Background: By this point in the 21st century, the treatment of tooth discoloration has evolved into an annual multibillion-dollar, highly sophisticated, scientific, and clinical discipline. However, the origins of the treatment date back thousands of years to ancient clinicians and beauticians who used rudimentary, yet innovative, natural materials to mask undesirable tooth discolorations. Function The oral cavity plays 3 important roles in the protection and preservation of systemic health; it is involved in nutritional intake, communication, and host defense. The teeth are involved in all 3 roles, and dental diseases can be a source of multiple problems, including oral and systemic infections and difficulty in chewing, swallowing, or phonation. Anatomy Cursory familiarity with basic dental anatomy and calcification and with the eruption sequence of teeth is helpful before physical examination. A tooth is composed of a crown (ie, the portion exposed to the oral cavity) and 1 or more roots (ie, the portion enveloped in bone and the periodontium)The crown of each tooth has 5 surfaces: buccal (facing the cheek or lip), lingual (facing the tongue), mesial (between the teeth), distal (between the teeth), and chewing (occlusal for molars and premolars, incisal for incisors and canines). In the transverse section, the tooth has 3 distinct layers. These include a surface enamel layer covering only the crown; an inner layer of dentin in both the crown and root; and the core area known as the pulp, which contains nerves, arteries, and veins Radiographically, the layers are easily identifiable because they have different radiopacities. Enamel is the most mineralized of the calcified tissues of the body, and it is the most radiopaque of the 3 tooth layers. Dentin is less radiopaque than enamel and has a radiopacity similar to that of bone. The pulp tissue is not mineralized and appears radiolucent. Primary (ie, deciduous) teeth number 20, and secondary (ie, adult) teeth number 32. A phase of mixed dentition exists, depending on the age of the patient (typically, 6-14 y). This phase is associated with simultaneous exfoliation or the eruption of primary and secondary teeth (see Tables 1-2).

Table 1. Calcification and Eruption Sequence of Primary Dentition

Calcification begins (months)30-360-124-278-214-510-12	3-4
Eruption (years)12-135-610-1210-1111-128-9	7-8
Maxillary teeth	2nd Molar 1st Molar 2nd Premolar 1st Premolar Canine Lateral incisor	Central incisor
Mandibular teeth
Calcification begins (months) 30-360-127-3021-244-53-4	3-4
Eruption (years) 12-135-611-1210-129-107-8	6-7

Table 2. Calcification and Eruption Sequence of Secondary Dentition

Primary Teeth Calcification Begins (Weeks In Utero) Enamel Completed (Months After Birth)	Eruption (Months)
Maxilla
Central incisor13-161.5	8-12
Lateral incisor14.5-16.52.5	9-13
Canine15-189	16-22
1st Molar14.5-176	13-19
2nd Molar16-23.511	25-33
Mandible
Central incisor13-162.5	6-10
Lateral incisor14.5-16.53	10-16
Canine16-189	17-23
1st Molar14.5-175.5	14-18
2nd Molar17-19.510	23-31

Pathophysiology:
Tooth discoloration is caused by multiple local and systemic conditions (Vogel, 1975) Extrinsic dental stains are caused by predisposing factors and other factors such as dental plaque and calculus, foods and beverages, tobacco, chromogenic bacteria, and metallic compounds, and topical medications. Intrinsic dental stains are caused by dental materials (eg, tooth restorations), dental conditions and caries, trauma, infections, medications, nutritional deficiencies and other disorders (eg, complications of pregnancy, anemia and bleeding disorders, bile duct problems), and genetic defects and hereditary diseases (eg, those affecting enamel and dentin development or maturation).

Causes of extrinsic discoloration

Extrinsic stains are defined as stains located on the outer surface of the tooth structure and caused by topical or extrinsic agents. The Nathoo classification system of extrinsic dental stain describes 3 categories as follows (Nathoo, 1997):

• Nathoo type 1 (N1): N1-type colored material (chromogen) binds to the tooth surface. The color of the chromogen is similar to that of dental stains caused by tea, coffee, wine, chromogenic bacteria, and metals.
  Nathoo type 2 (N2): N2-type colored material changes color after binding to the tooth. The stains actually are N1-type food stains that darken with time.

• Nathoo type 3 (N3): N3-type colorless material or prechromogen binds to the tooth and undergoes a chemical reaction to cause a stain. N3-type stains are caused by carbohydrate-rich foods (eg, apples, potatoes), stannous fluoride, and chlorhexidine.

