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After studying this chapter, the student will be able to do the following:
1. Define tooth whitening and explain the difference between vital and nonvital tooth whitening.
2. Explain the difference between intrinsic and extrinsic stains, and list examples of each.
3. Identify two chemical agents used for vital tooth whitening, and explain the process by which whitening agents whiten teeth.
4. Identify two chemical agents used for nonvital tooth whitening.
5. List the factors that affect the success of tooth whitening.
6. Compare and contrast patient-applied and professionally applied vital whitening.
7. List contraindications for both patient-applied and professionally applied tooth whitening procedures.
8. Discuss measures to prevent or alleviate tooth whitening side effects.
9. Become familiar with the statement made by the ADA on the safety and efficacy of tooth whitening.
dicalcium phosphate dihydrate
neutral sodium fluoride
nightguard vital whitening
precipitated calcium carbonate
tooth whitening or tooth bleaching
vital tooth whitening
Teeth that are naturally discolored or have become stained can be treated with a whitening agent. Depending on the cause of the discoloration or the type of stain, one of several whitening techniques may be used. The procedure is often referred to as tooth whitening or tooth bleaching.
A nonvital tooth is treated differently than a vital tooth. A nonvital tooth gives no response to temperature change or electrical stimulus. The pulp in this tooth is no longer living, hence the term “nonvital.” The pulp cavity within a nonvital tooth may contain necrotic pulp, no pulp, or an inert material placed when an endodontic procedure known as a root canal was completed.
The terminology used when vital teeth are treated is vital tooth whitening. A vital tooth (a tooth with living pulp tissue) can be whitened in the dental office by the dental team or at home by the patient. When the whitening treatment is done at home by the patient, it is frequently called nightguard vital whitening because the whitening agent is applied to the teeth inside a custom tray resembling a nightguard appliance. A trayless tooth whitening system is now available. Trayless systems use flexible, adhesive, polyethylene strips that are coated with a whitening agent. Tooth whitening is a cosmetic procedure and the most frequently performed of all cosmetic dental procedures. A patient’s perception regarding his or her appearance is critical in determining whether tooth whitening is sought and/or accepted. The dentist and dental hygienist may be satisfied with the results of a prescribed whitening treatment, but the patient may or may not be satisfied, again depending on his or her perception.
I. Treatment Options: Restoration or Whitening
Occasionally, tooth whitening fails to achieve the desired cosmetic result. When the discoloration or stain is severe, restoration of the tooth may be the treatment of choice. Full crowns, either all porcelain or porcelain bonded to metal, require a significant amount of tooth removal from all surfaces. Facial veneers, either porcelain or composite, are a more conservative restorative option because less tooth removal is required. In some clinical situations, restoration of teeth may not be the preferred treatment because of the need to conserve tooth structure. A treatment plan may include whitening of some teeth and restoration of others. When restoration of teeth is planned in conjunction with whitening, whitening is usually accomplished first so that the esthetic restorations can then be matched to the resulting shade of the whitened natural teeth. An immediate relapse in the whitening effect occurs immediately after the treatment is completed. For this reason, esthetic restoration of teeth should be delayed for 2 weeks after the completion of tooth whitening.
Restorative treatment that involves bonding to enamel, such as facial veneers, must be delayed for a minimum of 2 weeks after whitening is completed, because recently whitened tooth enamel produces a weaker bond to restorative materials.
Whitening is the most conservative treatment option for the esthetic improvement of discolored or stained teeth. No tooth structure is sacrificed in the preparation of vital teeth for whitening. In the treatment of nonvital teeth, an opening into the pulp chamber, either from the lingual surface of anterior teeth or from the occlusal surface of posterior teeth, is necessary. Many factors potentially affect the outcome of the whitening procedure. The success of the procedure depends on the following factors:
- Cause or type of discoloration or stain
- Degree or intensity of discoloration or stain
- Whitening agent selected
- Strength of the whitening agent
- Length of exposure of the tooth to the whitening agent
- Whitening technique
- Vitality of the tooth
- Presence of a restoration in the tooth
II. Causes of Tooth Discoloration
A. Nonvital Teeth
A tooth with a necrotic pulp or one that has been endodontically treated has a tendency to darken with the passage of time. Significantly darkened teeth should be noted during clinical examination, and the cause of darkening should be investigated.
An injury to a tooth may cause the pulp tissue to become necrotic, with no sign or symptom of necrosis other than a noticeable darkening of the tooth. The decomposition of pulp tissues, especially the hemoglobin of the red blood cells, produces a dark stain that penetrates the dentinal tubules.
After a tooth has been diagnosed as nonvital, appropriate endodontic treatment must be performed. The most common endodontic procedure is root canal therapy. When a root canal procedure is performed, the contents of the pulp cavity, including both the root canal(s) and the coronal pulp chamber, are removed. The pulp chamber and root canal(s) are then filled with an inert material, such as gutta-percha (a natural resin). The entire procedure is performed under aseptic conditions and usually requires multiple appointments. After a nonvital tooth has been successfully treated, a full crown is usually recommended to strengthen the tooth. If an endodontically treated tooth is not restored with a crown, a nonvital whitening treatment may be performed to lighten the color (shade) of the darkened tooth.
