|
Extrinsic Staining vs. Intrinsic Staining
 Whitening success depends largely on the type of staining present in a dentition. Intrinsic staining is stain that was incorporated into a tooth, either while the tooth was developing or after it has erupted. There are a few main culprits that cause intrinsic staining. The first is through high systemic intake of fluoride during the development of the tooth. Tooth development occurs constantly from the second half of fetal development until approximately age 18. Too much systemic intake of fluoride causes a condition called fluorosis or mottled enamel. In most cases the enamel of the tooth will appear white and chalky. However, sometimes it will appear brown. Either way, bleaching can be used to reduce the contrast of the mottled enamel to healthy enamel and make the condition less noticeable. Sometimes, though, surface defects or "pits" may be present as well making other restorative procedures (veneers or bonding) a more esthetic option. Whitening these teeth prior to restoration is a good idea to give a more consistent shade underneath the restoration.
 Another cause of intrinsic staining is medications; more specifically the antibiotics tetracycline and minocycline. Use of these antibiotics during tooth formation can cause a bluish-grey stain on the portion of the tooth developing at the time of use. Severity of staining will differ depending on the type and duration of use. Minocycline is a derivative of tetracycline and the staining appears similar in both. However, they differ in that minocycline can stain teeth both during development and after eruption.3, 4 This drug use to be widely prescribed for treatment of acne though, due to this side effect, it has fallen into disfavor. The mechanism by which minocycline stains teeth is not fully understood at this time. Prolonged bleaching can drastically diminish the appearance of this staining but can never fully remove the discoloration. Patients are often unsatisfied with the result and will require veneers or bonding to restore.
Perhaps the most common cause of extrinsic staining for already erupted teeth is trauma. Trauma to a tooth induces an inflammatory reaction consisting of hemorrhage from the pulp into the dentinal tubeles. This causes a slight pinkish change in the color, often only noticeable in the gingival 1/3 of the tooth. As the hemoglobin breaks down, it leaves iron sulfide in the tubules, which produces a darker black color. This type of staining typically responds well to prolonged whitening. Likewise, if a tooth becomes necrotic secondary to trauma, a similar process occurs. However, treatment in this case includes root canal therapy to remove the necrotic material.3
Other causes of intrinsic staining are hereditary. Imperfections in the formation of either enamel or dentin can cause discolored teeth. Both amelogenesis and dentinogenesis imperfecta, along with enamel hypoplasia are examples of hereditary causes of intrinsic staining. Diseases like porphyria can also cause discolored teeth due to excess porphyrins in the blood during mineralization of the teeth. Affected teeth are usually pinkish brown.5
Age also causes an intrinsic discoloration of teeth. This is due to changes in the physical composition of the tooth. Over the years, layer of enamel are lost, exposing more of the darker shaded dentin. Likewise, reparative dentin is formed over time and any pigments present in the systemic circulation at that time can be incorporated into the tooth. Dental restorations can also cause changes in tooth color. Amalgams restorations can give a tooth a grayish-blue appearance even if the restoration itself is not visible. This is less common today with the improvement and increased utilization of multi-shaded composite resin restorations.
 Extrinsic staining is far more common than intrinsic staining. Extrinsic stains are those that cling to the exterior of the tooth or penetrate into the very outer layers of enamel. A majority of staining is caused by the interaction of pigments from food and beverages with the plaque covering the enamel surface. This plaque, and consequently the stains as well, are removed at each dental recall appointment. When stains penetrate the microscopic cracks and fissures of the teeth, they cannot be removed by toothbrushing or dental cleanings. The most common causes of extrinsic staining are coffee, tea, red wine and smoking. These four culprits are all things that most people are not willing to give up just to have whiter teeth. This is one reason for the optimistic outlook on the future of the tooth whitening industry.
Continue on to
|
Color
