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Professional Dental Terminology for the Dental Assistant and Hygienist

Course Number: 542

Tooth Whitening

Tooth color is determined by several factors. Both the enamel and the dentin play roles in the determination of what color is seen in the oral cavity. Both the enamel and the dentin are formed by millions of tiny crystals in a lipid/protein matrix.

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As stated earlier, enamel is the hardest substance in the body. The thickness of healthy enamel varies by tooth. Enamel is thinnest on incisors (about 2 mm) and thickest on molars (2.5 to 3 mm).

It is composed primarily (about 95%) of calcium phosphate molecules that are packed so tightly together that they are known as apatite crystals. Apatite crystals have often been called hydroxyapatite, which means it has attached oxygen and hydrogen groups, however pure hydroxyapatite does not really exist. Tooth mineral is more like a contaminated carbonated hydroxyapatite.

If fluoride ions replace some of the oxygen and hydrogen ions in the crystal, it becomes fluorapatite. Fluorapatite forms a stronger crystalline lattice and is more resistant to acid attack.

All these crystals in the matrix line up into a cluster that is perpendicular to the tooth surface and are known as enamel rods. There are tiny spaces between the crystals and fluids fill the spaces (protein, lipids and water) between the rods. Although these spaces are too small for bacteria to enter, other ions such as oxygen, hydrogen, fluoride, and calcium phosphate can enter. If the enamel is demineralized, it provides a more porous area for the carious process.

The natural color of the teeth comes from both the enamel and the underlining dentin. This color can range from a yellowish white to grey. The color of the dentin is a major contributor to overall tooth color. Genetically determined, dentin color ranges from yellowish white to grayish white.

Dentin is the largest tooth structure. It is calcified with tubules filled with plasma-like fluid, much like the enamel. As a living tissue, dentin conducts thermal sensitivity and pain from enamel to the nerve root, resulting in hypersensitivity.

Changes in tooth color can occur through several different means. They can be extrinsic or exogenous due to things such as food, drinks, tobacco and drugs. They usually adhere to the tooth deposits but can also adhere to the tooth structure itself.

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Intrinsic, or endogenous stains can also cause color changes within the tooth. These include staining from aging, oral disease, trauma, medications, systemic conditions, and heredity.

As teeth grow older, the pulp shrinks and the dentin becomes thicker, which can cause teeth to look more yellow. Oral diseases, such as exposed root surfaces from gingival recession or restorations, also affect tooth color.

During trauma, vital pulp tissue can die. If trauma does not destroy the tooth, bleeding into tooth structures can occur causing darkening over time. Enamel defects can result from trauma during tooth formation or inherited dental disorders, such as amelogenesis imperfecta.

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Medications taken during tooth formation can result in enamel defects. A common cause is the antibiotic tetracycline. Fluorosis, or excess fluoride consumption, can also cause mottled and spotted teeth, as shown here.

Nikki to Group: “Our last patient of the day is Ms. Daniella Johnson. Ms. Johnson has both intrinsic and extrinsic staining on her teeth. She will be on the hygiene schedule but also would like to talk about the possibility of using a whitening product or having in-office whitening. Jessica will discuss some of the options with her and then she will see Dr. Jay to discuss what she wants to do.”

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Jessica to Daniella: “Daniella, I understand that you are interested in tooth whitening or bleaching. After we complete your cleaning appointment and see what stains remain afterwards, we will discuss the various options and take a look at your tooth color by matching it to a chart and then determine what method is the most appropriate for you. Then Dr. Jay will come in to do the exam and discuss her recommendation with you.”

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Dr. Jay to Daniella: “Your teeth have mostly superficial or extrinsic stains. The tooth whitening procedures available to you will remove the stains on your teeth, leaving them potentially up to five to ten shades whiter. However, we don’t know exactly how your teeth will respond to treatment. These before and after photos will give you a better idea of the results that you might expect. Because you are a coffee drinker, you should be aware that whitening will not prevent future staining.”

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Dr. Jay to Daniella: “There is a spectrum of options for extrinsic stain removal that range from short- to long-term and from low to high efficacy. Some of these you can perform at home, while others are performed here in the office.”

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There are several means of removing extrinsic stains at home, such as using a whitening toothpaste or whitening mouth rinse along with the oral prophylaxis in the dental office. Tooth enamel can be further whitened by chemical tooth bleaching using gel trays. This can be done at home over a series of weeks to months. You can also use whitening strips or whitening emulsions (which can also utilize LED lights for enhanced effectiveness) at home, which typically require less time than gel trays and can get similar results. Sometimes bleaching procedures can cause tooth sensitivity. This will usually resolve when you discontinue the bleaching process. A toothpaste to relieve sensitivity may also be helpful.

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In-office bleaching usually is done in a separate appointment where the teeth are isolated and a bleaching material is applied. The bleaching effect may be enhanced through the use of a laser or special light.