Dental dyschromia  

Dental dyschromia 

The natural appearance of a tooth depends on the different tissues that compose it, that is, enamel, dentin and pulp. Depending on the thickness of the tissues, their structure and composition, the tooth will have a certain shade, brightness and saturation. 

Enamel can be discolored by contact with saliva and food

The dentin that occupies the internal areas gives the general shade of the tooth, therefore it is responsible for its color,

The pulp:

This is the living, innermost part of the tooth. 

Made up of nerves and blood vessels, it has a dark red color. 

For young teeth with a large cameral chamber, it can give a pinkish tint to the tooth.

Teeth become darker as an individual ages, this effect is all the more rapid and marked depending on the history of dental caries or dental discoloration. This is a physiological process, not a dyschromia.

1. Definition 

The word dyschromia is composed of the prefix “Dys” which refers to an anomaly (Larousse), and the word “chrome” with its suffix “-ie”, which refers to the color. In the dental field, dyschromia can be defined as the variation in the visual appearance of the color of one or more teeth, over a more or less extensive surface area.

2. The mechanisms of coloring

The dental organ is composed of mineralized tissues which, despite their density, have a certain permeability, making possible the passage of liquid flows and facilitating exchanges. These exchanges can be exacerbated during an alteration of the enamel surface (fissures and cracks).

 Thus, certain molecules coming from the oral environment can infiltrate the dental organ through saliva, or come from the bloodstream via the pulp.

1. The exogenous pathway 

The tooth is a place of permanent exchange with fluids, whether internal with the blood contained in the pulp, or external in relation to the oral cavity.

Thus chromatophores (colored pigments contained in foods and drinks) chemically bind to organic tissues contained in inter-prismatic zones and fissures, or even with calcium ions

2. The endogenous pathway 

Some drugs, such as tetracyclines, have pigmented groups that have the ability to bind to dentin by forming a complex with calcium ions.

After oxidation by light, these pigments (hydroquinones) give rise to brown colorations

3. Classification of dyschromias 

3.1 extrinsic or acquired dyschromias 

These are superficial stains, usually affecting only the enamel of the tooth. They appear after tooth eruption and are caused by substances external to the host

Depending on the cause, these extrinsic discolorations are divided into direct or indirect dyschromia.

• Direct staining is the result of the fixation of the chromogen on the acquired exogenous film, the shade varies according to the color of the chromogen.
• Indirect discoloration is the result of a chemical reaction between a substance and the tooth surface.

3.2 Intrinsic dyschromias

Unlike extrinsic staining, they are due either to the incorporation of chromogenic pigments into dental tissues or to the modification of the thickness of these tissues. They affect the entire enamel-dentin structure. They are included more or less deeply in the organomineral complex of the tooth.

4. Clinical forms of dyschromia 
   1. Extrinsic dyschromias

Many factors promote the accumulation of dental deposits and stains: 

• Enamel defects, 
• Salivary composition and flow, 
• Poor oral hygiene, 
• Age which can be associated with discolorations due to a combination of extrinsic factors such as coffee, tea, tobacco, medications and other physiological changes.

Nathoo proposed a classification based on their physicochemical interactions with the dental surface.

4.1.1. Dyschromia due to plaque and its derivatives

1. Dental plaque

It contains numerous colonies of microorganisms constituting soft, amorphous granular deposits accumulated on the surface of the teeth. 

Initially, they are found in small quantities and are not visible. Then, by accumulation, the plaque forms a visible globular mass with a color varying from gray to yellow.

2. Tartar 

Tartar is the result of plaque calcification.

We distinguish:

• Subgingival tartar , brownish or even black in color, due to the iron contained in the blood.
• Supragingival tartar , white or yellowish in color, which may be colored secondarily by contact with food or tobacco.

Tartar is easily removed by professional descaling

2. Dyschromia due to lifestyle habits
3. Tobacco stains

Dark brown, black in color, and are located mainly on the cervical third of dental crowns, on the edge of restorations, in grooves, fissures or on dentine exposed following abrasions.

