Tooth whitening

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Before and After Tooth Whitening

The process of tooth whitening lightens the colour of a tooth.[1] Tooth whitening can be achieved by either changing the intrinsic colour or by removing and controlling the formation of extrinsic stains.[2] The chemical degradation of the chromogens within or on the tooth is termed as bleaching.[1] Hydrogen peroxide (H2O2) is the active ingredient most commonly used in whitening products and is delivered as either hydrogen peroxide or carbamide peroxide.[1] Hydrogen peroxide is analogous to carbamide peroxide as it is released when the stable complex is in contact with water. When it diffuses into the tooth, hydrogen peroxide acts as an oxidising agent that breaks down to produce unstable free radicals. In the spaces between the inorganic salts in tooth enamel, these unstable free radicals attach to organic pigmented molecules resulting in small, less heavily pigmented components.[3] Reflecting less light, these smaller molecules create a "whitening effect".[3] There are different products available on the market to remove stains.[1] For whitening treatment to be successful, dental professionals should correctly diagnose the type, intensity and location of the tooth discolouration.[3] Time exposure and the concentration of the bleaching compound, determines the tooth whitening endpoint.[1]

Natural Tooth Shade[edit]

The perception of tooth colour is multi-factorial. Reflection and absorption of light by the tooth can be influenced by a number of factors including specular transmission of light through the tooth; specular reflection at the surface; diffuse light reflection at the surface; absorption and scattering of light within the dental tissues; enamel mineral content; enamel thickness; dentine colour, the human observer, the fatigue of the eye, the type of incident light and the presence of extrinsic and intrinsic stains.[4] Additionally, the perceived brightness of the tooth can change depending on the brightness and colour of the background.[4]

The combination of intrinsic colour and the presence of extrinsic stains on the tooth surface influence the colour and thus the overall appearance of teeth.[2] The scattering of light and absorption within enamel and dentine determine the intrinsic colour of teeth and because enamel is relatively translucent, the dentinal properties can play a major role in determining the overall tooth colour.[4] On the other hand, extrinsic stain and colour is the result of coloured regions that have formed within the acquired pellicle on the enamel surface and can be influenced by lifestyle behaviours or habits.[2] For example, dietary intake of tannin-rich foods, poor toothbrushing technique, tobacco products and exposure to iron salts and chlorhexidine can affect the colour of a tooth.[2]

With increasing age, teeth tend to be darker in shade.[5] This can be attributed to secondary dentin formation and thinning of enamel due to tooth wear which contributes to a significant decrease in lightness and increase in yellowness.[5] Tooth shade is not influenced by gender or the colour of a person's skin.[5]

Tooth Staining and Discolouration[edit]

Tooth discolouration and staining is primarily due to two sources of stains; Intrinsic and extrinsic (see Figure 2).[1] In essence, tooth whitening primarily targets those intrinsic stains in which cannot be removed through mechanics such as a debridement (clean) or prophylaxis, in the dental office.[6] Below explains in depth the differences between the two sources of which contribute to such discolouration of the tooth surface.

Figure 2. Examples of tooth staining. Extrinsic staining examples: A. Smoking; B. Wine stain; and C. Food stain. Intrinsic staining examples: D. Age yellowing; E. Decay; F. Orthodontic white spot lesion; G. Mild fluorosis; H. Amalgam restoration; I. Tetracycline stain; J. Genetic (amelogenesis imperfecta); K. and non-vital colouring.

Extrinsic Staining[edit]

Extrinsic staining, is largely due to environmental factors including smoking, pigments in beverages and foods, antibiotics, and metals such as iron or copper. Coloured compounds from these sources are adsorbed into acquired dental pellicle or directly onto the surface of the tooth causing a stain to appear.[7]

