How safe is tooth bleaching?

We can't pick up a magazine or watch television without seeing a tooth whitening ad, with overly white teeth grinning at us, beckoning us to have our own "dazzling" pearly whites. Of course everyone wants sparkling white teeth and an attractive smile! Unfortunately our teeth can become discolored over a period of time from many sources such as coffee, tobacco, colas, some antibiotics, excessive fluoride, tooth and nerve disease, aging, and heredity (Interdent, Inc.). The popularity of at-home tooth bleaching systems gained momentum in 1989, following a published research study in Quintessence International, by Harald O. Heymann of the University of North Carolina Dental School (Berry 225). Since then tooth bleaching has been the subject of much research by the American Dental Association. The ADA wants these products to be safe for consumers, as well as effective.

The most common tooth whitening materials used by dentists today are those containing 10 percent carbamide peroxide. The carbamide peroxide breaks down into hydrogen peroxide and releases a highly reactive form of oxygen. The oxygenating agents then penetrate the tooth enamel and usually lighten the tooth shade. Some discoloration from tetracycline antibiotic therapy is less likely to be lightened (Russell 27-28).

Properly fitting bleaching trays are made by a dental assistant at the dental office, from impressions and diagnostic models of the teeth. Patients can use the bleaching gel in two- to three-hour intervals or overnight. The importance of properly fitting trays cannot be exaggerated. Per T. Reiakvam, DDS, says, "The process is very design sensitive. The bleaching trays must not touch the gingival tissues." Daniel Neumann, DDS, said, "The way the bleaching tray is made is critical to the patient's comfort and how well bleaching works." A marketing brochure explains to dental patients, "There is a significant difference in both the comfort and safety of dentist-designed trays vs. unsupervised over-the-counter one-size-fits-all boil and bite trays" (Life-Like Cosmetic Solutions). The vinyl tray material must be trimmed one-half millimeter short of the gumline to minimize trauma to the soft tissues. After the bleach has been loaded into the tray, then seated over the teeth, the excess bleach should be removed by toothbrush or a cotton gauze so the material does not sit on the gum tissues (Schulte 1331).

In 1991 the ADA asked the Food and Drug Administration to investigate the safety of whiteners and to determine whether they should be labeled as cosmetics or drugs. The FDA requires greater evidence of safety and effectiveness for drugs than for cosmetics. The ADA also asked manufacturers of bleaching materials to provide data, from studies longer than six months, on the safety and effectiveness of their products. This has motivated the studies to be funded by the makers of the bleaching materials. One would expect biased results from manufacturer's research, but studies are often conducted by dentists at universities (Russell 27).

Various scientific research studies have been published in the Journal of the American Dental Association. "The Effects of Bleaching Application Time on the Dental Pulp" concluded that some people experience increased sensitivity to hot and cold temperatures following tooth bleaching treatments, but this can be alleviated by shortening the bleaching time and applying fluoride (Schulte 1334).

Several studies have been done concerning the effects of bleaching on soft tissues in the mouth. In "Effects of a Bleaching Agent on Human Gingival Fibroblasts" Dr. Tipton determined that "despite protective mechanisms, bleaching agents may adversely affect fibroblasts ... if they gain access to the underlying gingival connective tissue. In situations where there may already be tissue injury, as in the case of alcohol use or smoking, the toxic effects may be exacerbated" (DSC Online). Gingival fibroblasts are those cells that develop connective gum tissue around the teeth.

In "Assessing the Effects of a 10 Percent Carbamide Peroxide on Oral Soft Tissues" James W. Curtis, Jr., DMD et al, discovered that "Under the supervision of a dentist, tooth bleaching is not harmful to oral tissues. In fact, the amount of plaque is even lowered during the first week of bleaching." Dr. Curtis added that "the six-week study may not be long enough to determine future conditions of the mouth" (1221-22).

Plaque is the accumulation of food debris and microorganisms on tooth and gum surfaces. It is the primary cause of tooth decay and gum disease. Karen Roberts, RDH, stated in an interview that "the bleach kills the bacteria, as does three percent peroxide with baking soda, which some periodontists prescribe for patients with gum disease. Peroxide may burn the gum tissues, but carbamide is different than peroxide. If the bleaching trays fit well, the gingival tissues should not be touching the bleach. I think the bleach actually cleans the mouth well."

None of the studies allowed people to participate who had gum diseases such as gingivitis or periodontitis, or pre-existing gingival lesions, or who use tobacco or alcohol. Dr. Schulte stated the importance for any dental problems to be taken care of before whitening is considered (1334). Another study by researchers found that dental bleaching agents can damage some filling materials. The carbamide peroxide can break down glass ionomer restorations and dentists would probably not prescribe bleaching for patients with these fillings (JADA 126. 560).

Although some negative results from studies have been published, there are also many positive outcomes from tooth whitening procedures. Researchers wanted to know the long-term effects of the bleaching processes done in 1989. In "Bleaching Patients Pleased with Long-Term Results," 30 of those previous patients were asked to complete a survey to evaluate long-term effectiveness, as well as side effects of the bleaching from three years earlier. None of the 30 people reported any post-treatment effects such as sensitivity, gingival irritation, tooth fracture, or a need for root canal therapy from tooth nerve damage (JADA 126. 714).

