Tooth bleaching
Encyclopedia
Dental bleaching, also known as tooth whitening, is a common procedure in general dentistry
Dentistry
Dentistry is the branch of medicine that is involved in the study, diagnosis, prevention, and treatment of diseases, disorders and conditions of the oral cavity, maxillofacial area and the adjacent and associated structures and their impact on the human body. Dentistry is widely considered...

 but most especially in the field of cosmetic dentistry
Cosmetic dentistry
Cosmetic dentistry is generally used to refer to any dental work that improves the appearance of a person's teeth, gums and/or bite. Many dentists refer to themselves as "cosmetic dentists" regardless of their specific education, specialty, training, and experience in this field...

. A child's deciduous teeth
Deciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...

 are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker due to changes in the mineral structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...

 of the tooth, as the enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 becomes less porous. Teeth can also become stained by bacterial pigments, foodstuffs and tobacco. Certain antibiotic medications (like tetracycline) can also cause teeth stains or a reduction in the brilliance of the enamel.

According to the FDA, whitening restores natural tooth color and bleaching whitens beyond the natural color. There are many methods to whiten teeth, such as brushing, bleaching strips, bleaching pen, bleaching gel, laser bleaching, and natural bleaching. Traditionally, at-home whiteners use overnight trays containing a carbamide peroxide
Carbamide peroxide
Carbamide peroxide, also called urea peroxide, urea hydrogen peroxide , and percarbamide, an adduct of hydrogen peroxide and urea. Like hydrogen peroxide, it is an oxidizer. This compound is a white crystalline solid which dissolves in water to give free hydrogen peroxide; the solubility of...

 gel which reacts with water to form hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

. Carbamide peroxide has about a third of the strength of hydrogen peroxide. This means that a 15 percent solution of carbamide peroxide is the rough equivalent of a five percent solution of hydrogen peroxide.
Over the counter kits whiten with small strips that go over the front teeth. The peroxide oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...

 penetrates the porosities in the rod-like crystal structure of enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 and bleaches stain deposits in the dentin
Dentin
Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

. Power bleaching uses light energy to accelerate the process of bleaching in a dental office. The effects of bleaching can last for several months, but may vary depending on the lifestyle of the patient. Factors that decrease whitening include smoking and the ingestion of dark colored liquids like coffee, tea and red wine. Dentures
Dentures
Dentures are prosthetic devices constructed to replace missing teeth, and which are supported by surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable, however there are many different denture designs, some which rely on bonding or clasping onto teeth or dental...

 can also be whitened using denture cleaner
Denture cleaner
Denture Cleaner, also known as denture cleanser, is a cleaner used to assist in denture cleaning. Chemical denture cleaners can come in cream, liquid, powder or tablet format. Some chemical denture cleaners are effervescent and others are not...

s.

Internal staining of dentin can discolor the teeth from inside out. Internal bleaching can remedy this. If heavy staining or tetracycline damage is present on a patient's teeth, and whitening is ineffective, there are other methods of whitening teeth. Bonding, when a thin coating of composite material is applied to the front of a person's teeth and then cured with a blue light can be performed to mask the staining. A veneer
Veneer (dentistry)
In dentistry, a veneer is a thin layer of restorative material placed over a tooth surface, either to improve the aesthetics of a tooth, or to protect a damaged tooth surface. There are two main types of material used to fabricate a veneer, composite and dental porcelain...

 can also mask tooth discoloration.

Methods

According to the American Dental Association there are different options to whiten one's teeth that include: in-office bleaching, which is applied by a professional dentist; at-home bleaching, which is to be used at home by the patient; over-the-counter, which is applied by patients; and options called non-dental, which are offered at mall kiosks, spa
Spa
The term spa is associated with water treatment which is also known as balneotherapy. Spa towns or spa resorts typically offer various health treatments. The belief in the curative powers of mineral waters goes back to prehistoric times. Such practices have been popular worldwide, but are...

s, salons, or other similar places). Whitening products intended for home use include gels, chewing gum
Chewing gum
Chewing gum is a type of gum traditionally made of chicle, a natural latex product, or synthetic rubber known as polyisobutylene. For economical and quality reasons, many modern chewing gums use rubber instead of chicle...

s, rinses, toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

s, among others. The ADA has published a list of accepted over-the-counter whitening products to help people choose appropriate whitening products.