  • Dental plaque: Dental plaque is a clear biofilm of bacteria that naturally forms in the mouth, particularly along the gumline, and it occurs due to the normal development and defences of the immune system.[8] Although usually virtually invisible on the tooth surface, plaque may become stained by chromogenic bacteria such as Actinomyces species.[9] Prolonged dental plaque accumulation on the tooth surface can lead to enamel demineralisation and formation of white spot lesions which appear as an opaque milk coloured lesion.[10] The acidic by-products of fermentable carbohydrates derived from high sugar foods contribute to greater proportions of bacteria such as mutans streptococci and lactobabilli in dental plaque. Higher consumption of fermentable carbohydrates will promote demineralisation and increase the risk of developing white spot lesions.[8]
  • Calculus: neglected plaque will eventually calcify, and lead to the formation of a hard deposit on the teeth, especially around the gumline. The organic matrix of dental plaque and calcified tissues undergo a series of chemical and morphological changes that lead to calcification of the dental plaque and therefore leading to the formation of calculus.[11] The color of calculus varies, and may be grey, yellow, black or brown.[9] The colour of calculus depends on how long it has been present in the oral cavity for; normally starts off yellow and over time the calculus will begin to stain a darker colour and become more tenacious and difficult to remove.
  • Tobacco: tar in smoke from tobacco products (and also smokeless tobacco products) tends to form a yellow-brown-black stain around the necks of the teeth above the gumline[9] The nicotine and tar in tobacco, combined with oxygen, turns yellow and over time will absorb into the pores of enamel and stain the teeth yellow. The dark brown to black stains along the gum line of the teeth are the result of the porous nature of calculus immediately picking up the stains from nicotine and tar.
  • Betel chewing.[12] Betel chewing produces blood-red saliva that stains the teeth red-brown to nearly black.[13] The extract gel of betel leaf contain tannin, a chromogenic agent that causes discolouration of the tooth enamel.[14]
  • Tannin is also present in coffee, tea, and red wine and produces a chromogenic agent that can discolor teeth.[15][16] Large consumptions of tannin-containing beverages stain the dental enamel brown due to the chromogenic nature.[17]
  • Certain foods, including curries and tomato-based sauces, can cause teeth staining.[18]
  • Certain topical medications; Chlorhexidine (antiseptic mouthwash) binds to tannins, meaning that prolonged use in persons who consume coffee, tea or red wine is associated with extrinsic staining (i.e. removable staining) of teeth.[19] Chlorhexidine mouthwash has a natural liking for sulphate and acidic groups commonly found in areas where plaque accumulates such as along the gumline, on the dorsum of the tongue and cavities. Chlorhexidine is retained in these areas and stain yellow-brown. The stains are not permanent and can be removed with proper brushing.[20]
  • Metallic compounds. Exposure to such metallic compounds may be in the form of medication or occupational exposure. Examples include iron (black stain), iodine (black), copper (green), nickel (green), cadmium (yellow-brown).[21] Sources of exposure to metal include placing metal into the oral cavity, metal containing dust inhalation or oral administration of drugs. Metals can be penetrated into the tooth causing permanent discolouration or can bind to the pellicle causing surface stain.[20]

Intrinsic Staining[edit]

Intrinsic staining primarily occurs during the tooth development either before birth or at early childhood. Intrinsic stains are those that cannot be removed through mechanical measures such as debridement or a prophylactic stain removal. As the age of the person increases, the teeth can also appear yellower over time.[15] Below are examples of intrinsic sources of stains;

