Regulatory and Scope of Practice Aspects of Bleaching Treatment

Presently, all extracoronal tooth bleaching products remain unclassified by the FDA. This includes all peroxide-based products used in the in-office, dentist-dispensed products for at-home use, OTC (patient-purchased) products, as well as products used in non-dental settings.
In the early 1990s, the FDA proposed regulating the peroxide-based bleaching materials as drugs and sent warning letters to manufacturers.
Tooth whitening products are developed and marketed according to U.S. ―cosmetic‖ regulations. These regulations are more limited than those for drugs or medical devices. This may lead to the perception that the products are innocuous, though they have the potential to cause harm and may result in undesirable effects to the teeth or oral mucosa.
The recent appearance of tooth-bleaching businesses in non-dental settings has led to state dental board decisions, attorney general opinions, and legislation in some states. Some jurisdictions have taken recent action to better limit patient risks associated with tooth bleaching. These include: Florida, Iowa, Massachusetts, Nevada, New Jersey, Tennessee, and the District of Columbia.

Concerns regarding tooth bleaching in non-dental settings have been raised. Non-dental personnel are not educated in the use of disease screening or diagnostic tests (such as radiographs), and are not licensed or qualified to provide dental examinations. Dental and other healthcare workers receive required education and training in infection control procedures to protect patients and themselves from infectious diseases that may be spread by blood or saliva. The staff in non-dental facilities are not licensed and the level of education and training in infection control or other important emergency and safety procedures is unknown.
Tooth bleaching in the United Kingdom (U.K.) emerged in conflict with existing regulations that applied to hairdressers and the use of hydrogen peroxide. Steps toward resolution of this conflict are underway, including an extensive review of tooth bleaching safety data. As noted previously, the Scientific Committee for Consumer Products (SCCP) in Europe supported the safety of tooth bleaching materials containing up to 6.0% hydrogen peroxide for use by dental professionals.38 The FDA’s position was challenged legally, and in alignment with court decisions, the FDA suspended attempts to classify the bleaching materials. To date, the FDA has taken no further action to classify tooth bleaching products. 3 Such adverse effects are generally related to low pH and poor product quality. 13,23 It is expected that this SCCP recommendation will eventually be ratified by the European Council and by the U.K. government. The timeline for these actions is unclear at present.

Safety Concerns with Tooth Bleaching Materials

Concerns regarding the safety of all bleaching treatments and products have long existed, but were heightened since the introduction of at-home bleaching.5-8 Discussions in this section focus on peroxides and their use as active ingredients in tooth bleaching materials. Important concerns related to patient examination and diagnoses are addressed elsewhere in this report.

