Vital tooth whitening, when administered correctly, is by all accounts one of the safest, most conservative, least expensive, and most effective aesthetic procedures currently available to patients. This article traces the evolution of the technology, describes what is known about the mechanism of action and explores such issues as toxicology and side effects associated with tooth whitening. The article also describes the various tooth-whitening systems, which include dentist-supervised night-guard bleaching, in-office or power bleaching, and bleaching with over-the-counter bleaching products. Combination treatments and light-activated treatments are also discussed. Finally, the article summarizes the areas of research needed in this field.
Aesthetics of the teeth is of great importance to many patients. Public demand for aesthetic dentistry, including tooth whitening, has increased in recent years. Patient interest in whitening and articles on whitening in popular magazines suggest that tooth color is a significant factor in the attractiveness of a smile. An attractive smile plays a major role in the overall perception of physical attractiveness . Studies confirm the importance of attractiveness on perceived success and self-esteem . Compared with restorative treatment modalities, whitening, also referred to as bleaching, is the most conservative treatment for discolored teeth. This public demand for a whiter smile and improved aesthetics has made tooth whitening a popular and often-requested dental procedure, since it offers a conservative treatment option for discolored teeth. Whitening often enhances the treatment and encourages patients to seek further aesthetic treatment .
Successful whitening treatment depends on the correct diagnosis by the practitioner of the type, intensity, and location of the tooth discoloration. It is imperative to determine if the discoloration is extrinsic, which is associated with the absorption of such materials as tea, red wine, some medications, iron salts, tobacco, and foods, onto the surface of the enamel and, in particular, the pellicle coating , or intrinsic, where the tooth color is associated with the light-scattering and -absorption properties of the enamel and dentin , as seen in tetracycline staining, amelogenesis and dentinogenisis imperfecta, hypoplasia, erythroblastosis fetalis, and porphyria. Additionally, discoloration results from the aging process. As teeth age, more secondary dentin is formed and the more translucent enamel layer thins. The combination of less enamel and darker, opaque dentin creates an older-looking, darker tooth . The practitioner must identify the type of discoloration, diagnose the cause, and then define the appropriate treatment plan.
Evolution of the technology
Tooth bleaching is not a new technique in dentistry. It was reported more than a century ago . In 1916, Adams reported the use of hypochloric acid to treat fluorosis. In 1937, Ames reported a technique using a mixture of hydrogen peroxide and ethyl ether on cotton, heated with a metal instrument for 30 minutes, and applied over 5 to 25 visits to treat mottled enamel. Younger used this technique in 1942 in 40 children with dental fluorosis. This and similar techniques using concentrated hydrogen peroxide and heat have been accepted treatment since the 1930s . In 1966, the combined use of hydrochloric acid and hydrogen peroxide was promoted to remove brown stain from mottled teeth . In 1970, Cohen and Parkins published a method for whitening tetracycline-discolored dentin of the teeth of young adults treated for cystic fibrosis. This was the first publication indicating that there is chemical penetration of hydrogen peroxide to the dentin to whiten teeth. Previous study concentrated entirely on the removal of extrinsic staining only. In 1976, Nutting and Poe introduced the walking bleach technique, which uses 35% hydrogen peroxide and sodium perborate for whitening nonvital teeth. In 1968, Klusmeier described a technique using Gly-Oxide (Marion Merrel Dow, Inc., Kansas City, Missouri), a 10% carbamide peroxide oral antiseptic, which he placed in the orthodontic positioners of some patients to improve gingival health. He noted whitened teeth as well as tissue improvement as a result. He switched to Proxigel, which also contained 10% carbamide peroxide, in a custom-fitted night guard in 1972 because the viscosity of the Proxigel allowed it to stay in the tray .
The first commercially available 10% carbamide peroxide was developed and subsequently marketed by Omni International in 1989 based on the findings of Munro , who used a 10% carbamide peroxide solution to control inflammation after root planing in a vacuum-formed plastic splint. He noted whitened teeth. Haywood and Heymann published the first clinical study on tooth whitening using Proxigel in vacuum-formed custom trays. This is the technique known as “night guard vital bleaching” in common use today. Haywood and Heymann conducted laboratory and clinical investigations of this technique and reported it in the literature in 1989. They reported on night guard vital bleaching using 10% carbamide peroxide. The night guard was custom fabricated to hold the whitening gel in contact with the enamel surface.
The dental profession rapidly recognized the benefits of an at-home bleaching agent and it has become a popular method of lightening teeth . The acceptance of this procedure, according to a 1991 use-survey, found 78% of general practitioners perform tooth-whitening procedures with 59% recommending the doctor-prescribed at-home method . In another survey, 9,846 dentists stated using at-home whitening techniques and 79% of those recognized the technique’s usefulness and overall clinical success . Ninety-one percent of 8,143 dentists responding to a 1995 Clinical Research Associates (CRA) questionnaire stated that they had used vital tooth bleaching with 79% reporting success and 12% reporting that they were not satisfied with the concept .
Many companies followed Omni International’s lead, marketing carbamide-peroxide–containing agents directly to consumers. In response to this direct marketing, the Food and Drug Administration issued a statement to manufacturers requiring appropriate safety and efficacy documentation in 1991 , and the American Dental Association subsequently developed guidelines for acceptance . Currently available peroxide-containing tooth-whitening materials include professionally dispensed and supervised products for use by patients at home, professional-use in-office products, and over-the-counter products for sale directly to consumers.