  • Tooth wear and ageing: Tooth wear is a progressive loss of enamel and dentine due to tooth erosion, abrasion and attrition. As enamel wears down, dentine becomes more apparent and chromogenic agents are penetrated in the tooth more easily. The natural production of secondary dentine also gradually darkens teeth with age.[22]
  • Dental caries (tooth decay):[12] The evidence regarding carious tooth discolouration is inconclusive however the most reliable evidence suggests that carious lesion allows for exogenous agents to enter dentine and hence increased absorption of chromogenic agents causing discolouration to the tooth.[22]
  • Restorative materials: The materials used during root canal treatments such as eugenol and phenolic compounds contain pigment that stain dentine. Restorations using amalgam also penetrate dentine tubules with tin over time therefore causing dark stains to the tooth.[22] 
  • Dental trauma[12] which may cause staining either as a result of pulp necrosis or internal resorption. Alternatively the tooth may become darker without pulp necrosis
  • Enamel hypoplasia: Enamel hypoplasia causes enamel to be thin and weak. It produces a yellow-brown discolouration and can also cause enamel’s smooth surface to be rough and pitted which causes the tooth to be susceptible to extrinsic staining, tooth sensitivity, malocclusion and dental caries.[23] The evidence regarding enamel hypoplasia is inconclusive however the most likely cause is infection or trauma caused to the primary dentition. Disturbances to the developing tooth germ during neonatal and early childhood stages such as maternal vitamin D deficiency, infection, drug and medication intake can cause enamel hypoplasia.[22]
  • Pulpal Hyperemia: Pulpal hyperemia refers to inflammation of a traumatised tooth which can be caused by a stimuli such as trauma, thermal shock or dental caries. Pulpal hyperemia is reversible [24] and produces a red hue seen initially after trauma which has the ability to disappear if the tooth becomes revascularized[22]
  • Fluorosis:[21] Dental fluorosis causes enamel to become opaque, chalky white and porous. The enamel can break down and cause the exposed subsurface enamel to become mottled and produce extrinsic dark brown/black stains.[25] Dental fluorosis occurs due to excessive ingestion of fluoride or overexposure to fluoride during the development of enamel which usually occurs between the ages 1 to 4. Fluoridated drinking water, fluoride supplements, topical fluoride (fluoride toothpastes) and formula prescribed for children can increase the risk of dental fluorosis. Fluoride is considered an important factor in the management and prevention of dental caries, the safe level for daily fluoride intake is 0.05 to 0.07 mg F/Kg/day.[26]
  • Dentinogenesis imperfecta:[21] Dentinogenesis imperfecta is a hereditary dentine defect which causes the tooth to become discoloured usually blue or brown in colour and translucent giving teeth an opalescent sheen.[22] The condition is autosomal dominant which means that the condition runs in the family.
  • Amelogenesis imperfecta:[21] The appearance of amelogenesis imperfecta depends on the type of amelogenesis, there are 14 different subtypes and can vary from the appearance of hypoplasia to hypomineralisation which can produce different appearances of enamel from white mottling to yellow brown appearances.[22]
  • Tetracycline and minocycline. Tetracycline is a broad spectrum antibiotic,[27] and its derivative minocycline is common in the treatment of acne.[28] The drug is able to chelate calcium ions and is incorporated into teeth, cartilage and bone.[27] Ingestion during the years of tooth development causes yellow-green discoloration of dentine visible through the enamel which is fluorescent under ultraviolet light. Later, the tetracycline is oxidized and the staining becomes more brown and no longer fluoresces under UV light.[9][29]
  • Porphyria:[9] A rare metabolic disorder where the body struggles to metabolise porphyria which leads to accumulation or the excretion of porphyrins in teeth. The excretion of porphyrins produce purple-red pigments in teeth.[30]
  • Hemolytic disease of the newborn:[9] This disease occurs when a newborn’s red blood cells are being attacked by antibodies from the mother caused by an incompatibility between the mother and baby’s blood. This condition can produce green staining of teeth due to jaundice which is an inability to excrete bilirubin properly.[31]
  • Root resorption:[32] Root resorption is clinically asyptomatic however can produce a pink appearance at the amelo-cemental junction.[22]
  • Alkaptonuria:[32] Metabolic disorder which promotes the accumulation of homogentisic acid in the body and may cause brown colour pigmentation in the teeth, gums and buccal mucosa.[33]


Prior to proceeding to tooth whitening alternatives, it is advised that the patient comes into the dental office to have a comprehensive oral examination that consists of a full medical, dental and social history. This will allow the clinician to see if there is any treatment that needs to be done such as restorations to remove caries, and to assess whether or not the patient will be a good candidate to have the whitening done. The clinician would then debride (clean) the tooth surface with an ultrasonic scaler, hand instruments and potentially a prophy paste to remove extrinsic stains as mentioned above. This will allow a clean surface for maximum benefits of which ever tooth whitening method the patient decides to go with.[6] Below will discuss the various types of tooth whitening methods including both internal application of bleaching and external application through the use of bleaching agents.


VITA classical A1-D4 shade guide arranged according to value
VITA classical A1-D4 shade guide arranged according to chroma; A: red-brown, B: red-yellow, C: grey, D: red-grey

Before the treatment, the Oral health professional should examine the patient: taking a health and dental history (including allergies and sensitivities), observe hard and soft tissues, placement and conditions of restorations, and sometimes x-rays to determine the nature and depth of possible irregularities. If this is not completed prior to the whitening agents being applied to the tooth surface, excessive sensitivity and consequences may occur.

