Teeth Whitening


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teeth whitening

Tooth whitening

Tooth whitening (termed tooth bleaching when utilising bleach), is either the restoration of a natural tooth shade or whitening beyond the natural shade.

Restoration of the underlying natural tooth shade is possible by simply removing surface stains caused by extrinsic factors, stainers such as tea, coffee, red wine and tobacco. The buildup of calculus and tartar can also influence the staining of teeth. This restoration of the natural tooth shade is achieved by having the teeth cleaned by a dental professional (commonly termed "scaling and polishing"), or at home by various oral hygiene methods. Calculus and tartar are difficult to remove without a professional clean.

To whiten the natural tooth shade, bleaching is suggested. It is a common procedure in cosmetic dentistry, and a number of different techniques are used by dental professionals. There is a plethora of products marketed for home use to do this also. Techniques include bleaching strips, bleaching pens, bleaching gels and laser tooth whitening. Bleaching methods generally use either hydrogen peroxide or carbamide peroxide which breaks down into hydrogen peroxide.

· 1Natural tooth shade

· 2Tooth staining and discoloration

o 2.1Extrinsic discolouration

o 2.2Intrinsic discolouration

· 3Methods

o 3.1In-office

§ 3.1.1Light-accelerated bleaching

§ 3.1.2Nanoparticle Catalysts for Reduced Hydrogen Peroxide Concentration

§ 3.1.3Internal bleaching on non-vital teeth.

o 3.2At home

§ 3.2.1Night-guard vital bleaching

§ 3.2.2Whitening toothpastes

§ 3.2.3Over-the-counter (OTC) Whitening Strips and Gels

§ 3.2.4Whitening Rinses

§ 3.2.5Natural (alternative) methods

· 4Indications

· 5Contra-indications

· 6Risks

o 6.1Hypersensitivity

o 6.2Irritation of mucous membranes

o 6.3Uneven results

o 6.4Return to original pre-treatment shade

o 6.5Over-bleaching

o 6.6Damage to enamel

o 6.7Weakened Dentine

o 6.8Effects on existing restorations

o 6.9Bleachorexia

o 6.10Other risks

· 7Maintenance

· 8History

· 9Society and culture

· 10See also

· 11References

Natural tooth shade

The perception of tooth color is the result of a complex interaction of factors such as: lighting conditions, translucency, opacity, light scattering, gloss, the human eye and brain.[1] Teeth are composed of a surface enamel layer, which is whiter and semitransparent, and an underlying dentin layer, which is darker and less transparent. These are calcified, hard tissues comparable to bone. The natural shade of teeth is best considered as such; an off-white, bone-color rather than pure white. Public opinion of what is normal tooth shade tends to be distorted. Portrayals of cosmetically enhanced teeth are common in the media. In one report, the most common tooth shade in the general population ranged from A1 to A3 on the VITA classical A1-D4 shade guide.[2]

Females generally have slightly whiter teeth than males, partly because females' teeth are smaller, and therefore there is less bulk of dentin, partially visible through the enamel layer. For the same reason, larger teeth such as the molars and the canine (cuspid) teeth tend to be darker. Baby teeth (deciduous teeth) are generally whiter than the adult teeth that follow, again due to differences in the ratio of enamel to dentin. As a person ages the adult teeth often become darker due to changes in the mineral structure of the tooth, as the enamel becomes less porous[citation needed] and phosphate-deficient. The enamel layer may also be gradually thinned or even perforated by the various forms of tooth wear.

Tooth staining and discoloration

Teeth may be darkened by a buildup of surface stains (extrinsic staining), which hides the natural tooth color; or the tooth itself may discolor (intrinsic staining).[3]

Extrinsic discolouration

Extrinsic stains can become internalised through enamel defects or cracks or as a result of dentine becoming exposed but most extrinsic stains appear to be deposited on or in the dental pellicle.[4] Causes of extrinsic staining include:

· Dental plaque: although usually virtually invisible on the tooth surface, plaque may become stained by chromogenic bacteria such as Actinomyces species.[5]

· Calculus: neglected plaque will eventually calcify, and lead to the formation of a hard deposit on the teeth, especially around the gumline. The color of calculus varies, and may be grey, yellow, black or brown[5]

· 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[5]

· Betel chewing.[6]

· Certain foods and drinks. food-goods and vegetables rich with carotenoids or xanthonoids.[citation needed] Ingesting colored liquids like sports drinks, cola, coffee, tea, and red wine can discolor teeth.[7]