The ADA recommends to have one's teeth checked by a dentist before undergoing any whitening method. The dentist should examine the patient thoroughly: take a health and dental history (including allergies
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...

 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.

There are two main methods of gel bleaching—one performed with high-concentration gel, and another with low-concentration agents. High-concentration bleaching can be accomplished either in the dental office, or at home. Performing the procedure at home is accomplished using high-concentration carbamide peroxide, which is readily available online or in dental stores and is much more cost-effective than the in-office procedure. Whitening is performed by applying a high concentration of oxidizing agent to the teeth with thin plastic trays for a short period of time, which produces quick results. The application trays ideally should be well-fitted to retain the bleaching gel, ensuring even and full tooth exposure to the gel. Trays will typically stay on the teeth for about 15–20 minutes. Trays are then removed and the procedure is repeated up to two more times. Most in-office bleaching procedures 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 tissue
Soft tissue
In anatomy, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body, not being bone. Soft tissue includes tendons, ligaments, fascia, skin, fibrous tissues, fat, and synovial membranes , and muscles, nerves and blood vessels .It is sometimes...

s. The bleaching agent is either carbamide peroxide
Carbamide peroxide
Carbamide peroxide, also called urea peroxide, urea hydrogen peroxide , and percarbamide, an adduct of hydrogen peroxide and urea. Like hydrogen peroxide, it is an oxidizer. This compound is a white crystalline solid which dissolves in water to give free hydrogen peroxide; the solubility of...

, which breaks down in the mouth to form hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

, 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.

Low-concentration whitening is far less effective, and is generally only performed at home. Low-concentration whitening involves purchasing a thin mouthguard or strip that holds a relatively low concentration of oxidizing agent next to the teeth for as long as several hours a day for a period of 5 to 14 days. Results can vary, depending on which application is chosen, with some people achieving whiter teeth in a few days, and others seeing very little results or no results at all. Dentists as well as some dental laboratories can fabricate custom fitted whitening trays that will greatly improve the results achieved with an over-the-counter whitening method.

A typical course of bleaching can produce dramatic improvements in the cosmetic appearance of most stained teeth; however, some stains do not respond to bleaching. Tetracycline staining may require prolonged bleaching, as it takes longer for the bleach to reach the dentine layer. Case studies have been performed on people with tetracycline stained teeth. They used custom bleaching trays every night for 6 months and saw dramatic results and improvement. White-spot decalcifications may also be highlighted and become more noticeable directly following a whiting process, but usually calm back down with the other parts of the teeth becoming more white. The white spots become less noticeable, with the other parts of the teeth becoming more white. Bleaching is not recommended if teeth have decay or infected gums. It is also least effective when the original tooth color is grayish and may require custom bleaching trays. Bleaching is most effective with yellow discolored teeth. However, 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
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...

 veneers or dental bonding.

Although there is a wide range of whitening products and techniques available, the results after using them may vary from very positive results to almost non-existent results.

The whitening shade guides are used to measure tooth color with Vitapan Classic Shade Guide being the most widely used with 16 shades. These shades determine the effectiveness of the whitening procedure, which may vary from two to seven shades.

Treatment times and recommendations are dependent on the condition of a person’s teeth at time of treatment.
It should be noted that the use in cosmetic dentistry of concentrations above 0.1% of hydrogen peroxide are illegal in the UK, but almost all teeth whitening methods use many times this concentration. Dentists as well as whitening clinics in the UK ignore this law and so far this law has not been enforced.

