Assessing dentin color changes from nightguard vital bleaching

Background. At-home bleaching with 10 percent carbamide peroxide in a custo m-fitted tray has been reported to change the color of dentin. The purpose of this study was to validate the color change of dentin and to determine w hether the color change was uniform or occurred from the outside (the denti noenamel junction) to the inside (the pulpal wall). Methods. The authors sectioned 10 extracted human teeth incisogingivally th rough the midfacial long axis, and sealed their cut surface against glass m icroscope slides. Identifying marks were placed on the glass over the tooth sections to serve as a color control and in the dentinal areas closest to the dentinoenamel junction and the pulpal wall. Teeth were bleached for 10 days with 10 percent carbamide peroxide. Photographs were taken from the gl ass-covered side of the teeth, digitized and converted to gray-scale levels (consisting of 256 shades of gray ranging from black to white). Marked are as were measured with a National Institutes of Health Image software progra m and analyzed statistically for changes in lightness between the control m arks and the inner and outer dentinal marks over time. Results. Paired t-tests and analysis of variance indicated a significant in crease in lightness (P = .01) for the inner and outer dentinal areas during bleaching compared with the control areas. No significant differences were found in the rate of change for the inner and outer dentinal areas (P = .8 9). Conclusions. The increase in lightness confirms that a significant color ch ange occurred in the dentin during bleaching with 10 percent carbamide pero xide. This change occurred throughout the dentin at a uniform rate, rather than from the outside inward. Clinical Implications. The results of this study show that at-home bleachin g with 10 percent carbamide peroxide can change the color of dentin, which is important to treat intrinsic stains from tetracycline treatment, trauma and aging or inherited discolorations. The bleaching material easily penetr ates the tooth to change the dentin color at the same rate throughout, indi cating that the type of stain may be the important factor in determining bl eaching success.