Is a bleaching light really needed for whitening treatments?

- Is the practice based on science? What do research studies say? | What does the light supposedly do? Why is a blue LED light used?

Teeth bleaching lights - Is using one necessary?

A lot of manufacturers would like you to think so.

Several (but certainly not all) makers of professional teeth whitening systems suggest that a bleaching light should be used when their whitener is applied. Here are some examples:

Professional (in-office) whitening systems that utilize a bleaching light.

Aladdin®, Beyond®, BriteSmile®, iBrite®, Iveri®, Lumalite LumaCool®, LumiSmile®, LumaLux®, Sinsational Smile® and Zoom®

And in the last few years, many at-home systems have started to include a do-it-yourself (blue, LED) whitening light with their products too. Some of these are:

At-home kits that come with a bleaching light.

AuraGlow®, Cali White®, Active Wow®, Crest 3D White®, Shine Whitening®, Pearl Teeth®, SmileBrilliant®, Glo Brilliant®, Snow® and MagicBrite®.

The question then becomes ...

Is using a light unit really necessary?

Spoiler Alert: It's not.


Over the past several decades there's been continued debate in the dental community about whether or not "light activation" really benefits (speeds up, enhances) the tooth-whitening process.

What's the light supposed to do?

In a nutshell, here's the usual explanation that's given about what a bleaching light does.

Picture of light activation of tooth whitening gel.

Some systems recommend "light activation" of the whitener.

  • A manufacturer formulates its whitener with a special catalyst (a "photocatalyst") that's sensitive to the kind of light output by the company's bleaching light.

    (Nowadays, that's frequently a blue-wave length LED light.)

  • After the whitener has been applied, shining the light on the patient's teeth activates the photocatalyst.
  • Once activated, the catalyst in turn triggers a reaction that assists in the decomposition of the hydrogen peroxide molecules in the whitener into its reactive components.

    (These components are termed "free radicals." They are the molecular agents that actually breakdown the stain molecules in your tooth's enamel.)

  • Because the whitener's production of free radicals is enhanced (the catalyst either helps to create more of them, or create them more rapidly, or both), your whitening results are enhanced too (whiter teeth, quicker acting).

Is this plausible?

Well, somewhat ...

It is true that creating more free radicals, or producing them at a quicker pace, does enhance whitening results. But whether today's bleaching lights accomplish this feat is the question.

It seems that the current state of affairs is one where manufacturers of light-based systems continue to claim that they do. But independent researchers, when trying to confirm these claims, still continue to come up short.

What has dental research shown about the effectiveness of using bleaching lights?

When reading through published dental research, it's easy enough to conclude that the use of a bleaching light adds no significant benefit. As evidence, in our next section ...

  • We first explain some of the historic studies that initially lead the way to this conclusion.

    (Yes, that's right. Even the newly introduced at-home products you see are dredging up a practice that studies began discrediting well over a decade ago.)

  • And then we cite the findings of a recent literature review. With it, you'll see that after evaluating studies published over 25+ years, they too have concluded that using a light provides no real benefit.


Research studies -

Study - Hein 2003

Picture of a case in a split-arch tooth whitening study.

In a split-arch study, each side receives a different version of the treatment.

( A no vote on bleaching light effectiveness. )
This study used a split-arch design (the first to do so in published research) to evaluate the effectiveness of 3 professional-grade whiteners (LumaArch®, Optilux 500® and Zoom!®) with and without the use of a bleaching light.

(Split-arch design is the gold standard of teeth-whitening results testing because outcome differences due to variances among test subjects are eliminated.)

The paper's conclusions were that the use of the lights did not lighten teeth more than the use of the whiteners by themselves.

Section references - Hein

Study - Tavares 2003

( A yes vote on bleaching light effectiveness.)

This study evaluated the BriteSmile® system.


The authors reported that the use of a bleaching light did make a substantial difference in the whitening outcome.

Criticisms of this study:

  • It did not use a split-arch design. (The "gold standard" type of testing described above.)
  • The improvement in tooth shade was measured immediately after the treatment session was completed. (Our "Kugle study" section below explains why this is a study flaw.)

Section references - Tavares

Graphic showing an in-office tooth-bleaching light.

An in-office tooth-bleaching light.

Study - CRA 2003

( A no vote on bleaching light effectiveness.)
Coincidentally, during about the same time frame when the Tavares study came out, Clinical Research Associates (CRA) published the findings of their own evaluation of professional whitening systems (and the use of bleaching lights) in their March 2003 newsletter.
This review used split-arch design to study 7 in-office products (LaserSmile®, LumaArch®, Niveous®, Opalescence Xtra Boost®, PolaOffice®, Rembrandt® 1 Hour Smile-Whitening Program, and Zoom®).