· 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.[8]

· Metallic compounds. Exposure to such metallic compounds may be in the form of medication or other environmental exposure. examples include iron (black stain), iodine (black), copper (green), nickel (green), cadmium (yellow-brown).[3]

Intrinsic discolouration

Changes in the thickness of the dental hard tissues would result in intrinsic discolouration. There are a few causal factors that may act locally or systematically, affecting only a single tooth or all teeth and cause discolouration as a result. Several diseases that are known to affect the developing dentition especially during enamel and dentine formation can lead to discolouration.[9] Causes of intrinsic staining include:

· Dental caries (tooth decay)[6]

· Dental trauma[6] 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

· Hyperemia

· Fluorosis[3]

· Dentinogenesis imperfecta[3]

· Amelogenesis imperfecta[3]

· Tetracycline and minocycline. Tetracycline is a broad spectrum antibiotic,[10] and its derivative minocycline is common in the treatment of acne.[11] The drug is able to chelate calcium ions and is incorporated into teeth, cartilage and bone.[10] 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.[5][12]

· Porphyria[5]

· Hemolytic disease of the newborn[5]

· Root resorption[9]

· Alkaptonuria:[9] 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.[13]

Causes of extrinsic and intrinsic staining include:

· Age: the tooth enamel becomes thinner over time, which allows the dentine to shine through [14]

· Bruxism (clenching and grinding of the teeth) can lead to micro-cracking of the incisal edges of the teeth. Extrinsic stains may settle more readily into these cracks, and a thin layer of enamel can be left. This thin enamel layer is partially transparent, allowing the dark background of the mouth to shine through, affording a darker appearance of the incisal edge.


Whitening methods can usually be divided into two types. The first type includes methods that removes surface stains from teeth and includes toothpastes, air polishing and micro abrasion. The second type removes stains that have penetrated the enamel and therefore cannot be removed by the first type. The second type is referred to as "bleaching", typically using either hydrogen peroxide or carbamide peroxide which breaks down into hydrogen peroxide.

Bleaching solutions generally contain hydrogen peroxide or carbamide peroxide, which bleaches the enamel dentine junction to change its color.[15] The peroxide penetrates the porosities in the rod-like crystal structure of enamel and breaks down stain deposits in the dentin.


Before the treatment, the dentist may 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.

The whitening shade guides are used to measure tooth color. These shades determine the effectiveness of the whitening procedure, which may vary from two to seven shades.[16] 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; coffee, fizzy drinks, red-colored sauces 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.

The advantages of this technique are that the results happen at one sitting at the dentist, it does not take a longer time for results to show like it does when the home bleaching technique is used. This is good if fast, effective results are required.

However the disadvantages of this technique is that this is a one off treatment and if further whitening is needed the treatment will need to be carried out all over again. However, with at home bleaching, more bleaching gel can be purchased from the dentist and the same trays can be used, as long as they are intact and have no holes in them.

Light-accelerated bleaching

Power or light-accelerated bleaching, sometimes colloquially referred to as laser bleaching (a common misconception since lasers are an older technology that was used before current technologies were developed), 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.[17] 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.[18][19]

The ideal source of energy should be high energy to excite the peroxide molecules without overheating the pulp of the tooth.[20] 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.

In-office, the teeth are polished using pumice, the bleaching agent is added. The teeth are washed with a lot of water then polished again.

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.[21] 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 on non-vital teeth. 

Internal staining of dentine can discolor the teeth from inside out. Internal bleaching can remedy this on root canal treated teeth. Internal bleaching procedures are performed on devitalized teeth that have undergone endodontic treatment (root canal treatment) but are discolored due to internal staining of the tooth structure by blood and other fluids that leaked in. Unlike external bleaching, which brightens teeth from the outside in, internal bleaching brightens teeth from the inside out. Bleaching the tooth internally involves drilling a hole to the pulp chamber no more than 2mm below the gingival margin, cleaning any infected or discoloured dentine, sealing, and filling the root canal with gutta-percha points, cleaning the inside of the canal using etchant and placing a peroxide gel or sodium perborate tetrahydrate into the pulp chamber so they can work directly inside the tooth on the dentine layer.[citation needed] In this variation of whitening the whitening agent is sealed within the tooth over a period of some days and replaced as needed, the so-called "walking bleach" technique.[citation needed]. A seal should be placed over the root filling material to minimise microleakage. There is a small risk of external resorption.