A variety of peroxide compounds, including carbamide peroxide, hydrogen peroxide, sodium perborate and calcium peroxide, have been used as active ingredients for bleaching materials; however, essentially all extracoronal bleaching materials currently available for whitening of vital teeth in the United States contain carbamide peroxide and/or hydrogen peroxide. Recently, products containing chlorine dioxide were introduced in the United Kingdom, but there is no evidence that tooth bleaching products using chlorine dioxide as the active ingredient are safer than peroxide-based materials. In fact, safety concerns have been documented with chlorine dioxide and its use for tooth bleaching treatment due to the low pH of the material and resultant tooth etching.9
Most OTC bleaching products are hydrogen peroxide-based, although some contain carbamide peroxide. Carbamide peroxide decomposes to release hydrogen peroxide in an aqueous medium: ten percent carbamide peroxide yields roughly 3.5% hydrogen peroxide. In-office bleaching materials contain high hydrogen peroxide concentrations (typically 15-38%), while the hydrogen peroxide content in at-home bleaching products usually ranges from 3% to 10%; however, there have been home-use products containing up to 15% hydrogen peroxide. Safety issues have been raised regarding the effects of bleaching on the tooth structure, pulp tissues, and the mucosal tissues of the mouth, as well as systemic ingestion. Regarding mucosal tissues, safety concerns relate to the potential toxicological effects of free radicals produced by the peroxides used in bleaching products. Free radicals are known to be capable of reacting with proteins, lipids and nucleic acids, causing cellular damage. Because of the potential of hydrogen peroxide to interact with DNA, concerns with carcinogenicity and co-carcinogenicity of hydrogen peroxide have been raised, although these concerns so far have not been substantiated through research.5,10,11 However, studies have shown that hydrogen peroxide is an irritant and also cytotoxic. It is known that at concentrations of 10% hydrogen peroxide or higher, © 2009 American Dental Association. All rights reserved. 3
the chemical is potentially corrosive to mucous membranes or skin, and can cause a burning sensation and tissue damage.5,12,13 The amount of products applied during office bleaching treatment and other formulation variables can change the potential to cause damage. However, severe mucosal damage can occur if gingival protection is inadequate with high strength tooth whitening products. Clinical studies have also observed a higher prevalence of gingival irritation in patients using bleaching materials with higher peroxide concentrations.14,15
Data accumulated over the last 20 years, including some long-term clinical study follow up16,17, indicate no significant, long-term oral or systemic health risks associated with professional at-home tooth bleaching materials containing 10% carbamide peroxide (3.5% hydrogen peroxide). However, these data were collected from studies which include examinations by dental professionals, and there is no safety evidence on bleaching materials that do not involve such examinations by dental professionals, regardless of hydrogen peroxide concentration or application venue. Additionally, consumers are not generally aware of how to report adverse events through FDA’s Medwatch system. If a licensed dental professional is not consulted when patients use OTC bleaching products, adverse effects due to product abuse may go unreported.
Regarding hard tissues, transient mild to moderate tooth sensitivity can occur in up to two-thirds of users during early stages of bleaching treatment.18 Sensitivity is generally related to the peroxide concentration of the material and the contact time; it is most likely the result of the easy passage of the peroxide through intact enamel and dentin to the pulp during a five- to 15-minute exposure interval. However, there have been no reported long-term adverse pulpal sequellae when proper techniques are employed. The incidence and severity of tooth sensitivity may depend on the quality of the bleaching material, the techniques used, and an individual’s response to the bleaching treatment methods and materials. To date, there is little published evidence documenting adverse effects of dentist-monitored, at-home whiteners on enamel, but two clinical cases of significant enamel damage have been reported, apparently associated with the use of OTC whitening products.19,20 This damage may be related to the low pH of the products and/or overuse.
In vitro
To address the safety of bleaching materials, the ADA convened a panel of experts in 1993. The ADA subsequently published its first set of guidelines for evaluating peroxide-containing tooth whiteners.22 These guidelines have been revised periodically.
In March 2005, the European Scientific Committee on Consumer Products (SCCP) concluded the following: ―The proper use of tooth whitening products containing >0.1 to 6.0% hydrogen peroxide (or equivalent for hydrogen peroxide-releasing substances) is considered safe after consultation with and approval of the consumer's dentist.‖13 The © 2009 American Dental Association. All rights reserved. 4
SCCP, in January 2008, again recommended that up to 6% hydrogen peroxide is a safe limit to use for at-home tooth bleaching; however, it did not recommend use of such products without dental consultation.23
In summary, available data indicate that extracoronal bleaching treatment in the dental office or at home may cause short-term tooth sensitivity and/or gingival irritation. More severe mucosal damage is possible with high hydrogen peroxide concentrations. While available evidence supports the safety of using bleaching materials of 10% carbamide peroxide (3.5% hydrogen peroxide) by dental professionals, there are concerns with the use of at-home bleaching materials with high hydrogen peroxide concentrations. Studies designed specifically to assess the long-term safety of high hydrogen peroxide concentration in at-home bleaching materials are needed, especially for repeated use of these products. There appears to be insufficient evidence to support unsupervised use of peroxide-based bleaching materials.
Similar to other dental and medical interventions, questions have been raised about the safety of tooth whitening treatments during pregnancy. In the absence of such evidence, clinicians may consider recommending that tooth whitening be deferred during pregnancy.
The safety of tooth bleaching for children and adolescents is also a consideration. More research is needed to establish appropriate use and limitations for these patients. However, bleaching is a conservative approach compared with restorative options when tooth discoloration causes significant concern. If possible, delaying treatment until after permanent teeth have erupted is recommended, as is use of a custom-fabricated bleaching tray to limit the amount of bleaching gel.24 Close professional and parental/guardian supervision are needed to maximize benefits and minimize adverse effects and overuse. studies suggest that dental restorative materials may be affected by tooth bleaching agents.1,21 These findings relate to possible physical and/or chemical changes in the materials, such as increased surface roughness, crack development, marginal breakdown, release of metallic ions, and decreases in tooth-to-restoration bond strength. Such findings have not appeared in clinical reports or studies.