The whitening shade guides are used to measure tooth colour. These shades determine the effectiveness of the whitening procedure, which may vary from two to seven shades.[34] These shades may be reached after a single in office appointment, or may take longer depending on the individual. The effects of bleaching can last for several months, but may vary depending on the lifestyle of the patient. Consuming tooth staining foods or drinks that have a strong colour may compromise effectiveness of the treatment. These include food and drinks containing tanins such as; coffee/tea, red wines, curry etc.

In-office bleaching procedures generally use a light-cured protective layer that is carefully painted on the gums and papilla (the tips of the gums between the teeth) to reduce the risk of chemical burns to the soft tissues. The bleaching agent is either carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide, or hydrogen peroxide itself. The bleaching gel typically contains between 10% and 44% carbamide peroxide, which is roughly equivalent to a 3% to 16% hydrogen peroxide concentration. The legal percentage of hydrogen peroxide allowed to be given is 0.1–6%. Bleaching agents are only allowed to be given via dental practitioners, dental therapists and dental hygienists.

Bleaching is least effective when the original tooth color is grayish and may require custom bleaching trays. Bleaching is most effective with yellow discolored teeth. If heavy staining or tetracycline damage is present on a patient's teeth, and whitening is ineffective (tetracycline staining may require prolonged bleaching, as it takes longer for the bleach to reach the dentine layer), there are other methods of masking the stain. Bonding, which also masks tooth stains, is when a thin coating of composite material is applied to the front of a person's teeth and then cured with a blue light. A veneer can also mask tooth discoloration.

Advantages of the in chair whitening technique is that it is faster and more effective in comparison to the take home bleaching options. Depending on which practice you have the whitening completed, you can also get bleaching trays made up for you so that after the whitening treatment is completed, you are able to use these trays in the future for maintenance of your bleaching with at home kits or for the use of your desensitising products. The trays that are custom made for you may take up to one week following your appointment. The desensitising products may be given to you on the day of your in chair whitening treatment so that you can take them home with you. Some clinics stock desensitising agents and some clinics do not, therefore you may be required to source them from elsewhere.

Light-accelerated bleaching[edit]

Power or light-accelerated bleaching, uses light energy which is intended to accelerate the process of bleaching in a dental office. Different types of energy can be used in this procedure, with the most common being halogen, LED, or plasma arc. Use of light during bleaching increases the risk of tooth sensitivity and may not be any more effective than bleaching without light when high concentrations of hydrogen peroxide are used.[35] Recent research has shown that the use of a light activator does not improve bleaching, has no measurable effect and most likely to increase the temperature of the associated tissues, resulting in damage.[36][37] light accelerated bleaching now comes in ranges of intensities such as the phillips zoom light [38] which can aid in reducing post op sensitivity while maintaining effectiveness.

The ideal source of energy should be high energy to excite the peroxide molecules without overheating the pulp of the tooth.[39] Lights are typically within the blue light spectrum as this has been found to contain the most effective wavelengths for initiating the hydrogen peroxide reaction. A power bleaching treatment typically involves isolation of soft tissue with a resin-based, light-curable barrier, application of a professional dental-grade hydrogen peroxide whitening gel (25–38% hydrogen peroxide), and exposure to the light source for 6–15 minutes. Recent technical advances have minimized heat and ultraviolet emissions, allowing for a shorter patient preparation procedure.

For any whitening treatments it is recommended that a comprehensive examination of the patient is done including the use of radiographs to aid in the diagnosis of the current condition of the mouth, including any allergies that may be present. The patient will need to have a healthy mouth and free of periodontal disease or caries and to have had a debridement/clean done to remove any tartar or plaque build up.[38]

It is recommended to avoid smoking, drinking red wine, eating or drinking any deeply coloured foods after this as the teeth may stain considerably straight after treatment.