The staining results from the deposition of tar and its deep penetration through the enamel surface to the enamel-dentine junction and then the dentinal tubules. 

The degree of coloring is related to:

• The amount of tobacco consumed 
• Its frequency, 
• Type of tobacco used, 
• Roughness of the enamel and 
• The patient’s smoking habits. 
• A pipe smoker will have strong localized colorations at the mouthpiece while a tobacco chewer will have more generalized colorations.

2. Food colorings

It is a brown discoloration due to the deposit of tannins contained in tea, coffee and other beverages. It is found in patients with insufficient or inappropriate brushing.

This coloration is characterized by a thin pigmented film devoid of bacteria, and is most often located on the vestibular surface of the upper molars, on the lingual surface of the lower incisors and, less frequently, on the palatal surfaces of the anterior maxillary teeth.

3. Dyschromias due to chromatogenic bacteria
4. Black coloring

Black chromogenic bacteria (Actinomyces) produce hydrogen sulfite, which will interact with salivary iron on the tooth surface to generate a deposit of ferric sulfite.

Fine black lines mainly located at the necks, they appear at the vestibular and lingual surfaces of the teeth, and can extend to the proximal faces; extremely adherent to the enamel surface. Difficult to remove by brushing and tend to recur. 

There are many classifications specific to this type of coloration, based on the criterion of extension of the colorations on the dental surface.

2. Green coloring

Thick, tenacious and recurring deposit generally in the form of a band located on the vestibular surface of the anterior maxillary teeth at the level of the cervical third, more specifically concerns children (especially boys); Attributed to bacteria and fungi which can only grow in the presence of light, hence its anterior location.

3. Orange coloring

It affects only 3% of the population, Sits on the vestibular surface of the anterior teeth (maxillary and mandibular) at the level of the cervical edge and the gingival third, Associated with poor oral hygiene; Due to the action of chromogenic bacteria such as penicillium and aspergillus.

4.1.4 Metallic dyschromias

Induced by metal dust (industry), certain oral medications or locally applied therapeutic agents; 

Metals combine with the acquired film and produce surface staining or penetrate the tooth and cause permanent staining, 

Enamel is permeable to various ions and molecules: 

• Industrial exposure to iron, manganese and silver can cause black tooth discoloration ; 
• Mercury has a gray coloring ; 
• Copper and nickel, a green coloring ; 
• Iron-containing drugs used in the treatment of anemia produce black discolorations.
• Mouthwashes with potassium permanganate, purplish discoloration 

5. Brown antiseptic dyschromias:
6. Due to chlorhexidines

Found after prolonged use of the product (available as mouthwash, gel, varnish, toothpaste, oral irrigator);

Chlorhexidine is absorbed on the surface and is slowly released in active form by plaque calcium and saliva, 

It is easy to remove this type of staining because it is very superficial and does not adhere very well to the surface of the enamel.

2. Colorations due to quaternary ammoniums: 

These antiseptics (such as benzalkonium chloride), also present in some mouthwashes and toothpastes, can also cause brown discoloration.

4.2 Intrinsic dyschromias

Intrinsic colorations are linked to the organo-mineral complex of the tooth, they are due to the incorporation of chromogenic substances within the enamel-dentin complex

4.2.1 Pre-eruptive intrinsic colorations of genetic origin

A. Amelogenesis imperfecta

There are four forms of amelogenesis imperfecta, which are themselves subdivided into subgroups.

• Hypoplastic form: there is a decrease in the thickness of the enamel, pits and horizontal grooves, with or without coloration ranging from yellow to brown 
• Hypomature form: the thickness of the enamel is normal, but there are discolorations and opacities;
• Hypocalcified form: the enamel has an initially normal thickness but wears away quickly. Its color can range from yellow to brown or orange;
• Hypomature/hypoplastic forms and taurodontism : These forms are accompanied by brown mottling, pits and hypomineralized areas. The enamel may have normal or thinned thickness. The clinical appearance of these teeth is very unaesthetic and gives an impression of lack of hygiene. Patients suffer functionally and aesthetically

B. Dentinogenesis imperfecta

It is a hereditary disease that affects the formation of dentin. Due to an abnormality of type I collagen, (It affects the deciduous and permanent teeth, their colors are between blue-gray and more or less dark brown; these teeth are very fragile and fracture easily.