Should you be whitening your teeth?

Teeth whitening is not for everyone. Before choosing to whiten your teeth it is important to see your dentist to determine if your teeth are suitable for the treatment. Teeth whitening is not recommended for everyone because of various issues relating to gum and tooth sensitivity, the natural colour of a person’s teeth and presence of fillings, crowns and veneers. Unlike many untrained operators offering teeth whitening treatments, only dentists can assess a person’s suitability for the treatment. Without a proper assessment it is not possible to rule out any permanent side effects or other risks associated with the process. If administered by untrained individuals, whitening procedures can cause discoloured teeth, heightened tooth sensitivity and gum problems. When assessing your teeth for whitening, your dentist will:

whitening commence

Ensure your mouth is healthy before

•

discolouration

Diagnose the cause of any

•

whiten your teeth

Discuss with you the best method to

•

influence the whitening process (e.g.

antibiotic staining)

Advise if there are factors which may

•

and veneers need replacement (as

these won’t change colour)

Assess whether your fillings, crowns

•

Identify areas of gum recession

•

how it may be managed.

Teeth whitening should only be carried

out on people who have their adult teeth,

unless otherwise advised by a dentist.

Discuss possible tooth sensitivity and

Some considerations

There are a couple of easy and cost

effective ways to keep your teeth looking

whiter and brighter, naturally.

Chairman of the ADA’s Oral Health

Committee, Dr Peter Alldritt says the best

way to keep a healthy white smile is to

maintain good oral health.

“Practising good oral hygiene is a basic

way to assist in making your teeth look

whiter naturally.”

“Brushing and flossing your teeth daily

assists in removing surface stains on

your teeth,” Dr Alldritt says.

For healthier and better looking teeth,

you should:

•

minutes using a fluoride toothpaste

Brush your teeth twice a day for two

•

Floss your teeth daily

•

Drink water throughout the day

•

Consume a sensible diet

•

professional clean

Visit your dentist regularly for a

What to avoid:

•

found on the surface of the tooth,

which are caused by dental plaque,

tars (in tobacco), tannins, coloured

foods and frequent use of certain

mouthwashes.

Extrinsic stains are superficial stains

•

stain teeth include herbal and black

tea, coffee, red wine and spicy foods

like curries. Smoking cigarettes also

causes unsightly stains on teeth, which

can be extremely difficult to remove.

Common foods and beverages that

•

surface can be removed by a dentist

performing a professional scale and

clean.

Extrinsic stains on the tooth’s

PATIENTS’ USUAL WORRIES ANSWERED

Are there any Side Effects?

There are side effects associated with whitening but, over the last 20 – 30 years, they have been proven to be transient

and fully reversible, depending on what whitening system is being used. It should be noted that the whitening

materials have been in use for more than 50 years. The side effects are usually some mild sensitivity to cold and also

some gum soreness. Approximately 60-70 per cent of patients have very mild side effects that are easily managed.