An alternative to the walking bleach procedure is the inside-out bleach where the bleaching cavity is left open and the patient issued with a custom-formed tray to place and retain the agent, typically a carbamide peroxide gel inside the cavity. The patient changes the gel over 24 hours and uses a tray to retain it, they return to the dentist where this is sealed. On review once sufficient shade change has occurred the access cavity can be sealed, typically with a dental composite.

At home

At-home whitening methods include gels, chewing gums, rinses, toothpastes, paint-on films, and whitening strips.[22][23] Most over-the-counter methods utilize either carbamide peroxide or hydrogen peroxide.[23] Although there is some evidence that such products will whiten the teeth compared to placebo, the majority of the published scientific studies were short term and are subject to a high risk of bias as the research was sponsored or conducted by the manufacturers.[23] There is no long term evidence of the effectiveness or potential risks of such products.[23] Any demonstrable difference in the short term efficiency of such products seems to be related to concentration of the active ingredient.[23]

Night-guard vital bleaching

Night guard vital bleaching is another increasingly popular method of dentist prescribed at home teeth whitening. These methods have gained popularity due to the fact that significant results can be achieved overnight without the removal of any tooth tissue making it a conservative method of lightening tooth shade.The process of night guard vital bleaching involves alginate impressions of the patients’ teeth in the first visit, this is then casted into stone and a custom-made vacuum form tray is made. The patient is provided with bleaching solution, which is placed into the tray for use overnight. The number of nights the tray is used would be dependent on the extent of staining and the shade desired by the patient. Due to the recent spike in the use of home teeth whitening products there is a lack of research regarding long term implications such as side effects and duration of results. Research has found that ‘nightguard vital bleaching is a safe, effective, and predictable method to lighten teeth. The whitening effect lasted up to 47 months in 82% of the patients, with no adverse side effects reported at the end of the study’.[24]

Whitening toothpastes[

Whitening toothpastes are different to regular toothpastes in a way that they contain a higher content of abrasives and detergents to fight off tougher stains. Most contain low concentrations of carbamide/hydrogen peroxide rather than bleach – this lightens the colour of teeth. These whitening toothpastes make teeth one to two shades lighter.[25] Toothpastes (dentifrices) which are advertised as "whitening" rarely contain carbamide peroxide, hydrogen peroxide or any other bleaching agent.[26] Rather, they are abrasive (usually containing alumina, dicalcium phosphate dehydrate, calcium carbonate or silica), intended to remove surface stains from the tooth surface.[26] Sometimes they contain enzymes purported to break down the biofilm on teeth.[26] Unlike bleaches, whitening toothpaste does not alter the intrinsic color of teeth. Excessive or long term use of abrasive toothpastes will cause dental abrasion, thinning the enamel layer[26] and slowly darkening the appearance of the tooth as the dentine layer becomes more noticeable. An alternative method of whitening at home, which competes with the use of a whitening paste, is the use of a patent whitening mouthwash. The mouthwash shows marginally better efforts at whitening compared to the use of paste.[27]

Over-the-counter (OTC) Whitening Strips and Gels

Whitening strips work by the placement of a layer of peroxide gel on the labial surfaces of teeth through the use of plastic strips that are shaped to fit there. Many different types of whitening strips are available on the market, after being introduced in the late 1980s.[28]Each variety of whitening strips has its own set of instructions to suit the product, for example, different strips can be used at different frequencies to reach the same whitening end point.

Whitening gels are also peroxide based, like the strips, and applied straight onto the tooth surfaces via the use of a small brush. Following manufacturer’s instructions they can lighten teeth by 1-2 shades.[28]

Whitening Rinses

Another method used by people at home to whiten teeth is the use of whitening rinses - these contain oxygen sources, like hydrogen peroxide. To see a 1 -2 improvement in tooth shade could take up to 3 months.[28]

Natural (alternative) methods

One purported method of naturally whitening the teeth is through the use of malic acid.[29][unreliable medical source?][30][unreliable medical source?] The juice of apples, especially green apples, contains malic acid. On the other hand, excessive consumption of acidic beverages will slowly dissolve the enamel layer, making the underlying yellower dentine show through more noticeably, leading to darkening of the tooth's appearance. One study indicates that malic acid is a weak tooth whitening agent.[31]