• Hereditary dentinogenesis imperfecta Type I: Associated with osteogenesis imperfecta, sometimes with associated deafness. The teeth wear down rapidly after eruption, the enamel crumbles and reveals softer dentin.
• Hereditary dentinogenesis imperfecta Type II : most common form, not associated with osteogenesis imperfecta, but sometimes with deafness. Clinical signs often affect both sets of teeth and are similar to type I.

3. Erythroblastosis fetalis :

It corresponds to a fetal-maternal blood incompatibility. It is due to an opposing Rhesus factor, it is characterized by the destruction of a large number of erythrocytes and pigmentation of the dentine of the teeth in formation, often associated with enamel dysplasia and shape anomalies. 

4. Thalassemia

It is a genetic disease of hemoglobin, which is characterized by significant anemia. The teeth take on a pinkish-red color due to the presence of blood pigments through the dentinal tubules.

4.2.2. Congenital pre-eruptive intrinsic colorations

1. Congenital erythropoietic porphyria

Hereditary disease, Also known as Günther’s disease also known as “vampire disease”, porphyria is a condition characterized by the presence in the body of massive amounts of Porphyrins. It is characterized by an excessive production of porphyrin pigments in the dental structures which causes red or reddish-brown coloration of temporary and permanent teeth

2. Neonatal hemolytic jaundice

It is a very common transient blood disease in newborns, especially premature babies, due to fetal-maternal Rh incompatibility which leads to hemolysis.

It causes hyperbilirubinemia responsible for an indelible yellow or green coloration of the dentine of the deciduous teeth, due to deposits of biliverdin. The permanent teeth are not affected.

3. Vitamin D-dependent hereditary rickets 

It is caused by a deficiency of vitamin D2. It can lead to:

• Hypocalcemia responsible for enamel hypoplasia, present either in the form of bands around the enamel or in small punctate interruptions forming depressions and pits.

Hypophosphatemia responsible for defects in the maturation of interglobular dentin

4. Cyanotic congenital heart disease

A child with a congenital heart defect that causes cyanosis may have abnormally pale upper incisors that are chalky white or bluish white in appearance.

This coloration would come from a depletion of oxygen in the pulp blood, or even from dryness of the teeth linked to the mode of oral breathing.

5. Melanodontia 

This is a dysplasia of the enamel of temporary teeth already developed on the arch, leading to the crumbling and disappearance of the enamel, gradually exposing the underlying dentine which will blacken as a reaction.

The mandibular incisors are not affected, while the maxillary central incisors, then the lateral incisors, the canines and, finally, the occlusal surfaces of the molars, will gradually take on a black color.

6. Fetal distress

Tooth discoloration abnormalities may be noted as a result of fetal distress inducing abnormalities in the formation of dental organ structures.

These may be infectious diseases contracted by the mother, such as syphilis leading to pigmentation of the enamel (Hutchinson teeth), or rubella, leading to hypoplasia of the enamel of deciduous and permanent teeth. 

A pregnant woman may also be exposed to ionizing radiation which causes a decrease in the translucency of the enamel and a blue-green discoloration of the teeth. 

Finally, deficiencies in calcium, magnesium, phosphorus, vitamins A, C and D as well as diabetes in pregnant women can also be the cause of enamel hypoplasia.

MIH (Molar Incisor Hypomineralization) 

This is hypomineralization of systemic origin, affecting one to four first permanent molars, associated or not with damage to the permanent incisors. 

The etiology is poorly understood. It is a multifactorial condition. 

Structurally, dyschromic areas are characterized by a 20% reduction in the mineral content of the enamel.

