Agile aligner delivery

Dr. Rooz Khosravi discusses bringing clear aligner fabrication in-house with new technologies

Moving teeth with clear aligners has been around since the 1970s.¹ The invisible retainer was the term initially used to describe a clear tray moving a limited number of teeth. The first paradigm shift in aligner therapy was introduced in 1999, when computer-aided design and manufacturing (CAD/CAM) technology majorly improved the treatment planning and manufacturing of aligners. In the past two decades, orthodontists have slowly implemented aligner therapy in their daily practices. Additionally, advances in technology have accelerated improvements in both the components and the manufacturing of clear aligner systems. Examples of these improvements include the introduction of attachments of multiple shapes and forms, auxiliary components added to aligners (bite ramps, Class II corrector arms), and various types of plastic (single and multiple layers plastics).

The new wave of clear aligner therapy in 2020s

In-house fabrication of clear aligners is becoming a popular protocol in orthodontic practices. Some opt to use this approach in combination with the existing third-party manufactured aligner systems, while some exclusively provide aligners made at their clinic. Multiple factors have contributed to the rapid expansion of in-house aligner fabrication in orthodontic clinics in recent years.

3D digital technology

Digital technology — i.e., desktop 3D printers and intraoral scanners — are easier to operate as compared to a few years ago. The cost of acquiring such systems is also relatively low now.

Practitioners can purchase an intraoral scanner in the range of $14,000 to $40,000 and completely eliminate analog intraoral record acquisition. It is important to note that most of these scanners have advantages and disadvantages. Practitioners should consider the following costs:

1. initial investment
2. consumables to operate the scanner
3. storage of data
4. monthly or annual subscription for the pertinent software

Factors such as versatility of software features (e.g., treatment simulation, or web-based model viewer) associated with a scanner and its compatibility with other software platforms in a practice should be considered in addition to the cost of operation to utilize an intraoral scanner.

Adding desktop 3D printers to the digital workflow is trending in orthodontic offices. The majority of desktop vat photopolymerization printers used in dentistry fit in one of these 3D-printing protocols:

• laser beam stereolithography (SLA)
• digital light processing (DLP)
• LCD three-dimensional printing (also referred to as mask SLA printing) (see Figure 1).

Each of these approaches to 3D printing an object — namely, dental models — has pros and cons. DLP printers, such as SprintRay Pro (SprintRay Inc., Los Angeles, California) and Envision One (EnvisionTEC, Dearborn, Michigan), are among the most popular printers in orthodontics. Higher printing speed, accuracy, minimum training, calibration, and consistency seem to be driving the selection of these two printers. Fused Deposition Modeling (FDM) printers are also promising. Feasibility to print in high volume and limited post-printing processes are some of the strengths of FDM printers. However, further development of filament materials that match the needs of aligner manufacturing is required to further adapt this technology.

Digital platforms to move teeth

Digitally manipulating an STL model using open source software such as Meshmixer or Blender was part of the early phase of adopting digital technology in orthodontics — some clinics still use these software tools to move teeth. Multiple companies now provide complex digital platforms to modify digital models, move teeth, stage the treatment, add attachments, and optimize the models to be printed. Examples of these platforms are uLab systems, SureSmile® (Dentsply Sirona, York, Pennsylvania), ArchForm, 3Shape Clear Aligner Studio, and Maestro 3D. The mere existence of multiple platforms allows practitioners to choose one based upon their needs and expand in in-house aligner fabrication. Training courses offered by orthodontists or some companies on how to use these platforms aid in faster implementation of the software in the daily practice of orthodontics.

