Post Curing Box

  • If you are printing objects that are bio-compatible, you will need to do a complete UV post-cure. This can be done either with the Form Cure ($699) or the Kudo Post Curing Lamp ($249). Companies will typically push these whether or not your truly need them because they are high margin.

Additional Build Platform ($99)

  • Build platforms will last nearly indefinitely, but if you are looking to utilize the Form Wash System you will need a second build platform so you can print while your other build platform is being cleaned.

Comparing Horizontal and Vertical 3D Print Accuracy

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Going Vertical
Going Vertical

Many people only print dental models horizontally on the build platform in order to reduce or eliminate the need for “supports.” However, printing models flat takes up more space and limits your utilization of the build platform. As you scale up your 3D print manufacturing, you will want to print in bulk rather than tying up your printer for only a few models at a time.

By orienting models, occlusal splints, etc. in a more vertical fashion (as seen below) many more items to be printed at once, increasing the scale of your manufacturing.

Vertical Model with Supports

Many 3D printer manufacturers view the simple fact that a print did not fail as proof of it’s accuracy, but that is not necessarily the case. The question remains whether printing vertically with and without supports is as accurate as your traditional horizontal prints. The Z axis resolution (layer thickness) and XY resolution (which is based on the pointing precision of the lasers in a Laser-SLA printer) are different, so it is certainly possible that changing the orientation of the models might impact their print accuracy. Additionally, if there are no supports, or if the supports are inadequate, there can be distortion in the overhanging layers when they are printed.

Recently, we evaluated the dimensional accuracy of various 3D printers with models that were printed horizontally. We have now repeated this analysis to compare the accuracy of vertically printed models and the impact of supports. For this test, we compared a vertically printed model with supports on the Formlabs Form2 printer, at 100 micron Z resolution, to the same print completed horizontally. We also compared a vertically printed model without supports on a Structo DentaForm and an Enivisiontec Vida printer, at 100 micron Z resolution, to the same prints completed horizontally on their respective printers.

We found that, with the proper supports, there is no difference in the dimensional accuracy between horizontally and vertically oriented prints. Without supports being added to “overhangs” we observed a substantial decline in overall dimensional accuracy. The decline was less noticeable on the Structo DentaForm (these models were provided by the manufacturer and not printed in private practice).

We recommend that printed overhangs, most often present on vertically printed models, have supports added for the most accurate prints.

Heatmaps & Data for 3D Prints

Dimensional accuracy heatmaps and data for the horizontal and vertical prints that were analyzed are shown below:

Form2 100microns Broad

Form2 Horizontal Print @ 100 microns

The printed model demonstrated an average dimensional accuracy of 67 microns. The printed models were dimensionally accurate to within 80 microns over 65.64% of their surface area. The maximum deviation from the original model was 125 microns.

Form2 100microns Vertical Broad

Form2 Vertical Print @ 100 microns
(with supports)

The printed model demonstrated an average dimensional accuracy of 70.6 microns. The printed models were dimensionally accurate to within 80 microns over 65.57% of their surface area. The maximum deviation from the original model was 125 microns.

Envisiontec 73microns Broad

Envisiontec Vida Horizontal Print

The printed model demonstrated an average dimensional accuracy of 49.4 microns. The printed models were dimensionally accurate to within 80 microns over 83.58% of their surface area. The maximum deviation from the original model was 146 microns.

Envisiontec Vertical No Supports

Envisiontec Vida Vertical Print (without supports)

The printed model demonstrated an average dimensional accuracy of 82.4 microns. The printed models were dimensionally accurate to within 80 microns over 52.38% of their surface area. The maximum deviation from the original model was 147.3 microns.

Structo DentaForm Flat

Structo DentaForm Horizontal Print

The printed model demonstrated an average dimensional accuracy of 57.5 microns. The printed models were dimensionally accurate to within 80 microns over 66% of their surface area. The maximum deviation from the original model was 108.7 microns.

Structo DentaForm Vertical

Structo DentaForm Vertical Print (without supports)

The printed model demonstrated an average dimensional accuracy of 67.7 microns. The printed models were dimensionally accurate to within 80 microns over 61% of their surface area. The maximum deviation from the original model was 136.7 microns.

Dimensional Accuracy of 3D Printers

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3D Printer AccuracyThe Resolution Myth

Too often I see people confusing printer resolution with print accuracy. This is understandable mistake given the incremental way that 3D printers create objects; however, there is not a true relationship between accuracy and resolution. The accuracy of a print refers to how well that object conforms to its original form, while resolution is simply the smallest feature that can be printed in a particular plane. The smooth surface finish that results from printing at a higher resolution does not mean that you have an accurate product. Printers with lower, but acceptable, resolution specifications may actually deliver superior accuracy.

Dimensional Accuracy of 3D Printers

For orthodontic applications, we need 3D printers that can repeatedly deliver a high degree of accuracy. Since printer resolutions do not provide us with this information, a dimensional analysis of printed products must be performed. 

