Calibrating for Aligner/Retainer Fitment - Best Steps to Success

Calibrating your printer for the best retainer or aligner fitment is important for accurate movement and/or retention of the teeth, and critical for patient comfort and care.

 

Following this guide, you can calibrate your Pro or MoonRay printer for the fitment required by your practice or lab. It is important that the steps are followed in the order shown for a step by step approach.

 

For best results, it is ideal to have a scan or model of your own mouth, or a willing lab tech/assistant that can verify the fitment before printing live cases.

 

Note: Fitment of aligners and retainers can be very subjective. In general, we try to calibrate fitment for aligners to be more "active", or tight, for teeth movement, and retainers tend to be more "passive" or loose. As noted above, it is best to have a willing test subject to check fitment with a retainers/aligners created on the test models during the calibration process

 

Tools Needed:

 

  • 91% or higher Isopropyl Alcohol for washing models
  • Platform scraper
  • ProCure, or similar, UV post-cure oven
  • Digital Calipers
  • Test Dental Model/Arch for checking aligner/retainer fitment

 

Before Proceeding

Critical Steps for proper workflow:

  • Add additional wax or block-out material to models before creating the thermoform
  • Check that model design or tooth anatomy is not creating undercuts or incurring deformation during appliance removal
  • Check that the retainer or aligner medium is not too thin. For best results, 0.75-1mm for aligners, and 1.25mm or thicker for retainers works best
  • Check the PSI of the thermoform machine. A PSI range of 35-40 (2.5-3 Bar) is critical for proper appliance creation

Printed models, even when perfectly washed and cured, tend to be stickier than traditional stone models.

Undercuts, interproximals/diastema, and large recessions should all be considered for wax blockouts.

A silicone model removing spray can be very useful, even if you haven't needed it in the past.

 

We've teamed up with a few of our exceptionally high-volume Doctors and Laboratories for a quick solution.

This issue is caused by warping when removing the appliance immediately after the suckdown process.

Applying very light heat via warm water or a steamer, we can negate the warping.

A quick pinch with your fingers, or using bracket adjusting pliers, apply a slight but firm bend:

 

If you are still experiencing fitment issues after performing the above steps, calibration of the printer may help with creation of accurate models.

 

This calibration process is intended for printing models horizontally, flat on the build plate.

Please ensure that the material that is being calibrated is well mixed, and that the glass surfaces on the printer are completely clean and spot free. It is critical that all optical surfaces are free of any streaks, smudges, dust, resin, or fingerprints.

Cleaning the Optical Path of the SprintRay Pro

Cleaning The Mirror on MoonRay

Baseline Calibration

The first steps are to create a baseline calibration before proceeding. We want to ensure that the projector intensity, as well as the X and Y scaling are as close to factory specifications.

1. Perform the Fit and Tolerance calibration via the Material Fine Tuning menu in RayWare. This calibration has the greatest effect on the fitment of the aligners/retainers around the teeth themselves, and this will ensure that the printer's Exposure Length is calibrated to the correct level. This settings is similar to the brightness setting on a TV; it does not affect the distance from molar to molar, only the localized brightness of each layer. Here is an example below with a single layer from a standard dental arch:

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Projector intensity at a 5:

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Projector intensity at a 1:

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Note: changes to layers/images exaggerated to show a clearer example

 

 

Begin the calibration by going to Print > Fine Tuning > Material Fine Tuning

 

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Make sure you select the same Material and Layer Thickness that you want to calibrate:

 

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Then select Fit and Tolerance:

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Print the calibration model, clean, and post cure using the same method as your models

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a 2-4 score indicates that the parts are fitting within the expected tolerances, and we can move on to the next calibration step.

 

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A 5 score may indicate the projector is under-curing. Do not proceed if you achieve a 5 score more than 3 times, as this may indicate further issues. If this is the case, it is necessary to reach out to SprintRay Support.

A model that wont fit together, or a 1 score may indicate the printer is over-curing, but is most likely a result of a dirty optical path from the projector to the resin. Please use the following Help Center articles for reference on how to clean properly:

Cleaning the Optical Path of the SprintRay Pro

Cleaning The Mirror on MoonRay

 

 

2. The next step is to perform the Dimensional Accuracy calibration to dial in the machine's X and Y scaling. This setting affects the molar to molar distance, or the distance from the center line of the arch to the teeth. This adjusts fitment of the entire aligner/retainer, such as the "squeezing" from the outside inwards, or pressure from the inside outwards. This setting is comparable to adjusting the screen size of a TV:

 

                           Before adjustment                                                               After adjustment

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To perform the Dimensional Accuracy calibration, select in the same Material Fine Tuning menu we used for the Fit and Tolerance test. Make sure you select the correct Material and Layer Thickness:

 

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Select Automatic Calibration:

 

 

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Once printed, clean and post cure using the same method as your models. Then take an accurate measurement using the Digital Calipers down to the second decimal place in Metric. It is normal to have a +/- X/Y tolerance of 75-95µm, or +/- 0.075-.095. Press Finish once the values are entered:

 

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3. Perform a test print with a dental model that you can create an aligner/retainer on and check fitment, whether it be on a willing test subject, or a study model. 

