Root canal treatment (also known as endodontic therapy, endodontic treatment, or root canal therapy) is a treatment sequence for the infected pulp of a tooth which results in the elimination of infection and the protection of the decontaminated tooth from future microbial invasion. Root canals, and their associated pulp chamber, are the physical hollows within a tooth that are naturally inhabited by nerve tissue, blood vessels and other cellular entities. Together, these items constitute the dental pulp.

Endodontic therapy involves the removal of these structures, the subsequent shaping, cleaning, and decontamination of the hollows with small files and irrigating solutions, and the obturation (filling) of the decontaminated canals. Filling of the cleaned and decontaminated canals is done with an inert filling such as gutta-percha and typically a eugenol-based cement. Epoxy resin is employed to bind gutta-percha in some root canal procedures. Endodontics includes both primary and secondary endodontic treatments as well as periradicular surgery which is generally used for teeth that still have potential for salvage

The combination of intrinsic colour and the presence of extrinsic stains on the tooth surface influence the colour and thus the overall appearance of teeth. The scattering of light and absorption within enamel and dentine determine the intrinsic colour of teeth and because the enamel is relatively translucent, the dentinal properties can play a major role in determining the overall tooth colour. On the other hand, extrinsic stain and colour is the result of coloured regions that have formed within the acquired pellicle on the enamel surface and can be influenced by lifestyle behaviours or habits. For example, dietary intake of tannin-rich foods, poor tooth brushing technique, tobacco products, and exposure to iron salts and chlorhexidine can affect the colour of a tooth.

With increasing age, teeth tend to be darker in shade. This can be attributed to secondary dentin formation and thinning of enamel due to tooth wear which contributes to a significant decrease in lightness and increase in yellowness. Tooth shade is not influenced by gender or race

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People all around the world are dazzled by a bright smile. The problem with the color of teeth is that it changes with time. Associated with age, tooth discoloration is actually not a sign of aging. This is evidenced by the number of people in their twenties and thirties who are already struggling with dull, stained enamel.

The real causes of a dull smile are foods and beverages that we consume, sometimes on a daily basis. Most people have heard that beverages like tea, coffee, and red wine can diminish the brightness of the smile. We also know that smoking can cause teeth to turn yellow or brown over time. But how?

Staining occurs bit by bit, sometimes over years. When you eat a food, drink a beverage, or use tobacco products, tiny particles from those substances are deposited onto enamel, which contains thousands of microscopic pores, just like your skin. When these deposits settle into enamel, they often remain for life – or until they can be lifted.

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Tooth discolouration and staining is primarily due to two sources of stain: Extrinsic and Intrinsic. 

Extrinsic staining

Extrinsic staining, is largely due to environmental factors including smoking, pigments in beverages and foods, antibiotics, and metals such as iron or copper. Coloured compounds from these sources are absorbed into acquired dental pellicle or directly onto the surface of the tooth causing a stain to appear.

• Dental plaque: Dental plaque is a clear biofilm of bacteria that naturally forms in the mouth, particularly along the gumline, and it occurs due to the normal development and defences of the immune system. Although usually virtually invisible on the tooth surface, plaque may become stained by chromogenic bacteria such as Actinomyces species. Prolonged dental plaque accumulation on the tooth surface can lead to enamel demineralisation and formation of white spot lesions which appear as an opaque milk-coloured lesion. The acidic by-products of fermentable carbohydrates derived from high-sugar foods contribute to greater proportions of bacteria, such as Streptococcus mutans and Lactobacillus in dental plaque. Higher consumption of fermentable carbohydrates will promote demineralisation and increase the risk of developing white spot lesions.
• Calculus: neglected plaque will eventually calcify, and lead to the formation of a hard deposit on the teeth, especially around the gumline. The organic matrix of dental plaque and calcified tissues undergo a series of chemical and morphological changes that lead to calcification of the dental plaque and therefore leading to the formation of calculus. The color of calculus varies, and may be grey, yellow, black, or brown. The colour of calculus depends on how long it has been present in the oral cavity for; it typically starts off yellow and over time the calculus will begin to stain a darker colour and become more tenacious and difficult to remove.
• Tobacco: tar in the smoke from tobacco products (and also smokeless tobacco products) tends to form a yellow-brown-black stain around the necks of the teeth above the gumline. The nicotine and tar in tobacco, combined with oxygen, turns yellow and over time will absorb into the pores of enamel and stain the teeth yellow. The dark brown to black stains along the gum line of the teeth are the result of the porous nature of calculus immediately picking up the stains from nicotine and tar.
• Betel chewing: Betel chewing produces blood-red saliva that stains the teeth red-brown to nearly black. The extract gel of betel leaf contain tannin, a chromogenic agent that causes discolouration of the tooth enamel.
• Tannin is also present in coffee, tea, and red wine and produces a chromogenic agent that can discolor teeth. Large consumption of tannin-containing beverages stain the dental enamel brown due to the chromogenic nature.
• Certain foods, including curries and tomato-based sauces, can cause teeth staining.
• Certain topical medications: Chlorhexidine (antiseptic mouthwash) binds to tannins, meaning that prolonged use in persons who consume coffee, tea or red wine is associated with extrinsic staining (i.e. removable staining) of teeth. Chlorhexidine mouthwash has a natural liking for sulphate and acidic groups commonly found in areas where plaque accumulates such as along the gumline, on the dorsum of the tongue and cavities. Chlorhexidine is retained in these areas and stain yellow-brown. The stains are not permanent and can be removed with proper brushing.
• Metallic compounds: Exposure to such metallic compounds may be in the form of medication or occupational exposure. Examples include iron (black stain), iodine (black), copper (green), nickel (green), and cadmium (yellow-brown). Sources of exposure to metal include placing metal into the oral cavity, metal containing dust inhalation, or oral administration of drugs. Metals can be penetrated into the tooth causing permanent discolouration or can bind to the pellicle causing surface stain.