B. Vital Teeth
Teeth are naturally white and bright, with a translucence that contributes to their brightness. Teeth vary in color or shade from person to person, and as teeth age, they also darken. Some patients may ask if the natural shade or color of their teeth can be changed to improve their appearance. Whitening may be an effective treatment option for the esthetic improvement of healthy natural teeth.
Both vital and nonvital teeth are subject to staining. There are two types or classifications of stain: extrinsic stain and intrinsic stain.
1. Extrinsic Stain
An extrinsic stain occurs on the surface of the tooth. Causes of extrinsic staining include foods and drinks, such as coffee and tea, and tobacco, both smoked and smokeless. Some extrinsic staining can be removed, at least partially, by the patient using a toothbrush and dentifrice. Some dentifrices are formulated and marketed to aid in extrinsic stain removal, but they have limited effectiveness in removing severe staining. Extrinsic staining that is resistant to removal by the patient may be removed with scaling and polishing by the dentist or dental hygienist. Extrinsic stains that are resistant to complete removal can be effectively removed by whitening treatments. Whitening treatments are more effective against extrinsic than against intrinsic stains.
2. Intrinsic Stain
An intrinsic stain occurs within tooth structures (enamel or dentin).
a. Posteruptive Stain
Some intrinsic stain occurs after the tooth erupts. Causes for this type of stain include the following:
1. Amalgam restorations
Stains caused by silver amalgam cannot be successfully removed by the whitening process.
Caries should be removed and the tooth restored before whitening is attempted.
3. Endodontic treatment (root canal therapy)
Stains resulting from endodontic treatment can be successfully whitened.
b. Preeruptive Stain
Other intrinsic stains occur before tooth eruption, when the teeth are in the formative or calcification stage. These stains include the following:
1. Tetracycline Stain
Tetracycline antibiotics that are ingested during tooth calcification may cause an intrinsic tetracycline staining of both dentin and enamel. Tetracycline binds chemically with the hydroxyapatite crystals of dentin and enamel. When tetracycline-stained dentin or enamel is exposed to a black (fluorescent) light, the tetracycline crystals produce a fluorescent glow. Under natural and artificial light, tetracycline stains appear as gray or brown stains of varying intensity, usually occurring in horizontal bands within the tooth. Tetracycline-stained teeth are difficult to whiten. The milder the staining, the more successful is the result.
High levels of fluoride (>1 ppm) consumed from the drinking water during tooth formation and calcification may cause staining known as fluorosis. Fluoride-containing dentifrices and mouthwashes are potential sources of excessive systemic fluoride. Parents should be cautioned to supervise children who use a fluoride dentifrice or mouthwash to prevent accidental or intentional swallowing. In its milder form, fluorosis appears as white spots in the enamel, with no pitting. In more severe cases, fluorosis causes brown spotting and pitting of the enamel. Teeth with fluorosis are difficult to whiten. The milder the fluorosis, the more successful is the result.
3. Dentinogenesis Imperfecta and Amelogenesis Imperfecta
Dentinogenesis imperfecta and amelogenesis imperfecta are inherited conditions that result in defective dentin and enamel formation, respectively. Whitening will not significantly improve the appearance of teeth that are affected by dentinogenesis or amelogenesis imperfecta.
III. Whitening Agents
A. Hydrogen Peroxide
Hydrogen peroxide (H2O2) is a strong oxidizing agent that readily decomposes into water and oxygen. The decomposition of hydrogen peroxide releases free radicals of oxygen that react with pigments in both extrinsic and intrinsic stains, producing the whitening effect. Free radicals of oxygen contain an unpaired electron and, therefore, are highly reactive. Figure 17.1A illustrates the decomposition of hydrogen peroxide into water and free radicals of oxygen.
FIGURE 17.1. Decomposition of hydrogen peroxide. A. Hydrogen peroxide, a strong oxidizing agent, breaks down into water and oxygen. Oxygen reacts with the pigments in both extrinsic and intrinsic stains, producing the bleaching effect. B. Carbamide peroxide, a weaker oxidizing agent, breaks down into hydrogen peroxide and urea.
Hydrogen peroxide can penetrate enamel and dentin and may produce a reversible pulpitis, which is a temporary inflammation of the pulp tissue. Tooth sensitivity resulting from pulpitis is the most frequently reported side effect of the whitening process. Precautions must be taken to protect the patient’s eyes, face, and intraoral soft tissues (lips, cheeks, and tongue), as well as the patient’s clothes from hydrogen peroxide solutions.
Hydrogen peroxide is applied to the teeth in either a liquid or a gel form and in strengths varying from 5% to 35%. Figure 17.2 shows an example of a hydrogen peroxide tooth whitening agent (Zoom, Discus Dental).
