Crest Whitestrips® - Can you use additional kits? | How many? | How often? | How soon?

- After you've finished using one box, can you use another? How many total packs can you use? | Information from research studies. | Information from manufacturers. | Primary considerations.

After you've used one package of WhiteStrips®, can you use more?

At that point when a person has just finished using their initial kit of whitening strips, and especially if their results haven't been quite as dynamic as they had hoped, they'll wonder - Can I use additional boxes?

There are factors that must be considered.

This page discusses guidelines that can help you understand what issues are involved and need to be considered when determining how appropriate it may be to extend your strips treatments.

It also provides examples from published research about what was found to be the case with test subjects when extended use was evaluated (advantages, complications). And what a major manufacturer says about using additional packages of their products (how many, how soon).

What's the bottom line about using additional kits?

With some exceptions (see discussion below), it's usually reasonable enough to use a second box of WhiteStrips®, even immediately following your first one. But some level of consultation with your dentist is indicated if you're considering further use beyond that.

A picture of a box of Crest Whitestrips®.

How many boxes of Whitestrips® are permissible?

How many boxes of whitening strips can you use?

As a start for this subject, we'll tell you what the leading manufacturer in this field states.

The official word from Crest® about WhiteStrips®.

What we see stated on their website.

The Crest WhiteStrips® website (USA) suggests that at least for some of their products ...
  • "You can use one pack right after another." - Meaning two boxes of strips (as in a "twin pack" of WhiteStrips® as they are sometimes sold).
  • The same paragraph then states that they "recommend using Whitestrips twice per year."

    (We're assuming this frequency is based on the claim found on the same page that states treatment results can last 6 months to a year.)


But really, despite their spelling it out with those statements we still had questions.

We didn't understand whether ...

  • You can use two back-to-back kits of strips twice a year? (For a total of 4 packages.)
  • Or if you use two packs back-to-back, do you need to wait 12 months before performing treatments again? (For a total of only 2 kits of strips per year.)
So we emailed their customer support for clarification.

Section references -

What Crest® customer support stated.

Based on their email reply to us (January 2020), we can report that they generally recommend the latter regimen (only using two packages of strips per year), and that recommendation only applies to some (although most) WhiteStrips® products. With one product (Supreme), they only recommend using it once (a single package) per year.

Specific details found in their email.

How many Whitestrips® kits can you use per year?

Per their communication, using two kits per year (either back-to-back or separated by a period of time) is considered permissible when using their 3D White Classic Vivid, Glamorous White, 1 Hour Express, Gentle Routine, Shimmer White, Professional Effects or 3D White Whitestrips with Light products.

When it comes to their 3D White Supreme Flexfit Whitestrips (a product that has a comparatively higher concentration hydrogen peroxide whitener), they stated that only one kit should be used per year.

Details about using more than one package.

Their email stated that you can mix and match different types of kits, like using one 3D White Classic Vivid and one Glamorous White, or just two 3D White Classic Vivid.

More interestingly, one of their kit combination examples was specifically stated as "one 3D White Supreme Flexfit kit + one other 3D White kit." So a package of the higher peroxide concentration product can be used in conjunction with one "regular" kit, for a total of two per year. But not two of the 3D White Supreme Flexfit product.

When might you use more than one box of whitening strips?

Using two packages consecutively.

The only reason to consider immediately using a second kit is if the first one didn't produce results that were as dynamic as you were hoping. That is the single indication.

This is the type of situation that might present itself if your teeth had a significant level of discoloration initially. (It's well known that some types of tooth staining won't respond as quickly or fully to whitening treatments as others.)

But even then, using a second box of strips, while permissible under the guidelines of the product, may not make an appropriate choice. (We discuss this issue in our Dentist Supervision section below.)

How about two kits per year, some months apart?

Corresponding with Crest's® claims mentioned above, research suggests that the results achieved via whitening strips treatments can be expected to last 6 to 12 months (possibly even longer, our "Touch-up" page explains.

So choosing to use two complete kits per year might fall under the category of either improving your results or touching them up, or both.

An example of when using multiple boxes of strips would not be appropriate.

An obvious exception for multi-pack use would be the situation where the user has experienced substantial side effects with their first kit that were either very difficult to resolve or possibly even continue.

In these cases, the use of a second kit is contraindicated. And exactly what does constitute an appropriate whitening method for the person should be reevaluated.

Can there be exceptions to how many packages of WhiteStrips® can be used?

Yes, some people's teeth might be (appropriately) treated using multiple consecutive boxes of strips. But in considering this idea, the person enters into a realm where they probably don't have the knowledge or expertise to determine exactly what does constitute an appropriate exception. And with some cases, the issue of end-user whitener abuse might be a valid concern.

So generally, it's hard for us to suggest that exceeding a manufacturer's recommendation on your own ever makes a good idea. Especially considering how easy it is to get the level of oversight that's really indicated for extended use.

"Supervised" at-home use.

The most appropriate (and prudent) use of multiple boxes of white strips involves the situation where you seek your dentist's oversight. Formally, this might involve little more than mentioning to them that you have used the recommended number of packages and would like to consider using more, and just letting them take it from there.

Ideally ...

As your dentist, and especially if you've consulted with them before beginning any treatments, they'll know what your initial conditions were. And already have an opinion about what originally caused the discoloration of your teeth, which can be an important factor in understanding the extent of treatments that may be needed to resolve it.