Predisposing factors:
Certain factors predispose children and adults to extrinsic stains, including enamel defects, salivary dysfunction, and poor oral hygiene (Hattab, 1999). Microscopic pits, fissures, and defects in the outer surface of the enamel are susceptible to the accumulation of stain-producing food, beverages, tobacco, and other topical agents. Because saliva plays a major role in the physical removal of food debris and dental plaque from the outer and interproximal tooth surfaces, diminished salivary output contributes to extrinsic discoloration. Decreased output may be caused by local disease (eg, salivary obstructions and infections), systemic disease (eg, Sjögren syndrome), head and neck radiation therapy for cancer, chemotherapy, and multiple medications (eg, anticholinergics, antihypertensives, antipsychotics, antihistamines). The most common cause of extrinsic stains is poor oral hygiene (Hattab, 1999). The inability to remove stain-producing materials and/or the use of dentifrices with inadequate cleaning and polishing actions cause discolorations. Other factors Accumulations of dental plaque, calculus and food particles cause brown or black stains

Deposition of tannins found in tea, coffee, and other beverages cause brown stains on the outer (buccal, labial) and inner (lingual, palatal) surfaces of the teeth. Tobacco stains from cigarettes, cigars, pipes, and chewing tobacco cause tenacious dark brown and black stains that cover the cervical one third to one half of the tooth (midway on the tooth toward the gingival margin)

Pan (a combination of betel nut of the areca palm, betel leaf, and lime) is commonly chewed by more than 200 million persons in the western Pacific basin and South Asian region (Norton, 1998). It is used for its mild psychoactive and cholinergic effects, and it elicits a copious production of blood red saliva that results in a red-black stain on the teeth, gingiva, and oral mucosal surfaces.

Chromogenic bacteria cause stains, typically at the gingival margin of the tooth. The most common is a black stain caused by Actinomyces species. The stain is composed of ferric sulfide and is formed by the reaction between hydrogen sulfide produced by bacterial action and iron in the saliva and gingival exudates (Reid, 1977). Green stains are attributed to fluorescent bacteria and fungi such as Penicillium and Aspergillus species (Hattab, 1999). The organisms grow only in light and therefore cause staining on the maxillary surface of the anterior teeth. Orange stain is less common than green or brown stains and is caused by chromogenic bacteria such as Serratia marcescens and Flavobacterium lutescens.

Metallic compounds are also implicated in dental discolorations because of the interaction of the metals with dental plaque to produce surface stains (Hattab, 1999). Industrial exposure to iron, manganese, and silver may stain the teeth black. Mercury and lead dust can cause a blue-green stain; copper and nickel, green-to-blue-green stain; chromic acid fumes, deep orange stain; and iodine solution, brown stain. Topical medications cause staining. Chlorhexidine rinse (0.12%) causes brown staining after several weeks of use, particularly on acrylic and porcelain restorations. Cetylpyridinium chloride is an ingredient in several mouthwashes (eg, Cepacol, Scope) that can cause dental staining (Eriksen, 1979). Iron-containing oral solutions used for treatment of iron deficiency anemia cause black stains. Potassium permanganate mouthwash (violet-black stain), silver nitrate (black stain), and stannous fluoride (brown stain) also can induce dental discolorations (Hattab, 1999).

Causes of intrinsic discoloration
Numerous causes for intrinsic tooth discoloration exist. Stain distribution varies from localized (eg, 1 or 2 teeth) to a regional or generalized involvement of primary and secondary teeth. Localized discoloration may be a result of either preeruptive or posteruptive processes, whereas widespread involvement indicates a deviation in normal tooth formation. An understanding of the timing of tooth formation (particularly calcification and eruption sequences) can help explain the causes of intrinsic discoloration. Dental materials Dental restorations most commonly cause intrinsic discoloration. Amalgam restorations can generate corrosion products (eg, silver sulfide), leaving a gray-black color in the tooth, especially in large cavity preparations with undermined enamel. Pins, composites, and glass ionomer and acrylic restorations gradually can leave a gray hue in the tooth adjacent to the material. Other dental materials that cause intrinsic discoloration include eugenol, formocresol, root canal sealers, and polyantimicrobial pastes (Hattab, 1999). Dental conditions and caries Regarding attrition, abrasion, and erosion of tooth structure, as permanent teeth age, the dentition progressively becomes more gray and yellow. In the absence of extrinsic staining, this age-related phenomenon is due to a progressive loss in enamel from attrition or tooth wear that reveals the natural yellow color of underlying dentin.

Areas of complete enamel loss are most commonly found on the incisal (chewing) surfaces of anterior teeth. This loss frequently occurs in older adults, whose teeth show a contrast in colors between enamel and dentin. Tooth abrasion manifests as yellow areas in which the enamel surface is lost (eg, buccal cervical regions) as a result of overzealous toothbrushing with a hard-bristled or medium-bristled toothbrush.

The erosion of enamel caused by frequent ingestion of acidic foods and beverages and from the regurgitation of acid from the stomach (eg, anorexia or bulimia nervosa) can lead to a yellow tooth discoloration. In patients with anorexia or bulimia, a yellow discoloration develops on lingual tooth surfaces where the acid reflux material makes contact with the teeth. Certain tooth surfaces are at greater risk for dental caries. These surfaces include the occlusal grooves and pits of posterior teeth (class I caries), the smooth surfaces between teeth (class II caries for posterior teeth, class III caries for anterior teeth), and the smooth surfaces at the enamel-cementum interface at the free gingival margin (cervical, root surface, or class V caries; Caries also may involve the incisal edge of anterior teeth (class IV or VI). The pathogenesis of dental caries begins with an incipient lesion confined to the enamel layer. Once the enamel layer is breached, caries tends to rapidly progress in the dentin, undermining the superficial enamel layer. Incipient carious lesions are associated with plaque accumulation and manifest as chalky white areas of discoloration secondary to hypocalcification. Patients with orthodontic brackets are at great risk for caries because of suboptimal plaque removal. As caries progresses into the dentin, the overlying translucent enamel reveals the color of the underlying caries and appears yellowish brown. Extensive caries that involve destruction of both enamel and dentin produce a color that ranges from light brown, to dark brown or almost black

