Power bleaching or professional in-office bleaching is a term used to describe the treatment of discolored dentition with high-concentration oxidizing agents by the dentist chairside. Different techniques, devices, and material choices have been used in dentistry for treating discoloration with varying success. Some situations are better suited for extended treatment outside the dental office with lower concentrations of peroxide delivered in custom trays, whereas the appearance of a severely discolored nonvital tooth may best be treated using a classic “walking bleach” technique. The primary focus of this chapter will be on the power bleaching technique used to achieve more immediate results on multiple vital teeth, with special consideration given to treatment of the single vital tooth and when combined techniques may be employed.
In 1864, Dr. James Truman of the Pennsylvania College of Dental Surgery published Discolored and Necrosed Teeth, in which he described the technique for bleaching nonvital teeth. He is credited with the first successful method for bleaching teeth. His method included treating the patient every day for 1 to 4 weeks with chloride of lime combined with a weak acetic acid (Truman 1864). Techniques were refined throughout the decades using direct or indirect heat in attempts to accelerate the oxidation process (Harlan 1884, Nutting and Poe 1963, Cohen 1968, Chandra and Chawla 1974, Hanosh and Hanosh 1992). Direct heat techniques eventually became less prevalent because of the risk associated with cervical resorption. Chemical techniques using sodium perborate and/or superoxyl in the absence of heat continued with some success on nonvital teeth, but efficient techniques for multiple vital teeth were still lacking. Improvement in bleaching products in the mid-1990s including photosensitive formulas, and delivery systems such as light-cured barrier materials, increased use of in-office bleaching for multiple vital teeth (Barghi 1998). Combined with the introduction of at-home bleaching trays using carbamide peroxide, bleaching emerged as one of the most sought-after procedures in dentistry (Haywood and Heymann 1989).
CLINICAL AND RADIOGRAPHIC EXAMINATION
As with all dental bleaching, a comprehensive oral examination should be performed before power bleaching. A thorough clinical and radiographic examination of the hard and soft tissues should rule out the presence of any oral pathology or dental disease and determine the cause of the stain. The clinician should make special note of any existing dental restorations, formulating a plan with the patient to replace any restorations because of postbleaching color mismatch (see Figure 7.1), and note with the patient any clinical white spot lesions that may appear accentuated immediately after bleaching (see Figure 7.2). A history of tooth sensitivity should be discussed by asking the patient if the teeth are generally sensitive to thermal changes such as when drinking hot or cold beverages.
CASE SELECTION FOR IN-OFFICE TECHNIQUE
During the treatment planning process, observing the character and depth of discoloration can help discriminate whether the patient is a suitable candidate for in-office power bleaching.
Class I: Good candidate for in-office bleaching
Mild to moderate extrinsic stain (standard patient)
These are the standard patients with all forms of mild to moderate extrinsic staining. Superficial yellow to light-brown discolorations are typically from external sources such as dietary chromogens (tea, wine, coffee), poor dental hygiene, tobacco use, or staining mouth rinse (chlorhexidine); combined with aging, all of these can contribute to extrinsic staining (see Figures 7.3A and 7.3B).
Class II: Moderate candidate for in-office bleaching
Severe extrinsic to mild intrinsic stain
When the cause of the discoloration is intrinsic in nature, including hemorrhagic sources resulting from trauma, the outcome becomes less predictable. Vital teeth with mild intrinsic discoloration may respond well to in-office power bleaching after one appointment if the pulp chambers are not calcified (see Figures 7.4A–D). If the tooth is nonvital and pulpless, then it can be bleached both internally and externally simultaneously, improving the chances for a good outcome as compared with a vital tooth with no access to the pulp chamber (see Figure 7.5A–F). Although the procedure can be successful after one treatment, the patient’s expectations should be prepared for the possibility of multiple treatments for severe extrinsic to mild intrinsic stains, especially if a calcified pulp chamber is observed on the radiograph.
Class III: Poor candidate for in-office bleaching
Moderate to severe intrinsic stain
Teeth that may not be suitable for in-office power bleaching include those with moderate to severe intrinsic discoloration. The single nonvital tooth with severe intrinsic stain typically will require multiple treatments such as with the “walking bleach” technique. Improved bleaching can still be expected for the severely discolored tooth; however, patients must be motivated to continue with weekly appointments for multiple sessions. In some cases the patient may tire of repeated office visits and elect to discontinue treatment before reaching maximum expected outcome (see Figures 7.6A–E).
Dense vital tooth
A single vital tooth that has a calcified or reduced pulp chamber may not respond well to in-office bleaching. When a calcified pulp chamber is noted on the radiograph, the presumption is an increased tooth density in which the peroxide will not readily diffuse. In this case, long-term at-home bleaching may improve the color, but the patient ultimately should be prepared for restorative coverage with a laminate veneer if bleaching is unsuccessful (see Figures 7.7A–D).
