TOOTH WHITENING: With Abundance of Whitening Products, Patients Look to Dentists for Direction

Tooth whitening is one of the most conservative treatments in dentistry. Results from in-vitro studies initially raised concern that external tooth whitening would cause significant reduction in enamel microhardness; however, findings from subsequent in-situ studies and a clinical study did not support this.^2-5 In addition, an in-vivo study showed that whitening treatment does not alter the concentration of calcium and phosphorous on the enamel surface.⁶ The remineralizing potential of the saliva is the key component to the difference between in-vitro and in-vivo study results.⁷ The pH of whitening products may also play a role in the properties of the enamel surface. Whitening solutions with lower pH values may result in more significant erosion of enamel.⁸ Many whitening products are formulated with lower pH values to ensure the stability of hydrogen peroxide. Consequently, dentists should be cautious when choosing tooth-whitening agents.

Whitening products may be administered in the office (in-office), prescribed by dentists for home use (at-home with dentist-prescribed products), or purchased over-the-counter (OTC). With so many options and an overwhelming amount of information available to patients, clinicians should inform them of the key differences among tooth-whitening products, namely peroxide concentration, duration of application, means of delivery, and cost.

Dating back to the 1800s, in-office whitening treatment is one of the oldest—and yet controversial—vital tooth-whitening procedures. The practice of applying a high concentration of hydrogen peroxide (HP) on vital tooth surfaces for 10- to 15-minute intervals for up to 1 hour to achieve whitening of the tooth is well established,⁹ and there is strong evidence of in-office treatment efficacy.⁹ However, it is unclear whether or not a light source enhances the whitening effect, as the use of illumination is meant to accelerate bleaching.

A gamut of in-office whitening products varying from 15% to 40% HP are available. Some systems are accompanied by light sources; others are not. Light sources include quartz–tungsten–halogen lamp and derivatives, plasma-arc lamp (xenon discharge) and derivatives, metal halide, light-emitting diode, and several types of laser. When light activation is applied, manufacturers’ recommendations must be followed, using a limited duration of heat activation in order to avoid undesired pulpal responses.

Findings from studies vary significantly regarding the amount of whitening effect. Hydrogen peroxide concentration, number of applications, amount of application time, choice of shade guide, ambient light, and evaluator are factors that essentially account for the differences in results.

The in-office system is a good option if a rapid treatment is desired or patient compliance is a concern. However, it is expensive when compared with at-home whitening treatment. In-office whitening could also be applied as a “boost” therapy, to initiate the process, which might be followed by at-home whitening. A single application of in-office whitening is usually not sufficient to achieve optimal results, and patients usually desire to continue treatment.

The main concern of in-office treatment is the high concentration of HP. If the tissues are not well protected, the whitening agent can severely burn soft tissues. Another adverse effect is transient tooth sensitivity.

By the late 1980s, at-home whitening treatment using dentist-prescribed products made tooth whitening more popular. The 10% concentration of carbamide peroxide (CP) used in trays overnight has been considered the “gold standard.” Today, this technique uses either CP or HP in various concentrations with a custom-fitted tray. An alternative method employs a preloaded disposable whitening tray provided by the dentist; this option is recommended when the patient does not desire to have impressions taken but still chooses at-home dentist-supervised whitening treatment.

Carbamide peroxide concentration ranges from 10% to 35%, and HP concentration is 3% to 15%. A product with 10% CP yields roughly 3.5% HP. The at-home technique is still the most common whitening procedure, and the literature heavily supports the efficacy of using a tray whitening system with 10% CP.¹⁰ Some evidence shows tooth whitening with 10% CP to be successful on tenacious stains, such as those caused by tetracycline.¹¹ The treatment success depends greatly on patient compliance. Whitening persistent stains takes time, and patients need to be willing to adhere to a potentially lengthy regimen.

At-home whitening can be performed during the day or overnight. The 10% to 20% CP concentration can be applied in the tray and worn several hours a day or overnight. The higher concentration of CP (35%) and HP should be used for 30 to 60 minutes. A lower CP concentration applied for a few hours a day is a good option for patients with tooth sensitivity. A reduction in tooth sensitivity has occurred over the years due to the inclusion of desensitizing agents, such as amorphous calcium phosphate, fluoride, and potassium nitrate in the whitening gel formula.

Evidence suggests long-term effectiveness and safety, indicating no long-term oral or systemic health problems associated with the application of 10% CP overnight.¹² This peroxide concentration is the only one to be granted the ADA seal of approval.

Many consider OTC tooth whitening to be an affordable treatment. Several types of OTC systems are on the market. Whitening strips with 6% HP have been the most extensively studied and are efficacious in removing intrinsic stains.¹³ The most common patient complaint is the strips do not adapt well, which hinders patient compliance with the treatment regimen. One split-mouth design study reported that 83% of participants preferred at-home tray whitening to whitening strips.¹⁴

Other OTC tooth-whitening products include paint-on brushes, rinses, toothpastes, dental floss, chewing gum, and hand-held lights. Whitening toothpastes, gum, and floss remove superficial stains; however, these products do not change the inherent tooth color. Rinses and paint-on brushes have some whitening effect but without clinical relevance.¹³

HP is genotoxic in vitro, but such activity is not expressed in vivo. The development of preneoplastic or neoplastic oral lesions has not been shown. Generally, tooth-whitening products are safe for human use.¹⁵ Nonetheless, long-term safety of unsupervised whitening procedures has been a concern due to abuse and possible undiagnosed oral health problems. Diagnosis of the cause of tooth discoloration followed by an explanation of the estimated treatment time, benefits, and risks are significant considerations to address patient concerns and establish reasonable expectations.

Overall, tooth whitening does whiten teeth and thereby accomplishes its purpose. Patient satisfaction is usually high with tooth-whitening treatment, making it a popular procedure among dentists and patients alike.

Juliana B. da Costa, DDS, MS
Associate Professor
Preclinical Director,
Department of Restorative Dentistry
Oregon Health & Science University
School of Dentistry
Portland, Oregon

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