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Tooth Whitening or Dental Bleaching
Tooth whitening or dental bleaching is one the fastest and easiest ways to improve your appearance and put more sparkle in your smile. With tooth whitening, the color of the enamel is lightened, and the teeth look younger, healthier and brighter. Tooth whitening, sometimes referred to as "bleaching", offers a conservative treatment option for discolored teeth in comparison with resin-bonded composites, porcelain veneers or crowns. Successful whitening treatment depends on type, intensity, and location of the discoloration and a careful diagnosis by the dentist. Tooth discoloration can be superficial changes that affect the enamel surface, or can be deeper staining that affects the entire tooth structure. It is essential for the dentist to identify the type of the discoloration in the patient's teeth, diagnose the cause, and define the appropriate treatment plan. Discoloration in vital teeth can result from aging, tobacco use, chromogenic foods, medications, and pulpal pathology. More severe discoloration results from prescribed medication during tooth formation (theh second trimester in utero to 8 years of age). Various systemic conditions can also cause tooth discolorations. Amelogenesis imperfecta may result in hypoplasia or hypocalcification with yellow or brown stains, and dentinogenesis imperfecta may result in brownish-violet, yellowish, or gray discolorations. Patients with porphyria,a rare codition that causes an excessive production of pigment, may result in a red, purplish-brown, or brownish tooth discoloration. Aging usually brings thinning of the enamel, loss of theh transluscent enamel layer, and formation of secondary dentin. The combination of less enamel and darker, opaque dentin creates an older-looking, darker tooth. Tooth Bleaching Systems Tooth bleaching with various concentartions of peroxide has been demonstrated to be safe and effective in a variety of regiments, including in-office procedures, dentist-prescribed and supervised take-home treatments,and over-the-counter systems. The most acceptable whitening applications are in-office techniques, dentist-prescribed take-home systems, or a combination of both. Mechanism of Action Because the radicals have unpaired electrons, they are extremely electrophylic and ustable, and will attack most other organic molecules to achieve stability, generating other radicals. These radicals can react with most unsaturated bonds, resulting in disruption of electron conjugation and a change in the absorption energy of the organic molecules in tooth enamel. Simler molecules that reflect less light are formed, creating a successful whitening action. This process occurs when the oxidizing agent (hydrogen peroxide) reacts with the organic material in the spaces between the inorganic salts in tooth enamel. SIDE EFFECTS Toxicology The US Food and Drug Administration approved hydrogen peroxide and carbamide peroxide to be used for debriding oral wounds. Although whitening is a longer process that debridment, in vitro toxicological evaluation of whitening agents, such as 10% carbamide peroxide or 4% hydrogen peroxide, showed fewer or comparable side effcets of commonly used dental materials such as eugenol, dentifrices, mouthrinses, and composites. Studies have shown that daily exposure of carbamide peroxide should not excced 10 mg/kg. Average amount of whitening agent used is 502 mg per application. Even if the patient swallowed all of the gel, it would not exceed more than 8.37 mg/kg. There have been no credible studies in animals or humans that link tooth whitening to issues of oral cancer; therefore, the safety factor of whitening agents is high. Oral Side Effects Mucosal irritation occurs mostly as a result of ill-fitting trays, improper application of the whitening gel, or longer-than-prescribed use. Soft-tissue irritation generally is minimal, and is resolved either by adjustment of the whitening tray or shortly after cessation of the treatment. Tooth Sensitivity Studies have shown that sensitivity occurs in 55% to 75% of the treatment groups, compared with 20% to 30% of the placebo groups. The development of tooth sensitivity can be multilateral phenomenon, caused by an allergic or chemical sensitivity to the composition of the tray or the bleaching gel or the free radical formation of the gel. It can also result from overzelous toothbrushing. Glycerin, which is used to carry the active ingridient, can absorb water and thereby cause dehydration effect, also resulting in sensitivity. Sensitivity as a result of tooth bleaching is generally mild and transient. It occurs earlier in treatment and decreases as treatment continues. Occurence might be a result of the close contact of gel to the tooth and disappearance may be a result of a sensory accomodation. Tooth sensitivity and gingival irritation are always concerns when tooth bleaching is performed. Both in-office and take-home whitening procedures have been reported to induce sensitivity in a significant number of patients, but tooth whitening is generally well tolerated.
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