Recommendations for printing aligners
- start printing aligners with 3Dresyn OD Clear TF LTP Rigid or Flexible with Low Viscosity LV version since this version is the best for starters, for printing thin aligners at 0.5-0.8 mm with affordable SLA DLP & LCD printers without any heating system
- High Viscosity HV versions have improved mechanical strength but require printing aligners at 30-35ºC. Recommended cost effective heating systems
- Low Viscosity LV versions require printing temperatures around 25ºC. It is recommended to warm LV versions to around 35ºC before printing
- any LCD printer, even the low cost ones with prices of 100-200 Euro can be used for printing our resins with excellent mechanical performance, light fastness (non-yellowing), and dimensional accuracy
- it is recommended printing aligners vertically without any supports with 100 microns z layers for faster printing speed of 90-120 minutes vs 150-180 minutes needed with 50 micron z layers
- typical printing settings for most printers: 2-4 adhesion layers of 80 seconds, and std layers of 5-10-15 seconds with z layers of 50-100 microns
- with 5-10 seconds increased transparency and light fastness (non-yellowing) is obtained vs 10-15 seconds
- warm the resin initially to around 35ºC before printing to reduce viscosity with non-heated printers
- follow our postprocessing instructions without any corner cutting for making ultra safe clear aligners without any stickiness, haziness, and yellowing
- reduce printing exposure time as much as possible preserving printability (reduce also power if your printer permits it) to reduce yellowing
- facts: aligners printed at 8 seconds with 100 micron z layers with SLA DLP LCD Anycubic printers, with light powers below 1-2 mW/cm2 at 405 nm, exhibit superior light fastness and non-yellowing vs longer exposure times of 12-15 seconds per z layer. Exact times depend on the relative power of each printer which depends on the specific model and printer supplier
Cleaning of aligners
Prints of aligners become hazy or whitish when they are cleaned with isopropanol, ethanol or even with our milder Cleaning Fluid Bio. The use of alcohols also reduce significantly the mechanical properties of printed aligners, weakening and making them brittle. Learn more: Comparison of different methods for cleaning and post processing 3D printed resins
Equipment:
- a low cost wash & cure machine of 100 Euro can be used, such as Wash & Cure machine or a similar one can be used for cleaning and light postcuring prints of aligners
- light boxes with too high power with too long postcuring time can cause some yellowing and decrease of mechanical strength "embrittlement" due to over curing
- a thermal oven (optional, needed in method 2 is used)
Cleaning and postprocessing protocol
The following cleaning and postprocessing protocols are cost effective, fast, and easy. They are ideal for obtaining maximum mechanical and safety performance, as well as high transparency, without yellowing of clear aligner prints. Follow our postprocessing instructions without any corner cutting for getting optimum results:
Method 1: Light box post-curing of prints in immersion/dipping (recommended process)
Features:
- fast & easy process, recommended with the required usage of Cleaning Fluid NW1 Bio (odorless version yields improved transparency and biocompatibility)
- without the usage of Cleaning Fluid NW1 Bio maximum transparency of clear resins will not be obtained independently of the resin when alcohols such as ethanol or isopropanol IPA are used for cleaning since they cause whitening of prints
Process:
- remove aligner prints from the build platform with a spatula
- cut the supports
- optional step for maximum transparency of High Viscosity HV versions: after printing aligners (before washing in Cleaning Fluid NW1 Bio) eliminate the uncured resin from the aligner by gravity in an oven at 65ºC for 30-60 minutes (temperature above 65º may cause some yellowing)
- dip prints inside a washing basket in a washing container filled with warm Cleaning Fluid NW1 Bio:
- it is odorless, ultra safe and non-flammable
- warm the Cleaning Fluid NW1 Bio to 65ºC with eg a kettle (always below 65ºC to prevent yellowing)
- remove any uncured resin from the aligners positioned in the basket while stirring the warm Cleaning Fluid NW1 Bio at 65ºC with a magnet stirrer (wash mode of the Wash & Cure machine)
- once prints and washed and cleaned dip them again in the same (or another) transparent container filled with fresh and clean Cleaning Fluid NW1 Bio*
- postcure prints at room temperature inside Cleaning Fluid NW1 Bio in the light box for 15-30-45-60 minutes (cure mode of the Wash & Cure machine):
- light box curing times depend on the power and wavelength of your specific light box
- low light power postcuring units require longer times than high power postcuring units
- high light power postcuring units can cause yellowing and decrease of mechanical strength
- too long light box postcuring can also cause yellowing and decrease of mechanical strength
- optimum results are obtained at 20-30 minutes in the Anycubic Wash & Cure machine
- after light box postcuring remove Cleaning Fluid NW1 Bio from the surface of the aligners by spraying isopropanol on its surface to remove any rest of Cleaning Fluid NW1 Bio and residual stickiness
- if the prints are too sticky without yellowing, increase the light postcuring time inside clean Cleaning Fluid NW1 Bio
- if the prints are non-sticky with yellowing and embrittlement, decrease the light postcuring time inside clean Cleaning Fluid NW1 Bio until yellowing and embrittlement decrease
- once the prints are non-sticky and without yellowing not embrittlement the optimum settings have been determined, then prints can be dipped in boiling water** for 20-30 minutes to remove any residual taste caused by extractables, leachables, contaminants, residual uncured monomer, and byproducts
*Note: ideally use fresh unused Cleaning Fluid NW1 Bio to avoid contamination of prints with uncured resin from previous washings.