The brown color is attributed to the formation of Maillard pigments (reaction between proteins and small aldehydes produced by cariogenic bacteria), melanins, lipofuscins, and uptake of various food colors and bacterial pigments (Kleter, 1998). In some patients, caries self-arrest, and remineralization may occur; however, the brown discolorations usually remain. Trauma Trauma to developing, yet unerupted, teeth can disturb enamel formation (amelogenesis) and may result in enamel hypoplasia, which is visualized as a localized opacity on the erupted tooth. Such teeth commonly are referred to as Turner teeth . Unerupted permanent incisors commonly are affected after intrusion injuries to primary incisors in young children who fall on their faces. Trauma that occurs to erupted teeth also causes discoloration This discoloration frequently occurs in teeth that have fully formed roots and have sustained irreversible pulpal injury caused by avulsions, intrusions, luxations and subluxations, or fractures involving the pulp chamber. Trauma can cause intrapulpal hemorrhage and iron sulfide deposition along the dentinal tubules, producing a bluish black cast. Some occlusal trauma occurs over a protracted period of time (eg, excessive orthodontic forces). Rarely, this trauma leads to pulpal hemorrhage; however, it can produce a subtle grayish brown cast. Infections Periapical odontogenic infections of the primary teeth can disrupt normal amelogenesis of the underlying secondary (permanent) successors and involve a potential for localized enamel hypoplasia. Crown formation begins in utero; therefore, the potential for extensive intrinsic discoloration of the primary dentition may be present throughout pregnancy. Although rare, maternal rubella or cytomegalovirus infection and toxemia of pregnancy can lead to tooth discoloration, which generally manifests as a focal opaque band of enamel hypoplasia that is confined to the primary teeth forming enamel at the time of maternal infection.

Crown formation of the secondary dentition occurs until the child is aged approximately 8 years. Systemic postnatal infections (eg, measles, chicken pox, streptococcal infections, scarlet fever) can also cause enamel hypoplasia. The bandlike discolorations on the tooth are visualized where the enamel layer has variable thickness and becomes extrinsically stained after tooth eruption. Medications Since the 1950s, drugs from the tetracycline family have been associated with intrinsic tooth discoloration. Once in the bloodstream, tetracycline can be incorporated into the calcification process of developing teeth, in which it affects either primary or secondary dentition after maternal or childhood ingestion, respectively. Tetracyclines diffuse through dentin to the enamel interface, chelating calcium ions and incorporating into hydroxyapatite as a stable orthophosphate complex. The amount of drug incorporation is ultimately determined by the distribution of tooth discoloration and is equivalent to serum blood levels and the duration of exposure. When the affected teeth first erupt, they have a bright-yellow bandlike appearance that fluoresces under ultraviolet light, although upon exposure to sunlight, the color gradually changes to gray or red-brown (van der Bijl P, 1995) . Tetracycline use does not lead to discoloration once tooth formation is complete. Minocycline is a second-generation derivative of tetracycline. The ingestion of minocycline can lead to a green-gray or blue-gray intrinsic staining of teeth. Unlike with other tetracyclines, staining occurs during and after the complete formation and eruption of teeth (Patel, 1998). Minocycline is a poor chelator of calcium ions, but it is believed to bind to iron ions. This binding causes the formation of insoluble salts that are either exuded from gingival crevicular fluid to extrinsically stain the enamel or intrinsically incorporated into the secondary dentin (McKenna, 1999). Minocycline is prescribed for long-term acne therapy in adolescents and adults, although it is being replaced by medications such as clindamycin and isotretinoin that do not cause tooth discoloration.