At this stage, we are printing models as close to 1:1 as possible, and in most cases, the fitment is OK for aligners, as a tighter fitment is desired. If the fitment meets your standards, you can proceed with normal printing.

If you would like a looser fit, proceed to the next step.

 

Adjusting for Your Desired Fitment

Now that we have established a baseline calibration, and are printing as close to 1:1 as possible, we can make further adjustments to dial in the fitment.

Note: this step will require minor adjustments, and then printing one model to verify fitment, and may take a few prints to dial in, depending on your fitment needs.

In general there are two types of issues with fitment, and we want to be certain how the models are off so that we can adjust accordingly:

Retention: The retainers are too tight around the entire tooth and are painful to fully seat or remove. In general the molar to molar distance is good, and the full arch will nearly seat down fully, but retention around teeth prevents comfortable fit

Scaling: This is when the printed models molar to molar distance is off. This is usually when one side of the retainer will fit, but as you work the retainer around and down in the mouth, the other side may be a quarter of a tooth off and cause the retainer to lift or only seat partially. Or the retainers will fit towards the front and pop off near the rear of the mouth

If your models are too tight:

First, investigate the model post processing being done after the model is cleaned and fully cured. 

 

These steps must be performed first, and are critical for proper workflow!

  • Add additional wax or block-out material to models before creating the thermoform
  • Check that model design or tooth anatomy is not creating undercuts or incurring deformation during appliance removal
  • Check that the retainer or aligner medium is not too thin. For best results, 0.75-1mm for aligners, and 1.25mm or thicker for retainers works best
  • Check the PSI of the thermoform machine. A PSI range of 35-40 is critical for proper appliance creation

If you are still experiencing tight fitment:

 

For Tight Retention:

 

Appliance Fit Adjustment 

 

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This feature in the Material Fine Tuning Menu will allow manual adjustments of the outer dimensions of the teeth, allowing for an offset to be created that does not affect the molar to molar spacing of the model. The tool detects the outer dimensions of the teeth in each layer, and adds or subtracts the appropriate number of "pixels" that has been selected to adjust fit. 

 

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Dramatized example of the pixel offset performed using a positive Appliance Fit Adjustment

 

Select the material that you wish to adjust. 

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Note: this adjustment is not printer specific, and must must be made on each installation of RayWare used to generate print jobs.

 

Select the amount of adjustment you wish to make. 

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Positive values increase the offset added to each layer, which will result in models that print slightly larger, resulting in looser fitment of aligners/retainers.

 

Negative values decrease the offset of each layer, and subtracts a small amount away resulting in models that print slightly smaller, which will give you tighter fitment of aligners/retainers. 

If printing models with supports and using a negative Fit Adjustment value, you must use High Strength supports to prevent issues with supports not forming.

 

RayWare will note the Calibration History below, showing when the previous changes were made to the selected material.

 

Proceed with making a single adjustment and re-printing your test model to verify fitment

 

 

Scaling Issues (Molar to Molar Spacing)

 

 

Re-Perform Dimensional Accuracy

Re-perform the Dimensional Accuracy calibration test, but before inputting any measurements, ensure that the model is properly cleaned and post cured. Once complete, measure the Dimensional Accuracy model 3 times, and take the average of the 3 measurements, then input into RayWare

Manual Scaling for each model

You can also manually scale the models by small percentage values using the Scaling tool in RayWare:

Select a model, then enter a Scaling value of 99 to 101%

Note: always use the keyboard number row to input manual values, not the numpad

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Force a Scaling Value for All Prints

 

Go to the Material Fine Tuning menu and select Dimensional Accuracy, then select Manual Calibration:

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Then enter the desired Scaling Factors you wish to be applied to all prints for this Material and Layer Thickness:

 

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Print your dental test models and verify fitment.

 

 

If you are still having issues with getting your model sizing calibrated successfully, please contact our Support Department at 800-914-8004 and we can help you with any issues.

 

We can help with that!

If you're experiencing difficulties or have questions about any of your SprintRay products, submit a support ticket or contact us at 800-914-8004

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