Replacement Retainer From a Digital Scan: How to Use Your STL or PLY File

If your dentist or orthodontist already has a digital scan of your teeth, you may not need to take another physical impression to order a replacement clear retainer.

Editor’s Note
This article was published on September 2, 2026 to explain Sentinel’s digital-scan workflow for replacement retainers, including qualifying STL and PLY files, laboratory review, $20 digital-scan savings, and when a new impression or orthodontic evaluation may still be appropriate.

Sentinel accepts qualifying STL and PLY digital dental scan files for custom clear retainers. If the scan accurately represents the tooth position you want to maintain and contains the anatomy our laboratory needs, we may be able to fabricate your replacement directly from that digital record.

That means no putty impression—and Sentinel currently provides a $20 savings when you order using the digital-scan option.

Can a Retainer Be Made From a Digital Dental Scan?

Yes.

A professional digital dental scan creates a three-dimensional record of the teeth and surrounding anatomy. When that record contains the information needed for fabrication, it can be used to create a custom dental model and clear retainer without requiring a new physical impression.

At Sentinel, we accept qualifying STL and PLY scan files for replacement retainers.

The important question is not simply whether you have a file. It is whether that file accurately represents the tooth position you currently want the new retainer to maintain.

Why Check for an Existing Digital Scan First?

Many people who have completed braces or clear-aligner treatment have already had professional digital scans taken as part of their orthodontic care.

If one of those records is still current and represents the correct finished tooth position, it makes sense to check whether it can be used before recreating the same anatomy with an at-home impression.

This is especially useful for clear retainers.

In our laboratory experience, retainer fabrication depends on having complete, usable dental anatomy. A physical impression that is shallow, incomplete or missing important areas may need to be retaken before the retainer can be made.

A usable professional digital scan can eliminate that step altogether.

What File Types Does Sentinel Accept for Retainers?

Sentinel currently accepts qualifying:

• STL files
• PLY files

These are common three-dimensional dental file formats that may be exported from professional intraoral scanning systems.

If your dentist or orthodontist has scanned your teeth, ask whether they can provide your dental scan as an STL or PLY file.

You do not need to determine on your own whether the file contains everything required for fabrication. Once submitted, our laboratory reviews the record.

How to Order a Replacement Retainer Using Your Digital Scan

The process is straightforward:

1. Choose the digital-scan option when ordering your clear retainer.
   Select the option indicating that you already have a professional digital dental scan rather than choosing the at-home impression pathway.
2. Complete checkout.
   The digital-scan option currently includes a $20 savings compared with the impression-kit pathway.
3. Watch for your secure upload email.
   After checkout, Sentinel will send you an email containing a secure link for submitting your digital dental file.
4. Upload your STL or PLY file.
   Submit the scan file you received from your dentist, orthodontist or dental provider.
5. Our laboratory reviews the scan.
   We check that the submitted digital record contains the anatomy needed to fabricate the retainer.
6. If the record is usable, fabrication can proceed without an impression.
   Your custom clear retainer is then made from the approved dental record.

Where Do You Get Your STL or PLY File?

Start with the dentist or orthodontist who performed your digital scan.

You can ask whether they have a digital record of your teeth and whether they can provide an export in STL or PLY format.

This is particularly worth checking if you previously completed:

• Invisalign or another clear-aligner treatment,
• traditional braces followed by digital scanning,
• orthodontic retainer fabrication,
• restorative or cosmetic dental treatment involving an intraoral scan,
• or another procedure for which your teeth were professionally scanned.

Having had a scan in the past does not automatically mean the file is appropriate for a new retainer, but it is often worth asking.

How Recent Does the Digital Scan Need to Be?

There is no single expiration date that makes every dental scan usable or unusable.

What matters is whether the scan still represents the tooth position and dental anatomy that you want the new retainer to maintain.

A scan may no longer be appropriate if, since it was taken:

• your teeth have noticeably shifted,
• you had additional orthodontic treatment,
• a crown, veneer or other restoration changed the shape of a tooth,
• a tooth was removed or added to the arch,
• or another meaningful dental change occurred.

If the old scan still represents your current anatomy and the position you want to preserve, it may still be useful.

For a deeper explanation, see Can You Reuse an Old Digital Dental Scan? .

What If Your Teeth Have Shifted Since the Scan?