The color of the lesion is consistent with the depth of tissue involvement and the spots may be white, cream, yellow or brownish-brown.

4.2.3 Post-eruptive or acquired intrinsic dyschromia

1. Tetracycline staining

These dyschromias can be localized or generalized. Their action is very variable, ranging from simple uniform yellow coloration to bands sometimes associated with dysplasias or more or less pronounced gray-brown colorations, 

 The clinical appearance varies depending on the dose administered, the duration of treatment and the stage of mineralization of the teeth.

 Tetracycline is now contraindicated in pregnant women and children under 8 years old.

Classification of dyschromias by tetracyclines

Jordan and Boksmen in 1984 listed 04 degrees:

Class I: Slight yellow, gray or brown coloration, uniform over the entire coronal height.

Class II: More saturated but still uniform coloration without banding

Class III: Irregular, more saturated (dark gray or bluish) non-uniform coloration, clearly differentiated band appearance

Class IV Very intense, highly saturated coloration, in bands or non-uniform areas, exceptional (dark purple to highly saturated brown).

2. Discolorations due to Fluorosis

Fluorosis is linked to an overdose of fluoride during the phase of tooth formation and mineralization, that is to say between the 4th ^month in utero and the 8th ^year   . 

Excess fluoride disrupts the full development of enamel crystals,

At low doses, fluoride has a beneficial carioprotective effect; and beyond a certain dosage, it becomes harmful, especially in children between 0 and 4 years old, during the period of mineralization of the crowns of the incisors, 

Stadiums 

Stage 0: no evidence of fluorosis;

Stage 1: fluorosis limited to the top of the cusps with a snowy cap;

 Stage 2: white parchment appearance on at least 1/3 of the enamel surface;

 Stage 3: white parchment appearance on at least 2/3 of the enamel surface;

Stage 4: areas of discoloration with patches ranging from light to dark brown;

Stage 5: Discrete pitting with possible secondary staining of the bottom of the wells

Stage 6: slight pitting and change in enamel color;

 Stage 7: The pits fuse, forming large areas where the enamel is missing, dark brown colorations are often present

3. Discolorations due to local toxic factors

dental trauma induces a pulp reaction, resulting in three types of dental discoloration: 

 The pink tint , which results from pulp hemorrhage or internal resorption of dental tissues. 

The yellow tint, which represents an obliteration of the pulp canal

The dark shade , varying from brown to black, of which different hypotheses on the cause of this dyschromia exist but no consensus. According to the study published in May 2019 by Holan G., the dentin complex would not be affected. This dark shade suggests pulp necrosis.

4. Post-traumatic pulp hemorrhage

During trauma resulting in pulp hemorrhage, the dentinal tubules are invaded by blood which undergoes hemolysis. 

The resulting hemoglobins are in turn destroyed, producing a bluish-black mixture that will color the tooth dark gray. 

As the blood breaks down, the tooth will go through the different shades of the breakdown products.

• Pulp necrosis without hemorrhage

It follows physical trauma, such as shock, overheating, milling or even chemical aggression linked for example to resins, composites, styling products, antiseptics. 

Pulp degeneration results in the degradation of protein products from the necrotic tissue, causing the gray-brown discoloration of the crown. 

The type and intensity of staining depends on the time elapsed between loss of pulp vitality and endodontic treatment. 

The longer the colored pigments remain in place, the more they penetrate and the worse the prognosis for a lightening treatment.

5. Staining by iatrogenic procedures

Some dental biomaterials can have repercussions on the tissues they aim to restore. The observed colorations depend on the extent and its longevity. Resins can color the tooth gray because of the silicates they contain.

1. The amalgam

It causes, through ionic migration or corrosion, more or less significant coloration of the tooth and surrounding tissues. Even when handled well, silver amalgam colors teeth bluish gray.

B. composites 

A tooth restored with composite resin may exhibit yellow or gray discoloration, caused by infiltration at the edge of the filling and percolation of oral fluids. 

Dental dyschromia  

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Dental dyschromia