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Introduction to 3D Printing of aligners

Do you want to make aligners with 3D printing?

We will focus on existing aligners manufacturing processes where Stereolithography SLA printing is used because of its low relative costs since professional SLA, DLP & LCD printer prices range from 300-2.000 Euro

SLA, DLP, LCD and Inkjet 3D printing of aligners with photoreactive 3D resins. Types of manufacturing processes

Existing Indirect manufacturing process of aligners: 2 steps/processes
Printing of dental models by SLA, DLP, LCD and Inkjet 3D printing + vacuum thermoforming of thermoplastic disks with these typical properties:
  • flexural strength 60-70 MPa
  • elastic modulus <1000-1700 MPa
  • tensile strength 50-70 MPa
  • Shore hardness D70-80
  • typical thickness 0.8/0.6 mm before/after thermoforming
  • example of commercial aligner: Invisalign
  • existing most common production method of commercial aligners

3Dresyn OD UHR White for printing "try in" devices, impression trays and models

 

Direct Manufacturing: 1 step/process

Up to now direct printing of dental aligners by SLA DLP LCD and Inkjet printers have resulted in these two state of the art limiting scenarios:

  • case 1: too fragile, good retention & rigidity but easy breakable at low thickness <1mm
    • flexural strength <60 MPa
    • elastic modulus 1200-1700 MPa
    • tensile strength <30-50 MPa
    • Shore hardness D70-80
    • thickness 0.6 mm
  • case 2: too flexible, foldable with low retention at low thickness <1 mm
    • flexural strength <60 MPa
    • elastic modulus <1000 MPa
    • tensile strength <30 MPa
    • Shore hardness <D70
    • thickness 0.6 mm

Drawbacks

  • overall with no exception competitor´s state of the art 3D resins based on strong irritant low performing monomers used for decreasing the viscosity of SLA, DLP, LCD and Inkjet 3D resins decrease their biocompatibility and their overall mechanical properties

3Dresyns Solutions:

  • Printing of dental aligners by SLA, DLP, LCD printers at low room temperature but also at medium and high printing temperature: 50ºC for improved performance: higher aligner durability
  • Direct printing of aligners with our new biocompatible and functional 3D resins. We have developed 3 versions for printers working at low, medium and high temperature:

Note: direct printing of aligners requires detailed integration of aligners specifications and control of the overall workflow and process variables (software, aligner thickness, resin, printer type, print settings, postcuring and cleansing protocols, etc). All the mentioned variables affect and determine final aligner properties: pressure and retention on teeth, mechanical properties and biocompatibility.

Since different printers and settings provide different mechanical properties for any 3D photoreactive resin, the usage of different dosage of Fine Tuners and hardness / rigidity adjusters can be used to tune, balance and maximise performance properties for any given 3D printing system.  

    Invisalign Lleida

    Indirect manufacturing: 2 steps/processes

    Indirect manufacturing of aligners via injection of tough thermoplastics like polyamide at 290ºC or our injection and casting resins at 80ºC in injection molds printed by SLA with our 3D resins for injection molding 3Dresyn IM-HDT has these pros and cons:

    • 2 step process: time consuming
    • easy control of aligner properties when injecting "non reactive" thermoplastics such as polyamide,  because not  catalysed, thermal nor photochemical reactions occur with its intrinsic performance variability depending on curing protocols
    • improvement of the mechanical and retention properties of the aligner since injection can be done at high temperature permitting the usage of higher viscosity and stronger thermoplastic materials
    • decreasing production costs (laser cutting is not required) and attachments can be incorporated in the design of the aligner
    Printing molds of the aligners in sacrificial or durable molds printed by SLA, DLP, LCD and Inkjet 3D printing followed by resin injection or casting of 3Dresyn RIC UTD50 at high temperature ≥80ºC or injection of tougher thermoplastics such as nylon at much higher temperatures c.290ºC or higher.
    Tougher aligners can be made by indirect manufacturing vs direct printing by SLA, DLP & LCD printing but our results show that directly printed aligners by SLA exhibit sufficient an even exceeding durability and retention for the most demmanding orthodontic systems.
    About inkjet printing: unless higher printing head temperatures ≥80-90ºC are used in inkjet printers for printing aligners and similar thin applications, resulting materials will carry on having lower inherent mechanical properties than their tougher and stronger counterparts printed by more affordable SLA DLP & LCD printers    

      Direct vs Indirect manufacturing of aligners

      Benefits of Direct printing of aligners

      • ideal 1 step process
      • Faster and less labour and waste
      • Relative costs for direct and indirect manufacturing can be similar

       Drawbacks

      • Overall lower but sufficient mechanical properties than indirect manufacturing  since the toughest materials  such as nylon injected at 290ºC have in practice improved mechanical properites vs most directly printed 3D resins in affordable SLA, DLP, LCD printers 

      The Present and the Future

      Note: Indirect manufacturing of aligners and dentures can be done with a range of injection resins. Read: Polyamide as a Denture Base Material: A Literature Review and Physical properties and color stability of injection-molded thermoplastic denture base resins

        Conclusions
        • Indirect manufacturing is ideal for making ultra tough and thin applications such as aligners, flexible partial dentures, with thickness below 1-1.5 mm but can be also used for making rigid durable dentures with traditional dental materials such as:
          • injected PMMA with flexural strength 65-70 MPa, elastic modulus 1800-3000 MPa, tensile strength 40-60 MPa and Shore hardness D80-85, but also other dental applications such as crown and bridges with ceramic feedstock injection and custom designed implants for bone regeneration systems with Titanium feedstock injection
        • Direct manufacturing by SLA DLP & LCD 3D printing is ideal for direct printing of rigid and thicker dental applications, above 1-1.5 mm, with our resistant and  biocompatible Dental 3Dresyns for direct printing of night guards, surgical guides, durable dentures, durable crown and bridges, etc
        • Direct manufacturing of functional tough aligners and similar thin dental applications, below 1-1.5 mm, can also be printed succesfully with affordable, below 1000€, SLA DLP & LCD printers with our new aligners 3Dresyns: 
        • Direct and Indirect manufacturing have pros and cons which can be evaluated with our technical support to help you to choose your optimum process for making aligners and similar applications

        Discover our Special offer of 3D consulting for choosing your optimum 3D printer setups

        IMG_4640

        Aligners — evident

        Why Getting Quality Dentures is the Way to Go - Angela S. Fennell DMD, PC  Huntsville Alabama

        Who Needs Flexible Partial Dentures? | European Denture Center

        Please contact us to consult about our 3D resins and your specific performance goals at: info@3Dresyns.com