Will the Colour Fade?

The colour change is usually not permanent. On average, there is a some colour rebound in the first 2 weeks, then a

slow regression of colour over 2-3 years. This is why the at home system is essential, to balance this rebound and to

reduce the regression of the colour. The good news, however, is that to maintain the colour costs approximately $40

every 6 – 12 months if only the at home gels are used for maintenance. This is a very easy and successful way of

maintaining the colour. As with any cosmetic procedure, appropriate maintenance is necessary.

Will the Structure of the Teeth be Affected?

The materials do affect the structure of the teeth slightly. Many studies have likened the effects of the whitening

materials to drinking a can of soft drink, which is rapidly reversed by the body’s natural repair systems (saliva).

What About My Existing Fillings?

Unfortunately, filling materials and materials used in crown and bridgework will not change colour. It is therefore

necessary that teeth whitening be carried out prior to any other cosmetic treatment in order to achieve the best possible

overall look of the teeth for years to come. However, teeth whitening tends to brighten the teeth as well so the old

crown and bridgework colour tends to blend through better after whitening

Teeth Whitening Procedure

Tooth whitening (or bleaching) is a simple, non-invasive dental treatment used to change the color of natural tooth enamel and is an ideal way to enhance the beauty of your smile. Because having whiter teeth has now become the number one aesthetic concern of most patients, there are a number of ways to whiten teeth

Cosmetic teeth whitening training video

Mechanism of tooth bleaching

Bleaching is a decolourisation or whitening process that can occur in solution or on a surface. The colour producing materials in solution or on a surface are typically organic compounds that possess extended conjugated chains of alternating single or double bonds and often include

heteroatoms, carbonyl, and phenyl rings in the conjugated

system and are often referred to as a chromophore.

Bleaching and decolourisation of the chromophore can

occur by destroying one or more of the double bonds in

the conjugated chain, by cleaving the conjugated chain, or by

oxidation of other chemical moieties in the conjugated

chain. Hydrogen peroxide oxidises a wide variety of

organic and inorganic compounds

. 

The mechanisms of

these reactions are varied and dependent on the substrate,

the reaction environment, and catalysis. In general, the

mechanism of bleaching by hydrogen peroxide is not well

understood and it can form a number of different activeoxygen species depending on reaction conditions, including

temperature, pH, light and presence of transition metals.

Under alkaline conditions, hydrogen peroxide bleaching

generally proceeds via the perhydroxyl anion (HO2

). Other

conditions can give rise to free radical formation, for

example, by homolytic cleavage of either an O–H bond or

the O–O bond in hydrogen peroxide to give H + OOH and

2 OH (hydroxyl radical), respectively. Under photochemically

initiated reactions using light or lasers, the formation

of hydroxyl radicals from hydrogen peroxide has been

shown to increase.

The mechanism by which teeth are whitened by oxidising

materials such as hydrogen peroxide and carbamide peroxide

are currently not fully understood. Considering the

available literature, evidence points towards the initial

diffusion of peroxide into and through the enamel to reach

the enamel dentine junction and dentine regions. Indeed, in

vitro experiments by a number of authors have demonstrated

the penetration of low levels of peroxide into the pulp

chambers of extracted teeth after exposure times of 15–

30 min from a range of peroxide products and solutions.

The levels of peroxide measured in these experiments is

considerably much lower than that needed to produce pulpal

enzyme inactivation.

As peroxide diffuses into the tooth, it can react with organic

coloured materials found within the tooth structures leading

to a reduction in colour. This is particularly evident within

dentine as demonstrated by McCaslin et al.who showed,

using hemi-sectioned human teeth mounted on glass slides,

that following external bleaching with carbamide peroxide,

colour changes occurred throughout the dentine. Indeed, the

treatment of dentine specimens with 10% carbamide peroxide,

5.3% and 6% hydrogen peroxide has been shown to give

a significant reduction in yellowness and an increase in

whiteness.35,36 In addition, Sulieman et al. showed using

sectioned extracted teeth stained internally with black tea

chromophores that significant bleaching occurred within the

dentine, particularly on the buccal surface where a 35%

hydrogen peroxide gel had been applied.