This is where the distinction between a retainer and orthodontic treatment becomes important.

A Sentinel clear retainer is a passive appliance. It is intended to maintain an appropriate tooth position—not to recreate unfinished orthodontic treatment or predictably move teeth back to where they were years ago.

If your teeth have visibly shifted since your old scan, do not automatically assume that making a retainer from either the old file or a new record is the right next step.

An orthodontist can determine whether the current position should simply be retained or whether additional active treatment is appropriate first.

Read Can Retainers Move Teeth Back? for more on that distinction.

What If the Scan File Is Incomplete?

A file issue does not always mean that you need to have your teeth scanned again.

Depending on what was originally captured and exported, the solution may be as simple as obtaining a different export or additional information from the dental office.

That is why we review the submitted record before fabrication rather than asking customers to judge the technical quality of their own scan files.

If something is missing, our team can let you know what is needed.

Digital Scan vs. At-Home Impression for a Clear Retainer

Both can be valid ways to create the dental record used for a custom retainer.

We do not frame this as “digital is always better.”

If you already have a usable professional digital record, it is simply sensible to check that option first. If you do not, the at-home impression process remains available.

Why Is Anatomy Capture So Important for Clear Retainers?

A clear retainer closely reproduces the shape of the teeth.

That means the dental record used for fabrication needs to contain the contours and areas required to make the appliance correctly.

With an at-home impression, one of the most common problems we see in the laboratory is anatomy that is almost—but not quite—complete enough.

A back molar may be too shallow. An edge may disappear into thin impression material. A section of the arch may not be captured as clearly as needed.

Sometimes the impression is beautifully done. Sometimes a retake is necessary.

This is one reason an existing professional digital scan can be such a useful option for replacement-retainer customers.

Is a Digital Scan More Accurate Than an Impression?

We would not make that blanket claim.

A good digital scan can provide an excellent dental record. A good physical impression can also provide an excellent dental record.

Likewise, either method can be unusable if important anatomy is missing or if the record no longer reflects the current teeth.

The practical question is simpler:

Do you already have a professional record that accurately represents the anatomy you need to maintain?

If yes, start there.

Can You Use a Scan From Invisalign Treatment?

Potentially.

Many people who completed Invisalign treatment had multiple professional scans during their orthodontic care.

The important issue is which stage of treatment the file represents.

A scan taken before treatment was complete may not represent the final position you want to maintain. A final or later scan that reflects your completed orthodontic result may be more relevant.

If you are unsure, ask your orthodontist which file reflects your finished treatment position.

For replacement options after Invisalign, see Invisalign Retainer Replacement Cost: Vivera & Clear Retainer Options .

Can Sentinel Use a Scan From Another Dentist or Orthodontist?

Yes, the digital scan does not have to originate from Sentinel.

If you have a qualifying STL or PLY record from a dentist or orthodontist, you can submit it through the secure upload process after ordering.

Our laboratory reviews the submitted file based on whether it contains the dental anatomy needed for fabrication.

What Kind of Retainer Does Sentinel Make?

Sentinel makes custom passive clear replacement retainers for people who have completed orthodontic treatment and need to maintain an appropriate current tooth position.

Our retainers are fabricated in our in-house dental laboratory using Essix Plus clear retainer material.

Each appliance is made from the approved dental record and individually trimmed and finished around the customer's anatomy.

Sentinel does not provide active aligner treatment or create orthodontic plans intended to move teeth.

What If You Do Not Have a Digital Scan?

You can still order a custom retainer.

Choose the at-home impression option when ordering. Sentinel will send the materials needed to create the physical dental record for your retainer.

Once the impression is returned, our laboratory evaluates it before fabrication.

If an area is too shallow or incomplete, we may ask for a retake rather than fabricating from a record that does not contain the anatomy we need.

For the broader replacement process, see Replacement Retainers: How to Replace a Lost, Broken or Worn Clear Retainer .

Ready to Order From Your Digital Scan?

If your orthodontic treatment is complete, your tooth position is appropriate to maintain and you already have a professional STL or PLY dental scan, start with the digital-scan option.

You'll receive a secure upload link after checkout, and our laboratory will review your file before fabrication.

You'll also receive the current $20 digital-scan savings for skipping the physical impression pathway.

View Sentinel Clear Dental Retainers .