The Invisalign® Cleaning System (Cleaning Crystals) - Do you need to use it?

| Effectiveness - What does research document about this product's use? | Can you just use it alone? | Best practices.

How important is it to use the Invisalign® Cleaning System?

If you wear Invisalign® aligners, you have no doubt heard about their Cleaning System and its packets of "Cleaning Crystals." And most likely related to its cost (each packet costs around a dollar), you may wonder how important it is to use this product to clean your aligners.

We've turned to published research for an answer.

As coverage of this question, we've ended up creating two separate pages:

  • One of them is this page. It discusses findings from published studies that have specifically evaluated the use of the crystals.
  • We've also created a companion page that discusses possible alternatives to the use of Invisalign's® crystals, once again, in light of the findings of research studies.


What are important factors to consider?

Different than you might expect, there are actually several different issues that must be weighed when evaluating an aligner cleaning method. They include:

  • How effective the product is in removing accumulated debris from your appliances and sanitizing them.
  • How the use of the method affects aligner transparency. (An issue that can be important in how visible wearing your appliances are to others.)
  • Does the cleaning method affect the physical properties of the aligner's plastic (and therefore alter the aligner's effectiveness in producing tooth movements)?


Fortunately, there have been a few published studies that have investigated these issues, and specifically as they apply to the use of Invisalign's® Cleaning Crystals (and possible alternatives).

Research - How effective are Invisalign's® crystals in disinfecting your aligners?

Study #1 - Levrini

Title: Scanning electron microscopy analysis of the growth of dental plaque on the surfaces of removable orthodontic aligners after the use of different cleaning methods.

This author has published two studies that have evaluated the effectiveness of the Invisalign® Cleaning System in regard to its ability to sanitize aligners.

An initial one evaluated the use of three different cleaning methods (rinsing with water alone, brushing with toothpaste alone, soaking using Invisalign's® Cleaning Crystals followed by brushing with toothpaste).

The appliances were then evaluated via an electron microscope to determine what level of bacterial colonization remained after each of the cleaning routines had been performed.

Illustration of cleaning Invisalign® tooth aligners.

One way to clean Invisalign® aligners is by soaking them.

Study findings.
As you might anticipate:
  • The cleaning method that included both brushing (before wearing the aligners) and using the Cleaning Crystals (once daily) was found to be the most effective one in reducing the bacterial load found on the appliances.
  • However, we think it's important to point out that the paper specifically stated that just brushing with toothpaste "gave excellent results."
  • We'll also mention that the study found that none of the three cleaning routines were totally effective in removing all bacteria and debris from aligner surfaces.


Brushing is needed too.

Discussion in this paper elaborated on the fact that studies have generally shown that the most effective methods for cleaning dental appliances (of all types) typically involve a combination of mechanical (brushing) and chemical (soaking) processes. And suggested that its findings corroborate this point. (We report on the need for this two-phase approach with denture cleaning here.)

What we found curious about this study.

We couldn't help but notice that this study did not evaluate the effectiveness of just using the Invisalign® crystals on their own. (Just soaking the aligners, without any brushing.)

Based on the paper's discussion about the importance of mechanical cleansing (brushing) in creating effective dental appliance cleansing, one might presume that they never considered that that protocol would be an effective option. But that is just our conjecture.

Section references - Levrini

Study #2 - Levrini

Title: ATP Bioluminometers Analysis on the Surfaces of Removable Orthodontic Aligners after the Use of Different Cleaning Methods.


This study (whose lead author was the same as the study above) was set up in a similar fashion as the one just discussed. The primary difference between the two was the way in which the level of bacteria remaining on the aligners was detected. (This one used bioluminometry.)

Study findings.
Similar to the first paper, this second study stated that:
  • A routine of just brushing with toothpaste "proved to be effective" in removing the accumulation of biofilm (dental plaque) from aligners.
  • But also determined that the best results (in terms of reducing the concentration of bacteria on aligner surfaces) were achieved by combining the brushing routine with the use of Invisalign's® crystals.
  • The study did not evaluate the use of the Cleaning Crystals alone (no brushing).

Section references - Levrini

Study #3 - Shpack

Title: Efficacy of three hygienic protocols in reducing biofilm adherence to removable thermoplastic appliance.


