Whitening

For some time, there has been consistent consumer demand for whiter, brighter teeth and an attractive smile.^1-3 Professionally administered (in-office) tooth whitening, also known as dental bleaching, remains a popular esthetic procedure and can be performed using a wide range of techniques and application protocols. Another common approach is at-home whitening with custom-fitted trays, which patients use to apply professional-strength bleaching gel (for use at night or during the day). Numerous over-the-counter (OTC) whitening products (e.g., strips, gels, rinses, chewing gums, or paint-on films) are also widely available for self-application at home.⁴

Extrinsic vs. Intrinsic Stains

Tooth (and dental) discoloration are terms used to describe any change in the color or translucency of a tooth,¹ as well as discoloration in multiple teeth or the entire dentition. Tooth discolorations are typically classified as extrinsic, intrinsic, or a combination of both types.⁵

Extrinsic stains commonly result from an accumulation of colored compounds on enamel. Extrinsic discoloration is primarily associated with environmental factors or individual behaviors, such as tobacco use, exposure to metal salts (e.g., iron or copper), or the consumption of highly pigmented foods (e.g., dark fruits) or beverages (e.g., red wine, coffee, tea, or cola drinks).^{1, 6-11}

Extrinsic tooth stains vary widely in color and severity, and can be exacerbated by lifestyle habits (e.g., smoking or chewing tobacco), poor oral hygiene, or frequent consumption of pigmented food or beverages.^{12, 13} A wide range of extrinsic stains can be effectively reduced with mechanical interventions such as brushing with a whitening toothpaste or professional prophylaxis.^{6, 7, 14} Some OTC whitening products (e.g., toothpastes, chewing gums) are effective primarily in removing extrinsic (surface) stains on enamel, and will not have a significant impact on intrinsic stains or the intrinsic color of the tooth.^{4, 15}

Intrinsic stains occur inside the tooth (within the enamel or the underlying dentin), and can arise due to systemic causes such as genetic disorders (e.g., dentinogenesis imperfecta, amelogenesis imperfecta) or local factors during tooth development or after eruption (e.g., fluorosis).^{1, 16, 17} Aging is another common etiology of intrinsic discoloration. With increasing age, enamel becomes more translucent and thinner, which allows the yellower dentin to show through and the overall tooth color may darken.^{1, 18} Other causes of intrinsic discoloration include certain antibiotic use in childhood (e.g., tetracycline),¹⁹ caries, amalgam restorations, and pulpal hemorrhage, decomposition or necrosis.^{5, 7, 20} Intrinsic discoloration can also occur with prolonged use of antiseptic mouthrinse (e.g., chlorhexidine rinse).²¹

Whitening Agents

Reducing intrinsic stains involves a chemical reaction that changes the color of the tooth. The most common ingredients used in bleaching are carbamide peroxide and hydrogen peroxide, which are used at different concentrations depending on the products or regimens used.²²

The bleaching action in chemically induced whitening is due primarily to the effects of carbamide peroxide, which releases about one-third of its content as hydrogen peroxide, a strong oxidizing agent.^{23, 24} Hydrogen peroxide diffuses easily through interprismatic spaces in the enamel, allowing for passage from enamel and dentin to pulp within ¹⁵ minutes of exposure.^{25, 26} The bleaching process is generally believed to occur when reactive oxygen molecules (generated from hydrogen peroxide) interact with organic chromophores (colored compounds) within enamel and dentin through a chemical oxidation process, which is influenced by various environmental factors (e.g., pH, temperature, light).^{17, 25, 27}

The extent of whitening attained through bleaching may be influenced by the type of intrinsic stain being addressed. For example, brown stains due to fluorosis or tetracycline^{28, 29} may be more responsive to bleaching than white stains associated with fluorosis or orthodontic treatment, which may appear less noticeable as the background of the tooth lightens.³⁰ The type of stain also can affect the length of and/or number of treatments required to arrive as close as possible to the desired result. For example, although stains due to tetracycline may be diminished, treatment can require three to four months of nightly treatment (on average).^{28, 31}

Patient Considerations and Preferences

Tooth whitening is a common elective procedure and a popular, less-invasive aesthetic treatment for patients seeking to enhance their smile and appearance. A clinical exam prior to the start of tooth bleaching procedures, with radiographs and other screening and diagnostic tests as appropriate, can help diagnose various factors contributing to the patient’s tooth discoloration.³² A standard dental exam, beginning with a health and dental history, may include questions about the patient’s perception of the cause of the dental discoloration, as well as allergies (which may include ingredients in bleaching materials), and any past or recent history of tooth sensitivity.^{32, 33}

Patient dentition characteristics also influence the safe provision of care and the treatment’s level of success in whitening vital teeth. Patients who have tooth-colored restorations (including crowns or implants) should be aware that only natural teeth will be affected by the bleaching agent and treatment could result in differences between natural teeth and restorations, which will not change color.²⁸ The American Academy of Pediatric Dentistry discourages full-arch cosmetic bleaching for child and adolescent patients in the mixed dentition and primary dentition.³⁴ Additionally, some research suggests that bleaching protocols may alter the surface roughness of enamel, which may also reduce the shear bond strength between enamel and composite and ceramic restorative materials.³⁵