To gather this data, we distributed a digital model of a patient’s lower dental arch to various orthodontic practices. They were given instructions to print the models and then scan the prints using the latest generation 3Shape Trios intra-oral scanner. This was performed for the following 3D printers: a Stratasys Objet Eden 260vs at both the High Definition (16Z, 42XY res)and High Speed print settings (30Z, 42XY res), a FormLabs Form2 at both 50 and 100 micron layer thickness (Z res), an Envisiontec Vida that was calibrated to 73 microns XY resolution (100Z res), and a Park Dental Research Juell Flash OC calibrated to 100 microns XY resolution (100Z res). Using the original .stl file of the mandibular arch and the .stl files of the scanned prints, the dimensional accuracy of the dentition and marginal gingiva on the printed models was assessed by an independent third party. To validate the consistency of the dimensional analysis, the Form2 50 micron file was submitted twice without the knowledge of the evaluator; the outcome of the analysis was the same.

Accuracy Results

All prints showed high dimensional accuracy with less than 100 micron average deviation. The differences in dimensional accuracy between printers were not clinically significant. Studies have shown that for a scan performed under extra-oral conditions the accuracy for a full dental arch is within 25microns and the minor differences between the printers were within the margin of scanning error.

Of the printers tested, the Envisiontec Vida showed the highest print accuracy; the Stratasys Objet Eden 260vs at the high speed print settings (30 micron layers) demonstrated the lowest print accuracy of the printers tested. 

The overall accuracy results underscore that fact that high resolution does not mean high accuracy. This was particularly evident in the performance of the Stratasys machine. The accuracy data recorded for the Eden 260vs was in line with the stated accuracy of the printer from 3D systems, but it’s print accuracy was significantly less than the printer’s resolution and was not significantly different than more cost-effective machines.

Another interesting finding was that the most accurate prints were attained with 100 micron layer thickness (Z res) and when a finer Z resolution was used on the same machine (50 microns on the Form2 instead of 100 microns) the accuracy of the print did not improve. This would suggest that the size of features present in orthodontic models and appliances are not small enough to warrant selecting a layer thickness smaller than 100 microns. This means that the faster print speeds attained at 100 micron Z resolution can be used on these printers without degrading accuracy.

Choosing a 3D Printer

Manufacturers’ stated printer resolutions are no guarantee of accuracy. When evaluating any new printer for purchase, the dimensional accuracy of the prints must be validated and contrasted with exiting purchasing options. However, the results of this analysis demonstrate that price certainly isn’t the determining factor in print quality and accuracy. All printers tested demonstrated similar and sufficient print accuracy for orthodontic use, and the extremely cost-effective Formlabs printers were just as accurate as much more expensive printers. If you are paying more for 3D printers in the current marketplace, you aren’t doing your homework and it is time to start make better financial decisions.

Given the price point of printers like the Form2 and it’s high level of accuracy, there is no reason not to integrate 3D printing technology in your orthodontic practice. Unfortunately, some doctors who have their own small orthodontic labs are attempting to discourage orthodontists from investing in 3D printers. They jumped the gun on the 3D printer market and still need doctors to outsource their 3D printing services to them in the hopes that they can recover their investment on overpriced 3D printers. Don’t fall victim to their agenda.

3D Printer Accuracy Heatmaps & Data

Dimensional accuracy heatmaps and data for the 3D printers that were analyzed are shown below:

Stratasys High Definition Broad

Stratasys Eden 260vs
High Definition Settings (16 Micron Layer Thickness)

The printed model demonstrated an average dimensional accuracy of 57.3 microns. The printed models were dimensionally accurate to within 80 microns over 78.55% of their surface area. The maximum deviation from the original model was 120 microns.

Stratasys High Speed Broad

Stratasys Eden 260vs
High Speed Settings (30 Micron Layer Thickness)

The printed model demonstrated an average dimensional accuracy of 84.15 microns. The printed models were dimensionally accurate to within 80 microns over 50% of their surface area. The maximum deviation from the original model was 170 microns.

Form2 50microns Broad

FormLabs Form2
@50 Micron Layer Thickness

The printed model demonstrated an average dimensional accuracy of 73 microns. The printed models were dimensionally accurate to within 80 microns over 64.7% of their surface area. The maximum deviation from the original model was 150 microns.

Form2 100microns Broad

FormLabs Form2
@100 Micron Layer Thickness

The printed model demonstrated an average dimensional accuracy of 67 microns. The printed models were dimensionally accurate to within 80 microns over 65.64% of their surface area. The maximum deviation from the original model was 125 microns.

Envisiontec 73microns Broad

Envisiontec Vida
@73 Microns XY Resolution

The printed model demonstrated an average dimensional accuracy of 49.4 microns. The printed models were dimensionally accurate to within 80 microns over 83.58% of their surface area. The maximum deviation from the original model was 146 microns.

Juell 100microns Broad

Park Dental Research Juell 3D-2
@100 Microns XY Resolution

The printed model demonstrated an average dimensional accuracy of 57.7 microns. The printed models were dimensionally accurate to within 80 microns over 68% of their surface area. The maximum deviation from the original model was 130 microns.

Structo DentaForm Flat

Structo DentaForm
@96 Microns XY Resolution

The printed model demonstrated an average dimensional accuracy of 57.5 microns. The printed models were dimensionally accurate to within 80 microns over 66% of their surface area. The maximum deviation from the original model was 108.7 microns.

Uniz Slash3D

Uniz Slash+
@75 Microns XY Resolution

The printed model demonstrated an average dimensional accuracy of 90 microns. The printed models were dimensionally accurate to within 80 microns over 40% of their surface area. The maximum deviation from the original model was 177 microns.

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