For tetracycline stained teeth, the colour is derived from

photo-oxidation of tetracycline molecules bound within the

tooth structures. In some cases, it is possible to bleach these

teeth to give significant and long lasting tooth whitening.

The mechanism by which peroxide affects the tetracycline

stain is considered to be by chemical degradation of the

unsaturated quinone type structures found in tetracycline

leading to less coloured molecules. However, in contrast

there appears to be a paucity of information available in the

literature regarding the nature and chemical composition of

the coloured materials naturally found within the dental hard

tissues and the mechanistic effects of peroxide on these

structures. Thus, this is clearly an area that requires further

research if the chemical mechanistic aspects of tooth

bleaching are to be significantly resolved.

HOME TRAY BLEACHING

When professional vital tooth bleaching using trays for athome use was first introduced to the profession, there were concerns over adverse reactions and patient complaints. The adverse reactions and patient complaints included: taste of bleaching gel, gingival irritation, uneven tooth bleaching, splotchy appearance of the teeth during the initial stages of bleaching, and tooth hypersensitivity while bleaching. These issues have been investigated and research has provided a better understanding. Manufacturers of tooth bleaching products have made changes in technique recommendations and product components to address these issues. Clinician and patient complaints concerning issues of taste have been addressed with an expanded selection of better flavors for improved patient acceptance. 

Gingival irritation has occurred with trays that were poorly fabricated either because of inaccuracy of casts or the need for scalloping the tray for higher concentrations of hydrogen and carbamide peroxide bleaching gels (22). During the initial bleaching, especially with higher concentrations of tray bleaching gels, patients have reported a splotchy appearance of the teeth during the first week (22). This uneven coloration of the teeth being bleached disappears after the first week of bleaching. Tooth sensitivity during bleaching has been the highest reported adverse reaction. In clinical research studies, tooth sensitivity during bleaching has been reported in a

range of 18%–78% of patients, either with at-home tray delivery or in-office procedures (23–25). The sensitivity due to tooth bleaching in clinical observations suggests that it

is transient, with no long-term effects (26). Some clinicians believed that this transient sensitivity was due to gingival recession. However, it has been shown that gingival recession is not a factor in the occurrence of tooth hypersensitivity when bleaching (27). There was no significant difference in reported sensitivity while bleaching based on the presence or absence of gingival recession. To minimize tooth sensitivity during vital tooth bleaching, the clinician can recommend that the patient decrease the time the tray is worn the first week, to no more than 1 hour a day for carbamide peroxide products or for higher concentration hydrogen peroxides, as little as 15 minutes a day or use lower concentrations of peroxide. Five Percent potassium nitrate (KNO3) formulation has been shown to be an effective desensitizer in toothpastes (FF, use three others). Noting this effectiveness, a number of manufacturers have added a 5% KNO3 desensitizing agents to their bleaching gels. The addition of KNO3 to bleaching gels does not provide the sensitivity relief that is seen with KNO3 in extended use with desensitizing toothpastes (23, 28). Two effect strategies using a KNO3- desensitizing toothpaste that have been clinically evaluated are brushing with the desensitizing toothpaste for 2 weeks before

