I.  Treatment Options: Restoration or Whitening

A.  Restoration

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.

B.  Whitening

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.

C.  Stain

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:

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:

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.

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).

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).

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.

Stay updated, free dental videos. Join our Telegram channel

Join