As a preliminary step in this study, it evaluated just soaking aligner samples in Invisalign's® Cleaning Crystals solution. (15-minute soaking duration with container shaking.)

Study findings.
In contrast to the two Levrini studies, this one didn't report such positive results for the use of the crystals. It determined that "this solution has no antibacterial effect against the tested bacteria."

Section references - Shpack

▶ Our conclusions about the need to use the Invisalign® Cleaning System.

The disparate findings of these studies make it difficult to know how much emphasis should be placed on the use of Invisalign's® crystals. It might be stated that:

  • A routine of (regularly and diligently) brushing your aligners alone probably provides an adequate level of cleaning ... (Here's more evidence about the effectiveness of aligner brushing.)

    But yes, the additional use of the Invisalign® Cleaning System may raise the level of disinfection a person can achieve, and therefore might be considered a best practice.


We would suggest that ...
  • Considering that brushing seems to provide a satisfactory level of aligner cleansing, and study results have been inconclusive about the effectiveness of the use of the crystals, then the use of this product tends to fall more so into the category of an adjunct.
  • In situations where effective brushing measures are not performed, it seems unlikely that using Invisalign's® crystals provides a level of assistance that can make up for this deficiency. (Thorough aligner cleansing isn't possible without effective mechanical cleansing.)


! An important footnote.

We think that it's important to state that there are issues and concerns associated with the practice of aligner brushing that are important to consider, especially when toothpaste is used.

We've dedicated an entire page to this issue: Aligner brushing as a primary cleaning method. In our opinion, this is a must-read.

Pictures of aids used with Invisalign® cleaning.

Our affiliate links can be used to shop  Invisalign® cleaning products/units  on  or

Innovative devices and solutions for cleaning issues encountered by Invisalign® wearers.

A picture of an Invisalign® tooth aligner.

An Invisalign® aligner.

What shouldn't a cleaning method do?

It may not have crossed your mind but there are some very important things that an aligner cleaning method should not do. They include:
  • It should not degrade the optical clarity of your appliances. - An issue that's associated with how visible your aligners may be to other people.
  • It should not affect the dimensional stability and/or physical properties of your aligners.

    These types of issues might affect the effectiveness of your appliances in creating tooth movements, and therefore affect your treatment progress.


Does using Invisalign's® Cleaning Crystals affect aligner plastics?

Since using the Invisalign's® Cleaning System is the recommended product, one might assume that the use of this cleanser doesn't affect aligner plastics at all.

From a practical standpoint, that stance seems to be true enough. But as we discuss below, that's not entirely what research suggests.

Research - What effects does the Invisalign® Cleaning System have on aligner plastics?

What type of plastic are Invisalign® aligners made from?

Obviously, to understand the effects that a cleaning method may have on Invisalign® aligners, this is a vital piece of information to know.

Generally, this is proprietary information held by the company. But the Material Safety Data Sheet for their Smarttrack® plastic (the material currently used) states that it's composition is multilayered "thermoplastic polyurethane / copolyester."

What research information is available?

We found published studies that investigated the use of cleaning solutions, including Invisalign's® Cleaning Crystals, with both polyurethane and separately copolyester test samples.

In our reporting here, we're making the assumption that known effects with either of these component plastics would have the potential to similarly affect Invisalign's® multi-layered plastic.


Study #1 - Wible

Title: Long-term effects of different cleaning methods on copolyester retainer properties.


This study was designed to investigate the effects of 8 cleaning methods on copolyester plastic. (One of the components of the plastic material used for Invisalign® aligners.)

The use of these cleansers was evaluated over a 6-month time frame of twice-weekly use. (48 exposures to the soaking solution.)

The plastic samples were evaluated for changes in:

  • Light transmittance - Essentially a measure of optical clarity, a factor that would correlate with how noticeable a person's appliances might be to others.
  • Surface roughness - An increase in surface roughness would affect both an appliance's appearance, and the ease with which microorganisms can colonize on it.
  • Flexural modulus - This is a measure of flexibility. Changes in aligner stiffness can affect the way it applies forces to the patient's teeth, and therefore may affect a patient's treatment progress.


Study findings.
It was determined that the long-term use of the Invisalign® Cleaning system:
  • Did not significantly affect the surface roughness of the plastic. (Only one of the 7 other methods did.)
  • Did not significantly affect the flexural modulus of the plastic. (All but one of the other 7 methods did.)
  • Did cause a statistically significant effect (decrease) in the plastic's light transmittance. (All other cleaning methods had this same effect too.)