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 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. Clinical trials have demonstrated that among these three options, halogen light is the best source for producing optimal treatment results. The ideal source of energy should be high energy to excite the peroxide molecules without overheating the pulp of the tooth. 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 a less time-intensive patient preparation procedure. Most power teeth whitening treatments can be done in approximately 30 minutes to one hour, in a single visit to a dental physician.

Criticism

Over many years Clinical Research Associates (CRA) have studied the effect of light and heat on bleaching. The latest of their studies was published in the most recent CRA Newsletter (March 2003), in which they reported on the characteristics of several in-office bleaching systems using light. The following quote includes part of the CRA conclusions from that newsletter: "Use of lights according to the manufacturer's directions did not improve whitening for any system tested." Systems tested in the CRA study were: LaserSmile, LumaArch, Niveous, Opalescence Xtra Boost, PolaOffice, Rembrandt 1 Hour Smile-Whitening Program, and Zoom. Tests on BriteSmile have not yet been completed. In these studies, light use did not speed or increase the bleaching over the use of bleaching chemicals alone; The slight difference in tooth color observed as a result of bleaching with lights and hydrogen peroxide versus bleaching with hydrogen peroxide alone appears to be temporary and caused by the light’s dehydration and heating of the teeth. The light might increase the whitening capability a few percentage points but it really isn't even enough to notice. After a few days to weeks, there appears to be no significant shade difference between teeth bleached with lights and those bleached without lights.
Although research varies as to the effectiveness of bleaching using lights, many of the lights used for in-office bleaching appear to be primarily a psychological factor for the patient.

Study shows that UV light tooth bleaching is dangerous to eyes and skin.

Risks

Side effects
Adverse effect (medicine)
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...

 of teeth bleaching include, but are not limited to:
  • Chemical burns from gel bleaching (if a high-concentration oxidizing agent contacts unprotected tissues, which may bleach or discolor mucous membrane
    Mucous membrane
    The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...

    s), sensitive teeth
  • Overbleaching (known in the profession as "bleached effect", particularly with the intensive treatments (products that provide a large change in tooth colour over a very short treatment period, e.g., 1 hour)
  • Pain if you have "sensitive teeth" caused by open dentinal tubules.
  • Risk of increased hot/cold sensitivity.
  • Increased risk of tongue cancer.


A recent study by Kugel et al. showed that 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. Rebound is experienced when a large proportion of the tooth whitening has come from tooth dehydration (also a significant factor in causing sensitivity). As the tooth rehydrates, tooth color 'rebounds' back toward where it started.

Home tooth bleaching treatments can very slightly reduce tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

. There have been long term Tetracycline studies done where patients received high concentration bleach, over night, for 6 months. These studies show that even over long term exposure, the amount of reduction in tooth enamel is insignificant.

The side effects that occur most often are a temporary increase in tooth sensitivity and mild irritation of the soft tissues of the mouth, particularly the gums. Tooth sensitivity often occurs during early stages of the bleaching treatment. Tissue irritation most commonly results from an ill-fitting mouthpiece tray rather than the tooth-bleaching agent. Both of these conditions usually are temporary and disappear within 1 to 3 days of stopping or completing treatment.

Individuals with sensitive teeth and gums, receding gums
Receding gums
Receding gums refers to exposure in the roots of the teeth caused by a loss of gum tissue and/or retraction of the gingival margin from the crown of the teeth. Gum recession is a common problem in adults over the age of 40, but it may also occur starting from the teens...

 and/or defective restorations should consult with their dentist
Dentist
A dentist, also known as a 'dental surgeon', is a doctor that specializes in the diagnosis, prevention, and treatment of diseases and conditions of the oral cavity. The dentist's supporting team aides in providing oral health services...

 prior to using a tooth whitening system. People who are sensitive to hydrogen peroxide (the whitening agent) should not try a bleaching product without first consulting a dentist. Also, prolonged exposure to bleaching agents may damage tooth enamel. This is especially the case with home remedy whitening products that contain fruit acids.