Nanoparticle Catalysts for Reduced Hydrogen Peroxide Concentration[edit]

A recent addition to the field is new light-accelerated bleaching agents containing lower concentrations of hydrogen peroxide with a titanium oxide nanoparticle based catalyst. Reduced concentrations of hydrogen peroxide cause lower incidences of tooth hypersensitivity.[40] The nanoparticles act as photocatalysts, and their size prevents them from diffusing deeply into the tooth. When exposed to light, the catalysts produce a rapid, localized breakdown of hydrogen peroxide into highly reactive radicals. Due to the extremely short lifetimes of the free radicals, they are able to produce bleaching effects similar to much higher concentration bleaching agents within the outer layers of the teeth where the nanoparticle catalysts are located. This provides effective tooth whitening while reducing the required concentration of hydrogen peroxide and other reactive byproducts at the tooth pulp.

Internal bleaching[edit]

Internal bleaching is a process which occurs after a tooth has been Endodontically treated. This means that the tooth will have had the nerve of the tooth extirpated or removed through a root canal treatment at the dentist or by a specialist Endodontist. Internal bleaching is often sought after in teeth which have been Endodontically treated as tooth discolouration becomes a problem due to the lack of nerve supply to that tooth. it is common to have this internal bleaching done on an anterior tooth (a front tooth that you can see when smiling and talking). A way around this is by sealing off the bleaching agent inside the tooth itself and replacing after weeks at a time until the desired shade has been achieved. The amount of time in-between appointments varies from patient to patient and operator preference until the desired shade has been achieved.[8] Even though this is a great option, the disadvantages to this treatment is a risk of internal root resorption of the tooth that you are internally bleaching. This may not occur in everyone or every tooth and is difficult to determine prior to completing the treatment.[8]

At Home[edit]

At home tooth whitening products are available from dentists or ‘over the counter’ (OTC).[41] At home whitening methods include; over the counter strips and gels, whitening rinses, whitening toothpastes and tray based tooth whiteners.[41] OTC products can be used for milder cases of tooth staining.[41]

OTC Whitening Strips and Gels[edit]

The plastic whitening strips contain a thin layer of peroxide gel and are shaped to fit the buccal/labial surfaces of teeth.[1] Many different types of whitening strips are available on the market, after being introduced in the late 1980s.[1] Specific whitening strip products have their own set of instructions however the strips are typically applied twice daily for 30 minutes for 14 days.[1] In several days, tooth colour can lighten by 1 or 2 shades.[1] The tooth whitening endpoint does depend on the frequency of use and ingredients of the product.[1]

Whitening gels are applied onto the tooth surface with a small brush.[1] The gels contain peroxide and are recommended to be applied twice a day for 14 days.[1] The tooth whitening endpoint like that of the whitening strips.[1]

Whitening Rinses[edit]

Whitening rinses work by reaction of the oxygen sources such as hydrogen peroxide within the rinse and the chromogens on or within the tooth.[1] It is recommended to use twice a day, rinsing for 1 minute.[1] To see an improvement in shade colour, it can take up to 3 months.[1]

Whitening Toothpastes[edit]

Whitening toothpastes are different to regular toothpastes in that they contain higher amounts of abrasives and detergents to be more effective at removing tougher stains.[1] Some whitening toothpastes contain low concentrations of carbamide peroxide or hydrogen peroxide which help lighten tooth colour however they do not contain bleach (sodium hypochlorite).[1] With continuity of use over time, tooth colour can lighten by one or 2 shades.[1]

Tray based tooth whiteners[edit]

This method of tooth whitening is achieved by wearing a fitted tray containing carbamide peroxide bleaching gel overnight or for 2–4 hours a day.[1] If manufacturer’s instructions are followed, tooth whitening can occur within 3 days and lighten teeth by 1 or 2 shades.[1] This type of tooth whitening is available over the counter and professionally from a oral health professional.[1]

Natural (alternative) methods[edit]

Baking Soda is a safe, low abrasive and effective stain removal and tooth whitening dentrifice.[42] Dentrifices that have excessive abrasivity are harmful to dental tissue, therefore baking soda is a desirable alternative.[42] To date, clinical studies on baking soda report that there have been no reported adverse effects.[42] It also contains acid-buffering components that makes baking soda biologically antibacterial at high concentrations and capable of preventing growth of Streptococcus Mutans.[42] Baking soda might be useful for caries prone patients as well as those who are after a tooth whitening effect.[42]


Some groups are advised to carry out tooth whitening with caution as they may be at higher risk of adverse effects.