This evaluation determined that the use of a light did not enhance the bleaching process over the use of just whitener alone.

Notes: At a later date, CRA extended their evaluation by testing that version of the BriteSmile® system that they had available to them (BrightSmile® had placed restrictions on what type of testing could be performed on their newer version) and concluded again that light activation did not affect bleaching efficacy. (Reported in Christensen 2003, CRA 2003, Haywood 2009)

Section references - CRA, Christensen, Haywood

Study - Kugel 2006

( A no vote on bleaching light effectiveness and an explanation. )

This paper's findings seem to explain the conflicting results found by Tavares vs. the Hein and CRA studies discussed above.


Using a split-arch study design, it was determined that results using a light-activated system did appear lighter but only initially.

When the subjects' teeth were re-evaluated at a point 2 weeks after their treatment, no difference was found between the light and non-light sides.

Explanation: This paper attributed the initial improvements seen with the teeth exposed to a bleaching light to the dehydration effect that occurs as teeth dry out during their treatment process, and not to an increase in whitening efficacy due to light activation.

  • As teeth become dehydrated their color tends to lighten.
  • Then, as they regain moisture (over the following hours and days), the lightening effect begins to fade.


This explains why the evaluation made 2 weeks after the treatments showed no difference in whiteness whether a light had been used or not.

  • Both whitening protocols created the same level of color improvement.
  • The extra lightening effect that was seen initially with cases where a bleaching light was used ended up fading over time. (It was due to a temporary dehydration effect.)

Section references - Kugel

A recent literature review -

This next piece of evidence we share comes from a paper we've selected because it evaluated published studies on this subject over a 25+ year time frame. That span encompasses the entire duration of the "teeth whitening mania" that's taken place in this country and its abundance of associated research.

Study - Maran 2017

( A no vote on bleaching light effectiveness.)

After evaluating research studies published between 1990 and 2016 and passing judgment on the standards according to which they had been conducted, the authors of this paper stated: "Although it is commercially claimed that in-office bleaching associated with light improves and accelerates color change, this study did not confirm this belief ..."

Study - Maran 2019
In an update of the original study expanded to include studies published into 2018, the authors stated that "Although many times dental professionals use 'laser whitening' as a form of marketing, this study confirmed that no type of light-activation for in-office bleaching can improve the bleaching efficacy."

Section references - Maran, Maran

So is the use of a bleaching light really necessary?

No, as evidenced by what's been discussed above, one would have to conclude that it's not. And it's hard to understand how anyone could arrive at any other conclusion.

Picture of an in-office bleaching light unit.

Bleaching light units look impressive.

Why do some dentists use bleaching lights?

In 2005, CRA (the group whose research was mentioned above) polled dentists about why they use a light. Some of the responses were:
  • Because it came with my system.
  • Because patients ask for it.
  • Because it's good for marketing.
These probably aren't the reasons you might have expected, or hoped for, since none of them have anything to do with increasing treatment effectiveness.

Section references - Haywood

What about the lights that come with at-home whitening kits?

We'll concede that the bulk of the information discussed above comes from research that evaluated the use of professional-level bleaching lights. And you might wonder if somehow the light that comes with your at-home kit is different, and therefore possibly is effective.

We'll point out that it seems fairly preposterous to suggest that the $5 light that comes with your at-home kit possesses some technology that the $1000 bleaching lights designed for dentists don't.

Why do manufacturers emphasize the use of lights?

Companies that make in-office systems are eager to claim that their product's bleaching light is an important part of the whitening process.

Why wouldn't they be? Doing so helps to ensure sales of their light units, a piece of equipment that can cost your dentist hundreds to thousands of dollars. Or in the case of an at-home kit, the slightly more expensive version of their product.

Additionally, the use of a bleaching light adds fanfare and makes a patient's whitening process seem more impressive. And the idea of having something special done tends to appeal to consumers and helps to drive demand for their product.


Picture of whitening gel applied that does not require light activation.

Treatment without light activation.

Are there any systems that don't require the use of a bleaching light?

Yes. To their credit, many systems, both at-home and professional (in-office) do not incorporate the use of a bleaching light into their protocol (or else consider it an optional step).
We're under the impression that these brands take this approach.
Professional whitening systems.
Kor Max®, Life-Like®, LumiBrite®, NUPRO®, Opalescence Boost®, Optic White®, Pola® and Venus White®
At-home whitening systems.

There are simply too many to try to mention them all here.

Are there any reasons why a light shouldn't be used?

1) The need for a bleaching light adds expense to the whitening process.