**Note: despite being Cleaning Fluid NW1 Bio ultra safe it has a residual bitter taste, which is transfered to the aligners. To remove it, instead of boiling the aligners in water, use combinations of water and Cleaning Fluid Bio (version 2) at 50%/50% ratio to remove the bitter taste.
Method 2: Light box post-curing of dry prints in air atmosphere (also recommended if you have an oven, but do not have Cleaning Fluid NW1 Bio)
This alternative method does not require the use of any cleaning fluid, but requires the use of a thermal oven for dripping out the uncured resin from the aligners after printing.
Features:
- ideal for dripping out of the uncured resin from the aligners by gravity in an oven at 65ºC without the need for using cleaning Fluid NW1 Bio, which despite being ultra safe and biocompatible confers a bit of bitter taste to the aligners.
- there is not any residual bitterness caused by Cleaning Fluid but still residual and extractables need to be removed by boiling the aligners in water
Process:
- after printing cut the supports and let the uncured resin drip out by gravity from the surface of the prints in the upside down position in an oven heated at 65ºC from 15 to 60 minutes (leave prints upside down for maximum drip out by gravity)
- the higher the viscosity of the resin the longer time needed for dripping out
- avoid temperatures above 65ºC to prevent yellowing
- postcure the dry prints in a normal light box for 15 minutes* at room temperature
- turn the prints upside down and postcure them for other 15 minutes*
- clean and remove any residual stickiness by spraying ispropanol isopropanol IPA on the prints (use a spray bottle to ensure that clean IPA is always used)
Options and different possible scenarios:
- if the prints are too sticky without yellowing, increase the light postcuring time
- if the prints are non-sticky with yellowing and embrittlement, decrease the light postcuring time until yellowing and embrittlement decrease
- once the prints are non-sticky and without yellowing, nor embrittlement, the optimum settings have been determined, then prints can be dipped in boiling water for 20-30 minutes* to remove extractables, leachables, contaminants, residual uncured monomer, and byproducts
*Note: The optimum time will need to be determined by experimentation since depends on many variables beyond our control, such as the resin, the printing and light box specifications, light power and wavelength, etc.
Discover how method 1 and 2 compare with the cleaning with conventional alcohols which cause embrittlement to aligners: Comparison of different methods for cleaning and post processing 3D printed resins
Summary
If the mentioned instructions are followed without any corner cutting, aligners with excellent mechanical and surface quality, transparency, light fastness and safety will be successfully made in less than 3 hours.
The higher the temperature the shorter the time needed for fully cleansing the aligners. Our resins for printing aligners have been designed to withstand high temperatures (boiling water) without mechanical degradation and yellowing once postcured. At the boiling temperature of water the cleansing yield is increased resulting in increased polymer conversion and removal of yellowing, extractables, leachables, contaminants, and byproducts.
Aligners will not be ready for use until maximum polymer conversion and full cleansing are achieved. Aligners should be tasteless and free of extractables and leachables. The safety and biocompatibility of printed aligners are responsibility of the aligner manufacturer since their quality and safety depend on the design, implementation, quality assurance and production "in house" of the right printing and postprocessing protocols.
Example of clear aligner, without any yellowing, printed at 100 microns z layers in less than 2 hours in a low cost, 200 Euro, monochrome Anycubic MLCD printer.
Design aligners directly with Maestro, Blue Sky Bio, or other aligner software.