Dental fluorosis is characterized by enamel discoloration resulting from subsurface hypomineralization due to the excessive ingestion of fluoride during the early maturation stage of enamel formation (DenBesten, 1999). Fluorosis affects primary and secondary dentitions with a broad range of clinical findings. In its mildest form, fluorosis appears as faint white lines or streaks on the enamel. Moderate fluorosis has more obvious opaque regions referred to as enamel mottling, whereas severe fluorosis appears with extensive mottling that readily chips and stains and leads to pitting and brown discoloration. An increase in the prevalence of mild-to-moderate fluorosis has been observed in the United States over the last decade, even in areas with nonfluoridated public water supplies (Pendrys, 2000). The trend is explained by early overuse and ingestion of fluoridated toothpaste; the inappropriate use of fluoride supplements; and in fluoridated areas, the use of powdered infant formula mixed with local water. Clinicians can help in preventing fluorosis by teaching parents about fluoride use and good toothbrushing habits for children. Fluoride sources are numerous and include naturally or artificially fluoridated drinking water, commercially available beverages, foods prepared in fluoridated water, chewable vitamins, oral healthcare products (eg, toothpastes, mouthrinses, oral fluoride supplements), and professional fluoride products prescribed by dentists. The fluoride concentration of naturally fluoridated water varies depending on geographic location. For example, in some areas of Africa, the concentration may be as high as 10 parts per million (ppm), whereas many other regions have a concentration of 0 ppm. Artificially fluoridated water supplies usually have a fluoride concentration of 1 ppm (Warren, 1999). Similar to tetracycline exposure, the dose and duration of fluoride exposure in developing teeth is correlated with the extent and severity of the clinical findings. Several clinical indices have been developed to measure fluorosis (Rozier, 1994). Nutritional deficiencies and other disorders Regarding nutritional deficiencies, vitamins C and D, calcium, and phosphate are required for healthy tooth formation. Deficiencies can result in dose-related or exposure-related enamel hypoplasia. Diseases that can cause hyperbilirubinemia and intrinsic tooth discoloration include sickle cell anemia; thalassemia; hemolytic disease of the newborn (HDN) due to either Rhesus factor, ABO, or other erythrocyte antigen incompatibility; biliary atresia; and other rare pediatric diseases. These diseases have the potential to cause hyperbilirubinemia and the subsequent dose-dependent incorporation of biliverdin (a by-product pigment of bilirubin) into developing teeth, producing a jaundicelike yellow-green tint on the tooth surfaces (Cullen, 1990). Intrinsic tooth discoloration is reported in patients with blood dyscrasias such as sickle cell anemia, thalassemia, and HDN. These diseases have the potential to cause hemolysis and the subsequent dose-dependent incorporation of biliverdin (by-product pigment of bilirubin) into developing teeth, producing a jaundicelike yellow-green tint on the tooth surfaces (Cullen, 1990). Genetic defects and hereditary diseases Genetic defects in enamel or dentin formation include amelogenesis imperfecta (AI), dentinogenesis imperfecta (DI), and dentinal dysplasia (DD). These are hereditary diseases with a propensity for intrinsic tooth discoloration. AI affects both primary and secondary dentitions and demonstrates numerous clinical manifestations that are classified into 4 types (Neville, 1995). Type 1 AI involves hypoplastic dentition. Hypoplastic teeth with rough or pitted enamel surfaces are at a greater risk for extrinsic staining . The teeth typically have an abnormally thin enamel layer that reveals the yellow color of dentin beneath the enamel. Type 2 AI involves hypomaturation. Teeth with hypomaturation have soft enamel with a mottled opaque white, yellow, or brown discoloration. Type 3 AI involves hypocalcification. The enamel in the hypocalcified type is yellow to orange, soft, and lost soon after eruption. Therefore, hypocalcified teeth develop dark stains and are at high risk for dental caries. Type 4 AI involves hypomaturation or hypoplastic dentition with taurodontism. DI occurs in 2 types. One type is associated with osteogenesis imperfecta, and the other type affects the teeth alone. The primary and secondary teeth are affected, and they have a brown or blue appearance with a distinctive translucent quality. The enamel chips off easily, and the teeth are prone to occlusal wear and caries. DD occurs in 2 types. Teeth with type 2 DD have a blue, amber, or brown translucence. Teeth with type 1 DD have crowns with normal morphology and coloration. Other hereditary diseases include erythropoietic (congenital) porphyria and epidermolysis bullosa (EB). Erythropoietic porphyria is a rare disease of porphyrin metabolism. The abnormally high levels of reddish brown or burgundy-red porphyrin pigments have an affinity for calcium phosphate and are incorporated into teeth during dental formation. The entire primary and secondary dentitions are pink, although case reports also describe the color as reddish brown or purple (Trodahl, 1972). Teeth fluoresce red under ultraviolet light. Patients with EB may have enamel hypoplasia and pitting, which produce a yellowish tint. Patients are at risk for caries.

Frequency:

• In the US: No United States epidemiologic data are available.

  An increase in the prevalence of mild-to-moderate fluorosis has been observed in the United States over the last decade, even in areas with nonfluoridated public water supplies (Pendrys, 2000). The trend is explained by early overuse and ingestion of fluoridated toothpaste; the inappropriate use of fluoride supplements; and in fluoridated areas, the use of powdered infant formula mixed with local water.

• Internationally: No international epidemiologic data are available.

Mortality/Morbidity:

• If tooth discoloration is not treated, it can affect the appearance of a person's smile and craniofacial complex, causing temporary, as well as permanent, social and psychological sequelae.
• Smiling is the end result of a complex neurologic, muscular, sensory, and psychological process. Because a smile is universally understood, an unattractive smile, due in part to discolored teeth, can have negative psychological, social, and clinical implications.

Race: No racial predilection exists for tooth discoloration. The fluoride concentration of naturally fluoridated water varies depending on geographic location. For example, in some areas of Africa, the concentration may be as high as 10 parts per million (ppm), whereas many other regions have a concentration of 0 ppm. Artificially fluoridated water supplies usually have a fluoride concentration of 1 ppm (Warren, 1999). Sex: No sex predilection exists for tooth discoloration. Age:

• Teeth generally become more yellow and gray with increasing age.