Bleaching is not recommended in 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. Tooth whitening is also not recommended in pregnant or lactating women.

Tooth whitening does not usually change the color of fillings
Dental fillings
This page is about types of dental restorative materials. For dental fillings see dental restorationsDental restorative materials are specially fabricated materials, designed for use as dental restorations , which are used to restore tooth structure loss, usually resulting from but not limited to...

 and other restorative materials. It does not affect porcelain
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...

, other ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

s, or dental gold. However, it can slightly affect restorations made with composite materials, cements and dental amalgams
Amalgam (dentistry)
Amalgam is an alloy containing mercury. The term is commonly used for the amalgam employed as material for dental fillings, which consists of mercury , silver , tin , copper , and other trace metals...

. Tooth whitening can restore color of fillings
Dental fillings
This page is about types of dental restorative materials. For dental fillings see dental restorationsDental restorative materials are specially fabricated materials, designed for use as dental restorations , which are used to restore tooth structure loss, usually resulting from but not limited to...

, porcelain
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...

, and other ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

s when they become stained by foods, drinks, and smoking, among other activities.

Although some over-the-counter bleaching products contain carbamide peroxide, most of them are H2O2 based, which has the potential to interact with DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

. Although there is concern with H2O2 carcinogenicity, there is insufficient research to support a conclusion. What the studies have been able to show is that H2O2 is both an irritant and cytotoxic
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...

. Clinical studies have found a higher occurrence of gingival irritation when patients use bleaching materials with higher peroxide concentrations.

Internal bleaching

Internal bleaching procedures are performed on devitalized teeth that have undergone endodontic therapy
Endodontic therapy
Endodontic therapy is a sequence of treatment for the pulp of a tooth which results in the elimination of infection and protection of the decontaminated tooth from future microbial invasion...

 (a.k.a. "Root Canal") 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, cleaning, sealing, and filling the root canal with a rubber-like substance, and placing a peroxide gel into the pulp chamber so the gel can work directly inside the tooth on the dentin layer. In this variation of whitening the peroxide is sealed within the tooth over a period of some days and replaced as needed, the so called "walking bleach" technique.

Agents

Various chemical and physical agents can be used to whiten teeth. Toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

 typically has small particles of silica, aluminum oxide, calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

, or calcium phosphate
Calcium phosphate
Calcium phosphate is the name given to a family of minerals containing calcium ions together with orthophosphates , metaphosphates or pyrophosphates and occasionally hydrogen or hydroxide ions ....

 to grind off stains formed by colored molecules that have adsorbed onto the teeth from food. Unlike bleaches, whitening toothpaste does not alter the intrinsic color of teeth.

Bleaching solutions contain peroxide
Peroxide
A peroxide is a compound containing an oxygen–oxygen single bond or the peroxide anion .The O−O group is called the peroxide group or peroxo group. In contrast to oxide ions, the oxygen atoms in the peroxide ion have an oxidation state of −1.The simplest stable peroxide is hydrogen peroxide...

, which bleaches the tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

 to change its color. Off-the-shelf products typically rely on a carbamide peroxide
Carbamide peroxide
Carbamide peroxide, also called urea peroxide, urea hydrogen peroxide , and percarbamide, an adduct of hydrogen peroxide and urea. Like hydrogen peroxide, it is an oxidizer. This compound is a white crystalline solid which dissolves in water to give free hydrogen peroxide; the solubility of...

 solution varying in concentration from 10% to 44%. Bleaching solutions may be applied directly to the teeth, embedded in a plastic strip that is placed on the teeth or use a gel held in place by a mouthguard
Mouthguard
A mouthguard is a protective device for the mouth that covers the teeth and gums to prevent and reduce injury to the teeth, arches, lips and gums...

.

The US FDA
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

only approves gels that are under 6% hydrogen peroxide or 16% or under of carbamide peroxide. The Scientific Committee for Consumer Protection of the EU also consider gels containing higher concentrations than mentioned above to be unsafe.
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