Intrinsic staining

Intrinsic staining primarily occurs during the tooth development either before birth or at early childhood. Intrinsic stains are those that cannot be removed through mechanical measures such as debridement or a prophylactic stain removal. As the age of the person increases, the teeth can also appear yellower over time.Below are examples of intrinsic sources of stains:

• Tooth wear and ageing: Tooth wear is a progressive loss of enamel and dentine due to tooth erosion, abrasion and attrition. As enamel wears down, dentine becomes more apparent and chromogenic agents are penetrated in the tooth more easily. The natural production of secondary dentine also gradually darkens teeth with age.
• Dental caries (tooth decay): The evidence regarding carious tooth discolouration is inconclusive, however the most reliable evidence suggests that carious lesion allows for exogenous agents to enter dentine and hence increased absorption of chromogenic agents causing discolouration to the tooth.
• Restorative materials: The materials used during root canal treatments, such as eugenol and phenolic compounds, contain pigment that stain dentine. Restorations using amalgam also penetrate dentine tubules with tin over time therefore causing dark stains to the tooth.
• Dental trauma which may cause staining either as a result of pulp necrosis or internal resorption. Alternatively the tooth may become darker without pulp necrosis.
• Enamel hypoplasia: Enamel hypoplasia causes enamel to be thin and weak. It produces a yellow-brown discolouration and can also cause the enamel’s smooth surface to be rough and pitted which causes the tooth to be susceptible to extrinsic staining, tooth sensitivity, malocclusion, and dental caries. The evidence regarding enamel hypoplasia is inconclusive, however the most likely cause is infection or trauma caused to the primary dentition. Disturbances to the developing tooth germ during neonatal and early childhood stages such as maternal vitamin D deficiency, infection, and medication intake can cause enamel hypoplasia.
• Pulpal hyperemia: Pulpal hyperemia refers to inflammation of a traumatised tooth which can be caused by a stimuli such as trauma, thermal shock, or dental caries. Pulpal hyperemia is reversible and produces a red hue seen initially after trauma which has the ability to disappear if the tooth becomes revascularized.
• Fluorosis: Dental fluorosis causes enamel to become opaque, chalky white, and porous. The enamel can break down and cause the exposed subsurface enamel to become mottled and produce extrinsic dark brown-black stains. Dental fluorosis occurs due to excessive ingestion of fluoride or overexposure to fluoride during the development of enamel which usually occurs between the ages of one to four. Fluoridated drinking water, fluoride supplements, topical fluoride (fluoride toothpastes), and formula prescribed for children can increase the risk of dental fluorosis. Fluoride is considered an important factor in the management and prevention of dental caries, the safe level for daily fluoride intake is 0.05 to 0.07 mg/kg/day.
• Dentinogenesis imperfecta: Dentinogenesis imperfecta is a hereditary dentine defect, associated with osteogenesis imperfecta, which causes the tooth to become discoloured usually blue or brown in colour and translucent giving teeth an opalescent sheen. The condition is autosomal dominant which means that the condition runs in the family.
• Amelogenesis imperfecta: The appearance of amelogenesis imperfecta depends on the type of amelogenesis, there are 14 different subtypes and can vary from the appearance of hypoplasia to hypomineralisation which can produce different appearances of enamel from white mottling to yellow brown appearances.
• Tetracycline and minocycline: Tetracycline is a broad-spectrum antibiotic, and its derivative minocycline is common in the treatment of acne. The drug is able to chelate calcium ions and is incorporated into teeth, cartilage, and bone. Ingestion during the years of tooth development causes yellow-green discoloration of dentine visible through the enamel which is fluorescent under ultraviolet light. Later, the tetracycline is oxidized and the staining becomes more brown and no longer fluoresces under UV light.