• Depending on the etiology , persons of different ages are susceptible to various types of internally induced and externally induced tooth discolorations.

History: The patient's history of tooth discoloration provides useful information regarding the etiology.

• Chief complaint and history of chief complaint
• In most patients, the chief complaint is related to aesthetics. The complaint is a result of mild-to-severe discoloration of any or all portions of the teeth, typically the anterior teeth. Stains associated with foods (eg, blueberries), beverages (eg, tea, coffee), tobacco products, medications (eg, tetracycline), and other causes (eg, anemia) most likely are painless; however, the patient complains of aesthetically unpleasant effects on the teeth and smile.
• Some patients may present initially with pain. Pain and discoloration can be a result of dental caries, deep dental restorations, severe developmental or acquired defects in the enamel or dentin, or trauma that leads to pulpal necrosis (Cohen, 1998).
• Enamel and/or dentin defects increase the potential for pulpal penetration by bacteria, which can lead to irreversible pulpal disease.
• Patients with early pulpal disease (ie, reversible pulpitis) have fleeting sharp pain that is elicited by a stimulus such as exposure to cold or something sweet.
• Chronic and untreated pulpal disease progresses to irreversible pulpitis, a condition resulting in pulpal death. Irreversible pulpitis produces poorly localized, lingering pain that is described as boring or gnawing and is aggravated by eating, exposure to a cold stimulus, or lying down (eg, many patients wake from sleep because of pulpitis pain). Analgesics (eg, acetaminophen, nonsteroidal anti-inflammatory drugs) often relieve irreversible pulpitis pain.
• The progression of pulpitis causes more pain, which is frequently severe in nature, aggravated by heat, and often relieved by application of cold. Occasionally, chronic pulpitis results in the spontaneous development of pain.
• Pulpal death and necrosis can lead to an acute apical periodontitis and an acute apical abscess, both of which can cause severe throbbing pain localized to the involved tooth, as well as regional lymphadenopathy.
• Ultimately, the abscess can progress to cellulitis and facial-space infection, which causes facial swelling, pain in the regional lymph nodes, fever, malaise, difficulty in eating or opening the mouth, and dysphagia. In extreme cases, the infection and associated inflammatory products can become life threatening if vital structures are involved (eg, cases of dyspnea due to compromised airway, infection of mediastinum, cavernous sinus).
• Medical history: A history of maternal or childhood diseases or the use of medications may explain tooth discoloration because the conditions can adversely influence normal tooth development. Knowledge of the onset and duration of maternal or childhood disease and the dosing of medications also helps.
• Family history: Several genetic diseases are associated with tooth-associated disorders the most common include AI, DI, and DD. Patients may be unaware of the diseases but often confirm that a family member had similar tooth discoloration.
• Social history: The use of tobacco and similar products, such as the chewing of areca (betel) nuts, commonly leads to staining of the teeth. Determining the type of tobacco habit (eg, smoking vs chewing) is important because the distribution of the stain may vary.
• Dental history: The dental history can reveal useful information regarding the last dental cleaning, amount and scheduling of fluoride intake, oral hygiene practices, use of mouthwash, and traumatic events involving dentition.
• Diet history: A history of nutritional deficiencies or ingestion of foods that can stain teeth is important.

Physical:
Physical characteristics of extrinsic discoloration Usually, discoloration colors include brown, black, gray, green, orange, and yellow; on occasion, a metallic sheen is present. The scratch test is usually used to distinguish between extrinsic and intrinsic discoloration. In terms of distribution patterns, primary or secondary teeth (or both, as in a child in the mixed dentition stage) may be involved. The distribution is either generalized to all teeth or localized to certain teeth or tooth surfaces. Extrinsic staining of 1 tooth is unusual. Extrinsic stains often are found on surfaces with poorer toothbrush accessibility (eg, at the tooth-gingival interface [cervical regions] and between the teeth [interproximal regions]). Regarding other physical findings, teeth with extrinsic tooth discoloration usually demonstrate no signs of pulpal disease. Physical characteristics of intrinsic discoloration Usually, discoloration colors include brown, black, gray, green, orange, and yellow; also, a metallic sheen may be observed. Unlike extrinsic discoloration, teeth with intrinsic discoloration may be red or pink. Under ultraviolet light, teeth with tetracycline staining and congenital porphyria may fluoresce yellow or red, respectively. Intrinsic discoloration cannot be removed by using the scratch test. In terms of distribution patterns, primary and secondary teeth may be involved. The distribution is either generalized to all teeth or localized to certain teeth or tooth surfaces. An intrinsic etiology usually exists when a single tooth is discolored. When multiple teeth are involved, patterns of banding are indicative of intrinsic staining. Regarding other physical findings, teeth with intrinsic discoloration may demonstrate signs of pulpal disease.