If people care about their looks and their health they will usually be happier and enjoy life more with a pleasing smile. Tooth whitening could make people more interested in their oral health. For instance, when a person goes through the difficult struggle of quitting the smoking habit, and wants to whiten their teeth, just this simple procedure could give them enough of a mental boost to stay off the tobacco. "Home bleaching affects patient behavior change. It is easily accomplished, relatively painless and inexpensive, and it makes an immediate positive change in patient self-esteem. Any technique that is safe and can be used to influence patients positively towards dental therapy should be encouraged" (Christensen 64-65).

The first bleaching products have changed since 1989. Over-the-counter kits are still available, but at a low percent of bleach, usually two to three percent hydrogen peroxide, about the same as toothpaste (Christiano 21). Manufacturers have been forced to use dentists and dental schools for product testing and have also improved their products over the last several years in order to more effectively sell to dental professionals and to compete in this lucrative market.

Some of the newer bleaching products such as Nite White Excel[ have removed some of the glycerine, which causes dehydration of the tooth matrix, thus causing some of the hot and cold temperature sensitivity problems some people experience. Nite White Excell comes in four concentrations: 5%-10%-16%-22% carbamide peroxide, and has two flavors: wild cherry and peppermint cream (Discus Dental).

Another recent advance in tooth whitening has been the use of lasers. Dr. Kelly Yarborough first experimented with laser bleaching on extracted teeth. Two types of lasers are used. First the patient's teeth are isolated and the gum tissues coated with a protective gel to prevent burning from the chemicals. The bleaching paste is painted on the teeth and a blue-light argon laser is used on each tooth for about 20 seconds, followed by a heat-intensive C[O.sub.2] laser focused on the teeth. This laser works with heat rather than light. The heat from the lamp can cause the teeth to feel uncomfortable. Then a protective coating of fluoride and calcium are sealed into the tooth with the argon laser. Dr. Yarborough assures patients that his laser bleaching even works on tough tetracycline stains. He also offers a five-year warranty. Yarborough started the BriteSmile company that was purchased by Ion Laser Technology, which is now marketing the technique (Schmidt 252-5). "Make sure the risk of something relatively new and unproved is worth the advantage. Even though in-office or at home bleaching is more time-consuming, we know they are both very safe and effective," said Dr. Mabrito (Gleason 79).

"The jury is still out on safety," said Dr. Reiakvam during an interview, as is the opinion of Dr. Kenneth Burrell (Berry 225, Russell 27). Even though these dentist-supervised products have been used for over ten years, studies have not been conclusive, and more research will be forthcoming. The public needs to understand the importance of possible trauma to the soft tissues of the mouth, as well as possible damage to the nerves of the teeth. The tooth nerve can take only so much trauma before permanent damage occurs and it gives up and dies.

Although the original research results seemed to suggest that bleaching products were not very safe, recent studies are changing the minds of dental professionals. If patients demand the procedure, it will continue to evolve and companies will create better and safer materials. As long as a person has no dental or other significant health problems, whitening teeth is probably a fine idea. A healthy happy smile will always increase a person's self-image.

Works Cited

All About Tooth whitening, Life-Like Cosmetic Solutions, Harbor Dental Bleaching Group, Inc., Santa Barbara, CA 1996. Berry JH. What About Whiteners? JADA 1990;121:223-25. Bleaching Patients Pleased With Long-Term Results. JADA 1995;126:714.

Carbamide Peroxide May Erode Glass Ionomers. JADA 1995;126:560.

Christensen GJ. To Bleach Or Not To Bleach. JADA 1991;122:64-5.

Christiano D. Brighter Smiles. American Health, Oct. 1995:21+.

Contrast PM. Interdent, Inc., Los Angeles, CA.

Curtis JW Jr, DMD et al. Assessing the Effects of 10 Percent Carbamide Peroxide on Soft Oral Tissues. JADA 1996;127:1218-23.

Discus Dental Catalog 1996, Discus Dental, Inc., Beverly Hills, CA.

Gleason SB. The Laser Craze. American Health, March 1997:77-79.

Neumann DJ. Personal Interview. 02 Mar. 1997.

Roberts KM. Personal Interview. 01 Mar. 1997.

Reiakvam PT. Personal Interview. 13 Mar. 1997.

Rosenstiel SF, Gegauff AG, Johnston WM. Clinical Trial of Home Bleaching Tests' Efficacy and Safety. Esthetic Dentistry, Dental Abstracts, 1997;42: 35.

Russell D. Safety Questions About Tooth Whiteners. Consumers Research. 1991; Feb: 27-8+.

Schmidt W. The Great White Hype. Vogue. 1996; Aug:252-5.

Schuhe JR, et al. Effects of Bleaching Application Time on the Dental Pulp. JADA 1994;125:1330-34.

Tipton DA. Effects of a Bleaching Agent on Human Gingival Fibroblasts. Dental Study Club Online. 1995;4:No.6,Dec.

Ellen F. Nuss has been a U.S. Naval Reserve Dental Technician for over 20 years, and was recently promoted to Master Chief Petty Officer. She is currently director of the Dental Technician Basic and Advanced Proficiency Courses, and is Secretary for the Mile High Chapter of the Naval Enlisted Reserve Association. She has been Dental Assistant Instructor for ConCorde Career Institute Denver Campus since 1990, Colorado Private School Association Allied Helath Educator of the Year 1993, and American Heart Association CPR Instructor Trainer.