As part of the initial patient interview, the advantages and disadvantages of in-office professional bleaching should be discussed relative to at-home bleaching and expected outcomes. The relatively higher cost and increased risk of sensitivity will be important disadvantages to note. By far the most appealing advantage for most is the prospect of “instant” results. The total time savings is material and tooth dependent. Clinical studies have shown that 7 days of at-home bleaching with 10% carbamide peroxide equals 45 minutes with 38% hydrogen peroxide (Auschill et al. 2005), or a 1-hour treatment with 28% hydrogen peroxide using supplemental light (da Costa et al. 2010). Patients should understand that results may vary.
Some patients have unrealistic expectations based on a distorted perception of their existing tooth color. The patient with extremely white teeth from habitual bleaching may in fact believe that his or her teeth appear yellow. These patients may have an obsession with or addiction to bleaching, colloquially known as “bleachorexia,” and should be advised against continual bleaching. Time should be taken to educate the patient regarding the extreme light color relative to the color of the lightest natural tooth shades. This can be accomplished by demonstrating to the patient his or her extreme white teeth next to, for example, the B1 tab from the VitaPan classical shade guide (Vita Zahnfabrik, Bad Säckingen, Germany) (see Figure 7.8).
ONE- AND TWO-COMPONENT SYSTEMS
Some bleach formulas will combine all the component materials into one syringe, or products may package activators and additives as separate components that require mixing.
One-component systems are typically bleach formulas that do not require mixing for activation. They consist primarily of highly concentrated hydrogen peroxide as the active ingredient in a gel form matrix such as glycerin or propylene glycol, along with stabilizers or photosensitizers (see Figure 7.9).
Two-component systems may require mixing of the active ingredient with a catalyst. Some systems require hand mixing of the components (see Figure 7.10), others may use syringe-to-syringe mixing (see Figures 7.11A and 7.11B), and still others may combine the components through an automix tip of a dual-barrel syringe (see Figure 7.12).
Carbamide peroxide has been shown to be effective for at-home bleaching (Hasson et al. 2006) when used in concentrations ranging from 10% to 22%. Higher concentrations ranging from 35% to 44% have been applied by dentists using an assisted bleaching technique. The carbamide peroxide, in this case, may be warmed and applied with a custom tray or directly to the teeth, avoiding the gingiva, and monitored in the office (Miller 1999). In-office bleaching with carbamide peroxide has generally been replaced with techniques using higher concentrations of hydrogen peroxide. Carbamide peroxide is considered less effective for in-office bleaching because of its slower rate of decomposition to form active oxygen and peroxide radicals.
Chlorine dioxide has also been used chairside by non-dental providers, especially in the United Kingdom. However, because of its acidic pH, reported damage to enamel, and lack of investigation for dental use in the scientific literature to date, the dental professional has not adopted the use of chlorine dioxide for in-office power bleaching (Greenwall 2008).
Hydrogen peroxide (H2O2) in high concentrations ranging from 15% to 40% has been used most effectively by the dental professional as the active ingredient for in-office power bleaching. As concentration increases, fewer applications of hydrogen peroxide are usually required (Sulieman et al. 2004).
ACTIVATORS AND PH
pH of bleach formula
The common recommendation for professional bleaching formulas is to have a neutral pH to avoid damage to enamel (American Dental Association Council of Scientific Affairs 2009). The optimum pH for hydrogen peroxide decomposition is considered to be around 9.5 to 10.8 (Goldstein and Garber 1995). Some bleach formulas may still contain acidic components to keep the active ingredient stable. A recent study showed the bleaching effect of acidic 30% hydrogen peroxide versus neutral 30% hydrogen peroxide to be equivalent (Sun et al. 2011). The pH becomes an important issue if it falls below the critical point of 5.2, at which enamel demineralization is expected to occur (Driessens et al. 1986, Shannon et al. 1993, Joiner 2007). However, an abundance of mineral ions found in human saliva and the formation of a natural salivary pellicle in vivo should have a protective effect against enamel demineralization (Hannig and Balz 1999, Hannig et al. 2004).
Activators and additives
In addition to hydrogen peroxide, power bleach formulas may contain proprietary activators, which may include a combination of alkaline pH adjusters, metal ions, or photosensitive catalysts to absorb and transfer energy to the peroxide and accelerate decomposition. Other added ingredients may include stabilizers for extended shelf life or materials to improve viscosity.