FIGURE 17.2. Zoom chairside hydrogen peroxide whitening agent. (Discus Dental).
B. Carbamide Peroxide
Carbamide peroxide (CH6N2O3) is a complex (secondary bonds) of two molecules, urea and hydrogen peroxide. It is applied to the teeth in either a liquid or a gel form and in strengths varying from 10% to 20%. Figure 17.3 shows examples of a carbamide peroxide gel (Rembrandt; Dent Mat, Santa Monica, CA) and paste (Colgate Platinum; Colgate Palmolive, New York, NY).
FIGURE 17.3. Carbamide peroxide whitening gels.
Carbamide peroxide decomposes into urea and hydrogen peroxide. Hydrogen peroxide then breaks down into water and oxygen (Fig. 17.1B). A 10% carbamide peroxide solution is equivalent to 3% hydrogen peroxide, whereas a 15% solution is equivalent to 5% hydrogen peroxide. Carbamide peroxide products are more stable (longer shelf life) than are hydrogen peroxide products. Most carbamide peroxide whitening gels contain Carbopol (BF Goodrich, Richfield, OH), which is a thickening agent that increases adhesion of the gel to the tooth, thereby prolonging exposure to the whitening agent.
C. Sodium Perborate
Sodium perborate is another weak oxidizing agent. It is sometimes used together with hydrogen peroxide to whiten nonvital teeth. Sodium perborate is the active ingredient in many household fabric bleaches, which are designated as being safe for colors.
IV. Whitening Techniques
A. Nonvital Whitening
Prior to the whitening procedure, a nonvital tooth endodontic treatment must be completed. The canal is opened by removal of the gutta-percha. Two methods can be used to attain bleaching: a power (heat- and light-activated) whitening or a walking bleach method.
The power whitening is done similarly to the vital tooth bleaching. Once the pulp chamber is cleared of debris, a bur may be used to clear the canal. The canal is sealed and the tooth is isolated with a resin dam. An in-office heat-, light-, or laser-activated bleaching material may be applied to the coronal surface of the tooth. Once activated and whitening is attained, the canal may be filled with an esthetic restorative material. Research has shown that bond strength of materials is weakest immediately after bleaching. With the weak bond postbleaching, esthetic restorations must be placed at least 7 days after the whitening procedure, preferably after 2 weeks.
Nonvital walking bleach is a second method of lightening endodontically treated teeth. Sodium perborate mixed with 35% hydrogen peroxide or one of the commercial in-office bleaches is placed in the cleared canal. The canal is packed with a cotton pellet and sealed with zinc phosphate or IRM. The endodontic patient will retain the bleach within the canal for 3 to 7 days; at that time, the patient will be reevaluated for results. The method can weaken the bond between tooth surface and esthetic restorations. Therefore, restorations must be done no sooner than 7 days after bleaching. Walking bleach can also increase free radical formation in the root canal of a nonvital tooth and lead to external resorption. Because of these side effects, the walking bleach method is not done as frequently.
B. Vital Whitening
Since the introduction of an effective patient-applied technique in 1989, tooth whitening has grown rapidly in popularity. Two whitening techniques are most popular:
- A professionally applied, in-office technique
- A patient-applied (at-home), professionally supervised technique. Over-the-counter whitening products are also available to the public. Some of these are not recommended; however, because they are used without professional supervision. These are discussed later in this section.
- As with any treatment modality, case selection is an important factor in determining a successful outcome. When vital teeth are to be whitened, the time that is required to achieve the desired result will vary with the technique that is chosen as well as with the type and degree of stain or discoloration. It would be difficult to say that one whitening technique is superior to another in terms of the final result that is achieved.
- It is important to note that the results achieved with any tooth whitening technique are not permanent. Some degree of relapse can be expected. Retreatment may be necessary as early as 6 months after initial treatment. For most patients, a retreatment frequency of every 2 years can be expected.
1. Professionally Applied, In-Office Whitening
The professionally applied, in-office whitening technique is often referred to as power whitening. As power whitening uses higher concentrations of hydrogen peroxide (15–35%), all soft tissues and eyes must be protected. Teeth to be whitened are isolated with a rubber dam or a paint-on liquid resin dam. Often, a light- or heat-activated method of accelerating the bleaching process is utilized, but their effectiveness has been questioned.
The paint-on resin dam (e.g., Liquid Dam or Pulpdent Kool-Dam) has become popular and is replacing the use of the conventional rubber dam. The paint-on resin dam may be autocure or light cure. When using a paint-on resin dam, the gingiva, tongue, and facial mucosa are protected with a coat of a petroleum-based lubricant. Figure 17.4 illustrates proper isolation for the power whitening procedure. In addition, the patient’s eyes are protected with appropriate safety glasses.
FIGURE 17.4. Patient isolated with retractors, cotton rolls, gauze, and paint-on resin dental dam awaiting power (light-/heat-activated) whitening procedure.