New generation of orthodontic assistants

Most assistants of a younger generation are very comfortable with acquiring skills to operate 3D intraoral scanners, to manipulate digital models, and to utilize 3D printers. A trend of transitioning to active (versus passive) treatment is on the rise in orthodontics. Specifically, digital orthodontics allows practitioners to create a therapeutic plan and fabricate appliances while the patient is not in the chair. Therefore, orthodontists are looking to a new workforce — namely, digital orthodontic assistants — who are accustomed to this relatively new daily operation. More flexibility in daily work schedules and possibility to work remotely are some of desirable attributes for such a position that could attract a new wave of orthodontic assistants. Needless to say, seasoned orthodontic assistants with a deeper knowledge and skill set in the orthodontic field who are interested in such positions may be more susceptible to digital training.

Direct-to-consumer orthodontic care

The new generation of remote clear aligner therapy — with the main premise of convenience at a lower treatment cost — has increased awareness of clear aligner therapy, especially in young professional adults. To some individuals, however, direct in-person interaction with the provider is a nonreplaceable choice while seeking orthodontic treatment. In the past few years, more orthodontists have been looking into offering treatment options that address this new wave of demands.

One approach is to reduce the cost of aligner fabrication in order to offer this treatment at a lower price point. In-house aligner fabrication is one of the solutions to this end after the workflow is dialed down properly.

The future direction of in-house aligners

All of these factors collectively push the in-house aligner fabrication to be further optimized and grow in the coming years. In-house aligner fabrication also helps with 1) combining these appliances with fixed orthodontic appliances, or 2) programming the use of these aligners during certain stages of treatment in order to create a better experience for patients.

Orthodontists are learning how to use digital technology to better communicate with the patient and their colleagues as well as to render a more convenient care plan while maintaining the high quality of treatment provided. Practitioners can reason that honing down on digital technology allows an orthodontic clinic to thrive in a market with an increasing number of direct-to-consumer companies and Dental Support Organizations (DSO) offering orthodontic treatment.

Agile aligner delivery

One of the advantages of fabricating aligners in-house is the higher speed of delivering care to patients. It is important to note that this agility comes with challenges associated with scaling aligner fabrication at a clinic. Agile aligner delivery workflow is an optimized protocol allowing practitioners delivering high-quality aligner therapy at a fast pace.

Agile aligner delivery workflow offers the choice of quickly starting the treatment for interested patients. Immediately rendering the care for such patients may increase the compliance with wearing aligners (a removable appliance) by relying on the higher motivation to correct orthodontic problems at the beginning of the treatment. It should be noted that speeding to start the treatment should not jeopardize the proper diagnosis and treatment planning in order to maintain a high-quality standard of care.

The implementation of agile aligner delivery workflow requires all parts of the in-house aligner manufacturing pipeline to work smoothly and in tandem. Ideally, a clinic should have a digital assistant in charge of this operation.

Each segment of the aligner manufacturing pipeline has to follow certain requirements. Specifically, practitioners need a digital scanner providing high-quality 3D models. Best practices in scanning should be established in a clinic in order to acquire good quality records. The orthodontic team should have proper training on scanning techniques. Improper scanning techniques could result in poor models, which turn into roadblocks in the aligner manufacturing pipeline. TRIOS® from 3Shape, 3M™ Tru-Definition, and iTero® from Align Technology seem to provide most of these requirements. It is vital to have back-up scanners at your clinic and opt to use one ecosystem to maintain simplicity in training as well as consumable ordering and inventory.

A robust yet simple digital platform is the core component of agile aligner delivery workflow. Digitally segmenting the teeth, modifying the models (e.g., adjusting the bite, removing brackets or attachments, and filling holes), moving the teeth, staging the tooth movements, adding the auxiliary parts of clear aligner system (attachments, pressure areas, elastic and button cuts, pontics, and blockouts) and preparing the digital models for 3D printing are sequential blocks of such platforms, and all should be synergistically linked. Lack of efficiency in each of these parts will slow down the process and will introduce the inability to scale the operation.

