51 Survey of dentists opinion on bleaching
Survey of members of the American Academy of Cosmetic Dentistry, conducted in 1992.
The periodontist Wagner, a colleague of Klusmier's, explored the use of the method in adults and subsequently discovered that the gingiva was somewhat less inflamed and that the teeth appeared whiter. Slowly the method spread and was adopted in 1988 by Haywood at the University of North Carolina. Haywood and Heymann (1989) developed a home bleaching technique that is still the currently used standard of care.
Carbamide peroxide has been long known among periodontists as an oral antiseptic substance. Munro described in 1968 that as a side effect of using carbamide peroxide in a splint, the teeth became whiter.
Based on his findings, the first commercial bleaching agent was developed for bleaching vital teeth, namely White & Brite (Omni) containing 10% carbamide peroxide.
Vital and nonvital tooth bleaching has not been around for very long, which is reflected in the list of commercial products being introduced on the market:
| 1989 | White & Brite by Omni |
| 1991 | Opalescence by Den-Mat |
| 1992 | Nite White by Discus Dental |
| 1994 | Platinum by Colgate |
The sales figures during the past 4 years have more than quadrupled. Bleaching is popular: patients wish to have white teeth and dentists see this as a new area to do business in.
A survey conducted by the Clinical Research Associates in 1994 gave an extremely positive trend: 92% of the 7 617 dentists surveyed bleached their patients' teeth patients as a matter of routine—in more than 90% of cases to the fullest satisfaction of the patients.
Only few innovations have had such a high degree of acceptance among both the public and professionals.
Scientific Studies
Haywood published his first studies in 1990. Extracted teeth were bleached for 5 weeks in the usual manner. Examination of the teeth using the scanning electron microscope revealed no changes in the enamel. The type of bleaching materials used did not affect the topography of the enamel.
In 1991 Yarborough published a literature review of the topic regarding effectiveness and safety of bleaching. Bleaching can be performed effectively with two substances, namely carbamide peroxide and hydrogen peroxide. Carbamide peroxide disassociates into H2O2, CO2, urea, and NH3. H2O2 is the effective agent here as well. Bleaching with H2O2 has the advantage that it takes place 3 to 6 times faster than with carbamide peroxide.
Murchison examined the effect of carbamide peroxide on enamel and concluded that a short-term application did not cause any significant change to the surface and physical properties of enamel (Murchison et al. 1992).
The majority of scientific studies show that it is safe to bleach teeth with 10% carbamide peroxide (Haywood 1992).
52 Effect of bleaching on micro hardness and morphology of enamel
Left (above): A natural enamel surface exhibits well-defined perikymata with irregular contours. It was used as a control and placed in saline.
Right (above): This enamel surface was etched too aggressively (50% H2O2). It is relatively porous and has poorly defined perikymata.
Left (below): Enamel bleached with Accel (35% H2O2) has clearly defined perikymata and a smooth surface. It was not damaged by bleaching.
Right (below): The enamal appears to be relatively intact after the surface was bleached with HiLite (main component also 35%H2O2).
Bar= 50 μm
Courtesy of C. Q. Lee
A Review of Bleaching Methods
Bleaching Vital Teeth
To bleach vital teeth, chemicals are placed on the enamel surface. This method is called external bleaching and can thus only change the discoloration of enamel.
Bleaching Nonvital Teeth
To bleach nonvital teeth, the chemicals are placed in the pulp chamber. In this way the coronal dentin is changed. The process is called internal bleaching.
In-Office Bleaching
These are very aggressive bleaching methods that were used previously when bleaching was done in-office: usually 33% H2O2 was used together with heat and light. Damage to enamel could occur with this method. The technique has been named power bleaching.
Bleaching teeth in the dental practice continues to play an important role. For example, when front teeth are treated with veneers, the cuspids can be brightened up by in-office bleaching. If one wants to achieve results very quickly, then in-office bleaching is preferred to home bleaching. Stronger chemicals are applied in such situations, but no additional energy sources (heat and light) are used. In most cases, three bleaching treatments are necessary.
Home Bleaching
Advantages
—The dentist needs to spend very little time treating the patient. A requirement is that the dentist has a dental assistant or hygienist who has the necessary qualifications needed for instructing the patient about the home bleaching procedure.
—This bleaching technique is usually more affordable than the in-office bleaching.
—The patients bleach their teeth whenever they wish to do so. They do not have to come to the dental office to do this.
—In home bleaching, in contrast to in-office bleaching, no rubber dam is required. Many patients have an acquired latex allergy and cannot tolerate the rubber dam.
—The bleaching process takes longer and is therefore safer for teeth.
Disadvantages
—Patients must collaborate actively. If they do not wear the bleaching tray, no therapuetic effect will occur. If they use their tray too much each day, the result is often hypersensitive teeth.
—There are patients who prefer to get their teeth bleached by the dentist or dental staff, even if this is means higher costs and longer treatment times.
—The bleaching process takes longer in the case of home bleaching than in the case of in-office bleaching.
Side Effects of the Bleaching Agent
—Bleaching agents contain peroxides. These enhance mutagenic effects of other chemicals, such as those present in cigarette smoke. Based on present scientific knowledge, patients should not smoke while wearing a bleaching tray. In the long run, the peroxides can also change oral flora. If bleaching is done over too long a period of time, Candida albicans can accumulate and hypertrophy of the papillae can occur.
—Power bleaching changes the structure of the hard tooth tissues and resulted in pulpitis in an animal experiment.
—A common adverse effect that occurs during bleaching is temporary hypersensitivity. This disappears in almost every case when the bleaching process is interrupted and the teeth are remineralized using a toothpaste containing fluoride.
—During in-office bleaching, etching bleaching