In part one, we looked at causes of tooth staining known as extrinsic tooth discoloration. In this article, we will look at Intrinsic tooth staining. There are various types if intrinsic tooth staining and the common ones include the following:
- A dead tooth
- Worn enamel
- Enamel defects
- A heavily filled tooth
Let’s go through each one in turn and the treatments available.
A Dead Tooth
This is the most commonest reason for a single tooth being dark. It will be dark because it either needs a root canal treatment or because it already has had a root canal performed on it, in the past.
A tooth becomes dead because it has either received a knock on it such as a blow or by falling. The root inside a normal healthy tooth contains the nerve of the tooth. The nerve keeps the tooth alive and nourished. This nerve detects changes to hot and cold. The proper dental scientific name for a tooth nerve is the pulp. In dental terms when a pulp dies, this is known as the tooth becoming non vital. As soon as the pulp becomes non vital, there is no longer any blood flow and the blood vessels disintegrate. This means that without blood, there are no white blood cells to fight infection. The root canal space becomes populated by bacteria which release toxins. These toxins cause inflammation of the surrounding periapical areas called periapical periodontitis. From this various states can occur. These states are a chronic infection, an acute infection, an abscess, a discharging sinus or a cyst.
Once it is diagnosed that the pulp is necrotic, the next decision is to see if a root canal can be performed or is an extraction the only option. If a root canal has been performed, it is important to realise that although the tooth will no longer be infected, it will still be discoloured. It may even get discoloured even more than before. The next stage is to then address the colour of the tooth and the 3 options are a crown, a veneer or internal whitening.
When the enamel of a tooth wears away or gets thinner, a tooth will appear more yellow and darker. This is because the underlying tooth layer called dentine is much more yellow and darker than the enamel coating on the outside of a tooth. Also, the layer of dentine actually becomes thicker as we get older and that is the reason why teeth look yellow in old age. If you go to your dentist regularly, he can see if your enamel is wearing away faster than it should be. A common cause is bruxism or teeth grinding at night. Grinding your teeth at night causes the enamel to gradually chip and wear away hence exposing the underlying yellow dentine layer. The forces of bruxism also stimulates the pulp of the tooth to produce even more dentine as production of dentine is a protective mechanism for the pulp. The cosmetic treatments for discolouration due to tooth wear include crowns, veneers, tooth whitening and composites.
Dental fluorosis is the ingestion of excessive concentrations of fluoride during the enamel formation phase of tooth development. The excess fluoride disturbs the natural formation of tooth enamel which ends up as the tooth appearing to have milky white and brown patches. The amount and severity depends on how much excess fluoride the child was exposed to and for how long and at what point in the development of the tooth. In mild cases, there may be a slight small yellow patch on a front tooth but in severe cases, many teeth are affected and the discoloration is very dark brown. The enamel in severe cases can end up grooved and dented. The cosmetic options for Dental fluorosis are microabrasion, crowns, veneers and tooth whitening.
There are different types of enamel defects which cause teeth to become discoloured. Enamel defects arise when the enamel is being formed in the gum prior to the fully formed tooth beginning to come through. This time period is between the last trimester of pregnancy and up to four years of the child’s age. There are different names given to this condition. These are known as enamel hypomineralization, enamel hypoplasia and enamel hypocalcification. Many different reasons exist as to why enamel defects occur. Reasons include severe illness during pregnancy or early childhood, ingestion of medications and often no reason can be found. A tooth which is affected by enamel defects is more likely to decay or suffer tooth wear as it is softer than normal health enamel. In addition, fillings in these teeth do not last as long as it is more difficult for a new filling to get to stick, in the first place resulting in the filling coming out or decaying around the edges again. For front teeth, the other additional problem is the tooth becoming discoloured as a result of improper enamel formation. There may be a combination of mottled white patches, brown and yellow areas where the enamel formation has been disturbed. Treatments include crowns, veneers, composites and tooth whitening.
A heavily filled tooth
A tooth which has a large filling will often discolour over a period of time. This can be because the old filling has started to leak and new decay has started under or around the filling. In this case, it is advisable to remove the old filling and remove the decay. Once the decay has been removed it is necessary to place a brand new filling or if there is not enough tooth structure remaining, an alternative means such as a crown or a veneer.
Of course, it can be that there is no decay but the filling itself has discoloured through the passage of time. In this case it is sometimes possible to polish up the old filling but usually, the best method is to completely replace the old filling with a new one. A good experienced dentist can match the colour of your new filling as close as possible to the tooth so that the filling looks invisible. It’s quite difficult for any dentist to do this type of cosmetic filling. The final result depends on factors such as the type of filling used, layering techniques, cavity margins, contouring and polishing.
Back teeth which have amalgam or mercury fillings also appear discoloured after a time period. The discolouration is due to the tin ions from disintegration of the amalgam. Dental amalgam is an alloy containing mainly mercury, copper, tin and zinc.
Decay can appear in different formats. Very early decay causes a white spot lesion. A white spot lesion is more porous than normal enamel and with picking up stains, it becomes a brown spot lesion. When the decay progresses, the enamel breaks through and an actually hole or cavity is evident. The decay can range in colour from light yellow to brown to black. In all cases, the decay needs to be removed by a dentist and the cavity filled with a cosmetic material for a front tooth. The two filling materials available for a front tooth are composites of glass ionomers.