Teeth stain for a variety of reasons. Staining is categorised as extrinsic or intrinsic. In basic terms, extrinsic stains can be removed with professional cleaning, whereas internal stains cannot.
For internal staining, we must rely on tooth whitening to enhance the colour of the teeth.
Below are some common examples of intrinsic and extrinsic staining.
The success of tooth whitening depends largely on the type of staining present. Intrinsic staining is discoloration that is incorporated into the structure of the tooth, either while the tooth is developing, or after it has erupted – this stain cannot be removed by prophylaxis (professional cleaning) and whitening is often the treatment of choice.
Some of the main causes of intrinsic staining are excessive fluoride intake over the period that the tooth develops. The resulting fluorosis manifests itself as either white and chalky enamel, or brown staining. Either way, bleaching can be used in most cases, to reduce the contrast of the mottled enamel and improve the appearance. In more extreme cases, these will still require either ICON resin infiltration, or more extensive restorative work.
Another major cause of intrinsic staining is the use of antibiotics, particularly tetracycline and minocycline. These impart a blue-grey banding on the teeth. The severity of staining will differ, depending on the type and duration of use. In both cases the staining is similar. However, minocycline can stain teeth both during development and after eruption. Prolonged whitening is usually required in these cases, but more often than not, it must be used in combination with bonding or veneers to achieve a satisfactory result.
The most common cause of intrinsic staining is trauma, which manifests itself in a two-fold process. Firstly, inflammation of the pulp causes haemorrhage into the dentinal tubules to give the tooth a pinkish tinge. The haemoglobin in the blood then breaks down to iron sulfide, leaving the tooth a grey, or dark black colour. This type of staining responds well to prolonged whitening. Likewise, if a tooth becomes necrotic secondary to trauma, a similar process occurs. However, treatment in this case must include root canal treatment to remove the necrotic material. This can then be followed by a course of internal whitening.
Other common causes of intrinsic staining are hereditary. Imperfections in the formation of either enamel or dentin can cause discoloured teeth. Both amelogenesis and dentinogenesis imperfecta, along with enamel hypoplasia, are examples of hereditary causes of intrinsic staining. Diseases like porphyria can also cause discoloured teeth owing to excess porphyrins in the blood during mineralization of the teeth. Affected teeth are usually pinkish brown.
Age also causes intrinsic discoloration of teeth. This is a result of changes in the physical composition of the tooth. Over time, layers of enamel are lost, exposing the darker underlying dentine. Sclerosis and secondary dentine can often take on a darker hue, which also contributes to age related discoloration
Extrinsic staining is far more common than intrinsic staining. Extrinsic stains are those that only affect the surface of the teeth and can be removed by prophylaxis. Mostly, these arise from the interaction of pigments from food and beverages with the plaque covering the enamel. This can easily be removed by dental prophylaxis and polishing. However, when this type of staining penetrates the microscopic cracks and fissures of the teeth, they cannot be removed by tooth-brushing or dental prophylaxis. In these instances, teeth whitening is required. The most common causes of extrinsic staining are coffee, tea, red wine and smoking.