initiating bleaching (23) and having the patient place a sensitivity toothpaste containing a 5% KNO3 1 week before initiating bleaching in the tray that will be used for bleaching for 30 minutes a day (29). Both strategies take into account the mechanism for desensitizing that KNO3 provides. Another strategy is to have a patient use a professionally dispensed desensitizing gel with 5% KNO3 for use with bleaching (30). Amorphous calcium phosphate (ACP) has been shown to be an effective desensitizer (31, 32). Recent research has shown that a paste (Prospec MI Paste, GC America) containing Recaldent®, a casein phosphopeptide- amorphous calcium phosphate (CPP-ACP), has been effective in reducing tooth sensitivity due to bleaching (29,33). One manufacturer, Discus Dental, has introduced bleaching products that contain ACP. A research study evaluating these ACP-containing bleaching gels demonstrated that ACP could be added to a 16% carbamide peroxide bleaching gel with significant reduction in clinical measures of dentinal hypersensitivity both during and after treatment (34). Over the years, there has been controversy about what

tray is best. When tray bleaching was introduced, the trays

were fabricated from thin and thick flexible vacuum-forming materials and thin rigid plastic materials. Some manufacturers created a foam-lined tray, believing it would hold the bleach on the teeth more effectively. From the current research that has evaluated a wide variety of tray configurations and types, and duration of wearing the tray, one can conclude the following:

• Thin flexible vacuum-formed materials are the standard

• Spacers on the stone model to create reservoirs is not

necessary, but using reservoirs results in the patient swallowing less bleaching gel (35, 36)

• Scalloping the tray to follow the gingival contours is not

necessary when using a 10% carbamide peroxide, but should be done for higher concentrations of carbamide peroxide or hydrogen peroxide equivalents. Overtrimming the tray leaving a portion of the tooth uncovered is not a problem because the bleach will penetrate beyond the tray (37)

• Custom-fitted trays provide improved bleaching geltooth 
contact (36)

• Most companies provide bleaching gel for a 2-week

application

• Higher concentrations of carbamide peroxide bleach

worn in a tray show faster initial improvements, but over a 6 week period comparing 10% carbamide peroxide to higher concentrations, there is no difference in the final result (38, 39)

• The concept of teeth lightening to a final certain level

has been termed as the “inherent lightness potential” of a tooth; there is an endpoint to how much lighter teeth will get (39)

• In most cases, moderate and dark tetracycline staining

can be treated with bleaching over an extended time of 3–6 months (40, 41)

• Concern over the effectiveness of the bleaching potential with overnight wearing of a tray has been addressed; wearing a tray overnight with a bleaching gel has demonstrated a degradation in peroxide concentration over time, but the bleaching agent is still effective. Hydrogen peroxide has a greater than 50% degradation within 30 minutes, whereas carbamide peroxide bleaching gels can be used overnight (21)

• 10% at-home carbamide peroxide bleaching gels are clinically safe when exposed to enamel, dentin, root surfaces, ceramics, cast metal, and composite resins (10); there is one case report of greening of amalgam during bleaching. At-home tray bleaching requires a number of steps to achieve success, which include accurate study casts that need to be trimmed to allow for a vacuum-down, thin, flexible mouthguard to be fabricated. The mouthguard can be trimmed to be scalloped (for the higher concentrations of bleaching peroxides) or with a 0.5–1 mm extension from the free gingival margin. The patient should be instructed on the how to place the bleaching gel in the trays and how to remove any excess gel after insertion. Although there are variations in the duration for wearing the tray, for most patients 2 weeks at least 1 hour a day will provide up to 90% of the whitening effect. Research has shown that a bleaching endpoint will be reached at 6 weeks independent of the concentration and type of peroxide used (Figure 2). Table 1 has a partial listing of at-home professionally

what is Teeth Whitening

Tooth whitening (or bleaching) is a simple, non-invasive dental treatment used to change the color of natural tooth enamel and is an ideal way to enhance the beauty of your smile. Because having whiter teeth has now become the number one aesthetic concern of most patients, there are a number of ways to whiten teeth. The most popular method is using a home tooth whitening system that will whiten teeth dramatically. Since tooth whitening only works on natural tooth enamel, it is important to evaluate replacement of any old fillings, crowns, etc. Replacement of any restorations will be done after bleaching so they will match the newly bleached teeth. Tooth whitening is not permanent. A touch-up maybe needed every several years, and more often if you smoke, drink coffee, tea, or wine.