  • Patients with unrealistic expectations
  • Allergic to peroxide
  • Pre-existing sensitive teeth
  • Cracks / exposed dentine
  • Enamel development defects
  • Acid erosion
  • Receding gums (gingival recession) and yellow roots, as roots do not bleach as readily as crowns
  • Sensitive gums
  • Defective dental restorations
  • Tooth decay. White-spot decalcification may be highlighted and become more noticeable directly following a whitening process, but with further applications the other parts of the teeth usually become more white and the spots less noticeable.
  • Active periapical pathology
  • Untreated periodontal disease
  • Pregnant or lactating women
  • Children under the age of 16. This is because the pulp chamber, or nerve of the tooth, is enlarged until this age. Tooth whitening under this condition could irritate the pulp or cause it to become sensitive. Younger people are also more susceptible to abusing bleaching.[43]
  • Persons with visible white fillings or crowns. Tooth whitening does not usually change the color of fillings and other restorative materials. It does not affect porcelain, other ceramics, or dental gold. However, it can slightly affect restorations made with composite materials, cements and dental amalgams. Tooth whitening will not restore color of fillings, porcelain, and other ceramics when they become stained by foods, drinks, and smoking, as these products are only effective on natural tooth structure. As such, a shade mismatch may be created as the natural tooth surfaces increase in whiteness and the restorations stay the same shade. Whitener does not work where bonding has been used and neither is it effective on tooth-color filling. Other options to deal with such cases are the porcelain veneers or dental bonding.[44]


Some of the common side effects involved in teeth whitening are increased sensitivity of the teeth, gum irritation and extrinsic teeth discolouration.[41]


Hypersensitive teeth are caused by the extreme low pH of bleach that cause the dentinal tubules to open up.[45] When struck by cold, hot or sweet stimuli, this manifests as increased hypersensitivity. Between 67-78% of individuals who use hydrogen peroxide and heat to conduct in office whitening experience sensitivity after the procedure.[46][47] Although it varies from person to person, sensitivity after whitening treatment can last up to 4–39 days.[48][49]

Potassium nitrate and sodium fluoride in toothpastes are used to ease discomfort following bleaching, however, there is no evidence to suggest that this is a permanent method to eradicate hypersensitivity.[50]

Irritation of mucous membranes[edit]

Hydrogen peroxide is an irritant and cytotoxic. Hydrogen peroxide with concentrations of 10% or higher, can cause tissue damage, be corrosive to mucous membranes and cause burning sensation to the skin.[51] Chemical burns are common while bleaching; if a high concentration of oxidising agent come in contact with unprotected tissue, irritation and discolouration of the mucous membranes may be the result. Poorly fitting bleaching trays are amongst the most common reason to chemical burns.

Uneven results[edit]

Uneven results are quite common after bleaching. Consuming less foods and drinks that cause surface staining of teeth will be beneficial to the result of teeth whitening.

Return to original pre-treatment shade[edit]

Nearly half the initial change in color provided by an intensive in-office treatment (i.e., 1 hour treatment in a dentist's chair) may be lost in seven days.[52] Rebound is experienced when a large proportion of the tooth whitening has come from tooth dehydration (also a significant factor in causing sensitivity).[53] As the tooth rehydrates, tooth color "rebounds", back toward where it started.[54]


Overbleaching, more often known as the “bleached effect”, occurs among treatments that promise a large change over a short period of time e.g., hours. Overbleaching can emit a translucent and brittle appearance.[55]

Damage to enamel[edit]

Teeth enamel can have an adverse negative effect by whitening treatment.[56] Evidence from studies show that carbamide peroxide present in whitening gels can damage the enamel surface. Although this effect is not as damaging as phosphoric acid etch,[57] the increased irregularity of the teeth surface makes the teeth more susceptible to extrinsic staining, thus having a detrimental effect on the aesthetics.