Your dentist is a business person just like anyone else. And if the whitening protocol they use includes the use of a light unit, it will simply add to their expenses and ultimately yours too.

In the case of at-home whitening kits, the same holds true. This is especially obvious in the pricing of various Whitestrips® kits that do and do not include a light.

2) Exposing the patient's teeth to heat must be avoided.

The concern.

Overheating teeth increases their potential for experiencing post-operative sensitivity, pain, and/or nerve tissue damage. An increase on the order of 10 degrees F within a tooth's nerve space is thought to be able to cause irreversible nerve damage. (Sulieman)


Historically, the whole idea of using a light with in-office procedures was to create a heating effect (dentists literally used heat lamps as bleaching lights). That's because hydrogen peroxide will breakdown into its reactive components (the free radicals mentioned above) more quickly when heated up.

Dentists know better nowadays. And today's professional-level lights are designed so they have minimal potential for creating a heating effect, or else are used in a manner (constantly moved around) so no substantial heating takes place. (Companies that manufacture bleaching lights often state that they have a "cool" or "cold" output.)

What about at-home lights?
Considering that nowadays the danger associated with heating teeth up is well known. And knowing that the at-home bleaching light phenomenon is a recent one (just the last several years). It's most likely that the products you see have been designed with cool/cold light sources (you might check to see if the product's packaging says so). (The most common light type seems to be a blue-wave length LED source.)

Section references - Sulieman

In-office tooth whiteners - Ingredients, Characteristics.

Every professional whitening system comes with its own unique whitener. And while the exact formulation of each brand varies, collectively they all share a number of similarities.

What active ingredient is used?

Professional-level whiteners are usually hydrogen-peroxide based products. Their concentration typically ranges between 17 and 50%. (For specific values, see our review of professional whitening systems.)

(At-home products usually use a whitener that contains the equivalent of 3 to 10% hydrogen peroxide. This difference in concentration explains why professional treatments can produce results so much more quickly. Use this link for other comparisons between at-home and in-office systems.)

How do tooth whiteners work?

The hydrogen peroxide component of a whitener breaks down to form "free radicals." It's these very reactive molecules that then create the tooth-whitening effect (by way of interacting with and breaking down the molecules that have caused the tooth's staining).

A neutral pH is best.

Manufacturers try to formulate their whiteners so they have a neutral (non-acidic) pH. That's because tooth enamel is a mineralized tissue and exposing it to an acidic whitener, especially for an extended period of time, could damage it.

Ensuring product freshness.

Many professional whiteners come prepackaged as two individual components. They are then mixed by the dentist, at the time of use. This approach helps to ensure product freshness because the active ingredients are not combined and allowed to react until right before the time of their application.

Other products come pre-mixed. The advantage here is there is no question about the precise strength of the whitener, it was mixed at the factory. As a way of helping to extend shelf life, pre-mixed products often need to be stored at a cool temperature (like in a refrigerator).

Desensitizing agents.

As a way of helping to minimize the risk for post-treatment tooth sensitivity, some systems incorporate desensitizers into the formulation of their whitener. The two most frequently used compounds are fluoride and potassium nitrate.


During the bleaching process, a patient's teeth can become dehydrated (discussed above). Creating a product whose water content is 10 to 20% can help to avoid this problem. (Sulieman)

Split-arch testing.

Picture of a case in a split-arch tooth whitening study.

In a split-arch study, each side receives a different version of the treatment.

Same person, left vs. right side comparisons.
Using this type of testing, each subject's upper and lower teeth are divided into left and right halves. (The term "arch" refers to a person's set of upper or lower teeth.)
All of the teeth on both sides are coated with the system's whitener, but only one side (top and bottom) receives exposure to the bleaching light.
If after the treatment there is a shade difference between the left and right sides, then the light had a beneficial effect. If not, then it was ineffective in providing any advantage.

This test is considered to be the gold standard for evaluating whitener effectiveness.


 Page references sources: 

Christensen GJ. Bleaching Teeth–Which Way is Best?

Haywood VB. In-office Bleaching: Lights, applications and outcomes.

Hein D, et al. In-office Vital Tooth Bleaching-What Do Lights Add?

Kugel G, et al. Clinical evaluation of chemical and light-activated tooth whitening systems.

Maran BM, et al. In-office dental bleaching with light vs. without light: A systematic review and meta-analysis.

Maran BM, et al. Different light-activation systems associated with dental bleaching: A systematic review and a network meta-analysis.

Sulieman AM. An overview of tooth-bleaching techniques: chemistry, safety and efficacy.

Tavares M, et al. Light augments tooth whitening with peroxide.

All reference sources for topic Professional Teeth Whitening.