At this point, uDesign from uLab Systems (Redwood City, California) and partly Sure-Smile aligner software are the two common platforms in the United States that offer such abilities with a promise of improving their features in the future. In my clinic, we spent, on average, a range of 5 minutes to 1 hour from the importing of digital models to the software to exporting the ready-to-print staged models using uDesign from uLab Systems. I found myself reviewing some of the more complex digital setups multiple times over the course of a few days to optimize the staging of the movement and sometimes the position and shape of attachments or pressure areas.

3D-printing technology has been rapidly changing these days. Multiple desktop printers are on the market, which could provide the requirements for agile aligner delivery workflow. DLP printers (e.g., Sprint-Ray Pro 95, Envision One, or Juell 3D) offer the best balance of speed and quality of a print in orthodontics. Formlab printers, one of the most common laser beam vat photo-polymerization also known as SLA, are a user-friendly and affordable option at the expense of printing speed.

LCD masking (also known as masked stereolithography, or mSLA) printers are entering the orthodontic field as well. LCD printers offer reasonably accurate models when properly calibrated. The lack of customer support with most of these printers and steep learning curve are challenges when practitioners consider opting for these printers. Nonetheless, the minimum initial investment to acquire one of these LCD printers is appealing to some orthodontic clinics. Additionally, developing a print farm with multiple LCD printers is, in theory, interesting; however, the saturation point to operate multiple units is low, given that most of these printers allow two to three horizontal models per print load. Intuitively, users opt to print vertically on these small build plates, accepting the inaccuracy of unsupported vertical 3D printing.

In summary, a 3D printer that can print six to eight models in approximately 30 minutes is a feasible option on the market in order to fulfill the requirements of the agile aligner delivery workflow.

The final part of the agile aligner delivery workflow is fabricating and packaging the aligners. The common positive desktop thermoforming units follow:

1. MiniSTAR S® or BIOSTAR® from Scheu-Dental distributed by Great Lakes Dental Technologies (Tonawanda, New York)
2. Drufomat by Dentsply Sirona

Using these units, an assistant can fabricate one aligner in the range of 1-2 mins. Specifically, practitioners should use a tandem method where one aligner is trimmed and polished while another aligner is thermoformed to optimize the time. Appropriate instruments, including sharp scissors, hole punchers, teardrop cutters, and polishing burs, are essential for a swift operation. Beck Instruments (Santa Ana, California), Hu-Friedy (Chicago, Illinois), and Allure (Whitinsville, Massachusetts) offer most of these instruments. The type of plastic used in aligner fabrication determines the trimming time. Some plastics are hard to cut and create a burden to your team. At our agile aligner delivery workflow, my clinic opted to exclusively use Zendura™ FLX (Bay Materials LLC, Fremont, California), which provides a balance of easier trim, patient comfort, and efficient tooth movement at a higher cost per sheet.

Desktop CNC (computer numerical control) aligner trimmer units are entering the orthodontic field. These robotic arms can trim aligners more consistently and with higher precision. Most of these units require further adjustment steps in the aligner manufacturing flow and are promising. uContour from uLab Systems (Redwood City, California) and 5AXISMAKER (5AXISWORKS LTD, London, United Kingdom) are a couple examples of these machines. To the best of my knowledge, uContour is the only unit that is fully integrated with the software (uDesign) to move teeth. Ideally, these units should have the ability to trim multiple models with minimal to no assistance from the user.

In summary, it is possible to deliver a set of six to eight active aligners in a couple of hours using an optimized agile aligner delivery workflow. Adjusting and optimizing each part of this pipeline is the key to success on this protocol. I would encourage practitioners to start on a smaller scale and build up the workflow. The choice of certain brands, described earlier, is based on my experience in the past few years striving to optimize the agile aligner delivery workflow. Most parts of this relatively small operation are rapidly evolving, and practitioners may use alternatives based on all these changes.

The agile aligner delivery workflow can be implemented in combination with the use of laboratories that offer aligner fabrication to offset some of the aligner manufacturing workload. Practitioners can imagine that the initial series of aligners for each sprint (new scan and new sets of aligners) could be quickly manufactured locally, while the remaining aligners are outsourced.