BLEACHING LIGHT DEVICES
The use of light to supplement the bleaching process in dentistry was reported as early as 1918 (Abbot 1918). Not until recently has the use of bleaching lights begun to become widespread. Although there are several light sources with different spectral distributions and efficiencies currently on the market, they all purport to accelerate or enhance the bleaching process. Initially, bleaching lights relied more on heat or thermal decomposition of the bleaching agent, whereas contemporary bleaching lamps aim to achieve photolysis of the bleaching agent at specific wavelengths.
Heat lamps (19th century–1980). Early bleaching lamps made use of an incandescent or photographic floodlight (see Figure 7.13). This type of light source produced a continuous spectrum with high infrared emission, which supplied a source of indirect heat. For vital teeth, temperatures were recommended in a range of 46°C to 60°C (115°F to 140°F). For nonvital teeth temperatures as high as 71°C (160°F) were recommended (Goldstein and Garber 1995). The risk of increasing the pulpal temperature beyond the critical threshold of 5.5°C, at which irreversible pulpal damage can occur, is a concern with any system that raises the temperature of vital teeth (Zach and Cohen 1965, Baik et al. 2001). The use of heating lamps has fallen out of favor for vital teeth and may be considered obsolete by today’s standards.
Halogen lamps (1980s–2000). These lights are a refinement of the incandescent light source with halogen gas added. The halogen gas causes evaporated tungsten to redeposit on the filament, improving the filament life and allowing a higher color temperature than the standard incandescent lamp. The higher color temperature supplies a cooler (more blue-green) continuous spectrum of light from near ultraviolet to deep infrared filtered to the usable region for the bleaching agent (see Figure 7.14).
High-intensity discharge (HID) lamps (1990s–current). These are high-powered lamps that produce light by ionizing noble gases (xenon, krypton) or metal halides between two electrodes. Depending on the conducting elements added to the arc stream, HID lamps may properly be referred to as metal halide lights and are often referred to as “plasma arc lights” in dentistry. These lamps are typically wide-spectrum lamps using bandpass filters to narrow the emission primarily to the short ultraviolet to blue light (380–500 nm) (see Figure 7.15).
Light-emitting diode (LED) lamps (2000–current). These are solid-state, semiconducting energy sources that supply near-monochromatic light. LED lamps are currently one of the most energy-efficient and rapidly developing light technologies. Because LEDs produce a discrete or narrow spectrum of light, the light source requires no additional filtration of extraneous energy and produces very little heat. As a result, an LED bleaching light system is dependent less on heat and more on the wavelength-specific photochemistry of the bleaching formula and possible energy absorption of the natural tooth chromogens contributing to bleaching effect (Figure 7.16).
Lasers. The popular consumer term for in-office bleaching with any type of light is often referred to as laser bleaching. However, a laser by definition is a device that produces a nearly parallel, monochromatic, and coherent beam of light by exciting atoms and causing them to radiate their energy in phase (coherent). Lasers have been slow to gain wide acceptance for dental bleaching because of a lack of scientific clinical trials and the high cost compared with alternative light devices. Deleterious effects associated with increased pulpal temperature of teeth are also a concern with the use of lasers (Luk et al. 2004, Baik et al. 2001).
The role of bleaching lights in dentistry is a topic for which there has been controversy and a lack of agreement. This lack of agreement can be attributed to variability associated with methods used to measure color, different light sources, and bleaching formula interactions (Ontiveros 2011). Some clinical studies have reported significant effects with bleaching lights (Tavares et al. 2003, Ziemba et al. 2005), whereas others have shown no effectiveness (Papathanasiou et al. 2002, Hein et al. 2003). Still others have found mixed results depending on tooth inclusion (Calatayud et al. 2010) or method of color measurement (Gurgan et al. 2009, Kugel et al. 2009, Ontiveros and Paravina 2009). The trend for future lamps may rely more on specialized light sources such as LEDs or lasers rather than filtered light to illuminate the teeth. As refinements in material photochemistry and improvements in spectral properties of bleaching lamps continue, the use of supplemental light devices in dentistry is expected to remain popular and continue to grow in the foreseeable future.
MONITORING OF BLEACHING
Bleaching can be monitored using visual and/or instrumental methods. Both methods can provide credible results if used appropriately.
Visual monitoring is by far the predominant method for evaluation of bleaching efficacy. The most important aspects of this method are observer and patient recruitment, shade-matching conditions, method, and tools.
It is not justified to recruit experienced practitioners or female observers for visual monitoring of tooth bleaching because there is insufficient evidence that experience and gender influence shade-matching performance for observers with normal color vision. However, significant evidence shows that differences exist among individuals of the same gender or people with similar experience. These differences can be quantified through various professional (nondental) tests such as Ishihara charts or the Farnsworth–Munsell 100-hue test. In the latter test, color discrimination ability of color-normal individuals ranges from low (16%), through average (68%), to superior (16%). There is also evidence that education and training can improve one’s color-matching skills.