Products Directly Available to Consumers

Bleaching compounds in over-the-counter whitening products are peroxide-based and typically contain carbamide peroxide or hydrogen peroxide at lower concentrations than in-office or dentist-prescribed, at-home bleaching techniques. A variety of OTC options are available with products that include toothpastes, whitening strips, and gels painted directly on teeth or delivered in trays. Products that bear the ADA Seal of Acceptance (a voluntary program for OTC oral care products), indicating that the company has demonstrated that the product meets ADA Seal Program requirements for safety and effectiveness when used as directed, include toothpastes and whitening strips.

Whitening toothpastes primarily rely on abrasives for mechanical removal of extrinsic surface stains, though some contain low levels of peroxide to help lighten tooth color.^{7, 36, 37} A 2020 systematic review found limited evidence that whitening dentifrices had similar efficacy to paint-on gel but less efficacy than whitening strips, with comparable adverse effects (e.g., sensitivity, oral irritation).³⁸ Most whitening strips rely primarily on peroxide to bleach teeth.^{33, 39}

In-Office Procedures and Products Available Through Dentists

Examples of products available through dentists include gels delivered in custom-made trays, either intended for at-home use or applied as an in-office treatment. In-office whitening treatment may involve application of a peroxide-containing gel, used with or without a light intended to accelerate and enhance the bleaching process (known as a light-activated system).⁴⁰ Another in-office bleaching procedure, known as “power bleaching,” uses concentrated solutions of hydrogen peroxide in water (with or without light activation), which may be applied for up to 30 minutes.¹⁷

Dentist-supervised whitening approaches include at-home and in-office options (note: whitening products supplied by dentists for use at home or applied by dentists in the office are considered “professional products,” and are not eligible for the ADA Seal of Acceptance). At-home whitening with custom trays involves whitening gel placed in trays by the patient at home. The trays are made in the office to fit comfortably and minimize contact of the gel with the patient’s gingiva. Peroxide concentration in at-home systems typically ranges from 10% to 38% carbamide peroxide and treatment times are dictated primarily by the concentration used.⁴¹ A systematic review by de Geus et al. found daily treatment times ranging from 2 to 10 hours for periods of 6 to 28 days.⁴²

Other in-office techniques for removing extrinsic stains include rubber-cup prophylaxis and enamel microabrasion, which may be completed before the provision of other in-office bleaching treatments that use gels with high peroxide concentrations or light-activated bleaching systems.¹⁵ Microabrasion uses an abrasive slurry (e.g., acidic gel with abrasive particles) to remove thin outer layers of the enamel surface.¹⁵ Microabrasion may also be supplemented by chemically induced whitening for enhanced stain removal and improved patient satisfaction with esthetic outcomes. This procedure is typically limited to treatment of extrinsic stains or defects that do not extend beyond the enamel.^{15, 43} Overall, the removal of intrinsic stains within the dentin is considered near impossible when using an external whitening procedure (i.e., chemical and/or mechanical) whitening treatments.¹⁷

Whitening of non-vital discolored teeth may be performed through intracoronal (internal) bleaching, a procedure that uses carbamide peroxide, hydrogen peroxide, or sodium perborate to provide adequate internal bleaching of non-vital teeth.⁴⁴ In rare instances, non-vital tooth bleaching has been associated with reports of external cervical resorption, but the overall incidence of this adverse effect is not considered common.^{45, 46}

Treatment Considerations

Examples of whitening treatment considerations may include the patient lifestyle, socioeconomic status, and present oral health.^{32, 33} Since restorative materials generally do not change color, identifying and documenting existing tooth restorations as part of the dental examination can help promote and achieve an acceptable tooth bleaching outcome. Restorations can also be a cause of tooth discoloration: metallic and other restorative materials on the lingual or occlusal surface of the teeth may influence tooth color significantly. Patient expectations may not be met or may be unrealistic without addressing cosmetic issues with existing restorations.¹⁵

While OTC whitening products tend to be less expensive than at-home or in-office approaches, there is often a time trade-off in that OTC products may take significantly longer than either of the other options to achieve similar levels of whitening. Auschill et al. found that an OTC bleaching technique took 16 days to achieve the whitening level of a seven-day, at-home tray system and a one-day, in-office procedure.⁴⁷

Sensitivity

One common adverse effect of OTC or dentist-dispensed, tray-based whitening is tooth sensitivity, which can be more prevalent with higher concentrations of active agents but is typically mild and transient.¹ Risk of temporary dental sensitivity is associated with all forms of bleaching,^{42, 48-50} possibly due to inflammation of the pulp as a result of peroxide exposure during the procedure.⁵¹

