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194 JADA, Vol. 135, February 2004 R E S E A R C H Background. Light-activated bleaching is a method of tooth whitening. The authors conducted a study to compare the whitening effects and tooth temperature changes induced by various combinations of peroxide bleaches and light sources. Methods. The authors randomly assigned 250 extracted human teeth halves into experimental groups (n = 10). A placebo gel (control), a 35 percent hydrogen peroxide or a 10 percent carbamide peroxide bleach was placed on the tooth surface and was irradiated with no light (control); a halogen curing light; an infrared, or IR, light; an argon laser; or a carbon dioxide, or CO2, laser. Color changes were evaluated immediately, one day and one week after treatment using a valueoriented shade guide and an electronic dental color analyzer. The outer enamel and inner dentin surface temperatures were monitored before and immediately after each 30-second application of light using a thermocouple thermometer. Results. Color and temperature changes were significantly affected by an interaction of the bleach and light variables. The application of lights significantly improved the whitening efficacy of some bleach materials, but it caused significant temperature increases in the outer and inner tooth surfaces. The IR and CO2 laser lights caused the highest tooth temperature increases. Conclusions. Dentists performing an inoffice bleaching technique with the use of an additional light source to accelerate tooth whitening should consider the specific bleaching agent being used, as well as the potential risks of heating teeth. Clinical Implications. A specific combination of bleach and light that demonstrates good color change and little temperature rise should be selected for in-office tooth bleaching. Effect of light energy on peroxide tooth bleaching KAREN LUK, D.D.S.; LAURA TAM, D.D.S., M.Sc.; MANFRED HUBERT, Ph.D. V ital tooth bleaching is a popular treatment modality in dentistry. The advantages of an in-office whitening procedure over an athome bleaching technique include dentist control, avoidance of soft-tissue exposure and material ingestion, reduced total treatment time and greater potential for immediate results that may enhance patient satisfaction and motivation. The typical in-office bleaching regimen involves the application of a 35 percent hydrogen peroxide formulation to the tooth surface. Proponents of “power bleaching” claim to reduce the total in-office bleaching time necessary by energizing the bleach material using various light sources, such as lasers and plasma arc lights. The theoretical advantage is the light source’s ability to heat the hydrogen peroxide, thereby increasing the rate of decomposition of oxygen to form oxygen free radicals and enhancing the release of stain-containing molecules. In one study, various light sources elevated the bleach temperatures; however, they also increased the intrapulpal temperature. Therefore, astute clinicians should consider the issue of pulp health before rendering this treatment on vital teeth. With respect to esthetics, our literature review showed that power bleaching has questionable whitening efficacy. Jones and colleagues demonstrated that a typical in-office laser bleaching session produced significantly fewer desirable color changes than did two at-home bleaching protocols. An article published in CRA Newsletter also reported no perceivable difference between energized versus nonenergized bleaching when performed under standardized conditions. In contrast, a recent study suggested that bleaching using a plasma Successful vital bleaching requires good whitening efficacy without pulpal damage. ARTICLE 3 J A D A C O N T I N U I N G E D U C A T I O N ✷ ✷  Copyright ©2004 American Dental Association. All rights reserved. arc lamp enhanced the whitening of the superficial and deeper layers of tooth structure, thus causing a significant change in tooth color. Further scientific evidence is needed to substantiate these findings. Light is absorbed, scattered, transmitted or reflected by a material. Most bleaching agents that have been developed for combined use with light sources include the addition of an activator or colorant to improve light absorption or to reduce tooth heating. Our preliminary work on the energy absorption characteristics of hydrogen and carbamide peroxide showed that selected bleaching materials (without colorants) strongly absorb light that has wavelengths less than 300 nanometers (in the ultraviolet range), from 2,800 to 3,600 nm and more than 6,000 nm. Such information suggests that the existing light sources used for tooth whitening that have an output in the 400 to 500 nm range of the color spectrum would be absorbed poorly by bleaches without colorants. We speculated that a light source with a spectral output in the range that is strongly absorbed by bleach would best enhance tooth bleaching. The purpose of this in vitro study was to compare the tooth whitening effects and tooth temperature changes induced by various combinations of peroxide bleaches and light sources. MATERIALS AND METHODS We randomly selected 125 human teeth that had been extracted within three months of experimentation. The teeth were cleaned and stored in distilled water at 4 C. All of the teeth had no or minimal caries and restorations, had no enamel cracking and were a shade B2 or darker on the Vita Lumin Shade Guide (Vita Zahnfabrik H. Rauter GmbH & Co., Bäd Sackingen, Germany). We divided the teeth into buccal and lingual halves using a high-speed handpiece, water irrigation and carbide burs. We then randomly assigned the tooth halves into 25 groups of 10. All of the teeth maintained a wet or moist condition during all phases of the experiment. One trained evaluator (K.L.) assessed the baseline shades of the teeth using the shade guide and a prototype electronic dental color analyzer. The shade guide can be ranked according to value (Table 1); a lower numerical value for shade denotes a lighter tooth shade. The electronic color analyzer assesses dental colors by calculating numerical values of brightness (B parameter) and level of colorization (C parameter) from measured spectral reflectance. A more positive B parameter and more negative C parameter represent improved color change compared with baseline measurement. We took photographs of the teeth before bleaching and a matching Vita shade tab of the teeth to be bleached under standardized lighting JADA, Vol. 135, February 2004 195 R E S E A R C H TABLE 1 VALUE-ORIENTED VITA LUMIN SHADE GUIDE* RANKINGS USED FOR SHADE TAB COLOR ASSESSMENTS.