• Inspection
• Visual inspection requires the use of a handheld dental mirror and a good light source, which permit examination of the varying shades and patterns of tooth color and the integrity and surface texture of all enamel surfaces.
• Transillumination is the simple process of directing a light source (eg, fibro-optic probe) through an anterior tooth from the buccal surface to the lingual surface. This process can facilitate inspection of tooth discoloration, particularly it is when associated with dental caries.
• Ultraviolet light exposure is not a common diagnostic tool, but it may offer further clues about the etiology of intrinsic discoloration because the tooth may emit a characteristic fluorescence.
• Scratch testing
• Discolored tooth surfaces are scratched by using a dental explorer, scaler, or similar sharp instrument to assess surface texture.
  Noncarious discolorations are hard and nonpenetrable.
  Light scratching with a dental instrument removes weakly adherent plaque that causes extrinsic discoloration.

• If the discoloration requires removal with a sharp dental scaler, the discoloration is considered to be tenacious.
• Exploration
• A sharp dental instrument also is used to explore soft and penetrable discolorations that probably are dental caries and/or faulty restorations.
• These dental disorders require definitive therapy.
• Percussion and palpation
• Percussion of a discolored tooth with the handle of a dental mirror and palpation of the tooth over the covered root surface may reveal additional information regarding pulpal disease.
• Discolored teeth associated with acute pulpitis, apical periodontitis, or apical abscess are sensitive to percussion and palpation.
• Pulp testing
• Pulp testing techniques are used to diagnose the pulpal status of teeth discolored as a result of dental caries, deep dental restorations, severe developmental or acquired enamel/dentin defects, or trauma leading to pulpal necrosis.
• Thermal testing of teeth is conducted by using the application of cold (ice or vapocoolant) or heat (thermoconductive material such as dental compound or gutta percha).
• Electric pulp testing is used to assess pulp vitality and degree of pulpal disease.
• Extraoral and intraoral soft tissue examination: Swelling, tender lymphadenopathy, trismus, and other signs associated with facial-space infection of odontogenic origin may accompany the physical presentation of a discolored tooth.
• Comprehensive head, neck, and oral examination
• Neck lymphadenopathy may be indicative of infection.
• An asymmetric mandible may be a sign of previous trauma.
• Ecchymoses may be suggestive of a bleeding disorder.

Causes: The causes of extrinsic and intrinsic dental discoloration are as follows (see also Pathophysiology):

• Extrinsic causes
• Brown stain
  • Tobacco products Dental plaque Tea, coffee, wine, and other beverages Certain foods Metals Iodine Chlorhexidine rinseCetylpyridinium chloride rinse Stannous fluoride
  • Khat leaf
• Black stain
  • Tobacco products Betel nut Dental plaque Chromogenic bacteria Tea, coffee, wine, and other beverages Certain foods
  • Metals
• Green stain
  • Chromogenic bacteria Tea
  • Metals
• Orange stain
  • Chromogenic bacteria
  • Metals
• Intrinsic causes - Localized color changes (in 1 or 2 adjacent teeth)
• White (opaque) stain
  • Mild trauma to teeth during enamel formation (secondary teeth), eg, Turner tooth Periapical infection of primary tooth Traumatic injury to primary tooth or teeth
  • Incipient caries (primary or secondary teeth)
• Yellow stain
  • Moderate trauma to teeth during enamel formation (secondary teeth), eg, Turner tooth Periapical infection of primary tooth Traumatic injury to primary tooth or teeth Trauma without hemorrhage Composites or glass ionomer or acrylic restoration Caries (active)
  • Focal tooth abrasion
• Brown stain
  • Severe trauma to teeth during enamel formation (secondary teeth), eg, Turner tooth Periapical infection of primary tooth Traumatic injury to primary tooth or teeth Composite, glass ionomer, or acrylic restoration Caries (active or remineralized)
  • Pulpal trauma with hemorrhage
• Blue, gray, or black stain
  • Amalgam restoration Glass ionomer or acrylic restoration Metal crown margin associated with porcelain fused to metal crown
  • Pulpal trauma with hemorrhage
• Intrinsic causes - Regional color changes
• White (opaque) stain
  • Infection (maternal or childhood) during enamel formation Trauma to multiple teeth during enamel formation Mild fluorosis (short-term exposure)
  • Nutritional deficiency
• Yellow stain
  • Infection (maternal or childhood) during enamel formationModerate fluorosis (short-term exposure) Trauma to multiple teeth during enamel formation Nutritional deficiency Epidermolysis bullosa Regional tooth abrasion or erosion
  • Diseases causing hyperbilirubinemia
• Brown stain
  • Infection (maternal or childhood) during enamel formation Severe fluorosis (short-term exposure)
  • Trauma to multiple teeth during enamel formation
• Blue, gray, or black stain - Tetracycline therapy (short-term exposure)
• Green stain - Diseases causing hyperbilirubinemia (eg, HDN, biliary atresia)
• Intrinsic causes - Generalized changes (involving primary and/or permanent dentitions)

• White (opaque) stain
  • Mild fluorosis
  • Amelogenesis imperfecta
  Yellow stain
  • Moderate fluorosis Amelogenesis imperfecta Dentinogenesis imperfecta Dentinal dysplasia Epidermolysis bullosa Diseases causing hyperbilirubinemia Hemolytic diseases
  • Generalized tooth attrition, abrasion, or erosion
  Brown stain
  • Porphyria
  • Tetracycline therapy (long-term exposure)
  Blue, gray, or black stain
  • Tetracycline therapy (long-term exposure)
  • Minocycline therapy
• Green stain - Diseases causing hyperbilirubinemia (eg, HDN, biliary atresia)

Lab Studies:

• A comprehensive head, neck, and oral examination is required. Neck lymphadenopathy may be indicative of infection, an asymmetric mandible may be a sign of previous trauma, and ecchymoses may be suggestive of a bleeding disorder.

