Introduction:
Firstly, it is important to have an understanding of the elements of a tooth. The color of a tooth is not uniform throughout; it varies in color gradation from the incisal edge to the gingival margin. The coronal portion or tooth crown mainly comprises three layers: the superficial enamel, the middle dentine layer, and the vascular innervated pulp or root canal of the tooth. Any change to these structures would not only potentially alter the outward appearance of the tooth but also cause a change in the transmitting or reflecting capacity of the tooth layers.
What Are the Factors Affecting Tooth Color?
As teeth age naturally, they tend to darken due to common physiological processes that affect tooth color. In some individuals, the color changes may be even more pronounced at an early age due to the laying down of secondary dentin (a layer of dentin that forms gradually after the primary dentin and serves as a protective response to stimuli or aging), the presence of extrinsic stains, or even the gradual wearing out of tooth enamel.
Any of these factors can influence the color of the underlying dentine layer beneath the enamel (the second layer of the tooth, which is more yellowish and less white than the enamel, the first layer). Furthermore, even tooth wear and gingival recession would be factors that influence tooth color with increasing age.
What Are the Types of Tooth Discoloration?
Tooth discoloration can be mainly classified based on the location of the stains, which can be either extrinsic or intrinsic, leading to a change in the color of the tooth crown. Besides these two categories, tooth discoloration may also occur internally, caused by various local or systemic factors. This creates another category known as internalized stains or discoloration.
1. Intrinsic Stains -
Intrinsic stains happen when there is a change in the structural composition of the hard tissue of the teeth. It might also be due to an alteration in the thickness of the hard tissues. The following factors influence the phenomenon of intrinsic discoloration or intrinsic stains:
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Alkaptonuria: This condition occurs as a result of incomplete tyrosine metabolism in the body, leading to a buildup of homogentisic acid. This causes a characteristic brown discoloration of the tooth crown, affecting the permanent dentition.
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Congenital Erythropoietic Porphyria: This is a rare recessive and autosomal disorder of metabolism. Due to an error in the body's porphyrin metabolism, there is an eventual accumulation of porphyrins within the bone marrow, red blood cells, and other tissues. This results in a red-brown tint observed in the urine, teeth, and feces. Also, it causes a red-brown discoloration of the tooth crown in individuals with this condition.
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Dentinogenesis Imperfecta: This is a condition characterized by opalescent teeth on dental transillumination. The teeth crown displays a color range from blue to brown, affecting both primary and permanent dentitions. Generally, primary dentition experiences more severe effects in this regard.
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Dentine Dysplasia: This is another condition that leads to intrinsic discoloration. Although the shape of the teeth remains normal, it affects both primary and secondary dentitions, causing the teeth to exhibit an amber translucency.
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Amelogenesis Imperfecta: A characteristic feature of this condition affecting the enamel-forming ameloblasts is the presence of 'snow-capped' enamel or even severe forms of hereditary hypoplasia of enamel. The enamel becomes very thin and hard, displaying a typical yellow-brown appearance.
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Administration of Tetracyclines: Apart from being considered teratogenic to the developing fetus, Tetracycline antibiotics are also associated with a high risk of drug deposition within both the bone and the dental hard tissues. The tooth crown may possess a characteristic yellowish or brown-gray appearance due to Tetracycline action on enamel, which becomes evident upon tooth eruption. However, these stains may diminish with time and proper dental management.
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Fluorosis: Excess fluoride content in water affects the enamel, causing areas of flecking or diffuse mottling on the tooth surface. The color of the enamel may be either a chalky white or even range to a dark brown or black appearance.
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Systemic Diseases, Defects, and Certain Syndromes: Defects in enamel formation can be influenced by various systemic diseases, defects, and specific syndromes. Some clinical examples of these syndromes include rickets (a condition caused by vitamin D deficiency, leading to impaired bone growth and softening), epidermolysis bullosa (a genetic disorder causing skin blistering due to structural protein abnormalities), pseudohypoparathyroidism (a rare hormonal disorder leading to impaired response to parathyroid hormone and low calcium levels), vitamin D-linked diseases (a group of conditions associated with vitamin D deficiency), and more.
2. Extrinsic Stains-
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Non-metallic Stains: The non-metallic stains are a form of extrinsic stains. These are not caused due to metals and are caused by external agents that discolor the tooth enamel or dentin. These agents are usually adsorbed onto the tooth surface, similar to how dental plaque or the acquired pellicle accumulates due to lowered oral hygiene. The possible factors causing non-metallic stains are certain dietary components, junk foods, certain medicaments, beverages, tobacco, and more.
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Metallic Stains: These extrinsic stains occur due to occupational exposure to metallic salts. Also, a wide number of medicines commonly contain metal salts. For example, metal-associated colors such as potassium permanganate exposure would produce a distinct violet to black color on the tooth crown (as used in some mouthwashes or rinses). Other common metallic salts in dentistry are silver nitrate salt, which causes a gray color, and stannous fluoride, which causes brown discoloration.
3. Internal Discoloration -
As mentioned earlier, this third category is because of developmental anomalies or acquired defects that tend to internally discolor the crown of the teeth.
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Developmental Defects: Fluorosis and enamel hypoplasia or hypocalcification are common examples that have been discussed earlier, causing intrinsic discoloration. Similarly, developmental defects like dentinogenesis imperfecta and dentin dysplasia (a genetic condition resulting in abnormal dentin formation, affecting tooth structure) can also expose the dentine either directly or in the later stages.
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Acquired Defects: These are tooth defects due to wear and tear, regressive alterations of teeth, or diseases of the tooth and the supporting tissues. This can occur at any phase in life, directly or indirectly related to sudden tooth discoloration. Dental restorations can also similarly influence the color of teeth, especially large dental restorations.
Conclusion:
To conclude, tooth discoloration can hence be a major aesthetic and functional concern. It is essential to understand the cause of tooth discoloration, firstly to establish the ideal dental management strategy. The dentist may adopt micro abrasive techniques and in-office bleaching to reduce the nature of intrinsic stains. Similarly, procedures like ultrasonic cleaning, rotary polishing of tooth surfaces, and professional dental teeth whitening can help relieve extrinsic stains. Tooth discoloration presents differently in individuals. Understanding the basic elements responsible for tooth color is crucial for dentists to implement any restorative aspect in the field of dentistry.