In-Office Whitening
Significant color change in a short period of time is the major benefit of in-office whitening. This
protocol involves the carefully controlled use of a relatively high-concentration peroxide gel, applied to the teeth by the dental assistant after the gums have been protected with a paint-on rubber dam. Generally, the peroxide remains on the teeth for several 8 minute intervals that add up to an hour (at most). Those with particularly stubborn staining may be advised to return for one or more additional bleaching sessions, or may be asked to continue with a home-use whitening system.

Professionally Dispensed Take-Home Whitening Kits
Take-home kits incorporate an easy-to-use lower-concentration peroxide gel that remains on the teeth for 30-90 minutes. The lower the peroxide percentage, the longer it may safely remain on the teeth. The gel is applied to the teeth using custom-made bleaching trays that resemble mouth guards.

costs of teeth whitening

The standard fee for teeth whitening and teeth bleaching procedures is about $500 in most cases. Costs can vary depending upon the area of the country you live in and the type of whitening treatment you undergo. Laser teeth whitening is typically over $1000. for example. In-home tray bleaching can cost between $50. and $100. dollars for a total teeth whitening system. Store-bought whitening strips can cost as little as $25. for a total treatment whitening system. Teeth whitening stores, stands and kiosks typically cost between $50. and $150. dollars per treatment

.

Generally speaking, the price of teeth whitening increases with the number of in-office treatments required by the patient. Dental insurance does not typically cover the cost of the teeth whitening procedure.

Factors influencing tooth whitening

Type of bleach

The majority of contemporary tooth whitening studies involve
the use of either hydrogen peroxide or carbamide peroxide.
This latter material is an adduct of urea and hydrogen

peroxide which on contact with water breaks down to urea

and hydrogen peroxide. For example, a 10% (w/w) carbamide

peroxide gel would yield a maximum of 3.6% (w/w) hydrogen

peroxide. In general, the efficacy of hydrogen peroxide

containing products are approximately the same when

compared with carbamide peroxide containing products with

equivalent or similar hydrogen peroxide content and delivered

using similar format and formulations, either tested in vitro

or in vivo. For example, Nathoo et al. demonstrated in a

clinical study that a once a day application of either a 25%

carbamide peroxide gel or a 8.7% hydrogen peroxide gel both

gave a statistically significant tooth shade lightening after 2

weeks use compared to baseline, but found no statistically

significant differences between products.

An alternative source of hydrogen peroxide is sodium

percarbonate and this has been used in a silicone polymer

containing product that is painted onto the teeth forming a

durable film for overnight bleaching procedures. The

peroxide is slowly released for up to 4 h and gave significant

tooth colour improvement after 2 weeks versus baseline.

However, the relative clinical or in vitro efficacy of sodium

percarbonate versus hydrogen peroxide tested in the same

product format and conditions has not been reported.

A tooth bleaching system based on sodium chlorite

applied to the tooth surface and activated under acidic

conditions has been described in the literature, however,

no efficacy data has been reported to date. Similarly, other

potential vital tooth bleaching systems have been outlined in

the literature with limited supporting evidence for their

efficacy. These include sodium perborate, peroxymonosulphate, peroxide plus metal catalysts and oxireductase

enzymes. The long-term acceptability and relative

efficacy of these alternative tooth bleaching systems requires  

significant further research

Concentration and time

 Two of the key factors in determining overall tooth whitening

efficacy from peroxide containing products are the concentration

of the peroxide and duration of application. For

example, Sulieman et al. compared the in vitro tooth

bleaching efficacy of gels containing 5–35% hydrogen peroxide

and found that the higher the concentration, the lower the

number of gel applications required to produce uniform

bleaching. Similar results were found by Leonard et al. who

compared the in vitro tooth bleaching efficacy of 5%, 10% and

16% carbamide peroxide gels and found the whitening was

initially faster for the 16% and 10% than the 5% concentration.