Imaging Studies:

• Dental radiographs can reveal defects in both tooth structure and alveolar bone. This information is critical for the identification of a potential cause of intrinsic discoloration.
• Intraoral radiographs are required to determine whether a dental-alveolar infection is present.

Procedures:

• The evaluation of a patient with dental discoloration requires a review of the systemic and oral conditions in the patient's history. This review includes the following:
• Past medical history
• Concurrent systemic conditions
• Medications (ie, medications taken during pregnancy, early childhood, and at present)
• History of an exposure to chemicals, trauma, or infection
• Exposure to fluoride
• History of dental treatment
• Daily hygiene
• Dietary habits
• A complete oral examination is required to help determine the etiology of tooth discoloration.
• To exclude periodontal and gingival disorders, a thorough examination of the periodontium, including an examination of the gingival sulcus by using a periodontal probe, is required.
• Caries are assessed by using a sharp explorer and intraoral radiographs.
• To assess the vitality of the affected teeth, cold testing with ice, tetrafluoroethane, or ethyl chloride spray or vitalometer testing with an electric pulp tester is necessary.

• A visual examination of the oral mucosal surfaces is helpful for identifying systemic conditions that affect soft and hard tissues (eg, bleeding disorders, minocycline staining).

Medical Care: Dental treatment of tooth discoloration involves identifying the etiology and implementing therapy. Medical treatment also may be warranted, depending on the etiology of the tooth discoloration.

• Diet and habits: Extrinsic staining caused by foods, beverages, or habits (eg, smoking, chewing tobacco; see Causes and Pathophysiology) is treated with a thorough dental prophylaxis and cessation of dietary or other contributory habits to prevent further staining.

• Toothbrushing: Effective toothbrushing twice a day with a dentifrice helps to prevent extrinsic staining. Most dentifrices contain an abrasive, a detergent, and an antitartar agent. In addition, some dentifrices now contain tooth-whitening agents.
• Professional tooth cleaning: Some extrinsic stains may be removed with ultrasonic cleaning, rotary polishing with an abrasive prophylactic paste, or air-jet polishing with an abrasive powder (Hosoya, 1989). However, these modalities can lead to enamel removal; therefore, their repeated use is undesirable (Weaks, 1984).
• Enamel microabrasion: This technique involves the rotary application of a mixture of weak hydrochloric acid and silicon carbide particles in a water-soluble paste (Croll, 1997). The resultant surface is smooth and has a glazed appearance. Enamel microabrasion is indicated for the removal of superficial intrinsic tooth discoloration, including that caused by fluorosis and decalcifications secondary to orthodontic brackets or bands. Enamel microabrasion may be used in conjunction with bleaching.
• Bleaching: Early bleaching techniques were developed almost a century ago, and all of the techniques involved a process of oxidation. Today, with proper patient selection, bleaching is a safe, easy, and inexpensive modality that is used to treat many types of tooth discoloration. Usually, bleaching is not indicated for the treatment of discoloration of the primary teeth. Bleaching includes 2 types of techniques: vital and nonvital.
• Vital bleaching
  • Bleaching of vital teeth is indicated primarily for patients with generalized yellow, orange, or light brown extrinsic discoloration (including chlorhexidine staining), although it may be helpful in ameliorating mild cases of tetracycline-induced intrinsic discoloration and fluorosis. Currently, the bleaching agents most commonly used are carbamide and hydrogen peroxide. When applied in higher concentrations and with heat, the agents produce more significant bleaching than they do without these measures. Power bleaching involves the use of a 30-35% hydrogen peroxide solution and must be performed by a dental professional because careful isolation of the teeth is required to protect the soft tissues from the caustic effects of the bleaching agent (Garber, 1997). The use of home bleaching systems are currently popular. The systems must be used under the careful supervision of dentists or dental hygienists. Patients apply a 10-15% carbamide peroxide solution into a custom-made mouthguard. After repeated daily and/or nightly (often while patients sleep) applications for 2-6 weeks, the teeth are gradually bleached. The public is advised to avoid the use of home bleaching systems that are not approved by the American Dental Association and those marketed for use without professional supervision. With darker stains, the best results are achieved by using a combination of office and home bleaching systems. Most patients also require periodic re-treatment. Clinicians should be aware of potential adverse reactions and contraindications for bleaching. Approximately two thirds of patients have short-term, minor tooth sensitivity to cold and/or gingival irritation. Tooth surfaces, particularly exposed roots or enamel surfaces with defects secondary to incomplete amelogenesis, are porous to the bleaching agent and are more likely to develop cold sensitivity. Gingival irritation usually is related to improper fitting of the custom-made mouthguard. Allergic reactions to the bleaching agent are exceedingly rare.
  • No adverse reactions are documented in pregnant or breastfeeding women or in patients who smoke; however, bleaching is not advised in these patients.
• Nonvital bleaching
  • Nonvital bleaching is indicated for the treatment of teeth with discoloration secondary to pulpal degeneration. This technique involves placing a mixture of 30% hydrogen peroxide and sodium perborate into the pulp chamber for as long as 1 week (Goldstein, 1995). For nonvital bleaching, a tooth with an unrestored crown is ideal.
  • Cervical external root resorption is a possible adverse sequela, especially in teeth that become pulpless before the patient is aged 25 years. Special intracanal barrier restoration helps to minimize this adverse reaction.