    (We found it interesting that the change took place after just 48 soaking exposures. Daily usage over the usual 2-week time frame aligners are worn for would create 14 exposures.)

    (The term "statistically significant" does not necessarily correlate with the words "visibly perceptible." So, how much of a noticeable change actually occurred would be a point of question.)

Section references - Wible

Study #2 - Agarwal

Title: Long-term effects of seven cleaning methods on light transmittance, surface roughness, and flexural modulus of polyurethane retainer material.


This study involved many of the same investigators that conducted the Wible study, and was set up in a very similar fashion (although only 7 cleaning solutions were investigated).

A primary difference between the two studies was that this one evaluated the effects of the cleaning solutions on polyurethane plastic. (The other of the two types of plastic used for Invisalign® aligners.)

Study findings.

In a nutshell, the findings of this study were very similar to the one just discussed. It found that the use of the Invisalign® Cleaning System (over a 6-month period of twice-weekly use):

  • Did not significantly affect the plastic's surface roughness. (Only one of the other methods did.)
  • Did not affect the plastic's flexural modulus. (Two of the alternative methods did.)
  • Did affect the light transmission of the polyurethane samples. (All tested cleaning methods did.)

Section references - Agarwal

▶ Our conclusions about what these studies suggest.

  • The use of Invisalign's® crystals may deteriorate the optical clarity of aligners over the longer term. (All other evaluated cleaning methods did too.)

    Due to the short 2-week time span over which aligners are most frequently worn, for most patients the level of change that occurs is probably (evidently) inconsequential.

  • The formulation of Invisalign's® Cleaning Crystals (sodium carbonate / sodium sulfate) appears to be one that minimally affects the two-component plastics used to fabricate their aligners.

    While you may consider this a given, we primarily mention this as a point of comparison to some alternative cleaning methods that one might consider using. (See link below.)


▶ Our conclusions about choosing to use the Invisalign® Cleaning System.

Based on the information and discussion found on this page, we think that it's justified to conclude that:

  • Just brushing your aligners (discussed next) is typically a satisfactory cleaning method on its own.
  • Since the use of Invisalign's® Cleaning Crystals may raise the level of disinfection possible, using them in conjunction with brushing would generally be considered a best practice (chemical + mechanical cleansing). Although from a practical standpoint, we would question the need to do so daily.
  • In regard to aligner cleansing and disinfecting, we'd anticipate that just using the Cleaning Crystals alone (no aligner brushing) would make the least effective choice by far.
  • All cleaning methods apparently have some effect on the physical properties of the plastics used to make Invisalign® aligners. However with Invisalign's® crystals, it seems that only aligner appearance is affected. And from a practical standpoint, probably only very minimally.

    In comparison, with alternative cleaning methods the question of their level of effect is harder to interpret. By using the Invisalign® Cleaning System, you are in effect purchasing peace of mind on this, possibly inconsequential, point.


As further reading on the subject of aligner cleaning ...



 Page references sources: 

Agarwal M, et al. Long-term effects of seven cleaning methods on light transmittance, surface roughness, and flexural modulus of polyurethane retainer material.

Align Technology, Inc. Material Safety Data Sheet - SmartTrack Aligner Material. 12/08/2015 Frequently Asked Questions.

Levrini L, et al. ATP Bioluminometers Analysis on the Surfaces of Removable Orthodontic Aligners after the Use of Different Cleaning Methods.

Levrini L, et al. Scanning electron microscopy analysis of the growth of dental plaque on the surfaces of removable orthodontic aligners after the use of different cleaning methods.

Shpack N, et al. Efficacy of three hygienic protocols in reducing biofilm adherence to removable thermoplastic appliance.

Wible E, et al. Long-term effects of different cleaning methods on copolyester retainer properties.

All reference sources for topic Straightening Teeth.

Add new comment

Comments (especially personal narratives) that don't contribute to the learning/teaching intent of our pages will be deleted. Comments that don't relate to the subject of the page they are posted on especially well will be moved to a more appropriate one, or deleted, after a few days.

Plain text

  • No HTML tags allowed.
  • Lines and paragraphs break automatically.
Please answer the question so we know you're a human.