Regarding dental hard tissues, transient mild to moderate tooth sensitivity can occur in up to two-thirds of users during early stages of bleaching treatment.⁵² With whitening strip or tray-based treatments, sensitivity may develop within two to three days after starting the program and usually resolves by the fourth day post-treatment.⁴⁸

Factors that may influence the development or extent of tooth sensitivity associated with bleaching include concentration of carbamide or hydrogen peroxide, the presence of adhesive restorations⁵³ or the contact time and intensity and duration of light use.^{48, 54, 55} However, a recent systematic review of in-office whitening found use of lower concentrations of hydrogen peroxide resulted in less tooth sensitivity and greater objective color change.⁵⁶

A variety of approaches to prevent bleaching sensitivity have been explored, such as pretreatment use of nonsteroidal anti-inflammatory drugs^{57, 58} and pretreatment application of 5% potassium nitrate and 2% sodium fluoride gel.^{59, 60} Further research is needed to confirm the efficacy of these approaches in reducing tooth sensitivity.

Gingival Irritation

Gingival irritation can result from contact with peroxide-based gels when whitening strips or any gel-based product is used for whitening. It is typically due to poor-fitting trays or improper application of the protective barrier or gel.^{22, 48} Li suggests that use of local anesthesia be avoided during in-office bleaching so that patients can detect any burning sensations, which could indicate gel seepage through the barrier, and that patients be instructed to alert the dentist to any discomfort during the procedure so that integrity of the barrier can be checked.²²

A 2018 Cochrane review on the use of home-based whitening products found that tooth sensitivity and oral irritation were the most common adverse effects, which were more prevalent at higher concentrations but also considered mild and transient.¹ A comparative systematic review of tray-delivered carbamide peroxide gels versus hydrogen peroxide products (for at-home bleaching) found that both whitening systems had relatively equal levels of tooth sensitivity and gingival irritation.⁶¹ As with sensitivity, gingival irritation is typically transient and resolves shortly after completing the treatment.²² Additionally, a 2022 systematic review concluded that hydrogen peroxide-containing products used for tooth whitening do not appear to have carcinogenic effects on the oral mucosa.⁶²

In contrast to well-researched professional and OTC approaches to tooth whitening, do-it-yourself (DIY) methods using fruits or other household items (e.g., coconut oil) have been promoted by print and online media as alternative, cost-effective means to whiten teeth. The list of DIY or natural whitening techniques includes use of acid-containing fruits, vinegar or products containing charcoal and the practice of swishing coconut oil in the mouth (known as oil pulling).

The limited studies to date on DIY or natural whitening interventions raise questions regarding the efficacy and safety of these approaches. Kwon et al. examined the ability of a strawberry/baking soda mixture to whiten teeth, but were unable to find measurable improvement.⁶³ Yaacob et al. reported that a mixture of charcoal and table salt was abrasive and ineffective (the teeth had a yellow cast, which the authors attributed to removal of the enamel during the brushing, revealing the dentin underneath).⁶⁴ Moreover, the report documented deep concave abrasion cavities on labial surfaces of the anterior teeth following use.⁶⁴

Several activated charcoal product types (e.g., toothpaste, powder, mouthwash, tablets) are available in the consumer marketplace, but to date there is insufficient evidence demonstrating that charcoal-based oral care products or modalities provide measurable benefit in whitening vital teeth with adequate safety and effectiveness.^65-67 Additionally, there is an absence of documented tooth whitening derived from oil pulling, which has also been associated with adverse events ranging from lipoid pneumonia to upset stomach and diarrhea.^{68, 69}

ADA Policy on Tooth Whitening Administered by Non-Dentists (Trans.2008:477)

Resolved, that the American Dental Association supports educating the public on the need to consult with a licensed dentist to determine if whitening/bleaching is an appropriate course of treatment, and be it further

Resolved, that the Council on Scientific Affairs compile scientific research to describe treatment considerations for dentists prior to the tooth whitening/bleaching procedure in order to reduce the incidence of adverse outcomes and report these findings to all state dental associations, and be it further

Resolved, that the American Dental Association petition the Food and Drug Administration to properly classify tooth whitening/bleaching agents in light of the report from the Council on Scientific Affairs, and be it further

Resolved, that the American Dental Association urges constituent societies, through legislative or regulatory efforts, to support the proposition that the administering or application of any intra-oral chemical for the sole purpose of whitening/bleaching of the teeth by whatever technique, save for the lawfully permitted self-application and application by a parent and/or guardian, constitutes the practice of dentistry and any non-dentist engaging in such activity is committing the unlicensed practice of dentistry.

American Dental Association
Adopted 2008

Fabrication of Oral Appliances Used With Tooth Whitening Products (Trans.2002:397)

Resolved, that only licensed dentists or their supervised dental auxiliaries, in compliance with applicable state law, be permitted to make impressions for the fabrication of appliances used with tooth whitening products, and be it further

Resolved, that this information be communicated to all organizations (e.g., state boards of dentistry and the Centers for Disease Control and Prevention) working to protect the public from harm and infectious disease.

American Dental Association
Adopted 2002; Reviewed and Retained 2016

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