Surgical Care:

• Dental restorations
• Teeth discolored by dental caries or dental materials require the removal of the caries or restorative materials, followed by proper restoration of the tooth. Partial (eg, laminate veneers or full-coverage dental restorations may be used to treat generalized intrinsic tooth discoloration in which bleaching is not indicated or in which the aesthetic results of bleaching fail to meet the patient's expectations.
• Patients with severe dental involvement may be candidates for extractions; after which either partial or complete removable dentures or osseointegrated implant-borne prostheses can be used.
• Patients with genetic defects in the formation of enamel or dentin present with a wide range of clinical manifestations. In some patients with severe AI or DI, extractions may be required; after which removable dentures or implant-borne prostheses can be used.
• Dental extractions and implantations
• Dental extractions may be required for severely carious teeth that are nonrestorable or for teeth with large periodontal defects that are refractory to periodontal rehabilitation.
• Severely involved teeth with AI or DI also may require extraction.
• Tooth replacement with osseointegrated implants is a feasible option in many patients, depending on the medical condition of the patient, the quality and quantity of the maxillary and/or mandibular bone, and the proximity of the tooth to nerves and sinuses.
• Persons who smoke are poor candidates for implantation.
• Dental professionals with training in implant surgery and extensive experience should perform the operation.

Consultations:

• Consultations with the appropriate medical providers may be required if the underlying etiology of tooth discoloration is related to a systemic disease (eg, porphyria, AI).
• Endodontists, prosthodontists, periodontists, and oral and maxillofacial surgeons and/or dental specialists may assist with therapies.
• Dentists trained in aesthetic dentistry may provide expert consultation for cosmetic dental procedures.

Diet:

• Provide counseling to the patient if the source of the extrinsic dental staining is the result of diet or habits (eg, eating blueberries, using chewing tobacco).
• Removal of the extrinsic source is critical for effective treatment.

Activity:

• Recommend that all patients perform daily oral hygiene by using a toothbrush, a dentifrice, and dental floss.

• Individuals who wear dentures should brush the prostheses after each meal and use commercially available denture soaks and scrubs to keep the prostheses free of plaque, calculus, and stains.

Further Outpatient Care:

• Patients who undergo dental procedures (eg, bleaching, restorations) for tooth discoloration should be monitored periodically.
• In addition to routine dental and periodontal evaluation, some patients may require additional bleaching treatments to maintain aesthetic results.

Deterrence/Prevention:

• Clinicians can help in preventing fluorosis by teaching parents about fluoride use and good toothbrushing habits for children.
• Changes in dietary and toothbrushing habits and professional cleaning and treatment may help in preventing tooth discoloration (see Medical Care).
• See Pathophysiology and Causes.

Complications:

• All irreversible dental treatments have the potential to cause complications.
• Bleaching (eg, home bleaching) and restorative procedures are safe if performed by or under the supervision of a dentist with appropriate training and experience.
• Vital bleaching causes short-term tooth sensitivity (1-4 d) in two thirds of patients (see Medical Care).
• Patients with preexisting restorations, cervical erosions, enamel cracks, large pulp chambers, or sensitive teeth before treatment are at higher risk for postbleaching sensitivity.
• The use of a mild bleaching agent, shortened application time and frequency, and topical fluoride therapy can reverse this sensitivity (Nathanson, 1997).
• Allergic reactions to bleaching agents are rare.
• Restorative procedures, including bonding and the use of laminate veneers and fixed prostheses (eg, crowns and bridges), can result in pulpal or periodontal complications; however, careful treatment planning and therapy can minimize these complications.
• Depending on the anatomic site, the proximity to vascular and neurologic vessels, and the oral and systemic condition of the host, oral surgical procedures infrequently can cause sequelae such as hemorrhage; pain; swelling; infection; and motor, nerve, or sensory deficits.

Prognosis:

• The prognosis is excellent if an etiology is identified and if the appropriate dental and medical care providers are involved in the comprehensive diagnosis and treatment of the condition.

Patient Education:

• Educate patients about the necessity of daily oral hygiene and about the medications implicated in dental discoloration.

• Educate patients who are treated for medical disorders associated with dental discoloration about the risks of tooth-related disorders.

Medical/Legal Pitfalls:

• Failure to remain alert to the potential adverse effects of certain medications on dentition