And from your reporting, they'll have an idea of what level of results have been gained, using what concentration (peroxide level) and what number of whitening strip kits. And based on their knowledge and experience with other patients, be able to draw a conclusion about how realistic it is that further treatments will produce an added effect.

Just as important, as you enter into the territory of extended use (on your own at home) and its realm where side effects may become an increasing issue, you'll have someone to consult if needed.

If you haven't already consulted with your dentist ...

This is still the person that needs to be brought into the loop about your continuing on with further treatments. No one knows more about the issue of whitening your teeth, and you and your teeth in particular. It's important to take advantage of this resource.

Even without complete background information, your dentist will still be able to form a valid enough estimate about the potential for achieving a further whitening effect by using additional boxes. And, of course, having them already in the loop if side effects need to be managed is an important asset.

What can be expected when using additional packs of whitening strips?

Some examples of extended use from research -

a) Swift

Title: Effects of duration of whitening strip treatment on tooth color: A randomized, placebo-controlled clinical trial.

This study evaluated the use of Crest Whitestrips® (6% hydrogen peroxide), twice daily, 30 minutes each application, over 2, 4 and 6 week periods. Per the instructions of this product, this equates to using a 2nd and 3rd kit consecutively.

  • The study found that the greatest level of effect was gained during the first 2-week period (equating to the use of one kit). But continued use out to the 4 and 6-week points did produce a further effect (reduction in yellowness, increase in lightness).
  • 35% of the subjects did experience some level of side effects. Most symptoms were noticed during the initial use of the strips (median onset at day 3). No subject's treatment was modified or discontinued due to side effects.


What we feel this study points out about using additional boxes of strips.

This study did find that extended treatment did produce better whitening results. But in their paper, the authors specifically pointed out this may have been due to the comparatively dark shade of their subjects' teeth initially.

It discussed that in comparison, people whose teeth are comparatively lighter in shade initially typically experience a whitening plateau (a point where the continued use of bleaching products produces no further effect) and reach this point relatively rapidly (like within the number of kits recommended by the manufacturer). (We discuss this issue further below.)

So for many people, the use of additional kits may hold little potential for added whitening, while placing them at the continued potential for experiencing complications. Objectively being able to determine when this plateau effect has occurred (and therefore the point where further treatment will be fruitless) is a part of what having your dentist's supervision over your activities can offer.

We'll also point out that while side effects were not found to be a significant problem for the subjects, this was not a foregone conclusion. And due to the uncertainty of experiencing complications, all of the subjects had supervision during the weeks of their treatment.

b) Garcia-Godoy

Title: Placebo-controlled, 6-week clinical trial on the safety and efficacy of a low-gel, 14% hydrogen-peroxide whitening strip.

This study was somewhat similar in nature to the Swift one above. A six-week extended-use period was evaluated. However with this study, a 14% (Crest Whitestrips® Supreme) product was used by the test subjects.

In a similar fashion as with the Swift study, a continued color improvement was noticed over the entire 6-week period. And this study concluded that there was no evidence of increased adverse events (side effects) with extended treatment through 6 weeks.

(Once again, however, we will point out that all subjects had supervision (someone to consult with if needed) during the weeks of their treatment by a dentist.)

Section references - Swift, García-Godoy

Do these studies suggest that using additional boxes of whitening strips on your own is OK?

No, we won't concede that point. Instead, we feel that they confirm that having your dentist involved makes the only appropriate plan when extended treatments are considered.

a) Side effects.

We will agree that the two studies above do suggest that side effects aren't usually a problem with extended (up to 6 weeks) use of both the high and low peroxide concentration WhiteStrips® products evaluated.

But that wasn't a forgone conclusion of either study. Instead, the possibility of experiencing side effects was anticipated, and the subjects were monitored ("supervised") in case they did arise and needed to be managed.

That's a different scenario than takes place with unsupervised at-home use (where there's no support system already in place if assistance is needed).

b) Teeth whitening potential.

The Swift paper specifically discusses the issue of the "whitening plateau" (a point where no further whitening takes place) that is expected to occur with teeth bleaching treatments.

The only possible justification for using additional kits of whitening strips is if the plateau has not yet been reached. But without a dentist's supervision, we don't think that most people can determine when this endpoint has occurred. And the indiscriminate use of teeth whiteners is never appropriate.

Picture of documenting a tooth's color using a dental shade guide.

Using a shade guide to document the color of teeth.

Dental shade guides.
A dentist documents the continued progress in whitening effect via the use of a dental shade guide. And by using one, can determine when a patient's treatment plateau (that point where no further lightening effect takes place) has been reached.

A person, on their own, could emulate this step. (We do see tooth shade guides available online, ranging from high-end professional ones to inexpensive paper ones, and even free printable ones). But short of having this type of objective before-and-after comparison, feel that essentially no at-home users can determine accurately when their whitening plateau has been reached.

Just our advice.

In any case were an objective measurement using some type of shade guide isn't taken, and especially when the use of several additional whitening strips kits are involved, one would have to be concerned that some level of whitener abuse may be taking place.

As stated above, the indiscriminate use of whitening products is never appropriate. And it would be our feeling that anyone who has concluded differently must either know far more, or far less, about this subject than we do.


 Page references sources: - Frequently Asked Questions.

García-Godoy F, et al. Placebo-controlled, 6-week clinical trial on the safety and efficacy of a low-gel, 14% hydrogen-peroxide whitening strip.

Swift E J, et al. Effects of duration of whitening strip treatment on tooth color: A randomized, placebo-controlled clinical trial.

All reference sources for topic Teeth Whitening Strips.

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