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What causes teeth staining, yellow teeth, and tooth discoloration?

Published by
SmileLabs, LLC
Written by
Zachary Hilgers, DDS (Retired)
March 30th, 2010
© All Rights Reserved


A question that is frequently asked is, “What are the causes of teeth staining or yellowing?”  This page gives the answer to this question in detail. This is because we want consumers and our current and future Authorize SmileLAB™ Dealers to understand the etiology, or many reasons behind, the manner in which teeth become undesirably discolored, and which types of discoloration can SmileLABS™ treatments help eliminate or correct, and which types will not significantly change color with our cosmetic teeth whitening products and techniques.


There are basically two types of teeth stains. These are extrinsic stains and intrinsic stains. Extrinsic refers to the type of stain that is deposited or formed on the outside surfaces of teeth. Extrinsic stains are generally separate from the actual make up or structure of the teeth, and in general can be more easily removed from the teeth because the stain or color is not part of the chemical and mineral structure of the teeth.

Intrinsic color or staining means that the color of the teeth that we see comes mostly from the inside of the teeth and has become part of the internal mineral and chemical structure of the tooth. These stains or colorations are much more difficult, if not impossible, to remove from the inside of the teeth. We will now look at the various types of extrinsic and intrinsic stains and see how they can or cannot be affected by our cosmetic bleaching process.


Different types of food and drinks will cause stains to be deposited on the outside surfaces of the teeth. Some of the more obvious stain-causing beverages are coffee, tea, colas and red wines. The long-chain chromophore (color containing) molecules in these drinks will attach themselves to the outer enamel surfaces, as well as penetrate into the enamel via the tiny microscopic channels or tubules that are part of normal enamel anatomy. Certain obvious fruits and vegetables also can cause stains, like blueberries and cherries, but also some not so obvious ones such as apples and potatoes can be broken down by bacteria that leave an end-product that is quite dark, if not brown or black, that can adhere to the enamel and can penetrate the tubules and cause stain and discoloration to form.

Tobacco, in the form of smoking or chewing, also leaves extrinsic stains on or in the teeth enamel. Over the many years of tobacco abuse, truly horrible dark stains are accumulated and deposited on the teeth.

Although the example shown above should seek a good dental cleaning first, it should be noted that most mild to moderate tobacco stains and discolorations caused by foods and beverages can generally be removed or greatly reduced by cosmetic whitening. It would help if the smoker would cease smoking altogether so that new stain would not again quickly recur, but such is not always a reasonable expectation of a tobacco-addicted customer.

It should be noted that severely inadequate oral hygiene in the form of brushing and flossing, if uncorrected over a long period of time, can result in large quantities of calculus (tartar) build-up to occur. This calculus is easily stained by the foods and beverages we eat and drink.

The calculus on some some customer's teeth might have been there for years and have actually turned black! If, as a SmileLABS™ lab owner, you ever come across someone with teeth that look like this, don’t even think of whitening their teeth! Refer them immediately to their dentist to get the tartar removed and allow the teeth and gums to become healthy again, if possible.

Certain dental restorative materials, such as amalgam, or so called “silver fillings,” can over time have stain leach out of the restorations that deposit onto the enamel and cause discolorations.

If dental decay is allowed to run rampant through a person’s mouth, the decay itself is brown or black colored.

Again, if you as a lab owner see a customer with teeth that very obviously have these conditions, an immediate referral to their dentist is the best and only thing you can do for these unfortunate individuals. Cosmetic teeth bleaching will not in any way help these people.


One of the common types of stains or colorations inside teeth can be caused by a person’s genetics. While the enamel on teeth is mostly of a pearly white color, the underlying layer of tooth structure below the enamel is the much more naturally yellow hard tissue known as the dentin. In most individuals, the outer white enamel is generally thick enough to cover completely the yellow dentin underneath. However, some people are born with a genetic disposition towards very thin or even nonexistent enamel. This leaves their teeth with a distinct yellow caste to their teeth. This condition is not treatable by cosmetic bleaching.

It should also be noted that a person’s advancing age can cause the outer layer of enamel to wear away and become much thinner, again showing more of the dentin’s yellow color to come through. Unfortunately, bleaching such teeth will not improve the overall yellow appearance of thinned enamel.

Lastly, there are two other types of intrinsic stains, with which all lab owners should become familiar. Most people that have these conditions will know they have them and will tell the lab owner so, but you should be able to recognize these two relatively common discolorations.

Both of these conditions occur very early in a customer’s life, usually before the age of 8 years, when the individual still has most of his or her primary dentition (baby teeth). These stains are incorporated into the teeth as the dental hard structure of the enamel is still forming in the as-yet unerupted permanent teeth.

The first is what are known as tetracycline-stained teeth. Tetracycline is a broad spectrum antibiotic used to treat various infections. It is still in use today, however when first introduced, its stain-producing characteristics were unknown. If the medication was given to a pregnant woman or to children under the age of eight, some of the drug was bound up into the forming permanent teeth’s enamel of the child. When the adult teeth eventually erupted, a brown or grayish type of striated or banded stain was visible within these permanent teeth. The tetracycline had become incorporated into the hydroxyapatite crystals (normal mineral structure) of the enamel.

The other common stain of this type is known as fluorosed teeth, or as fluorosis. It is also caused by the uptake of not a medication, but of fluoride into the enamel of growing permanent teeth. This condition is not caused by the very low concentration of fluoride that is commonly added to municipal water supplies. It is caused by a naturally occurring high concentration of fluoride in rural water tables in the ground, or by a young child that swallows an inordinate amount of fluoride toothpaste. Although the resulting enamel is unusually hard, its appearance is very unsightly.

Unfortunately the enamel discolorations caused by tetracycline and fluorosis cannot be corrected by cosmetic teeth bleaching. Only a dentist can help these customers by covering up the stains with either dental porcelain crowns or veneers.


In this paper we have learned that only extrinsic stains caused by certain foods, beverages, or tobacco products can be removed by SmileLABS™ cosmetic teeth whitening products and treatments. All other types of discolorations need to be referred to the customer’s dentist, who may or may not be able to help them. It is important that every SmileLABS™ lab owner be able to understand and recognize these different types of stains and discolorations, so that he or she is able to predict for their customers the best possible results from the teeth whitening process and to also know when to refer the customer back to the dentist before any type of whitening is contemplated.

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