However, the efficacy of the 5% approached the higher

concentrations when the treatment time was extended. In a

clinical study using custom made bleaching trays, Kihn et al.

showed that a 15% carbamide peroxide gel gave significantly

more tooth whitening than a 10% carbamide gel after 2 weeks

use. This result was confirmed in another clinical study

reported by Matis et al. However, in this latter study, by

extending treatment time to 6 weeks, the differences in

tooth lightness were no longer of statistical significance. The

initial faster rate of bleaching for higher concentrations of

carbamide peroxide has also been observed when bleaching

tetracycline stained teeth in vivo over a 6 months period.85systems. Typically, an image of the anterior teeth is

captured under controlled lighting conditions by a digital

camera together with suitable calibration tiles or standards

and then subsequently analysed via computer software to

determine the colour of the individual teeth, often expressing

them in terms of CIE Lab values. For example, after 14 days use

of a 10% carbamide peroxide tray-based system, the mean

change from baseline in L* and b* were 2.07 and 1.67,

respectively.

Heat and light     

The rate of chemical reactions can be increased by increasing

the temperature, where a  8C rise can double the rate of

reaction. The use of high-intensity light, for raising the

temperature of the hydrogen peroxide and accelerating the

rate of chemical bleaching of teeth was reported in 1918 by

Abbot.Other approaches for heating the peroxide have

historically been described to accelerate tooth bleaching, such

as heated dental instruments.However, excessive heating

can cause irreversible damage to the dental pulp.Contemporary

approaches and literature has focussed on accelerating

peroxide bleaching with simultaneous illumination of

the anterior teeth with various sources having a range of

wavelengths and spectral power, for examples, halogen curing

lights, plasma arc lamps, lasers and light-emitting diodes.

For some light sources, significant increases in pulpal

temperatures have been measured using in vitro models

during tooth bleaching.The light source can activate

peroxide to accelerate the chemical redox reactions of the

bleaching process. In addition, it has been speculated that

the light source can energise the tooth stain to aid the overall

acceleration of the bleaching process. Some products that

are used in light activated bleaching procedures contain

ingredients that claim to aid the energy transfer from the light

to the peroxide gel and are often coloured materials, for

examples, carotene and manganese sulphate.

Case studies have demonstrated the efficacy of light

activated peroxide tooth bleaching systems. However,

the literature evidence from in vitro and clinical studies

for the actual effect of light on tooth bleaching versus a

suitable non-light control is limited and controversial. An in

vitro study using naturally coloured extracted human teeth

showed that the application of various light sources significantly

improved the whitening efficacy of some bleach

materials, but not for others. Other in vitro studies have

clearly shown significant tooth whitening benefits for peroxide

plus light versus suitable control conditions

However, these studies artificially stained the tooth specimens

with, for examples, black tea, coffee, tobacco and red

wine, i.e. ingredients commonly found to promote extrinsic

stains. These chromophores are likely to be different to that

which may be found naturally inside the tooth.

Tavares et al. conducted a tooth whitening clinical study

to compare 15% hydrogen peroxide gel illuminated with a gas

plasma light source versus 15% peroxide alone versus placebo

gel plus light, all treatments lasting 1 h. The change in Vita

shade from baseline for peroxide plus light, peroxide alone

and placebo plus light were 8.35, 5.88 and 4.93, respectively,

with peroxide plus light being significantly different to the

other two groups. In contrast, Hein et al.demonstrated no

additional effect of any of the three light sources tested over

the bleaching gel alone for three commercial products in asplit mouth clinical design. Thus, further work is clearly

required in order to unequivocally demonstrate the additional

efficacy benefit of light activated tooth whitening systems

versus their non-light activated controls.