Weakened dentin[edit]

Intracoronal bleaching is a tooth whitening method that uses 30% more hydrogen peroxide. Such tooth whitening method can weaken the mechanical properties of dentine and could also lead into severe tooth sensitivity.[58]

Effects on existing restorations[edit]

Dental Amalgam – Exposure to carbamide peroxide solutions increase mercury release for one to two days.[58][59]

Resin Composite – bond strength between enamel and resin based fillings weakened.[60]

Glass Ionomer and other cements – Study suggesting that solubility of these materials may increase.[61]


Bleachorexia is the term that is used to describe an individual that develops an unhealthy obsession with teeth whitening.[43] This condition is similar to body dysmorphic disorder. The characteristics of bleachorexia are the continuous use of whitening products even though the teeth cannot possibly get any whiter, despite repeated treatment.[55] A person with bleachorexia will continually seek out different whitening products, hence, it is recommended that a target shade is agreed before starting the treatment procedure to help with this problem.[55]

Other risks[edit]

Evidence suggests that hydrogen peroxide might act as a tumour promoter.[62] Although cervical root resorption is more evidently observed in thermo-catalytic bleaching methods, intracoronal internal bleaching may also lead to tooth root resorption.[62] Moreover, severe damage to Intracoronal dentine and tooth crown fracture can occur due to this bleaching method.[62]

However, the International Agency of Research on Cancer (IARC) has concluded that there is insufficient evidence to prove that hydrogen peroxide is a carcinogen to humans.[63] Recently, the genotoxic potential of hydrogen peroxide was evaluated. The results indicated that the oral health products that contain or release hydrogen peroxide up to 3.6% will not increase the cancerous risk of an individual,[64] hence, it is safe to use in moderation.


Teeth whitening remedies have been present since the ancient times. Although some methods from the past might seem absurd and questionable, they were somewhat effective in their duties. Many methods were time consuming and involved the use of hazardous chemicals. Primarily, non-vital teeth were used for whitening.[65]

The Ancient Romans believed in using urine with goat milk to make their teeth look whiter.[66] Pearly white teeth symbolized beauty and marked wealth. In the late 17th century, many people seeked barbers, who used a file to file down the teeth before applying an acid that would, in fact, whiten the teeth. Although the procedure was successful, the teeth would become completely eroded that led it to become decayed.[67] Guy de Chauliac suggested the following to whiten the teeth: "Clean the teeth gently with a mixture of honey and burnt salt to which some vinegar has been added."[55] In 1877 oxalic acid was proposed for whitening, followed by calcium hypochlorite.[55]

In the late 1920s, mouthwash containing pyrozone (ether peroxide) was found to reduce caries while providing a whiter appearance to the teeth.[65] By 1940s and 1950s ether and hydrogen peroxide gels were used to whiten vital teeth, whereas non-vital teeth were whitened using pyrozone and sodium perborate.[65][68]

In the late 1960s, Dr William Klusmeier, an Orthodontist from Fort Smith, Arkansas introduced the customised tray bleaching. However, it was not until 1989 when Haywood and Heymann published an article that supported this method and became accepted by people. Carbamide peroxide with a shelf life of 1-2 years as opposed to hydrogen peroxide with a shelf life 1-2 months was seen as a more stable agent to whitening teeth.[65]

Society and Culture[edit]

Teeth whitening has turned into the most promoted and mentioned methodology in restorative dentistry. In excess of 100 million Americans brighten their teeth using different methods; spending $15 billion in 2010.[69] The US Food and Drug Administration just endorses gels that are under 6% hydrogen peroxide or 16% or less of carbamide peroxide. The Scientific Committee for Consumer Protection of the EU consider gels containing higher fixations can be dangerous.[70]

As per European Council guidelines, only a certified dental professional can lawfully give tooth whitening products utilizing 0.1 – 6% hydrogen peroxide, and that the patient 18 years of age or above.[71] Over the past couple of years, there have been rising worry over unlicensed staff giving low quality tooth whitening treatment. Evidence has shown that teeth whitening practices have been offered by salons and health centers under incompetent staff without any sufficient dental background.[72] A group of perceived dental professionals and associations called The Tooth Whitening Information Group (TWIG) was built up to advance protected and beneficial tooth whitening information and direction to assist the general population. Reports can be made by the general population to TWIG through their website with respect to any individual giving unlawful tooth whitening services, or if an individual has personally undergone treatment done by a non-dental professional.

In Brazil, all whitening items are classed as cosmetics (Degree II) in government body.[43] There are worries that this will bring about increasing abuse of whitening products and thus there have been calls for reanalysis.[43]

See also[edit]


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